Is There Something Sketchy About Skechers Shape-up® Shoes?
An Honors Thesis Submitted
in Partial Fulfillment of the Elon University Honors Program
By Mae C. Langford
May, 2012
Approved by:
______Dr. Joyce Davis, Thesis Mentor
______Dr. Caroline Ketcham, Exercise Science (Reader)
______Dr. Paul Miller, Exercise Science (Reader)
ABSTRACT Skechers® is the most well known manufacturers of toning shoes, producing the
Skechers Shape-up® with a curved, rocker-bottom design. While the current economy has decreased sales of traditional athletic shoes by 1.4 percent, toning shoe sales have skyrocketed from $17 million in 2008 to $145 million in 2009 (Untapped market, 2010) with Skechers® leading the way. Other rocker-bottom design shoes have been shown to increase muscle activation in the lower extremities (Romkes, 2006). Skechers® claims wearing their Shape-up® shoe will increase muscle activation, improve posture, improve cardiovascular health, decrease joint stress, promote weight loss, and improve circulation.
The purpose of this study was to examine the effect of wearing Skechers Shape-up® shoes. Twenty-three women ages 18-65 completed a six-week walking program wearing
Skechers Shape-ups®. A pre-post test design was utilized to investigate effects on kinematics and kinetics of the lower extremity, dynamic balance, posture, muscle tone, and joint stress. Results showed a significant improvement in dynamic balance, p ≤ 0.05 with no effect on any other measures. These results suggest that walking in Skechers
Shape-up® shoes may be a valid therapy for maintaining and rehabilitating dynamic balance and the prevention of falls.
DEDICATION
I dedicate this thesis to the Honors Fellows Class of 2012 ACKNOWLEDGEMENTS I would like to thank the Elon Honors Fellows Program for giving me the unique opportunity and financial support necessary to participate in extensive research as an undergraduate student. I am also grateful for the generous funding from the Glen Raven
Endowment, which made the purchasing of shoes for this research possible. Thank you to the faculty in the Exercise Science Department at Elon University, without whom, I would not have had the knowledge or the inspiration needed to complete my research. In particular, thank you, Dr. Ketcham and Dr. Miller for editing and giving valuable input to my final written thesis.
In particular, I would like to thank my mentor Dr. Joyce Davis. Thank you for your unending support throughout this process. Your drive to learn more about your field in order to help me in my academic endeavors constantly benefitted my project. You are always able to help me see the humor in my many mistakes and your ability to push me to work harder and reach for a greater understanding helped me to produce a better product. It goes without saying I could not have written this thesis without you.
To my family and Brent, thank you for your love and support throughout this thesis process. You were always willing to read my very rough, rough-drafts and have always been my greatest fans. I appreciate all the things you do and have done for me.
There are not words to express my gratitude.
TABLE OF CONTENTS
Page
ABSTRACT…………………………………………………………………………..ii
DEDICATION……………………………………………………………………….iii
ACKNOWLEDGEMENTS………………………………………………………….iv
TABLE OF CONTENTS……………………………………………………………..v
LIST OF TABLES AND FIGURES……………………………………………..….vi
INTRODUCTION……………………………………………………………………1
Specialty Shoe Designs…..….………………...... …1 MBT® Research……………….…….………...……………………....2 Skechers Shape-ups®…………….….………...………………………3 Walking for fitness………….………………...……………………....5 Purpose of the Study…………..………………...... 8 METHODS…………………………………………………………………………...9
Participants…………………………………………………………...9 Testing Procedures…………………………………………………...9 Walking Intervention…………………………………………….….11
RESULTS……………………………………………………………………………13
Weight………………………...……………..………………………13 Posture……………………………..………………………………..13 Balance…………………………..………………………………….14 Knee and Ankle Kinematics……...…………………………………14 Kinetics………………….………..…………………………………16
DISCUSSION ……………………………………………………………………….19
Weight…………………………………………………………...….19 Posture……………………………….……………………….….….19 Balance…………………………………………………….……..…21 Knee and Ankle Kinematics………….……………………..………22 Kinetics……………………...………..……………………..………23 LIMITATIONS……………………………………………….……………………..25
CONCLUSION……………………………………………………….……………..27
REFERENCES………………………………………………………………………28
APPENDIX A ……………………………………………………………………….34
APPENDIX B ……………………………………………………………………….36
APPENDIX C………………………………………………………………………..37
APPENDIX D………………………………………………………………………..38
APPENDIX E…………....…………………………………………………………..39
APPENDIX F…………....…………………………………………………………..40
APPENDIX G…………....…………………………………………………………..41
LIST OF TABLES AND FIGURES
TABLE Page
1 Participant Characteristics……………………………………………..9
2 Weight Data………………………………………………………..…13
3 Posture Data…………………………………………………………..13
4 Y-Balance Data……………………………………………………….14
5 Gait Pattern Data……………………………………………………...18
6 Peak EMG Data………………………………………………………18
FIGURE
1 Ankle Kinematic Graphs……………………………………………..15
2 Knee Kinematic Graphs……………………………………………...16
3 Representative Individual EMG of the Medial Head of the
Gastrocnemius and the Tibialis Anterior………………...……………17 INTRODUCTION
The United States shoe market was a $13-billion-per-year industry selling more than 350 million pairs of sports shoes annually in 2002 (Pribut & Richie, 2002).
Specialized athletic shoes are the face of sports footwear and can trace their roots back to
1917 when Converse® released its first performance basketball sneaker, the Converse All
Star® (Sneakerhead.com, 2010). The market has long-since diversified its offerings since
1917 when Converse All Stars® were the only basketball shoes available. A person simply has to walk into a shoe store to see brands like Nike®, Reebok®, New Balance®, and Skechers® lining the walls floor to ceiling with all kinds of shoes for all kinds of activities. The consumer has to decide whether they need shoes for cross-training, walking, or running, just to name a few. There are features to consider such as shocks and different kinds of spikes and of course customers cannot forget about color and visual design; for instance, it is even possible to go online and custom-create the color of some athletic shoes. With diversity and specificity as the goal, the increasingly expanding market has opened up opportunities for many innovations in specialty shoe designs.
