Running head: MOTOR IMAGERY IN SPORT AND BRAIN’S PLASTICITY
THE IMPACT OF MOTOR IMAGERY ON SPORT PERFORMANCE AND THE BRAIN’S PLASTICITY
Bachelor Degree Project in Cognitive Neuroscience Basic level 22.5 ECTS Spring term 2019
Johanna Lingvall
Supervisor: Anders Milton Examiner: Sakari Kallio
2 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Abstract
New neuroimaging techniques have made it possible to examine imagery and found evidence for that imagery share similar neural correlates as in perception. Imagery can be used in different areas to enhance performance, and it is a popular technique in sports. Similar to physical practice
(PP), motor imagery (MI) can result in brain plasticity. The aim of this thesis is to describe what imagery means and describe different theories of imagery. This is to further look into what impact MI has on performance in different sports, and then to further see if there are any changes in brain plasticity as a result of using MI. There is a lack of studies done on MI, performance and brain plasticity in sport. To answer the latter focus of this thesis, studies of healthy persons and patient studies using MI to improve performance and examining changes in the brain have been used. In order to do that this thesis aims to do a literature review. The results indicate that MI combined with PP can improve sport performance. It has also been showed that MI alone can be as good as PP. Most studies found that MI combined with PP can result in brain plasticity, and only one study did not found evidence for it. It has also showed that MI alone can result in brain plasticity. Future research should include larger samples, matching subjects, and comparing the effects of MI in several kinds of sports.
Keywords: motor imagery, sport performance, brain plasticity, mental imagery
3 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY List of Abbreviations fMRI Functional magnetic resonance imaging
PET Positron emission tomography
TMS Transcranial magnetic stimulation
EMG Electromyography
BOLD Blood oxygenation level-dependent
MI Motor imagery
PP Physical practice
MP Mental practice
NP No practice
IG Imagery group
CG Control group
M1 Primary motor cortex cM1 Contralateral primary M1
SMA Supplementary motor area cSMC Contralateral sensorimotor cortex
PMC Premotor cortex
S1 Primary somatosensory cortex
PPC Posterior parietal cortex
PETTLEP Consist of items: physical, environment, task, timing, learning, emotion,
and perspective
VMBR Visuo-motor behavioral rehearsal
SDA-M Structural dimensional analysis of mental representation
MIQ Movement Imagery Questionnaire 4 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY MIQ-R Movement Imagery Questionnaire-Revised
5 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Table of Contents Abstract ...... 2
Introduction ...... 7
Mental Imagery ...... 12
Where, When and Why to Use Imagery ...... 12
Different Types of Imagery ...... 13
Imagery in Sport...... 14
Effective Imagery ...... 14
Imagery Ability and Individual Differences ...... 15
Theories of Imagery ...... 17
Bioinformational Theory ...... 17
Psychoneuromuscular Theory ...... 18
Symbolic Learning Theory ...... 19
The PETTLEP-Model ...... 20
Imagery and Neural Correlates ...... 22
The Visual Organization ...... 23
Visual Imagery and Visual Perception ...... 24
Imagery of Rotation ...... 25
Motor Imagery ...... 25
Time Duration ...... 27
Motor Imagery and Neural Correlates ...... 27 6 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Action Observation ...... 29
Autonomic Responses ...... 30
Learning and Performance ...... 30
Motor Imagery and Sport Performance ...... 32
Golf ...... 32
Gymnasts ...... 34
Tennis ...... 36
Volleyball ...... 38
Motor Imagery, Performance, and Brain Plasticity ...... 40
Healthy Participants ...... 41
Stroke Patients ...... 42
Spinal Cord Injury ...... 46
Discussion ...... 48
References ...... 52
7 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Introduction
Since the time of Plato imagery has been of interest. Plato thought that all humans’ memories were grounded on images. Then, imagery has continued to be discussed over centuries.
In the early 1970s, the cognitive revolution accelerated and the interest in imagery emerged
(Kosslyn, Behrmann, & Jeannerod, 1995). New neuroimaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) has made it possible to examine the neural correlates of imagery in humans. These techniques have allowed researchers to find that imagery shares similar neural correlates as in perception (Kosslyn, Ganis,
& Thompson, 2001).
Corbin defines (as cited in Suinn, 1997) mental practice as the “repetition of a task, without observable movement, with the specific intent of learning” (p.189). Mental imagery has been described as seeing in the mind’s eye or as visualization (Thomas, 1997) and there are different types of imagery (e.g. auditory, kinesthetic, visual, and olfactory imagery). According to
Martin, Moritz, and Hall (1999) mental imagery is interchangeable with imagery.
Athletes or elite athletes practice and compete at different levels in their sports (e.g. university, nationally or internationally level). Non-athlete refers to anyone who doesn’t exert any sport. Athletes and non-athletes differ in such as technical skills, and physical abilities (e.g.
Swann, Moran, & Piggott, 2015).
Imagery can be used as a technique to enhance sport performance (Arvinen-Barrow,
Weigand, Thomas, Hemmings, & Walley, 2007). It has been reported to be the most common technique used among athletes in an aim to enhance performance (Parnabas, Parnabas, &
Parnabas, 2015). It has been demonstrated that 90% of the Olympic athletes in America uses imagery, and 97% of them believe imagery to have a positive effect on their performance
(Weinberg & Gould, 2008). Imagery has also been reported to be used by non-athletes (Jones & 8 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Stuth, 1997). It has been reported to be used by musicians, stroke patients and by surgeons (e.g.
Keller, 2012; Ridderinkhof & Brass, 2015). A musician who uses imagery (especially kinesthetic imagery) enhances the strength of an isometric movement, which can improve the performance
(Lotze, 2013; Zatorre & Halpern, 2005).
Motor imagery (MI) can be described as “…an active process during which the representation of a specific action is internally reproduced within working memory, without any corresponding motor output” (Jackson, Lafleur, Malouin, Richards, & Doyon, 2003, p. 1171).
Studies have demonstrated that MI can work as a tool in rehabilitation (e.g. Page, Levine, &
Leonard, 2007). MI might be beneficial for people in recovery from hemiparesis or cerebral infarction (Liu, Chan, Lee, & Hui-Chan, 2004; Stevens & Stoykov, 2003). According to Sanders et al., (2008) surgeons frequently use imagery as a tool in preparation for an operation and it has also been found to be beneficial to improve surgical skills.
According to Holmes and Calmels (2008) imagery in sport is normally used with having one’s eyes closed. Athletes might imagine their own sports performance involving movements that are required for that situation (Weinberg, Butt, Knight, Burke, & Jackson, 2003). Imagery has been reported to be used in many different sports for example wrestling, diving, (e.g. Highlen
& Bennett, 1983), gymnastics, (e.g. Mahoney & Avener, 1977), golf, (e.g. Bernier & Fournier,
2010), and soccer (e.g. Salmon, Hall, & Haslam, 1994). Imagery can be used in sport to improve a specific movement, which in turn, can make the physical performance better (For a meta- analysis see Feltz & Landers, 1983). For example, Taekwondo athletes (from university, district, state, and national level) that use imagery have shown to improve their performance (e.g.
Parnabas et al., 2015).
Brain plasticity refers to the neural reorganization of the human brain which shapes due to physiological changes, one’s experiences, pressures, and environmental changes. As we learn, 9 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY grow, and develop in life, changes occur in the input of any neural system resulting in the neural reorganization, which can be short or long-lasting (Berlucchi & Buchtel, 2009; Pascual-Leone,
Amedi, Fregni, & Merabet, 2005). For instance, differences in gray matter volume and cortical thickness in auditory cortices have been found in expert musicians (Zatorre, Fields, & Johansen-
Berg, 2012). According to Berlucchi and Buchtel (2009), a compensatory modification occurs in the neural organization when human lose functions as a result of aging or brain damages.
According to Pascual-Leone et al., (2005) brain plasticity has been demonstrated to occur at cell- and molecular levels and as well at behavioral, anatomical and physiological levels. It is stated that brain plasticity is an ongoing condition of the nervous system which occurs throughout one’s life (Pascual-Leone et al., 2005).
The PP of a movement can result in brain plasticity. For example, weeks of PP of sequence finger movements has shown to result in stronger activation in the primary motor cortex
(M1) and has shown to last for weeks after the practice (Ungerleider, Doyon, & Karni, 2002).
Furthermore, in a study by Pearce, Thickbroom, Byrnes, and Mastaglia (2000) they used transcranial magnetic stimulation (TMS) and found that elite badminton players had an increase in amplitude and shifts in the cortical motor maps of the hand used in badminton. In another
TMS-study, Fourkas, Bonavolontà, Avenanti, and Aglioti (2008) found increased corticospinal facilitation of the muscles of expert tennis players during MI of tennis. When the tennis players engaged in MI of golf or table tennis no such activations were found (Fourkas et al., 2008).
It has been demonstrated that similar plastic changes that occur in the motor system due to the real physical movement also can occur when using MI (see review Mulder, 2007). Several studies have examined MI and brain plasticity in rehabilitation and have shown enhancement in performance (e.g. Jackson, Lafleur, Malouin, Richards, & Doyon, 2001; Ietswaart et al., 2011). 10 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY There are still not many studies done on sport performance using MI and the brain’s plasticity. Therefore, if there are plastic changes as a result of using MI in people in rehabilitation and other areas, the same plastic changes should occur in people using MI in sport and improve their performance.