Specialty Shoe Designs
Specialty designs range from shoes intended for specific sports such as volleyball or soccer, to minimalist shoes, and recently to toning shoes. Minimalist shoes are designed to give runners the experience of running barefoot while still wearing a shoe
(Parks, 2010). Joining the ranks of brand names like Nike®, Saucony®, and Brooks;
Vibram® introduced their FiveFingers® shoe featuring a minimalist barefoot design in
2005. Their shoe has a glove-like appearance where each toe has its own compartment within the shoe. The sole of the shoe is thin and allows for the wearer to feel as though
1 they are running more naturally or as the company claims, they allow the wearer to feel as though they are running barefoot (Vibramfivefingers.com, 2010).
Toning shoes are another specialty category of footwear. They feature an unstable sole design which forces the wearer to engage muscles while seeking to find equilibrium
(Porcari et al., 2010). Toning shoes on the market include different designs such as the uniformly curved rocker-bottom sole and a second design featuring a separately cushioned heel and toe. The first toning shoe was a rocker-bottom design, introduced to the market by Masai Barefoot Technique® in the late 1990’s (MBT®).
MBT® Research
As the oldest of the toning shoe options, the MBT®shoe has been researched most throgouhly. By far, the largest area of investigation of the rocker -bottom shoe is in gait kinematics (Long et al., 2007; Romkes, Rudmann, & Brunner, 2005; Nigg, Hintzen, &
Ferber 2005, & Vernon, Wheat, Naik, & Pettit, 2004). While the exact effect of wearing the MBT®’s on gait is still debated, these studies all found significant changes at the ankle joint during the gait cycle. No significant changes were found at the knee.
Researchers have concluded that MBT®’s may be helpful in a variety of areas of rehabilitation including cast immobilization technology, arthritis and osteoarthritis, muscle weakness in the lower extremity, lower back pain, achilles tendonitis, and plantar fasciitis (Long et al., 2007; Romkes et al., 2005; Nigg et al., 2005; & Vernon et al.,
2004). The MBT® shoe redistributes pressure while still allowing the wearer to maintain functional walking patterns. Furthermore, Nigg et al. (2005), Romkes et al. (2005) and
Vernon et al. (2004) suggest that increases in muscle activation and strength can be attributed to MBT®’s rocker-bottom design.
2 A handful of studies have been conducted investigating the effects of the MBT® rocker-bottom shoe design on factors other than gait kinematics such as balance, muscle activity, posture and metabolic activity. One such study conducted by Ramstrand,
Thuesen, Nielsen, and Rusaw (2010) found that women over the age of fifty significantly improved in standing balance, reactive balance and stability limits after wearing MBT®’s for eight weeks. Gasser, Stäuber, Breil, Hoppeler and Vogt (2008) also found evidence of improved balance. Landry, Nigg, and Tecante (2010) found an increase in muscle activity in smaller extrinsic foot muscles, which increases stability during quiet standing. Landry et al. (2010) also found that wearing the MBT®’s increases postural sway or the wearer’s ability to adjust posture in order to maintain balance. These results are similar to those found by New and Pearce (2007).
Along with balance, Gasser et al. (2008) investigated the effects of wearing
MBT®’s on metabolic activity. For this experiment, they weighted their control shoe to account for the weight differences in the MBT® and a traditional athletic shoe. They found that wearing the MBT®’s on a daily basis is likely to increase calorie consumption
(Gasser et al., 2008).
Skechers Shape-ups®
Although MBT® pioneered the design, Skechers Shape-ups® are the most widely marketed rocker-bottom shoes. While the current economy has resulted in decreased sales of traditional athletic shoes by 1.4 percent, toning shoe sales have skyrocketed from $17 million in 2008 to $145 million in 2009 and Skechers® reported record high earnings and revenues in 2010 (Untapped market, 2010; Wells, 2010). The Shape-up® shoe has secured Skechers®’ place as the best selling athletic shoe in the U.S. (Skechers uses
3 home-field sway, 2010). Skechers® claims their version of the MBT® rocker-bottom shoe can help consumers “get in shape without setting foot in a gym” (Skechers® Brochure, n.d.). While there is some scientific evidence to support MBT®’s advertisements of positive health benefits, there is little evidence to support the claims made by Skechers®.
According to Skechers®, wearing their Shape-up® shoe will improve posture, strengthen the back, improve circulation, firm buttock muscles, tighten abdominal muscles, tone and firm thigh muscles, reduce joint stress, firm calf muscles, and burn more calories
(Skechers® Brochure, n.d.).
Few studies have examined the validity of the claims made by Skechers® in their ad campaign for Shape-up® shoes. Those studies have found conflicting results. Porcari et al. (2010) found no significant increases in muscle activation or exercise response to walking following the use of Skechers Shape-ups®. Gautreau, Petalus, Rodriguez and
Edwards (2009) reported significantly higher average changes is weight loss, decreases in percent body fat, and improved posture in the group wearing the Skechers Shape-ups®, however their experimental group also reported a significantly higher activity level than their control group (Gautreau et al., 2009). The greater level of physical activity in the
Skechers Shape-ups® group likely contributed to the changes seen in body composition.
The only other studies that examine the effects of wearing Skechers Shape-ups® are abstracted and published on the Skechers® website and cannot be found in peer-reviewed journals. A Skechers® News Release, however, reported that their claims of increased muscle activation, improved posture, improved cardiovascular health, less stress on joints, weight loss, and improved circulation have been found to be valid (Business Wire,
2010). Again, these findings have not been published in a peer-reviewed journal.
4 Walking for Fitness
Regardless of design, manufacturers of toning footwear assume the wearer is going to participate in physical activity. The benefits of physical activity have been well documented as inactivity has been linked to many risk factors associated with cardiovascular and other diseases. These can include increased risks for diabetes, obesity, emotional distress and orthopedic problems (Bush, Leenders& O’Sullivan, 2004; Nies,
Chruscial& Hepworth, 2003). Forty percent of adults over the age of 18 in the United
States are completely sedentary in their leisure time (Nies, Chruscial& Hepworth, 2003).
As obesity rates continue to rise in the United States physical activity is increasingly important (Richardson et al., 2008).
Engaging in an active lifestyle can decrease the risk of coronary heart disease in women of all ages and may prevent osteoporosis in aging women (Nies, Chruscial, &
Hepworth, 2003; Duncan, Gordon & Scott, 1991). Regardless of age, physical activity is beneficial to health and the evidence is growing in support of psychosocial and economic benefits of physical activity in aging populations (Bush, Leenders& O’Sullivan, 2004;
Culos-Reed, 2008). It is even possible that physical activity may ameliorate disease, delay decline and reduce depression in aging populations (Nies, Chruscial, & Hepworth,
2003). Physical activity can also help reduce mortality rates, reduce disability risks, reduce anxiety, improve moods states, improve health related quality of life and can decrease cognitive impairments (Culos-Reed, 2008).
One of the most common forms of physical activity is walking. Walking programs are useful modes of physical activity because walking is a free, accessible, nonthreatening activity allowing individuals to participate regardless of fitness level, age,
5 gender, or skill (Bush, Leenders, & O’Sullivan, 2004; Culos-Reed, 2008; Murhy, Nevill,
Neville, Biddle, & Hardman, 2002). Engaging in an activity like walking improves physical activity-related self-efficacy and establishes a sense of competence (Bush,
Leenders& O’Sullivan, 2004).
In order to receive the fitness benefits of walking, it is necessary to exercise multiple times a week. Varying exercise prescriptions have been suggested. Nies,
Chruscial and Hepworth (2003) suggest people should participate in moderate physical activity 5 times each week for 30 minutes each session. Tully, Cupples, Chan, McGlade, and Young (2005) found brisk walking for 30 minutes 5 days per week for 12 weeks was sufficient to produce significant increases in functional capacity and decreased blood pressure. Murphy et al. (2002) found a 6 week walking program of 30 minutes, five days each week decreased cardiovascular disease risk, reduced anxiety, improved aerobic fitness, improved confidence for walking and altered fat distribution.
For the general population, there is inconclusive evidence drawing conclusions about the effect of walking on balance. There are two dimensions to balance, static and dynamic. Static balance is the ability to maintain equilibrium in a fixed position. More applicable to walking, dynamic balance is the ability to maintain equilibrium while moving (Tritschler, 2000).
The American College of Sports Medicine recommends balance training such as walking over a difficult terrain or strengthening the lower extremity for older adults to aid in fall prevention (Chodzko-Zajko et al., 2009). Even though the evidence is weak that gait exercises improve balance in older people, falls can result in serious injury to older
6 adults and walking is still recommended as a possible way to improve balance (Chodzko-
Zajko et al., 2009;Howe, Rochester, Neil, Skelton, Ballinger, 2011).
Although walking has been shown to be beneficial in many ways and is an easy task to participate in for many different groups of individuals, there are still barriers to people using walking as a form of exercise. In aging populations, barriers may include a fear of injury when doing physical activity, issues of social isolation, lack of knowledge about physical activity, lack of availability and access to physical-activity programs, and a lack of motivation (Culos-Reed, 2008). Nies, Chuscial and Hepworth (2003) stated women may be reluctant to use public exercise facilities, programs may not be conveniently located, and work may cause time conflicts. Monetary resources may also limit physical activity by keeping individuals from participating in health clubs and fitness classes or by keeping individuals from purchasing home equipment (Nies,
Chruscial & Hepworth, 2003). Women may also experience a lack of energy, medical restrictions, family conflicts, a lack of time, and a lack of social support (Nies, Chruscial,
& Hepworth, 2003).
Skechers® has found a marketing niche by creating a fitness regimen around a pair of shoes, which would allow people to walk on their own schedule, in a place of their choosing, and without needing to purchase expensive home exercise equipment.
Endorsed by starlet Kim Kardashian in the 2011 Super Bowl game, and costing only
$100, the Skechers Shape-ups® are an attractive fitness option in the eyes of consumers who want to “get in shape without setting foot in a gym” (Skechers® Brochure, n.d.).
However, considering the lack of scientific evidence, the validity of the claims that
7 wearing Shape-ups® will improve posture, muscular strength, circulation, muscle tone, and decrease joint stress is suspect.
Purpose of the Study
The purpose of this study was to examine the claims made in the Skechers® advertisements by studying the effects of wearing Skechers Shape-up® shoes following a six week walking program.
Effects on the following parameters were investigated:
o Gait Kinematics of the lower extremity
o Gait Kinetics of the lower extremity
o Dynamic Balance
Effects on the following claims from the Skechers®ad were investigated:
o Posture (operationally defined as the frontal and sagittal alignments of
the head, neck, shoulders, lower back and hips)
o Muscle Tone (as measured by the strength of muscle activation)
o Joint Stress (as measured by weight, more weight leads to a greater
stress on the joints)
8 METHODS
Participants
Following approval from the Institutional Review Board, twenty-seven female participants (ages 19-63) were recruited for this study with the promise of a new pair of
Skechers Shape-up shoes®. The participants had a mean age x=39.09 years and a mean weight x=67.80kg.
Table 1.
Participant Characteristics
Participants Mean Age (yr) Mean Weight (kg) n=23 x=33.09 x=67.80
Participants were recruited through an advertisement on the Elon University webpage for announcements called E-net and through word of mouth. Twenty-three women completed the study. Participants who did not complete the study cited scheduling or medical conflicts. The participants served as their own control with a pre/post test design. Some measures were recorded at a three week midpoint. All of the participants wore the Skechers Shape-up® shoes for the six-week walking intervention.
Testing Procedures
Participants came into the lab for an hour-long pre-test session. They completed the Physical Activity Readiness Questionnaire (PAR-Q) and an informed consent document. Shoe size, weight, and height measures were recorded. See Appendix A, B, and C.