Imagery in sport has been criticized due to the absence of evidence in scientific studies and applied work that has been done in the field (Smith, Wright, Allsopp, & Westhead, 2007).
Different studies have used various methods and designs. Studies in the field lack replication and extension of studies. The use of different research designs has made it more difficult to get a clear picture of imagery and movements in the literature. Also, meta-analyses done in the field have been criticized. Different methods used in different studies might have an impact on the effect size provided in the meta-analysis (Goginsky & Collins, 1996).
The aim of this thesis is to first describe what imagery means and to describe different theories of imagery. This is to then look a little bit closer at whether MI has any influence on performance in different sports, and then look at which structural changes that arise in the brain as a result of the use of MI. In an attempt to answer if MI can have any impact on performance, this thesis will focus on studies done on different sports. The second focus of this thesis will be to focus on MI and performance and the brain’s plasticity. As mentioned before, there is a lack of studies on brain plasticity and MI on sport performance. Of that reason, different studies which refer to performance and brain plasticity using MI will be used in this thesis.
In order to do that this thesis aims to do a literature review. Relevant research articles have been collected from databases such as Scopus, Web of Science, and Google Scholar. In these databases, keywords like “motor imagery”, “sport performance”, “brain plasticity” and
“mental imagery” have been used. 11 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY It seems that researchers use different concepts when referring to imagery. They use concepts such as imagery, mental imagery, and mental practice, but the description of each conception refers to the same (e.g. Martin et al., 1999; Suinn, 1997). Some refer only to imagery when describing the imagery involving movement, and others refer to it as motor imagery (e.g.
Jeannerod & Decety, 1995; Weinberg, 2008). The concept of movement imagery has been used and seems to be the same as MI (e.g. Vergeer & Roberts, 2006). There do not seem to be a single concept of imagery. Therefore in this thesis, imagery, mental imagery, and mental practice will be synonymous.
After this introduction mental imagery will be introduced. More specifically this thesis will start to describe what mental imagery is, the use of imagery, what types of imagery there are, imagery ability, what makes imagery effective, and if there are any individual differences in using imagery. This will be followed by some central theories of imagery. Thence, an overview of findings behind the imagery and its neural correlation will be shown, this to give the reader a fundamental understanding of imagery. After that, MI will be introduced and it will be followed by the neural correlates of MI. This will give the reader a further understanding of MI. Thereafter studies have been collected in an attempt to answer the main research questions for this thesis.
First, this thesis will look into different studies in various sports to see if MI has any impact on sport performance. Then, this thesis will present different studies (e.g. patient studies) to further look at MI, performance and the brain’s plasticity. At last, this thesis will finish off with a discussion and finally a conclusion.
12 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Mental Imagery
Weinberg (2008) defines imagery as a created image in the mind involving all the senses that are involved in that experience and are activated despite the real sensory input. Imagery involves not only sensations. It involves different cognitive functions such as perception, memory, and thoughts (Thomas, 1997). Visual perception is the real input of what we see which
“…reflects the interaction of externally driven ‘bottom-up’ sensory information and internally generated ‘top-down’ signals, which guide interpretation of sensory input” (Lee, Kravitz, &
Baker, 2012, p. 1). In mental imagery, top-down signals are only used (Lee et al., 2012).
Imagery can be seen from an internal or external point of view. Internal imagery is when you experience the imagery in a first-person view and can feel your own movements (Callow &
Roberts, 2010; Ridderinkhof & Brass, 2015). External imagery is when you observe yourself from a perspective outside of your own body (Callow & Roberts, 2010). The internal view might include muscular responses, whereas the external view doesn’t include any sensations of movement (Hall, Rodgers, & Barr, 1990).
There is positive imagery and negative imagery. Positive imagery is when one imagines a performance going well and negative imagery includes seeing the failure of performance.
Positive imagery can improve performance, whereas negative imagery can make performance worse (Munroe, Giacobbi, Hall, & Weinberg, 2000).
Where, When and Why to Use Imagery
Imagery can be used in other places than in sports environments such as at home or at work (Weinberg et al., 2003). Some athletes use imagery before they fall asleep at night
(Cumming & Hall, 2002). For example, dancers use imagery in their dance settings, at home or at unrelated places (Nordin & Cumming, 2007). 13 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY In sport, imagery is more often used in relation to competition than to training. Athlete’s uses imagery before a competition to feel more confident and in control of their feelings (Munroe et al., 2000). At the end of the competitive season, athletes tend to use imagery more frequent
(Cumming & Hall, 2002). Athletes mostly use motivational general-mastery (MG-M), and cognitive specific (CS) imagery. All athletes at all levels seem to be using some form of imagery
(e.g. cognitive or motivational imagery). However, Cumming and Hall (2002) found that athletes competing at a higher level use imagery more than athletes at a lower level.
Except for using imagery to improve sport performance, it can also be used to stay motivated or to just stay focused (Weinberg et al., 2003). Imagery can be used to enhance self- confidence, to regulate the arousal-level, to cope with stress or in recovery from an injury (Martin et al., 1999). Imagery can be used by non-athletes to enhance performance in work. For example, one can imagine an upcoming presentation at work going well, which can enhance the presentation performance (Neck & Manz, 1992). It has also shown to be beneficial for managers to use imagery. Imagery makes it possible for the manager to visualize an ideal future of his or her organization. It can further lead to some adjustments in the organization, which in turn can make it more successful (Stanwick, 1996).
Different Types of Imagery
According to Weinberg et al., (2003), athletes have reported to use different kinds of imagery which are: (1) kinesthetic imagery, (2) visual imagery, (3) auditory imagery, and (4) olfactory imagery. Kinesthetic imagery involves how the movements feel when performing an action (Hall et al., 1990). Visual imagery includes how the imagery is seen and it can be seen from an external or internal point of view. It has been told by athletes that when using visual imagery it does not always reflect reality (e.g. the colors in the imagery differ from reality). 14 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Auditory imagery refers to the experience of different sounds (e.g. the sound of hitting a ball or hearing the sound from the audience). At last, olfactory imagery involves the experience of the smell connected to the sport. For example, the smell from the grass of the football ground
(Weinberg et al., 2003).
Imagery in Sport. According to Gregg, Hall, and Nederhof (2005) imagery seems to have both a cognitive and a motivational aspect that can affect the behavior result. There are specific and general levels of each aspect. When athletes mentally go through different strategies, routines or the plan of the game they are involved in the cognitive general (CG) imagery. The CS imagery is when athletes are imaging specific skills that are needed for their performance (Gregg et al., 2005). Athletes use motivational general (MG) imagery when they imaging arousal levels and how they would feel in the performance. The motivational specific (MS) imagery is used when an individual imagines her or his own personal goals. MG imagery has later been divided into two parts which are: motivational general-arousal (MG-A) imagery and MG-M imagery.
MG-A imagery includes the stress, arousal and anxiety levels that take place in performance.
MG-M imagery includes feel confident and the feeling of having control of the performance
(Gregg, Hall, Mcgowan, & Hall, 2011). Motivational imagery seems to be the one that athletes most frequently use (Williams & Cumming, 2011).
Effective Imagery
According to Smith (1987), there are two characteristics that seem to be important in creating effective imagery. To create effective imagery vividness and controllability should be included. According to Callow, Roberts, and Fawkes (2006), vivid imagery is clear and mirrors the sensations that would be experienced in reality. Vivid imagery should, if possible, include as many senses of the situation as possible. It has been argued that vivid imagery can more easily 15 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY increase performance than low vivid imagery. In vivid imagery, the sensations are induced and produce a greater physical response, which in turn has a greater impact on the imager’s behavior
(Callow et al., 2006). The images created are formed after people’s real experiences (Smith,
1987). There are positive effects of vivid imagery and performance. For instance, in one study participants performed a balance task. Those who used vivid imagery enhanced their performance of the task (Ryan & Simons, 1982).
The other characteristic that is important in creating effective imagery is controllability.
Controllability is the skill of changing your images according to what you want to imagine, and it seems to that with practice, controllability can increase (Hamberger & Lohr, 1980; Weinberg &
Gould, 2008). Controllability of imagery makes it easier to imagine a more successful than an unsuccessful performance. It increases the chances that the imagined performance will occur in the performance in reality (Smith, 1987).
Imagery Ability and Individual Differences
According to Abma, Fry, Li, and Relyea (2002), there are two different imagery abilities; visual and kinesthetic imagery ability. Visual imagery ability includes the skill to create clear pictures in the mind. Kinesthetic imagery ability includes the skill to experience sensations according to the created picture in the mind (Abma et al., 2002). According to Martin et al.,
(1999) imagery ability is the quality of one’s imagery and this seems to differ between individuals. Individuals who become good in using imagery are more likely to enhance their performance more than individuals with low imagery ability (Martin et al., 1999).