Following the initial data collections, participants completed the Y-balance test for dynamic balance while barefoot. The Y-balance test is a modified version of the Star
9 Excursion Balance Test. The test consists of 3 plastic pipes in a y-shape anchored by a solid block in the center. The participant holds a single leg stance on one foot on the block while sliding a marker down each pipe with the other foot. The scoring is based on the distance the participant is able to push the marker while maintaining balance. Each participant received the same directions by watching an online tutorial. The video, found at http://www.youtube.com/watch? v=yMO9TlFy5p8 demonstrates proper technique
(Move2perform, 2011). The participant then practiced her technique three times in each direction on each foot while standing on the ground. The participant then practiced the procedure on the device until they had completed three “good” trials in each direction on each foot. A “good” trial meant they were able to maintain dynamic balance while pushing the marker as far as possible. A trial was determined “not good” if the participant stepped off the center block, put weight on the sliding leg, or reached out to the testers for support. The participant was given a brief resting period of about 2 minutes before completing as many trials as necessary to record three “good” trials. The best trial in each condition was used for analysis. Dynamic balance measures were taken at the pre, mid and post-testing sessions.
Posture measures were recorded during the brief resting period between the practice and the test trials on the Y-balance test. The participant stood barefoot in front of a posture grid facing a Sony mini digital video camera recording at 30 Hz. A three second recording was taken from the front. The participant was then asked to turn and recordings were taken from the side (sagittal) view. Posture recordings were taken in the pre and post-testing sessions.
10 For kinetics, the Delsys Myomonitor (Delsys, Inc.) was used to collect electromyography (EMG) data. Electrodes were placed on the left and right lower extremities on the biceps femoris, vastus lateralis, medial head of the gastrocnemius, and the tibialis anterior. Placements were determined using the Noraxon Clinical SEMG
Electrode Sites illustration (Noraxon, 2011). The reference electrode was placed on the participant’s right knee. Participants then completed a series of maximal voluntary contractions for each muscle. EMG data was collected for each of the eight muscles while walking barefoot and shod (with shoes). This process was repeated in the post-test session.
For kinematics, Sony mini digital video cameras were set up on tripods to record movements in the sagittal and frontal planes. Participants were asked to walk across the room and back while the cameras recorded at 30 Hz. Participants walked at a self- selected speed. This was done both barefoot and shod. Two full walking passes were completed in each condition. This process was repeated in the post-test session. A summary of measures and instruments can be found in Appendix D.
Walking Intervention
Following the pre-test, participants completed a two week break-in period per the manufacture’s suggestions. The new Shape-ups® were worn for 25 minutes the first day increasing in 5 minute increments every two days for the first two weeks of exercise ending with 45 minute walking sessions. The participants were supervised while walking in their new shoes five days a week for a two-week period. They were not allowed to take the shoes home during the break-in period. Each day, the subjects began their session with a series of warm-ups provided by the manufacturer to reduce soreness. See
11 Appendix E. Subjects were asked to walk at a moderate-to somewhat heavy pace (3-4) using the 10-point Borg Rate of Perceived Exertion Scale (RPE). They were given the instructions to walk at a pace where they could carry on a conversation but would not be able to sing. The participants were told that they should experience a light sweat after their sessions. At the end of the walking sessions, the subjects reported their RPE, their soreness level, and any other comments they had about the shoes.
Following the two week break-in period, participants were given their shoes to take home and were asked to walk for a total of 160 minutes each week. They were instructed that their walking sessions should last at least 30 minutes. When walking on their own the participants logged information about the intensity of their exercise (still aiming for at least an RPE of 4), the time walked, their soreness level, and any concerns about the shoes on a provided log. See Appendix F. At the end of week three, participants came into the lab for mid-measures. After mid-testing the participants walked for another three weeks using the prescribed frequency and intensity guidelines. Post-testing was conducted six weeks following the pre-testing.
The data collected for weight, balance, posture, and kinetics were analyzed using a t‐test for paired samples. A significance level of p≤0.05 was used. For kinematics, qualitative analysis was utilized to assess sequencing, coordination and timing of the lower extremity.
12 RESULTS
Weight
A t-test for paired samples revealed no significant difference in the pre
(x=67.80kg) and post (x=67.63kg) weight.
Table 2.
Weight Data
Weight PRE (kg) Weight POST (kg) Significant x=67.80 ± 13.65 x=67.63 ± 13.61 No
Posture
The posture data was analyzed using a posture score card developed by
Beauchamp Chiropractic found in Appendix G (Beauchamp, 2011). Each participant was scored from the frontal and sagittal positions. A higher composite score indicates better posture. The highest possible score was a 20. A t-test for paired samples revealed no significant difference in the pre (x=16.13) and post (x=16.61) posture scores.
Table 3.
Posture Data
Posture Score PRE Posture Score POST Significant x= 16.13 ± 2.28 x= 16.61 ± 1.64 No
13 Balance
The highest score on the Y-balance test (in each condition for each participant) was selected for analysis. A t-test for paired samples revealed significant differences for four of the six conditions. No significant difference was seen in the forward direction on either foot.
Table 4.
Y-Balance Data
Test Balance PRE (cm) Balance POST (cm) Significant L-Front x=56.78 x=57.46 p=0.480 L-Left x=77.13 x=85.30 p=0.030* L-Right x=82.59 x=86.87 p=0.010* R-Front x=57.20 x=58.37 p=0.260 R-Left x=82.35 x=87.50 p=0.001* R-Right x=79.11 x=86.33 p=0.040*
Knee and Ankle Kinematics
The kinematic data were collected using two Sony mini digital video recorders with a sampling rate of 30 Hz. Data were analyzed using a 5-point lower extremity model in Human Motion Analysis (HU-M-AN) software. The x, y coordinates for each of the 5-points (hip, knee, ankle, heel, and ball of foot) were collected from the left leg. The
HU-M-AN software calculated and graphed ankle and knee angles throughout the gait cycle (see Figures 1 and 2). The cycle begins and ends with a heel strike. The line in the middle denotes toe-off. The cycles were synchronized by these critical points. Amplitude represents range of motion in degrees (y-axis) through one complete gait cycle (x-axis).
14 These were analyzed qualitatively to assess sequencing, coordination and timing of the lower extremity.
The ranges of motion, as determined by amplitude (see Figure 1), were very similar at the ankle and the pattern at the ankle (representing sequencing and timing) was relatively unchanged between conditions. No changes were seen in the amplitude or pattern of the knee between conditions (see Figure 2). The kinematic data for the knee and ankle did not warrant further quantitative analysis.
Ankle angle pre barefoot Ankle angle pre with shoes
Ankle angle post barefoot Ankle angle post with shoes
Figure 1. Ankle Kinematic Graphs
15
Knee angle pre barefoot Knee angle pre with shoes
Knee angle post barefoot Knee angle post with shoes
Figure 2. Knee Kinematic Graphs
Kinetics
The EMG signals for the left tibialis anterior and left gastrocnemius muscles were analyzed for each participant in the pre and post-testing sessions for the with and without shoe conditions. Only EMG trials that yielded clean signals were analyzed. Therefore, only fourteen of the participants were included in the EMG analysis. The root-mean- squared signals for each of the two muscles were graphed in pre and post graphs using the Delsys Analysis software (available from Delsys, Inc.). Typically, each data set had four gait cycles. The highest and lowest peaks were discarded and the two middle peaks for each muscle were determined to be most representative of typical activation in each condition. The two middle peaks were then averaged to get a level of activation for that muscle in that condition. This was done for each participant.
16
Figure 3. Representative Individual EMG of the Medial Head of the Gastrocnemius and the Tibialis Anterior
The graphed condition was then analyzed for timing patterns. The initial onset of the gastrocnemius until the next onset was considered one gait-cycle. This was determined using the onset-offset chart in Essentials of Electromyography (Kamen &
Gabriel, 2010). The timing between the onsets of the gastrocnemius and tibialis anterior in the barefoot condition and the onsets in the shod condition were compared. In the pre- testing session, twelve of the fourteen were similar. The same was true in the post condition.
17 Table 5.
Gait Pattern Data
Pre Condition Gait Pattern Post Condition Gait Pattern Same/Total Different/Total Same/Total Different/Total 12/14 2/14 12/14 2/14
The EMG signals were also analyzed for amplitude. The barefoot and shod conditions were compared only within testing days. Due to electrode placement it was not possible to compare scores between testing days. For each muscle in each condition, the two middle peak amplitudes were averaged to form a representative score. Scores were analyzed using a t-test for paired samples. No significant differences were seen in the activation levels between the shod and barefoot conditions for either muscle on the pre or post-testing days.
Table 6.
Peak EMG Data
Condition Barefoot mean (µ) With shoes mean (µ) Significant Tibialis Anterior Pre x= 48.15 ± 17.37 x= 50.25 ± 20.53 No Gastrocnemius Pre x= 53.10 ± 13.21 x= 56.25 ± 20.02 No Tibialis Anterior Post x= 48.85 ± 16.26 x= 45.26 ± 17.95 No Gastrocnemius Post x= 73.96 ± 23.88 x= 78.75 ± 38.26 No
18 DISCUSSION
The purpose of this study was to examine the claims made in the Skechers® advertisements by studying the effects of wearing Skechers Shape-up® shoes following a six-week walking program. The parameters examined include weight, posture, balance, ankle and knee kinematics, and kinetics
Weight
This study found no significant difference in weight following a six-week walking program wearing Skechers Shape-ups®. Gautreau et al.(2009) found significantly higher average changes is weight loss and decreases in percent body fat in their experimental group after wearing the Skechers Shape-ups® for eight weeks. This study does not support the finding that wearing Shape-ups® promotes significant weight loss. However, there was a slight trend towards weight loss. This study lasted two weeks shorter than the
Gautreau et al. (2009) study. It is possible that with an extended intervention, weight loss may occur. This study used weight loss as a measure of reducing joint stress. Due to the lack of statistically significant weight loss, this study cannot support the claim in the
Skechers® Brochure that the Shape-ups® reduce joint stress (Skechers® Brochure, n.d.).
Posture
To address the claim of improved posture in the Skechers® Brochure, posture was analyzed before and after the intervention using a standard posture chart (Skechers®
Brochure, n.d.). A 6-week walking program wearing Skechers Shape-ups® did not improve quiet standing barefoot posture as there was no statistically significant difference between the pre and post-composite posture scores. There was however, a trend towards improvement in posture after the walking intervention. As posture was not analyzed
19 while participants were wearing the Skechers Shape-ups® it is possible that posture differences may have been seen in that condition supporting the findings of New and
Pearce (2007). New and Pearce (2007) found a significant reduction in anterior pelvic tilt during the heel –strike and toe-off stages of the gait cycle in the MBT®s when compared to a normal shoe. They also found a decrease in trunk-flexion during heel strike in the
MBT®s. The only statistically significant finding during quiet standing in the MBT® shoes was an increase in plantar flexion. Using these findings, New and Pearce (2007) suggested that wearing the rocker-bottom MBT®s may have positive implications on low back pain.
Gautreau et al. (2009) tested lower back endurance using an isometric back extension test (Sorensen Test) to assess posture. Following an 8-week walking program, one group in the Shape-ups® and one in normal walking shoes, the experimental group was found to have improved back strength. However, no statistically significant differences were seen in glutei strength between the control and experimental groups.
Gautreau et al. (2009) suggested that as many studies have shown a relationship between adequate low back strength, glutei strength, and posture, low back and glutei strength can correlate to improved posture. No direct measure of posture was used in the only study to claim postural benefits of Skechers Shape-ups® even though it is a benefit touted in the
Skechers® Brochure (Skechers® Brochure, n.d.). However, the results of this study where a direct measure of posture was utilized did not support the Skechers Shape-ups® as a valid training tool for improving posture when the participant is barefoot.
20 Balance
This study found significant improvements in dynamic balance after a six-week walking program in the Skechers Shape-ups®. Skechers® does not claim that their Shape- up® shoes improve balance however the small body of research that exists suggest that rocker-bottom shoes may improve balance. Following a 6-week walking program in
Skechers Shape-ups® dynamic balance was improved. This supports the opinion of
Porcari et al. (2010). They studied the effects of Shape-ups® and other popular toning shoes and suggested balance improvement may be the only benefit of wearing toning shoes. Porcari et al. (2010) suggests unstable sole designs force the wearer to engage muscles while seeking to find equilibrium. More specifically, Gassser et al. (2008) suggested that increased utilization of small foot muscles caused by the MBT rocker- bottom shoes may optimize balance. This study supports these findings.