Rodgers, Hall, and Buckolz (1991) examined the effect of an imagery training program on imagery ability, imagery use, and performance in figure skating which were measured in a pre and post-test. There were two groups in the study; one imagery group and a verbal group. The 16 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY skaters were given two 15-minute individual imagery or verbal practice per week for 12 weeks over a 16 week period. The subjects in the imagery group would imagine finishing the entry to a jump. To imagine the performance, they were given a drawing to look at as help. The verbal group would instead describe their own performance of completing the entry to the jump. As a help, they were given different cue words. During this period all of the skaters practiced figure skating. The post-test showed that the imagery group showed significant differences in visual movement imagery ability compared to the verbal group. For example, they reported to more easily visualize their jumps. The imagery group had better control of their body and reported to feel the sensations involved in skating. They also become better at feeling specific aspects of their performance in comparison to the verbal group (Rodgers et al., 1991).
There seems to be no difference in between people’s ability to create an image. However, the imagery created can differ in clarity or how effective it is. The images can differ in seven ways that can affect the effectiveness of the imagery. In fact, it has been suggested that “…the images may differ in the vividness, controllability, visual representation, kinesthetic feelings, ease, emotional experiences, and effectiveness of image formation” (Gregg et al., 2011, p. 130).
For example, Cumming and Ste-Marie (2001) investigated if imagery ability would improve after five weeks of an imagery training program. The participants were females and exercised synchronized skating at a novice level. They used the Movement Imagery Questionnaire (MIQ;
Hall & Pongrac, 1983) to assess the subject’s imagery ability. MIQ involves 18 imagery tasks, whereas half of them involve visual imagery ability and the remaining involves kinesthetic imagery ability. After subjects had done the tasks of MIQ, the subjects were then asked to rate how easy or difficult it was to engage in the different imagery tasks. This was done on a 7-point rating scale. During the program, improvements in the skater’s visual and kinesthetic imagery ability were found. Cumming and Ste-Marie (2001) suggest that the skaters first improved in 17 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY visual imagery ability and then later improved kinesthetic imagery ability. This might be explained because performers focused on the visual aspects in the first phase of learning
(Cumming & Ste-Marie, 2001).
Theories of Imagery
In this following section, various central theories of imagery will be described. Then the sections after lead the reader to the research results that have been found regarding neural correlates of imagery.
Bioinformational Theory
The bioinformational theory includes the assumption that “…mental images can be understood as products of the brain's information processing capacity” (Hecker & Kaczor, 1988, p. 365). A mental image consists of propositional elements. When one creates imagery a network of propositional information gets activated. This information is stored in long-term memory. The propositional information can be separated into two different categories. The first category consists of stimulus propositions and its role is to report the stimuli of the mental imagery. The stimuli can give information about objects, such as the weight or the texture (Suinn, 1997). The second category consists of response propositions and it is responsible to keep information about the imager’s behavior in a specific situation. It also includes the information of physiological activity such as the experience of activating a muscle. The network of propositions is fundamental in imagery because it gives all specific information that is needed to create good imagery (Hecker & Kaczor, 1988). 18 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Psychoneuromuscular Theory
The psychoneuromuscular theory has been derived from the ideomotor principle. The ideomotor principle states that when one wants to learn different movements, imagery can ease the learning process. This is due to the patterns of neuromuscular activity that becomes activated when a person imagining movements as if the person is engaged in PP. It is hypothesized that the neuromuscular activity in imagery is reduced in magnitude compared to actual performance
(Weinberg & Gould, 2008). The ideomotor principle states that there is a connection between an action and the sensations experienced. In imagery, the idea of action would get access to the same sensations as in the actual action (Ridderinkhof & Brass, 2015). For example, patients with apraxia have difficulty in performing movements. In apraxia, left posterior parietal cortex (PPC) is damaged. Studies in non-human primates have proposed that different parts of PPC have a role in such as grasping and in movement intention. When neurons in a human’s PPC are stimulated through electrical stimulation the human gets an idea of action, which seems to happen deliberately. Furthermore, it has shown when neurons in PPC are stimulated in apraxia patients they have reported to have the intention to move (Ridderinkhof & Brass, 2015). For example, in a study by Desmurget et al., (2009) they examined intention using electrical stimulation on patients. This was done during brain surgery the patients underwent and they were awake during the operation. When right inferior parietal areas were stimulated patients reported to have a desire to move the contralateral arm, hand, and foot. Stimulation of the left inferior regions resulted in an intention to move lips or to talk. When they increased the intensity of electrical stimulation in the parietal regions, the patients reported thinking that they really had executed the movements
(Desmurget et al., 2009).
According to the psychoneuromuscular or ideomotor theory, the neuromuscular activity in the vivid imagery of movements seems to improve the motor schema in M1. It has been reported 19 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY by a number of studies that neuromuscular activations occur during imagery (Suinn, 1997). For example, in one case study, electromyography (EMG) response in athletes using imagery was examined. The athletes reported using internal imagery. One athlete was asked to mentally row
500 meters. During imagery, EMG activity increased with 45%. Also, muscle activities increased during imagery (Bird, 1984).
Symbolic Learning Theory
The symbolic learning theory was proposed by Sackett (1934), and it suggests that imagery works as a coding system in the brain, which helps one to get an understanding of one´s own movement. When practicing imagery the mental movement patterns will get stronger, which in turn, will help the imager to get familiar with a particular movement, and with time the movement can become automatic (Martin et al., 1999). According to Suinn (1997), symbolic learning theory assumes that “… mental practice gains are more due to the opportunity to practice the symbolic elements of a motor task than to muscle activation itself” (p. 195). Mental rehearsal in imagery makes it possible to get access to the information that requires performing a particular movement (Johnson, 1982).
Ryan and Simons (1981) tested the symbolic learning hypothesis. The participants were involved in one motor task and one cognitive task (physically and cognitively). In the study, a stabilometer and the dial-a-maze were used and all the subjects were tested in both of them. In the task with the stabilometer, the subjects would stand on a platform and hold it as still as possible. The subjects were divided into three conditions; PP, mental practice (MP) or no practice
(NP). Before all the subjects were tested, some of them were asked to first perform on both tasks.
To decide whether the tasks involved muscle activation or reasoning and thoughts, the subjects 20 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY would rate on a 5-point scale. All subjects rated that the dial-a-maze was more involved in the cognitive, and the stabilometer was higher rated as more involved in the motor component.
In the motor task, no differences in learning could be found in MP and NP condition, whereas PP condition increased in learning. In the cognitive task, both PP and MP were superior to NP condition. They found that imagery can enhance the cognitive aspects of a certain skill more than it enhances the motor aspects which support the idea of the symbolic learning theory
(Ryan & Simons, 1981).
The PETTLEP-Model
The PETTLEP-model is an imagery model, specifically to MI and it has been developed by Holmes and Collins (2001). PETTLEP consists of different items: physical, environment, task, timing, learning, emotion, and perspective. PETTLEP is grounded on neuroscientific evidence of functional equivalence. Functional equivalence refers to the common neural correlates of an imagined physical performance (Wakefield & Smith, 2009). Brain imaging techniques have made it possible to identify the brain areas activated in MI, motor preparation, and execution (Holmes & Collins, 2001). For example, similar activation of the cortical brain areas has been shown in both imagery and execution of a unilateral hand movement (Beisteiner,
Höllinger, Lindinger, Lang, & Berthoz, 1995). In the use of MI, PETTLEP might help the imager to create more effective MI (Holmes & Collins, 2001).
The physical item of PETTLEP includes an athlete’s physical experience in a sport situation. The imagery should include all appropriate senses that would be experienced in physical performance. To make the imagery as physical as possible, the athlete can wear his or her own sportswear during the time of imagery (Smith et al., 2007). 21 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY According to Smith et al., (2007) environment item refers to the imagined environment whereas sports performance occurs. It should be as alike the real environment to get a more similar motor representation (Smith et al., 2007). When it is difficult to imagine the right environment in imagery athletes can use environmental cues. Environmental cues can include different photographs and videos of that particular environment (Holmes & Collins, 2001).
The task item states the importance of the imagery to be similar to real activity. Therefore, one should include individual responses such as feelings, thoughts, and actions that would be experienced in real sports performance (Smith et al., 2007).
The time item is the amount of time that is enough to make imagery effective. In sports performance the time is important and therefore the imagery would be most effective using the right pace (Smith et al., 2007). According to Holmes and Collins (2001), the physical component in imagery (e.g. the weight of a basketball) can contribute to a more similar time to the performance in reality.
The learning item of PETTLEP refers to the adjustment of performance due to the imagery. When motor representations change the imagery should change according to that. This can help an athlete to learn a particular skill or technique (Smith et al., 2007).
The emotion item includes the emotions that are central to the achievement of functional equivalence and should be included in imagery. It should also include positive emotions and not negative thoughts because positive emotions can motivate and give the athlete more self- confidence (Smith et al., 2007).
At last, the perspective item refers to what perspective is used when imaging (Holmes &
Collins, 2001). It has been suggested that athletes should both use internal and external perspectives to make the imagery more effective. The better an athlete becomes in imagery the 22 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY easier it will be to switch from an internal to an external perspective and contrariwise (Smith et al., 2007).
Imagery and Neural Correlates
According to Kosslyn et al., (1995) imagery can be used to learn new information, such as verbal information. Imagery can arise through maintaining sensory input or when stored information in long-term memory is activated. For example, imagine you to have errands to do.
Instead of writing them down, you can visualize them. This is then encoded in the memory, which later can be recalled in an image. Kosslyn et al., (1995) state that imagery also can be used to recall colors, shapes, sizes, the texture of objects and spatial relations. Imagery seems also to have a role in reasoning and decision. For example, imagery can help one to decide whether furniture will fit into one’s home, which can make it easier to take the decision (Kosslyn et al.,
1995).
As mentioned before imagery underlies similar neural correlations as in perception, and it might also involve mechanisms that are used in motor control, emotion and memory (Kosslyn et al., 2001). It seems that the neural correlates of imagery consist of a whole network of brain areas
(Formisano et al., 2002). For example, in an fMRI study when visualizing faces or places different areas of the brain become activated. The visualization of faces activates the fusiform face area, whereas the visualization of places activates the parahippocampal place area (Kosslyn et al., 2001). Another example, in auditory imagery when imagine oneself listen to music, superior temporal gyrus (STG) becomes activated (Kosslyn et al., 2001; see also Zvyagintsev et al., 2013). 23 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY In the following sections, the visual organization will first be described. This is to be able to give a more fundamental understanding of visual imagery and imagery rotation, which will be followed and described in the sections after the visual organization is provided.
The Visual Organization
According to Pearson, Naselaris, Holmes, and Kosslyn, (2015) the human visual network are organized in a hierarchy. The top of the hierarchy consists of high visual areas. The high visual areas are involved in object recognition and have its location in the ventral temporal lobe.
The early visual areas are the bottom of the hierarchy, which are located in the occipital cortex.
These are sensitive to information about where things are (e.g. spatial orientation). Imagery shows stronger activation in high-level areas than in early visual areas. According to Pearson et al., (2015) it can be explained by the structures in the medial temporal lobe (MTL) which are involved in encoding memory which is physically closer to the high-level areas.
Behavioral and brain imaging data had indicated that imagery and visual working memory can share common neural correlates in the sensory cortex. One study found evidence for that imagery and visual working memory share common neural correlates. In the study, in the first task, the subjects would hold a pattern in their visual working memory. This was held in memory until they actually would get their memory tested. In the second task, the same subjects were given a cue to form and rotate an image in their mind. In the two different tasks, the blood oxygenation level-dependent (BOLD) activity was found in V1. Furthermore, the activation in
V1 made it possible to correctly decode the pattern held in the subject’s visual working memory and in the imagery task (see review Pearson et al., 2015). 24 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Visual Imagery and Visual Perception
Kosslyn (2005) come to the conclusion that visual imagery does not only rely on the same neural mechanisms as in visual perception. He also demonstrates that topographically organized early visual areas also have a particular role in different forms of imagery. According to Kosslyn
(2005), Areas 17 and 18 have been reported to be activated under visual imagery. Although, it seems to differ which neural mechanisms are involved depending on how the imagery is created or formed in the mind. For example, tasks in visual imagery that needs high resolution of the details of shape tend to activate both Area 17 and 18. Whereas in tasks in visual imagery that needs to use spatial images, neither of Area 17 nor 18 becomes activated (Kosslyn, 2005).
In an fMRI study by Ganis, Thompson, and Kosslyn (2004), they examined if visual imagery shares the same neural mechanisms as in visual perception. The study showed that visual imagery and visual perception share the same neural correlate, although the overlap is not entirely complete. The two conditions overlapped and activated frontal and parietal areas, whereas the activation in temporal areas differed (Ganis et al., 2004). The two conditions seem to differ in two ways. First, visual perception demands low-level organization processing, whereas visual imagery doesn’t. Second, imagery demands the activation of memory because of the lack of any direct perception (Kosslyn et al., 2001).
According to Fulford et al., (2018) different fMRI studies regarding the neural correlates of visual imagery have shown controversial results. It is still an ongoing debate about what role cortical visual areas have to imagery. It is not either clear which role supramodal brain systems
(e.g. default mode network) have in visual imagery. The results might also be contradictory due to the lack of the considerations of individual differences (Fulford et al., 2018). 25 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Imagery of Rotation
Cohen et al., (1996) did an fMRI study where the participants were involved in a mental rotation task. The results indicated to activate the ventral intraparietal area and the primary visual cortex. The study pointed to that the higher visual areas also became activated during mental rotation task. The area V5/ MT is known to respond to visual input of motion, which was active in the mental rotation task (Cohen et al., 1996). In another study, using PET, participants engaged in two mental rotation tasks. The first task involved in mentally rotating figures, whereas in the second task the participants would mentally rotate drawings of human hands. In the second task, they found activations in M1, premotor cortex, and posterior parietal lobe. In the task of rotating figures, they also found activation in the parietal lobe, but they didn’t found any activation in frontal motor areas (Kosslyn, DiGirolamo, Thompson, & Alpert, 1998). They further explained the activated areas in the task of rotating figures as if activations mirror the orientation of the object which can further be used as guidance to action. However, the imagery of rotating figures didn’t activate the motor program as in the task with rotating hands. They argue that objects can be rotated in different ways. The imagery of objects can either rely on motor processes or it doesn’t (Kosslyn et al., 1998).
Motor Imagery
After now have given a background of imagery, theories of imagery, and neural correlates of imagery, MI will be introduced and further explained.
As mentioned before, MI is described as seeing oneself performing different movements from an internal view in the mind in the absence of any physical movement (Decety, 1996;
Guillot et al., 2008). MI makes it possible for athletes or individuals to practice on different skills at any time without being dependent on one’s physical body (Ridderinkhof & Brass, 2015). 26 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY MI has shown to be beneficial in closed motor skills and in open motor skills. Closed motor skills can include different sports situations (e.g. weightlifting or tennis serving) which are not dependent on environmental cues (Ridderinkhof & Brass, 2015). Closed motor skills begin when the performer is ready and decide to move, which already had been planned by the command center in the brain. Whereas, open motor skills include sports such as tennis volley, boxing, the return of serve in volleyball or tennis or a hockey goalkeeper who try to stop the puck from the goal (Coelho, De Campos, Silva, Okazaki, & Keller, 2007; Ridderinkhof & Brass,
2015). Open motor skills are dependent on environmental cues which can be an opponent’s body language or the ball in motion in a game (Ridderinkhof & Brass, 2015). Furthermore, open motor skills involve decisions or responses to environmental cues. That kind of decisions must be taken after he or she had started the skill and this occurs at the same time when the performer is active in the game (Coelho et al., 2007). Coelho et al., (2007) investigated the effect of using positive imagery interventions on tennis serving (closed motor skill) and receiving serve skills (open motor skill). They found that positive imagery might be more beneficial when improving the performance of closed motor skills than in open motor skills. This was further explained, closed motor skills are more under a performers control and therefore it increases the chances of imaging movements more correctly (Coelho et al., 2007).
According to Ridderinkhof and Brass (2015), MI has shown to be effective in both learning new skills and the development of motor skills. The use of MI increases depending on what level one competes at. MI has not only shown to be beneficial in combination with physical training, but it has also been shown to be effective to only use MI. The only use of MI has indicated an enhancement in sport performance such as in platform diving, trampoline routines and in golf putting (Ridderinkhof & Brass, 2015). Isaac (1992) investigated the learning of physical movements in trampolinists by using imagery. The subjects were classified as novice or 27 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY experienced trampolinists. All subjects were divided into either the control or experimental group. In three six-week periods of practice, the subjects were aimed to learn or improve different skills. The experimental group did both practices the skills physically and mentally. The control group also practiced physically, and in their mental task, they engaged in problem-solving (e.g. puzzle). The results indicated that the experimental group showed a larger improvement in performance than the control group did (Isaac, 1992).
Time Duration
Several studies have shown similar time duration when comparing actual and mental movements (Jeannerod, 1994). In a study by Decety, Jeannerod, and Prablanc (1989) they aimed to measure walking time in imagery and in actual walking. The time was the same in both conditions. Although, in another experiment condition they also measured the walking time whereas the subjects would mentally carry 25 kg on their back while walking. The time increased with 30% in the mental condition, but the time of actual walking remained the same. This was further explained as when subjects physically carried the weight their forces increased, which made it possible for them to hold the same speed as without the weight. The increased time in the mental walking was interpreted as no increase of force was activated to manage the weight, and therefore an increase of time was shown (Decety et al., 1989).
Motor Imagery and Neural Correlates
In this section, MI and its underlying neural mechanisms will be explained to give a further understanding of MI. Thereafter, action observation, autonomic responses, learning and performance in relation to MI will be provided. 28 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Several studies point to the involvement of the M1 during MI (e.g. Porro et al., 1996;
Schnitzler, Salenius, Salmelin, Jousmäki, & Hari, 1997). It has been demonstrated that similar brain areas that are activated in an actual movement, is also activated during MI. However, studies have shown contradictory results. Some studies have not found any activation in the M1, whereas more recent studies using new techniques have found activations of the M1 during MI
(Abbruzzese, Assini, Buccolieri, Marchese, & Trompetto, 1999). For example, Ehrsson, Geyer, and Naito (2003) did an fMRI study and investigated if imagined voluntary movements of toes, fingers, and tongue overlapped with the real execution of movement. Similar areas were activated during imagery as in real movement. For example, toe movements showed activation in the contralateral primary M1 (cM1) and in the posterior part of the supplementary motor area (SMA).