Landry et al. (2010) makes a similar claim suggesting that rocker-bottom shoes may work similarly to wobble boards. These training devices have been utilized to strengthen muscle coordination and proprioception, both important to balance (Landry et al., 2010). Landry et al. (2010) had participants wear the MBT®s for a 6-week accommodation period and tested postural sway in three conditions: barefoot, shod in the
MBT®s and shod in a stable control shoe. They found an improvement in postural sway with MBT® usage.
Ramstrand et al. (2010) evaluated standing balance and reactive balance. They also evaluated limits of stability in their participants. The researchers found that in the limits of stability tests, the MBT® wearers (when compared to the control shoe group) demonstrated a significant improvement in their directional control (Ramstrand et al.,
21 2010). These findings are most closely related to our findings of significant improvements to dynamic balance. The Skechers Shape-ups® may be beneficial as a tool for balance training. Further investigations could analyze the activation of small foot muscles while wearing the Skechers Shape-up shoes® to better understand the mechanism of balance improvement. It is possible that the similarity in the rocker-bottom design between the MBT®s and the Skechers Shape-ups® can account for the noted balance improvements. Although this study found balance improvements, it is possible these improvements could be impacted by a learning effect on the Y balance test. Researchers have found a significant learning effect with the Star Excursion Balance Test. To account for this, the protocol suggests participants practice 6 times on each leg in each direction before performing the test (Y Balance Test™ Protocol). While this study followed the suggested protocol, the possibility of a learning effect exists.
Knee and Ankle Kinematics
While many other studies found kinematic differences at the ankle joint, the qualitative analysis of the kinematic graphs showing range of motion and timing of the knee and ankle throughout the gait cycle in this study did not warrant further quantitative analysis. Myers et al. (2006) analyzed different gait kinematics between a rocker-bottom and a baseline shoe. They found most of the changes in gait kinematics in the sagittal plane. The ankle joint in the rocker-bottom shoe experienced an increase in plantar- flexion from the terminal stance through the terminal swing (Myers et al., 2006). Long et al. (2007) also found a decrease in dorsiflexion in the late stance and initial swing phases and Romkes et al. (2006) found that the dorsiflexion angle decreased in the MBT® condition at terminal stance when compared to the normal shoe.
22 In contrast, Vernon et al. (2004) found that although lower limb kinematics were largely unchanged when comparing the MBT® to a normal walking shoe, significant ankle differences were seen in a significantly higher dorsiflexion. Researchers found a significant decrease in plantar-flexion when comparing the MBT® rocker-bottom to the control shoe (Vernon et al., 2004). Romkes et al. (2006) found similar results, stating that the dorsiflexion angle at initial contact increased at the ankle when comparing the MBT® shoe condition to a normal shoe. Long et al. (2007) also found an increase in dorsiflexion at initial contact and during mid-stance. The results of the Nigg et al. (2006) study also supported an increase in dorsiflexion during the first portion of the gait cycle when comparing the MBT® to the normal shoe. Nigg et al. (2006) supported the finding that other joint kinematics remained largely unchanged between the testing conditions. The exact motion of the ankle in the gait cycle when wearing rocker-bottom shoes is still debated. The results of this study did not indicate wearing Skechers Shape-up® shoes impacts the range of motion of the knee and ankle joints throughout the gait cycle.
Kinetics
This study found no significant difference in peak activation levels or patterns of the medial head of the gastrocnemius and the tibialis anterior between the shod and barefoot conditions pre or post intervention. These findings support the findings of Pocari et al. (2010) who found no significant difference in the activation of the gastrocnemius between Skechers Shape-ups® and traditional running shoes. Skechers®, however, claims their shoes will tone muscles (Skechers® Brochure, n.d.). The activation findings of this study suggest muscles in the lower legs are no more active when walking with Shape- ups® than they are when walking barefoot.
23 The findings of this study contradict the study featured on the Skechers® website which states there is more muscle activity in the calf in the Shape-ups® when compared to normal sport shoes (The Effects of Shape-ups, n.d.). Other studies have tested the
MBT®s for muscle activation and have found combinations of significantly increased gastrocnemius activity and increased tibialis anterior activity (Landry et al., 2010; Nigg et al., 2006; Romkes et al., 2006; Vernon et al., 2004). The discrepancy between Skechers
Shape-ups® research and MBT® research suggests it is inappropriate to apply research on the MBT®s to the Skechers Shape-ups® based on shape alone. There seems to be some other component to muscle activation. Future research should seek to address why the two similarly shaped shoes produce different activation results.
24 LIMITATIONS
Several limitations existed with this research experiment. The measurement of body weight was not appropriately measured. In order to get an accurate account of body weight it is necessary to measure the participant’s weight at the same time of the day on each measurement day. Due to scheduling difficulties, this was not always possible.
Therefore as weight fluctuates throughout the day, the collected weight measures were not reliable and so the findings may have been skewed. Other scheduling conflicts also occurred. Certain participants were not able to attend every day of the two-week break-in period. When that situation occurred, the participants were given strict instructions to walk on solid surfaces only for the designated amount of time. Participants were instructed to contact the researchers over the phone prior to and following the walking period. They were also instructed to stop the break-in session and call the researchers if any problems with the shoes occurred. In this manner, the break-in period was still supervised.
Another scheduling issue occurred when participants could not attend the mid and post data collection sessions. These three participants were dropped from the study.
The researchers opted to not use joint markers when collecting the kinematic data for gait analysis. This choice made gait analysis more difficult as it was at times hard to find the center of the knee and hip joints. A further limitation of this study in kinematic collection and analysis involved the difficulty of marking the heel and ball of the foot through the
Shape-up® shoe. The rocker-bottom design made it difficult to determine the heel-strike and toe-off stages in the gait cycle when participants were shod. This may have affected the validity of the kinematic analysis.
25 A further limitation of the kinematic system was related to the lack of integration between the kinematic and kinetic analysis systems. It was not possible to analyze the video and the EMG feeds in unison. Instead those two components had to be analyzed separately. The researchers had to analyze EMG cycles using typical activation patterns instead of being able to use the visual gait characteristics.
EMG collection was also difficult due to electrode placement. The researchers were novice electrode users and had to rely on a visual map of muscles and suggested surface electrode placement. In working with a non-athlete population, surface muscle definition was not always clear. Therefore, the EMG signals were not always clear and the researchers could not guarantee cross-talk between muscles was not recorded. Due to this level of cross-talk and interference in the EMG signal, certain participants had to be left out of the EMG analysis completely.
Researchers originally planned to use maximum voluntary contractions to normalize the EMG signals. However, the researchers chose to use a standing maximum contraction for the vastus lateralis and biceps femoris muscles. These were not true maximum contractions and were therefore not useful in the analysis of the EMG data.
26 CONCLUSION
This study found no support for the claims made in the advertisements for
Skechers Shape-up® shoes in this population of recreationally active females aged 19-63.
The only significant findings were in support of balance improvements that appear to result from the rocker-bottom shoe design. Future research may seek to explore the mechanisms contributing to balance improvement. These may include further analysis of muscle activation. Another avenue of future research could explore the caloric expenditure associated with wearing Skechers Shape-ups®. It would also be interesting to examine the material composition of the Skechers Shape-ups® compared to the MBT®s. It is possible the differences in material properties may account for the differences in research findings. Other populations with greater initial deficits may improve in other measures such as posture or weight after wearing the Shape-ups®. Future investigations could chose to analyze these special populations for a possible application of the shoes.
With lack of scientific evidence, the findings of this study indicate there may be something sketchy about Skechers Shape-ups®.
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33
APPENDIX A
Informed-Consent Form
Title of Study: Is there something sketchy about Skechers®?
Principal Investigator: Joyce A. Davis, PhD Elon Univenity Department: Exercise Science Phone Number: (336) 278-5873 You are being asked to take part in a research study. The investigators listed above are in charge of the study; other professional may help them or act for them.
What are some general things you should know about research studies? Research studies are designed to gain scientific knowledge that may help other people in the future. You may or may not receive any direct benefit from participating. There may also be risks associated with participating in research studies.
Your participation is voluntary. You may refuse to participate or may withdraw your consent to participate in any study at any time and for any reason.
Details about this particular study are discussed below. It is important that you understand this information so that you can decide in a free and informed manner whether you want to participate. You will be given a copy of this consent form. You are urged to ask the investigators named above, or staff members who may assist them, any questions you have about this study at any time. What is the purpose of this study? There have been few studies that have assessed the validity of the claims made by Skechers in their ad campaign for Shape-up shoes. Those studies have found conflicting results. Some studies have found that the Skechers claims of increased balance requirements from wearers are the only statistically significant results. Other studies found all of the claims made by Skechers for increased muscle activation, improved posture, improved cardiovascular health, less stress on joints, weight loss, and improved circulation are valid. The purpose of this study is to examine the claims made in the ad for the Skechers Shape-up shoe to determine the effects of wearing the shoe following a six-week walking program. This study seeks to add to the body of knowledge in efforts to determine whether the data supports the claims made in the Skechers' Shape-ups ad or refutes them as statistically insignificant. Bow many subjects will participate in this study? If you decide to participate, you will be one of 30 subjects in this research study. How long will your participation last? You participation in this study will last for approximately 6 weeks. What will hapoen if you take part in the study? During the course of this study, the following will occur: 1. You will report to Koury Athletic Center 2. You will read and sign the informed consent and fill out the participant information form 3. You will be asked to participate in the following things: walk along a wall in front of a camera to record your gait pattern, stand in front of a posture grid, have your blood pressure taken, complete a simple balance test, have your height, weight, circumferences, and heart rate measured, and fill out a questionnaire about physical activity. 4. EMG electrodes will be placed in several spots on various areas of the body for data collection during walking. 5. After researchers have determined that you are not experiencing any significant negative effects from the testing session and that the video was collected, the electrodes will be removed and you will be allowed to leave the laboratory Are there any reasons you should not participate? You should not participate in this study if you have any known medical disorder that will place you at increased risk of injury. What are the possible risks or discomforts? Potential risks for your participation in this study are minimal. The primary risks include physical injury, tape allergy, possible embarrassment from being videotaped and/or location ofEMG electrodes (though this will not exceed that embarrassment incurred from going to the gym). Every effort will be made to minimize these risks by watching you closely during each session. Dr. Davis has a doctoral degree (PhD) in Kinesiology and has performed similar experiments previously.
34 What are the possible benefits? You will receive your pair of Skechers Shape-Ups® and you may also gain levels of physical fitness through participation of the walking program. This research will allow investigators to identify the biomechanical differences that result in wearing Skechers Shape-Ups® and will allow the researchers to draw some conclusions about the effectiveness of the shoes on certain physical and affective measures What if we learn about new risks duriag the study? You will be given any new information gained during the course of the study that might affect your willingness to continue your participation. How will your privacy be protected? No subjects will be identified in any report or publication about this study. Although every effort will be made to keep research records private, there may be times when federal or state law requires the disclosure of such records, including personal information. This is very unlikely, but if disclosure is ever required, Elon University will take all steps allowable by law to protect the privacy of personal information. In order to protect your privacy, all records will be kept using a subject number in lieu of your name. Will you be paid for participating? Yes, you will receive a pair of Skechers Shape-Ups® Will it cost you anything to participate? You will not be charged for participating in this experiment. What will hapoen if you are injured by this research? In case of injury, you will have to rely on your own health insurance. If you are injured or become sick during this investigation, the researchers will assist you in obtaining appropriate medical treatment. You do not waive any liability rights for personal injury by signing this form. What if you want to stop before your oart in the study is complete? You can withdraw from this study at anytime, without penalty. The investigators also have the right to stop your participation at any time. This could be because you have an unexpected reaction, or have failed to follow instructions, or because the entire study has been stopped. What if you have questions about this study? You have the right to ask, and have answered, any questions you may have about this research. Ifyou have further questions, or if a research-related injury occurs, you should call Joyce A. Davis, PhD at (336) 278-5873. What if you have questions about yogr rights as a subject? This research has been reviewed and approved by the IRB at Elon University. If you have any questions or concerns regarding your rights as a research subject, you may contact the Chairman of the IRB at (336) 278-6346.