The results indicate that MI activates somatotopic organization of M1 systematically. They also demonstrate that the activated body part in MI activates the corresponding area in the nonprimary motor areas as well (Ehrsson et al., 2003). Taken together, M1 seems to be important when performing actions in MI.
Stroke patients have shown impairment of MI after a stroke incident. For example, in an fMRI study, stroke patients engaged in MI with the impaired limb. Greater ipsilateral activation was found in M1 and SMA. In comparison, healthy subjects engaged in MI showed contralateral activation in M1, the primary somatosensory cortex (S1), SMA, and pre-SMA areas (Munzert,
Lorey, & Zentgraf, 2009). The impairment of movements shown in MI in stroke patients have further been explained as the loss of sufficient motor planning processes (Munzert et al., 2009).
It might be that the activity in cM1 looks different in elite performers. Therefore, it is important to take individual differences in neural activity into consideration when interpreting the results of MI. For example, several studies with elite music performers imaging their music performance during MI have indicated that there is no activity in cM1, but stronger activations in 29 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY other regions (e.g. parietal and frontal areas). It has been construed as the neural correlations rather respond to temporal and spatial aspects of the imagined performance more than it responds to motor control (Holmes & Calmels, 2008). The more experience one gets of skill in MI the neural correlates might systematically change. This is to mirror a more abstract and less motor- centered internal representation of expert musicians (Lotze & Halsband, 2006).
Action Observation
In one well-known study by Rizzolatti, Fadiga, Gallese, and Fogassi (1996) mirror properties were tested and single neuron recordings in monkeys were used. They found that when the monkey observed the experimenter grasp an object the neurons fired in the monkey, which is called mirror neurons. It means that the neurons which fire in the monkey mirror the behavior of the experimenter and that the same neurons would fire if the monkey would perform the same action (Rizzolatti et al., 1996).
MI and observation seem to activate similar brain regions. For example, during MI it has revealed activation of M1, whereas observation of action has shown to activate precentral M1
(Jeannerod, 2001). In an fMRI study by Munzert, Zentgraf, Stark, and Vaitl (2008) they compared MI and action observers. The subjects were asked to imagine or observe gymnastic movements. In both conditions, similar activations were shown in motor and motor-related areas.
Also, cerebellum and sections of basal ganglia became activated (Munzert et al., 2008). In another study, monkeys were examined in two conditions. The monkeys were either to grasp an object or to observe a human to grasp an object. To compare the neural correlates in M1 in the study, they used the c-deoxyglucose method. Activation was found in S1 in both physical and observing condition (Raos, Evangeliou, & Savaki, 2004). 30 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY Autonomic Responses
The autonomic system (ANS) appears to be activated during MI (Jeannerod & Decety,
1995), and it seems to be similar responses that occur in a real action (Guillot et al., 2009).
Studies have found an increase in respiration, heart rate and blood pressure during MI (e.g.
Beyer, Weiss, Hansen, Wolf, & Seidel, 1990; Wang & Morgan, 1992).
Jeannerod (1995) state that there are differences in respiration and heart rates between physical activity and MI. A few seconds in of the physical activity, the heart rate shown to increase as much as 50% over the resting value. In contrast, a few seconds in MI showed an increase of 32% of the heart rate. The increase of such a heart rate during both conditions can be explained because of the effect of motor preparation and not due to the metabolic changes
(Jeannerod, 1995). Vegetative activation under motor preparation to exertion sees as being a part of the motor programming. It is activated when a motor activity starts. Vegetative activation prepares the body to upcoming metabolic changes and reduces the intrinsic delay which is required for both respiration and for the heart when an individual makes an effort (Jeannerod &
Decety, 1995).
Learning and Performance
Studies of rats have indicated that physical exercise increase levels of brain-derived neurotrophic factor (BDNF) especially in the hippocampus and cerebral cortex. This explains why voluntary physical exercise can increase brain vascularization, neurogenesis, functional changes in neuronal structure and neuronal survival which evolves in the hippocampus.
Hippocampus has an important role in both memory and learning, and it explains why learning improves due to voluntary physical exercise (Cotman & Berchtold, 2002). 31 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY It seems to be several explanations to the improvement of performance of movement.
Jeannerod (1995) explained it to be because of the increased activity in neural circuits. The increased activation, strengthen the synapses in regions that play a big role in movement (e.g. basal ganglia or cerebellum). This, in turn, can “…result in increasing the capacity of the system for tuning motoneuronal populations or sharpening coordination between agonist and antagonist muscle groups” (Jeannerod, 1995, p.1425).
In a PET study, Lafleur et al., (2002) observed dynamic changes in cerebral activity between early and higher learning phases of sequential foot movements. Nine healthy subjects participated. They were aimed to perform sequential foot movements both in the physical and in
MI condition. In the study, they used a foot-sequence task. EMG activity was recorded, and this was to control the contractions of the muscle activations in both conditions (Lafleur et al., 2002).
The results indicated that the physical and MI condition of sequential foot movement showed similar activations in the brain. The results suggest that cerebral plasticity occurs in PP and as well in MI when practicing the same skill. Furthermore, Lafleur et al., (2002) demonstrate that a corticocerebellar network is important for creating cognitive and motor routines that are engaged in the performance of sequential foot movements. PP, with time, will establish a motor program for that particular skill. It seems that frontostriatal circuits are involved in obtaining a sequence of movements. This neural network makes it possible to consciously remember the skills that will be performed, and the long-term conservation of the learned motor and cognitive routines (Lafleur et al., 2002).
In one study by Pascual-Leone et al., (1995) they aimed to investigate the effect of MI practice on learning new fine motor skills. With given instructions, the subjects would learn to play piano with one hand either by PP or in MI practice. Pascual-Leone et al., (1995) found the same plastic changes in the motor system in both MI and in the physical condition. 32 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY In a PET-study the cerebral functional changes of learning of some foot movements were observed by Jackson et al., (2003). The subjects that participated in the study got MI-practice many days in a row. The performance increased significantly. However, it showed a decrease in activation in the cerebellum, whereas median orbitofrontal cortex (mOFC) showed an increase in activation. The result indicates that learning new motor skills through MI practice produce cerebral plasticity changes and it is similar to the PP of the same action (Jackson et al., 2003).
Motor Imagery and Sport Performance
Studies on MI have been done in many different sports. For instance, an fMRI study found that PP of shooting for beginners can result in plastic changes. MI was used as a tool to get access to neural changes. The subjects were measured before and after 90 h practice of shooting.
Before the practice period, MI activated cortical areas such as premotor cortex (PMC) and SMA, and inferior parietal cortex bilaterally. After 90 h PP, MI activated not only the previously mentioned areas, but it also activated basal ganglia and putamen. It was further explained to reflect the improvement of shooting in the beginners (Baeck et al., 2012).
The following section consist of sports were the most relevant studies could be found.
Studies from different sports such as golf, gymnastics, tennis, and volleyball will be presented.
This will give the reader an overview of what different studies have found in various sports using
MI and its impact on sport performance.
Golf
Studies using MI in golf and its impact on performance have shown similar results.
Brouziyne and Molinaro (2005) demonstrate that shot performance in golf beginners can be improved through PP combined with MI and that it is more effective to use it in combination than 33 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY to only do PP. Smith, Wright, and Cantwell (2008) came to the same conclusion. The difference is that the latter used PETTLEP imagery in their study, in an aim to examine if imagery combined with PP can improve performance. In the study by Smith et al., (2008) 32 males participated and they competed at an international level in golf. The participants were divided into one of the groups; PETTLEP imagery, PP, PETTLEP + PP, or control group. In a six-week period, the groups got different tasks. In the PETTLEP imagery condition, the subjects were asked to imagine 15 bunker shots twice a week. In the PETTLEP + PP, the subjects would imagine 15 bunker shots once a week. They would also execute the shots physically once a week which were done on a different day than they would engage in PETTLEP. In the physical condition, they would physically practice 15 bunker shots twice a week. The control group was asked to read a biography about a golf champion twice a week.
In this study they used Movement Imagery Questionnaire-Revised (MIQ-R; Hall &
Martin, 1997). MIQ-R is a revised version of MIQ and measures a person’s ability to perform both kinesthetic and visual imagery. In the pre- and post-test the participants would perform 15 trial shots, which were assessed with scores. Interestingly, all groups but the control group showed a significant improvement when compared pre- and post-test. Although, the PETTLEP +
PP condition shown much greater improvement. Smith et al., (2008) therefore suggests that MI combined with PP can improve performance in golf.
In another golf-putting study done by Kim, Frank, and Schack, (2017), MI and action observation were used as cognitive strategies among novices in golf. The study lasted for three days. Golf performance was measured in a pre-test, a post-test, and a retention test. The subjects were divided into four different groups; action observation, MI, PP, and NP. They were asked to either observe (observe a video of a putting scene from a first-person perspective), imagine or to physically practice golf putting for 60 trials per day. After every 20 trials, they had a small break 34 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY before the next trial. In the MI condition, when subjects had completed one performance they were asked to raise one of their fingers as a sign. The NP group did not get any training at all
(Kim et al., 2017).
After each day the participants in both conditions filled in a questionnaire about how they experienced how easy it was to either observe or imagine the movements. They also used MIQ-R and structural dimensional analysis of mental representation (SDA-M; Schack, 2012). SDA-M is a measurement which provides psychometric information of the mental representation (e.g. in this case the mental representation of golf putt) in long term memory. The measurement includes data of mental representations of more advanced movements. That information makes it possible to further examine the state and the alterations of the mental representation of movements. Kim et al., (2017) found that golf putting enhanced by MI practice and action observation. On the first and second day, the scores from the questionnaire about how they experienced performance showed that action observation was significantly higher than the scores of MI condition. In the last day, no significant difference was shown between the two conditions. In the MI condition, the scores of the last day were higher than it was on the first and second day of practice. Kim et al., (2017) argue that action observation might be more appropriate than MI to novices, especially in the early learning phase of a new skill, because of the lack of prior experience.
Gymnasts
Smith et al., (2007) did two studies using PETTLEP imagery as an intervention. In the second study 40 junior gymnasts participated. They had no prior experience in imagery training.
All subjects in the study were divided into four conditions (physical, stimulus only imagery,
PETTLEP imagery, and control group). The task in the study was to do straight jumps on the beam, which was video-recorded. The videos were then evaluated by the gymnastics coach, who 35 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY didn’t know about the study. The physical condition would physically practice the jumps three times per week. In the stimulus only imagery condition, they were asked to imagine specific stimulus (e.g. the smell of gymnasium). All seven aspects of PETTLEP were used in the in
PETTLEP imagery. In the two imagery conditions, the subjects would imagine the jump twice in every session (with three sessions per week). Every session lasted from three to five minutes. The control group did not involve in MI, they would only engage in different stretch practices three times a week. All groups were asked to not physically practice as long the experiment went.
Smith et al., (2007) hypothesized that the physical condition would be more effective than
PETTLEP imagery and that PETTLEP imagery would be better than the stimulus only imagery and control condition. They also used MIQ-R to measure imagery ability.
The results showed significant improvements in the gymnasts using PETTLEP imagery in comparison to the stimulus only imagery group. However, no significant differences were shown between conditions PETTLEP imagery and physical group. In this study, PETTLEP imagery alone showed to be equally effective as actually physically performing the same task. Smith et al., (2007) found that PETTLEP imagery can improve sport performance. However, they argue that combining PETTLEP imagery with PP might have resulted in a greater effect.
In a recent study, Simonsmeier, Frank, Gubelmann, and Schneider, (2018) conducted a similar study using a crossover experimental design. The study included 56 females’ gymnasts in ages 7-15 years old. The gymnast expertise was rated as either low or high, meaning that the athletes competed to either a low or higher level. Simonsmeier et al., (2018) compared two conditions; PP combined with imagery and only PP. The study had two phases; imagery practice phase and regular practice phase. Each phase lasted for four weeks. All subjects would involve in both phases and were randomly assigned to either start with imagery practice or PP phase
(Simonsmeier et al., 2018). 36 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY The imagery that was used was based on PETTLEP. The imagery condition involved in both PP and imagery practice. Before they would engage in MI, they would first listen to an audio script and thereafter imagine the movement three times. This was done four times a week.
In the phase of PP they would only involve in regular PP PP and they would practice just as much each week. All subjects engaged equal time in PP each week. They used SDA-M and a manipulation task (multiple questions). They also used video recordings of the subject’s performance, which were assessed by judges with scores. The judges did not know which condition each subject belonged to (Simonsmeier et al., 2018).
The results demonstrated combining PP with imagery showed an increase in performance, but this was only shown for those with the high-expertise. It was further explained as the imagery intervention was too difficult to the low-expertise athletes, because of lack of experience which might have affected the imagery (Simonsmeier et al., 2018).
Tennis
Guillot, Genevois, Desliens, Saieb, and Rogowski (2012) investigated whether serve velocity in tennis would enhance by using MI. The participants had at least three years’ experience of playing tennis. During the study, the subjects also practiced physically. As measurements, MIQ-R, a questionnaire, and video-recordings were used. In this study, no positive effects of using MI to achieve better serve velocity were shown. However, there was a significant enhancement in serve accuracy. Serve accuracy includes successful shot ratio and regularity. Guillot et al., (2012) further argue that practice MI can help one to attain peak performance.
Robin et al., (2007) did a similar study, used MI to see if it could have any positive effect on the accuracy of the server returns in tennis. Serve returns includes receiving the ball from the 37 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY opponent who has just served. The tennis players participated in the study competed at a regional or national level. Robin et al., (2007) divided the subjects into three groups; good imager, poor imager, and control group. The measurement MIQ was used to decide if the subjects either belonged to good imager or poor imagery group. Also, video-recordings were used. All subjects were asked to perform a serve return as accurately as possible before and after the study were done. Before the study subjects would involve in a pre-test performing 15 trials of tennis serves.
The participants that belonged to good and poor imagery were asked to engage in both mental practice and PP. In a seven-week period, subjects would imagine 15 trials and engage in PP of 15 serve returns. The subjects engaged in mental practice first, and thereafter they would physically perform the skills. Each trial was about three minutes. The control group would instead spend equal time reading magazines (Robin et al., 2007).
Robin et al., (2007) compared pre- and post-test results and it showed that the tennis players belonging to the good imagers group performed significantly better than the group of poor imagers. Also, the good imagers showed an improvement in the accuracy of the server returns. Therefore, Robin et al., (2007) demonstrate that imagery ability can have a considerable impact on MI and in improving performance.
Noel (1980) examined whether using visuo-motor behavioral rehearsal (VMBR) could improve tennis performance. VMBR is a technique that can be used by athletes to practice a skill or to handle the stress associated with a particular situation. Fourteen male tennis players participated. All participants practiced tennis for an upcoming tournament as the study went. The subjects were ordered into two groups. Which group subjects belonged to depended on their tennis ability levels. The tennis ability levels were decided on what level subjects played (A-, B-,
C-, or D-level). Six participants were A- or B-level players and were classified as having high tennis ability. Eight participants were C- or D-level players and were classified as having low 38 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY tennis ability. Noel (1980) randomly divided the tennis players to either the VMBR or control group. The control group did not receive any intervention. In the VMBR condition, the subjects were given a tape included instructions of relaxation and also instructions for visualization practice. They were asked to practice the relaxation three times before they began to do both relaxation and visualization practice the following four days. The visualization practice included imaging warming up and practicing the tennis serve. The mental practice took about 30 minutes.
As measurements, the ratio of winning shots was observed, and also the subjects got to assess their own performance (Noel, 1980).
According to Noel (1980) after VMBR practice, results showed an improvement in performance for those with high tennis ability in the VMBR condition, whereas those with lower tennis ability decreased in performance in the VMBR condition. Also, those with high tennis ability in VMBR condition showed greater improvement in the tennis serves than the high tennis ability players in the control group. Furthermore, the results also showed that those in VMBR condition, with low tennis ability, decreased more in their tennis serve performance than those with the low tennis ability in the control group. No explanation was found why high ability players improved and low ability players decreased in performance of tennis serve, Noel (1980) speculate that the players with low ability can get out more of PP than from imagery. It also might be that the instructions of the tape describing the tennis serve were more appropriate for those with high tennis ability (Noel, 1980).
Volleyball
Ay, Halaweh and Al-Taieb (2013) found that MI might be beneficial for learning new skills in volleyball. Twenty four male students from a University with physical education participated. The subjects were randomly assigned to either an experimental or control group. 39 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY According to Ay et al., (2013) the experimental and control group would involve in eight sessions consisted of 60 minutes each over a four week period. Both groups got PP of the skill during the study. Also, both groups got to see a video recording of the skill, which was executed by a professional volleyball player. The experimental group was asked to read a script included a persuasive imagery belief and instructions of the particular movement. After reading the script, they would practice the movement in MI in seven to 10 minutes. Not only did the experimental group engaged in PP, watching a video, and engaged in MI, the subjects were also asked to engage in other imagery and concentration tasks daily at home. Except that the control condition did perform PP, they also got to read a persuasive script about the benefits of repeating a particular skill (Ay et al., 2013).