Subject's Agreement: I have read the information provided above. I voluntarily agree to participate in this study. I have had the opportunity to ask questions about being in this study and all my questions have been answered.
Signature of Research Subject Date
Printed Name of Research Subject
Signature of Person Obtaining Consent Date
Printed Name of Person Obtaining Consent
35
APPENDIX B
Physical Activity Readiness Questionnaire (PAR-Q) and You
Regular physical activity is fun and healthy, and increasingly more people are starting to become more active every day. Being more active is very safe for most people. However, some people should check with their doctor before they start becoming much more physically active. If you are planning to become much more physically active than you are now, start by answering the seven questions in the box below. If you are between the ages of 15 and 69, the PAR-Q will tell you if you should check with your doctor before you start. If you are over 69 years of age, and you are not used to being very active, check with your doctor. Common sense is your best guide when you answer these questions. Please read the questions carefully and answer each one honestly:
YES f 0 0 1. Has your doctor ever said that you have a heart condition and that you should only do physical activity recommended by a doctor? 0 0 2. Do you feel pain in your chest when you do physical activity? 0 0 3. In the past month, have you had chest pain when you were not doing physical activity? 0 0 4. Do you lose your balance because of dizziness or do you ever lose consciousness? 0 0 5. Do you have a bone or joint problem that could be made worse by a change in your physical activity? 0 0 6. Is your doctor currently prescribing drugs (for example, water pills) for your blood pressure or heart condition? 0 0 7. Do you know of any other reason why you should not do physical activity? Talk to your doctor by phone or in person BEFORE you start becoming much more physically active If or BEFORE you have a fitness appraisal. Tell your doctor about the PAR-Q and which questions you answered YES. you You may be able to do any activity you want- as long as you start slowly and build up gradually. Or, you may need to restrict your activities to those which are safe for you. Talk answered: with your doctor about the kinds of activities you wish to participate in and follow his/her advice. Find out which community programs are safe and helpful for you. Delay becoming much more active: • If you are not feeling well because of a temporary If you answered NO honestly to rui PAR-Q illness such as a cold or a fever - wait until you feel questions, you can be reasonably sure that you can: better; or Start becoming much more physically • If you are or may be pregnant - talk to your doctor active- begin slowly and build up before you start becoming more active. gradually. This is the safest and easiest way to go. Take part in a fitness appraisal- this is an excellent way to determine your basic fitness so that you can plan the best way for you to live actively. lnfOIDled UBe of the PAR-Q: Reprinted from ACSM's Healtb/Fitness Facility Standards 8lld Guidelines, 1997 by American CoUege of Sports Medicine 36 APPENDIX C Participant Record Form Date: ______ Name: ______ Age: _____ Height:------Weight: ______ Add~=------ Telephone Number:------ Please answer the following questions Which racial group best describes you? ------ Do you consider yourself an active person?------Have you experienced any injuries in the last 6 months? Ifso, what?------ Do you have any chronic injuries? Ifso, what and for how long?------ Daily Activities: Medical Diagnoses or treatments that may impact your ability to participate in a walking program (e.g. muscular or sensory impairment, operations, fractures, pain, etc.): Do you agree to NOT participate in other experiments or new exercise programs during the next eight weeks? __Yes No Have you participated in other experiments? (if yes, please describe date, researcher, experiment, topic, etc.) 37 APPENDIX D Testing day Instrument Measurement Category Pre Mid Post Physical PAR-Q X readiness Digital Scale (kg) Weight Claim: Weight X X X Anthropometric Fixed Tape measure Height X data Hip, thigh, and Retractable Tape measure Claim: Tone X X X calf girths Y-balance apparatus Dynamic balance Balance X X X Y-balance instructional Directions for X X X video balance test Posture Grid Posture Claim: posture X X Sony mini digital video Gait and posture cameras (sagittal and frontal Kinematic data X X characteristics planes) Delsys 8 ch. Electrical signals Muscle firing X X Electromyography in the muscles characteristics Used throughout BORG Scale RPE Exercise intensity walking program 38 APPENDIX E GET IN THE ROUTINE Worming up and cooling down are Important ports of your exercise routine, and should begin and end every session. I. Kick Back (Stretches calves and hamstrings) • Stand upright with feet parallel and hip distance apart, and balance centered. • Roll weight onto the back of the soft foam heel, hold for a count of live, then return to the center. Do not lock knees or lip backward. • Repeat 5 to l 0 limes. 2. Rock and Roll (Stretches calves, hamstrings and Achilles tendons) • Stand upright with teet parallel and hip distance apart, and balance centered. • Roll weight forward, balance on your toes, hold for a count of two. • Slowly rock back to the soft heel, hold for a count of two. • Rock back to your center of balance. Do not lock knees or tip backward. • Repeat 5 to l 0 times. 3. Roll and Rock and Roll (Stretches calves, hamstrings and Achilles tendons) • Follow the Rock and Roll stretch, but alternate feet so one rolls toward the toes and one rocks back. • Repeat 5 to 6 times. 4. The Lean (Stretches calves and Achilles tendons) • Place hands onto a wall, parallel and slightly above your head. • Lean onto the wall with your palms as you place one leg in front of the other. Keep your back leg straight and your front foot on the floor. • Bend the front leg and lean forward by moving your hips toward the wall. Hold tor a count of five. • Repeat 5 to 6 times on each side. 39 APPENDIX F Please walk a minimum of 160mins per week with a minimum of 30mins per entry, recommended 40mins x4 RPE: How hard was your workout? (0-10 shoot for 3 or higher) Soreness: How sore are you today? (0-10 (0=none 10=very painful) Date Walking Time RPE Soreness Comments: Questions or problems call or text Mae at xxx-xxx-xxxx REMINDERS: Stay off stairs in the shoes, walk on hard surfaces only, NO RUNNING in the shoes, and do not use an incline if you use a treadmill 40 APPENDIX G 41