In a pre- and post-test the subject’s physical performance was measured. Also, they used
MIQ-R to measure their imagery ability. The task in the study was to see whether the subjects could improve their forearm skill. More specifically, the forearm skill in volleyball is when the ball is received below the height of the head. They found significant improvement in imagery ability for both experimental and control group. Pre- and post-tests of the forearm pass skill scores showed a significant difference in both the experimental and control group. Ay et al.,
(2013) suggests that the improvement in the control group was due to the duration of practice and the repeated PP of the particular skill. However, the experimental group showed a bigger difference in scores when the pre- and post-test results were compared. Ay et al., (2013) further explained this as the practice of MI together with actual PP enhanced the learning of the forearm pass skill, which then improved the performance. In conclusion, they demonstrate that it might be more beneficial to use MI and PP together to enhance a particular skill or performance than using
PP alone (Ay et al., 2013). 40 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY The effect of MI has also been examined among novice volleyball players. Afrouzeh,
Sohrabi, Torbati, Gorgin, and Mallett, (2013) compared three different conditions; PP +
PETTLEP, PP + traditional imagery, and PP alone. It was 12 novice players in each condition, and the last condition served as a control group. Afrouzeh et al., (2013) purpose was to compare the effects of using either PP combined with PETTLEP imagery or traditional imagery combined with PP, to see if there were any differences in the effect of learning a skill in volleyball. In the condition of PETTLEP, all seven components of PETTLEP were used. In the traditional imagery condition, the subjects engaged in a relaxation intervention before they engaged in imagery, more specifically they would be engaged in MI. This condition was given a script as help to engage in
MI (Afrouzeh et al., 2013). Three times a week, for seven weeks the subjects would perform their tasks in the condition they belonged to. In the two imagery conditions, they were asked to first be engaged in imagery for 15 minutes. Thereafter, the imagery groups would physically practice passing for 30 minutes. The control group did only physically practicing. As measurements,
MIQ-R and a passing test were used (Afrouzeh et al., 2013).
According to Afrouzeh et al., (2013), all groups showed an improvement between pretest and post-test. However, the PETTLEP imagery group showed the greatest improvement of the groups. PETTLEP imagery was better than traditional imagery, and traditional imagery was better than PP alone. To conclude, Afrouzeh et al., (2013) point to combining imagery with PP can enhance performance.
Motor Imagery, Performance, and Brain Plasticity
This thesis has now provided an overview of studies in different sports using MI and what impact it has on performance. As mentioned earlier in the introduction, there are not many studies done on MI, sport performance, and brain plasticity. Of that reason, this following section will 41 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY consist of studies of healthy subjects and patients focusing on MI, performance and brain plasticity. If different studies using MI to improve performance result in brain plasticity, it probably also will result in brain plasticity in sport using MI.
Healthy Participants
Avanzino et al., (2015) aimed to do a study using TMS, to investigate if any plastic changes would occur in motor cortical areas as a result of using MI. Twenty-four healthy subjects participated, which included 12 females and males. All subjects were right-handed. All subjects were divided into two groups. Both groups would engage in PP and MI practice. The subject sat in a chair in a silent room when performed each task. On their right hand, they wore a sensor- engineered glove that would measure the speed of finger movements. In the PP, the subjects were instructed to engage in a motor sequence of finger movements in purpose to move the finger as fast as possible. They were asked to do a total of 300 finger movements consisted of four blocks and they got to rest 10 seconds between each block. In the MI practice, the subjects would be doing the same, but mentally. The physical and MI practice occurred on two different days with one week apart to evaluate the cortical excitability. Eight additional right-handed participants were involved in a control experiment. In the control experiment, the subjects engaged in finger sequences physically and had a longer rest period than in the other conditions. Before and after
PP and MI practice, the excitability of M1 was assessed. It was assessed by measuring motor evoked potentials (Avanzino et al., 2015).
Avanzino et al., (2015) found that engaging in either PP or MI practice enhanced motor performance. However, PP showed greater improvement than MI practice did. Both groups showed an increase in movement rate in the study. Avanzino et al., (2015) compared the movement rate in the MI condition with the control group, and the results indicated that MI 42 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY practice had a significantly higher movement rate than the control group. Similar to PP, MI practice did also result in the development of neuroplasticity. Avanzino et al., (2015) found that with MI practice, the connections between synapses strengthened. Furthermore, they suggest that
MI can develop neuroplasticity in M1 and it indicates the importance of motor regions that are involved in motor learning in MI (Avanzino et al., 2015).
Stroke Patients
MI practice combined with therapeutic rehabilitation program has been examined in stroke patients. Page, Szaflarski, Eliassen, Pan, and Cramer, (2009) investigated if it would be an improvement of the stroke patients affected arm, but also if any changes in cortical organizations would occur as a result of practice. In their study, 10 chronic stroke patients participated. The patients had stable, moderate deficits before the study. During a 10-week period, three times a week all patients got 30 minutes of therapy for the affected arms. In the therapy sessions the subjects would practice to handling different activities in daily life (e.g. grasping a cup). After every therapy session, the subjects would engage in MI practice for 30 minutes. The subjects listened to a recording to engage in MI. The first minutes of the recording the subjects were informed to relax. Thereafter, the subjects were informed to practice MI of different given tasks.
The tasks were similar to the tasks given in the therapy sessions (Page et al., 2009).
Page et al., (2009) used fMRI, and they observed changes in the BOLD signal volume when compared pre-intervention and post-intervention scans of MI. The BOLD-signal was significantly increased to wrist flexion and extension of the affected hand. More specifically,
Page et al., (2009) found that the BOLD-signal increased in premotor area and primary M1 ipsilaterally and contralaterally to the affected hand. Furthermore, the BOLD-signal decreased in the parietal cortex of the hemisphere ipsilateral to the affected hand. The decreased activation 43 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY reflects the improved movement performance. They further demonstrated that combining a rehabilitative program with MI can enhance movement and result in a cortical organization (Page et al., 2009).
Sharma, Baron, and Rowe, (2009) did a similar study, using fMRI and magnetic resonance imaging (MRI). The experimental group consisted of eight right-handed patients who suffered from a subcortical stroke. The control group consisted of 13 healthy subjects. The patients were assessed with the Action Research Arm Test (ARAT; Lyle, 1981). ARAT assesses the recovery of the upper extremity function after a cortical injury. The patient’s motor function of their arm was also assessed (e.g. elbow flexion). Both the experimental and control group would engage in PP and MI. The subjects were wearing gloves that would measure the performance of MI and also eliminate any improper movements. All subjects would first physically practice finger-thumb opposition sequence, and thereafter the subjects would engage in MI (Sharma et al., 2009). They found evidence for cortical neuroplasticity in patients suffered from a subcortical stroke. For example, they found that when the motor function was enhanced, the connections under MI increased. This was found between three connections. First, an increase was shown between ipsilesional premotor to M1. Second, an increase was observed between contralesional prefrontal cortex to the supplementary motor area. Third and lastly, the connection between contralesional PMC to the supplementary motor area to ipsilesional BA4 was decreased
(Sharma et al., 2009).
In another fMRI study, stroke patients would engage in either mental practice with MI or doing both MI and physical therapy (physical practice). The participants in the condition of MI would specifically perform upper limb functional motor tasks. They were involved in MI as they listened to a recording of guidance to MI. This was done for 60 hours during a three-week period.
In the second group, participants would do exactly the same as the first group, but in a period of 44 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY 14 days. They would as well involve in physical therapy for three hours per day. This was then compared with a group of healthy subjects (Bajaj, Butler, Drake, & Dhamala, 2015).
Bajaj et al., (2015) found no significant difference between the strength of networks in the group only involved in MI. However, they found a significant difference between the strength of networks in the second group who did both physical therapy and MI. For example, they found an increase in connection between the left primary motor area (LM1) and SMA and from SMA to left PMC (LPMC). In conclusion, they found evidence for combining MI and physical therapy which might be beneficial for stroke patients in the rehabilitation of recovery and strength motor behaviors (Bajaj et al., 2015).
Ietswaart et al., (2011) examined if MI would be beneficial for stroke patients who have persistent upper limb motor weakness. With a sample of 121 patients, the study consisted of three groups; one experimental group and two control groups. The patients received medical care and rehabilitation as the experiment went. The experimental group would engage in MI five times a week over a four-week period. One of the control groups would engage in other mental practice that not included movements. The second control group did not have any mental practice at all.
They only used the ARAT as a measurement to compare the results of the groups. Ietswaart et al.,
(2011) argued if MI results in brain plasticity the results of the study would show an improvement for the patients only engaged in MI. However, they didn’t found any significant results for using MI (Ietswaart et al., 2011).
Liu, Song, and Zhang, (2014) did an fMRI study and examined the link between activated brain areas and motor recovery after MI practice. This was investigated in stroke patients with neurological deficits affecting the right hand. Fifteen patients participated in the study. Ten of them would involve in the group MI and PP (treatment group). Five of the patients would involve in the group that only would engage in PP (control group). The subjects engaged in their given 45 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY practices for each working day in four weeks. During the MI practice, the subjects were given verbal information about different hand movements. The PP also consisted of doing different hand movements such as grasping. They used the Fugl-Meyer assessment to measure the subjects hand functions. This was done in a pre- and a post-test (Liu et al., 2014).
No significant difference was shown between the groups in the pre-test of the Fugl-Meyer assessment. However, post-test indicated that there was a significant difference between the treatment and control group. The scores from the test were higher for the treatment group than the control group.
Pre- and post-training was examined the correlation between fMRI activation intensity and the Fugl-Meyer assessment scores. Liu et al., (2014) found after the four weeks of practice that both groups showed an increase in activation in left S1 during PP than it showed before the practice period. The activation in left S1 increased in both PP and MI in the treatment group. This was positively correlated with the scores of Fugl-Meyer test which point to that the left S1 had a significant part in enhancing the performance of the hand function after MI practice. Liu et al.,
(2014) further explained the increased activation of S1 as if this region has a part in the recovery of hand function after MI practice. The result indicated that left S1 has a role in brain functional reorganization (Liu et al., 2014). However, no correlation was found in the control group. More specifically, the increased activation in S1 shown in the control group during PP was not found to be correlated with enhancing the hand function.
Furthermore, Liu et al., (2014) found that right cerebellum and corpus callosum become activated in the treatment group, but they also found activation of the right M1 was decreased.
The decreased activation in the right M1 was correlated with the scores of Fugl-Meyer assessment in the treatment group. This was correlated to the subject’s improvement of their hand functions. Only a small decreased activation was shown in the control group, and it was not 46 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY shown to be correlated with scores of the test. It is suggested that combining MI and PP can increase the functional reorganization of contralesional M1. It has been suggested that motor function of the hand connected with the infarcted M1 can result in plastic changes and instead reorganize into S1. In conclusion, they found results that point to functional reorganization. They further explained this as it might be correlated to the improvement of hand functions of the stroke patients (Liu et al., 2014).
Spinal Cord Injury
The effect of MI practice has also been evaluated among subjects with spinal cord injuries
(SCI). SCI is a neurological disorder which is associated with motor disability (Cramer, Orr,
Cohen, & Lacourse, 2007). The subjects with SCI had voluntary motor control of the tongue, but not of the right foot. Cramer et al., (2007) examined the effect of MI in 10 subjects with SCI, and
10 healthy subjects which served as a control group. There was a second control group in the study, but they only underwent the fMRI.
The participants would engage in MI for 60 minutes twice a day. The MI practice involved movements of the tongue and the right foot. The study was nine days long. On the first day, all subjects underwent behavioral, fMRI, and TMS evaluations. The following days until the eighth day, participants would practice MI at home. On a ninth day, the subjects underwent all evaluations done on the first day again (Cramer et al., 2007).
After seven days of MI practice, Cramer et al., (2007) found increased activation in the left posterior putamen, which was shown in both groups who underwent MI practice. The second control group that didn’t get any treatment didn’t show any difference in activation of the left posterior putamen. They found that after one week of MI practice of foot movements, both the treated control group and the group with SCI showed an increase of activation in left putamen. 47 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY However, greater activation in left globus pallidus and posterior putamen was shown in the group with SCI compared to the non-treated group. Cramer et al., (2007) suggested that MI practice can be helpful to restoration efforts in subjects with SCI.
Mateo et al., (2015) did a pilot-study and examined the grasp recovery in subjects with
SCI. Twelve subjects participated, a group of six with SCI and a healthy control group consisted of six subjects. The experiment lasted for 18 weeks. During this period participants with SCI also continued with their rehabilitation program.
The participant’s performance was measured in the first five weeks. This was measured with magnetoencephalography (MEG). The following five weeks after the first period, SCI participants would engage in MI practice for 45 minutes three times a week. The control group would instead imagine geometric figures in corresponding time each week as in the other group.
MEG activity was measured directly after the second period and then again after eight weeks. In
MI practice, the participants would imagine engaging in tenodesis grasp movements (Mateo et al., 2015).
Mateo et al., (2015) found that SCI group showed a decrease of activation in contralateral sensorimotor cortex (cSMC) across the five sessions of MEG. Further, the results showed that after five weeks of MI practice and rehabilitation, the number of voxels activated was significantly decreased and was similar to the activation in the control group. Voxels include computed 3D statistical maps. However, the control group didn’t show any such differences. The decrease of the number of voxels in SCI subjects was interpreted by Mateo et al., (2015) as a demonstration for the plasticity of the M1 as a result of MI practice.
It seems that the plastic changes in the motor cortex that result in the process of learning and practice occur in different stages. At the beginning of learning and practice, the activation of cSMC seems to increase. However, with further practice, the activation of cSMC seems to 48 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY decrease. They didn’t find any changes in the kinematics of reaching or grasping. However, all six SCI participants improved in wrist extension angle during grasping after MI practice (Mateo et al., 2015).
Discussion
This review has now explained what mental imagery means and different theories of imagery have been described. This was to further look into MI in different sports, to see whether it could enhance performance. This thesis has also looked closer into studies using MI to improve performance and if it occurs any changes in brain plasticity as a result of using MI.
Most results from studies that looked at MI and sport performance have found that MI can improve performance. However, performance seems to improve more when combining MI and
PP than using MI or PP alone. These results are consistent with Feltz and Landers (1983) study.
They analyzed 60 studies and found support for that MI can have an impact on a performance better than no practice at all. The studies from this thesis showed that MI can improve performance among both novices and experienced players. This is interesting since Feltz and
Landers (1983) found that imagery is more advantageous to experienced performers.
As mentioned in the introduction, meta-analyses in the research area have been criticized.
This is due to studies using different methods and designs, which might affect the effect size given in meta-analyses. In this thesis, studies used different methods and designs. Although most of the studies found that MI can improve performance, more studies are needed to confirm that.
Therefore, studies should replicate previous studies to fill that gap (Goginsky & Collins, 1996).
In perspective, some results pointed to that sport expertise and imagery ability might have an impact on MI in improving performance. This might be because of individual differences in imagery ability (e.g. Martin et al., 1999). MI seems to have an impact on sport performance, and 49 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY it might be that other appropriate types of imagery can improve performance in other areas in life.
It would be interesting to see which impact imagery can have in other areas than sport.
Several limitations have been found in the studies. Factors such as having too few samples and individual differences might have affected the results (e.g. Kim et al., 2017; Guillot et al., 2012; Robin et al., 2007). For future research, larger samples and longer practice period with MI is needed. Also, future research should compare the effects of MI among different sports, and investigate if the effects differ across abilities, age groups or sexes (e.g. Simonsmeier et al., 2018; Smith et al., 2007). It is suggested to further examine MI combined with PP in different sports when learning new techniques (e.g. Afrouzeh et al., 2013; Ay et al., 2013).
Brain plasticity seems to occur when combining PP and MI, which in turn enhances performance (see Feltz & Landers, 1983). The improvement of performance that results in brain plasticity are consistent with prior studies (see review Ruffino, Papaxanthis, & Lebon, 2017).
Some founding’s indicated that MI results in brain plasticity. However, this was only shown when combined MI with PP and only one study found contradictory results. Furthermore, one of the studies found that when only using MI might result in brain plasticity. For example,
Pascual-Leone et al., (2005), found evidence for improvement of performance when only used
MI. They found the same plastic changes in MI condition as in the condition only executed PP.
However, the performance didn’t increase in MI as much as it did in PP condition (Pascual-
Leone et al., 2005). Even if plastic changes occur as a result of only using MI, it might be more effective to combine MI and PP to enhance performance even more. Plasticity has been found in both healthy people and patients who use MI, and therefore similar changes in plasticity should occur for those using MI in sports. Plastic changes in the motor system can occur as a result of using MI (Mulder, 2007). In this thesis, several studies found that motor cortex especially M1 seems to have an important role in MI and in brain plasticity. This is consistent with previous 50 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY studies that have indicated that M1 has a role in MI (e.g. Porro et al., 1996; Schnitzler et al.,
1997). Yet, several limitations occurred as dropouts and small samples (e.g. Cramer et al., 2007;
Ietswaart et al., 2011). Also, such as no control group or that subjects damages were not unitary or different ages might have affected the results (e.g. Bajaj et al., 2015; Page et al., 2009).
Future research should match patients with similar ages, and also match subjects with the same lesion location or impairment (e.g. Bajaj et al., 2015; Page et al., 2009). Ietswaart et al.,
(2011) suggests for further research to combine PP and MI to see whether there is a therapeutic benefit of it to use on stroke patients.
Imagery is available for most people and can be used at any time. Imagery might be most used in sport, but it can also be used in other areas for improvement. Imagery is something we all have access to, and therefore it would be interesting to see if imagery can improve in other areas than just sport. Also, imagery has shown to be effective in rehabilitation. If imagery can be useful in rehabilitation, it might be useful for other areas as well? There is research on imagery and performance, but what if imagery might contribute to more than that? What if imagery can be used to improve well-being? Maybe research on this is on the way, but it would be exciting to see what more imagery can affect than just performance. It would also be interesting to see if future research could investigate the effect of meditation on imagery to see if it has any effect on imagery.
Brain plasticity has been found in both healthy subjects and patients using MI. Therefore similar neural changes would also occur for those using MI in sport. It would be of interest to see if future studies to examine MI in different sports and the brains plasticity to see if similar results would be found. The results presented in this thesis have shown that MI can improve sport performance and result in brain plasticity. It shows that more research on specifically MI, sport 51 MOTOR IMAGERY, SPORT PERFORMANCE AND PLASTICITY performance and the brain’s plasticity is needed. This thesis shows that more research is needed to get a clearer picture of imagery.
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