Spatial Movements of Head, Trunk and Upper Limbs in Locomotion with Natural Velocity

Phd Wiesław Chwała Department of Antropomotoricity, Biokinetics Workshop, Academy of Physical Education in Krakow, Poland 31-571 Krakow Phone nr (12) 683-10-01 e-mail: [email protected] Msc Wanda Forczek doctoral fellow, Academy of Physical Education in Krakow, Poland Mobile phone: +48 509432742 e-mail: [email protected]

SPATIAL MOVEMENTS OF HEAD, TRUNK AND UPPER LIMBS IN LOCOMOTION WITH NATURAL VELOCITY

Key words: human gait, Vicon system, angular changes, extremities,

1 ABSTRACT Perry suggests that during walking the body functionally divides itself into two units, passenger and locomotor. The first unit consists of head, neck, trunk and arms (that are named by Elftman as a HAT- a structure on top of the locomotor apparatus) and this part is responsible for its own postural integrity. The other part – locomotor is formed by two lower limbs and pelvis. Its main task is to carry the body forward (and also HAT). Besides locomotor is responsible for propulsion, stance stability, shock absorption. The aim of this study was an assessment of the values of angular changes in reference to the parts of HAT in all three planes of movement in able-bodied subjects during gait with natural velocity. The study was based on a sample of 40 healthy volunteers aged 20-25 years old. In order to avoid any disturbances of the right results the inclusion criteria aimed at keeping in the sample only subjects without any locomotor disorders: no history of orthopedic or neurosensory disorders. It was used during the spatial movement analysis three dimensional Vicon system.

INTRODUCTION

Walking is one of the most common and complex of all human activities. Perry suggests that during walking the body functionally divides itself into two units, passenger and locomotor. The first unit consists of head, neck, trunk and arms (that are named by Elftman as a HAT- a structure on top of the locomotor apparatus) and this part is responsible for its own postural integrity. The two lower limbs and pelvis form the locomotor system, that is responsible for carrying passenger unit forward. Other locomotor functions are: propulsion, stance stability, shock absorption. Lower limbs and pelvis movements during gait have been taken up many times [1, 3, 5, 7, 8]. The aim of this study is to analyze and evaluate the values of kinematic parameters of the gait with natural velocity refers to biokinematic chain of upper body. Natural velocity is defined as an individual’s normal walking speed. Its average value in this study was 1,41±0,16m/s. As far as movement kinematics of a subject during locomotion is concerned, it is necessary to intensify study of biomechanical values of upper body parameters, because research in this field is not complete and all three planes are rarely included. These studies can be applied not only as an evaluation of the change ranges and changes directions of parameters and results’ disparity in normal group of people, but as a biomechanical pattern of movement also if we want to identify dysfunction of body structure resulting from different sport injures. 2 Besides this analysis can contribute to better understanding of the gait mechanics and helps to undertake the right clinical treatment in case of any pathology.

METHODS

The study has been made in 2003 in Biomechanics Workshop in the Department of Antropomotoricity at the Academy of Physical Education in Krakow. The study was based on a sample of 40 volunteers aged 20-25 years old using the optoelectronic system Vicon with five cameras. With this system it was possible to establish the tri-dimensional trajectories of markers fixed on the subjects' skin. The cameras were linearised and the whole system calibrated according to manufacturer's instruction. Inclusion criteria aimed at keeping in the sample only subjects without any locomotor disorders: no history of orthopedic or neurosensory disorders, that can affect the results of the study. For each subject there were recorded 12 gait cycles with normal stabilized velocity. On the basis of the analysis of 480 normalized walking cycles there were established the mean values of biomechanical parameters that characterizes trajectories locomotion [6]. To the results' description there was applied division of the gait into eight phases, which was suggested by Perry in Los Amigos Medical Center (RLA). These are: Initial Contact - IC (0%) 2. Loading Response - LR (0-10%) 3. Midstance - MST (10-30%) 4. Terminal Stance - TST (30-50%) 5. Preswing - PSW (50-60%) 6. Initial Swing - ISW (60-70%) 7. Midswing - MSW (70-85%) 8, Terminal Swing - TSW (85-100%). Gait phases have been given in per cent gait cycle, which means: from the heel strike of an analyzed limb to the next heel strike of ipsilateral limb.

There is also in use another division of human gait where cycling character of the gait (phasing) is the main criteria [3]. This one consists of two phases:

a) Single support (floor contact with one leg) time of support is approximately 0,53 s b) Double support (both legs are in touch with the ground), time of support is approximately 0,15 s. Data connected with gait refers to frequency 90 steps/min [3] But usually gait is described in reference to the activity of one extremity. The gait cycle is divided into two phases, stance and swing and two periods of double support (Tab.1) The term ‘double support’ refers to the two intervals in a gait cycle in which body weight is transported from one foot to the other. Both feet are in contact with the supporting surface at the same time [8].

3 VICON system characteristics: The study was carried out with the Vicon system which serves to record and analyze movement in three dimensional space. This study is not invasive. There are fixed directly on the subjects' skin the passive markers that reflect localization of the characteristic points and joints’ axes works using the passive markers. The markers with semi-spherical form are made of a semi-reflecting material. Vicon enables to establish the tri-dimensional trajectories of markers in the form of points and their dimensional changes. This system consists of five video cameras, datastation (Fig.1) and infra-red projectors. The speed of image acquisition depends on the type of camera and its localization, that determines the speed of analyzed movements. The cameras work with standard frequency of 120 Hz. Vicon datastation consists of specialized computer that collects and analyses information recorded by cameras. Then it sends them to PC computer where applications to analysis of the research material were installed. At the beginning the study requires preparation of measurement area and system. Measurement area is a place within cameras’ field. During human locomotion study there was used the area of 8 meters length which allows to record four gait cycles. Then whole system was calibrated according to manufacturer's instruction. Markers indicated particular body segments, hence they were stuck mainly in joints axes, in the given distance from the symmetry joint centre and characteristic points on a head, chest, pelvis, that allows to reflect these body segments in space and measurement of the relevant parameters, e.g. width of chest or pelvis (Fig.2). The accurate location of the markers enabled the right description of the centers of joint symmetry [5]. The trials of movement were followed by measurements of the corresponding anthropometric parameters considering somatic body build which were introduced to a computer afterwards. When anthropometric data were applying to mathematic model GOLEM in BODY BUILDER application, there was a real location and subject’s body movement graphically shown. As a result it was achieved the set of kinematic parameters: spatio-temporal parameters, angular changes, velocities and angular accelerators within joints, anthropometric points’ trajectories in all three planes: sagittal, coronal and horizontal and finally length changes of the chosen muscles during normalized gait cycle.

4 RESULTS Shoulder angles Shoulder angle changes are related to the shoulder movements according to the trunk in three planes. Figure 3.a presents two-directional shoulder movement in sagittal plane as follows: flexion is seen from IC to the end of TST; and from the beginning of ISW to the end of gait cycle (TSW) – extension. The shoulder stays in a position of maximum extension (32°) at the onset of stance, and maximum shoulder flexion is reached near the end of terminal stance and slightly later the elbow completes its flexor action. As far as this joint is concerned the range of angle changes is approximately 39±8°. We can notice two neutral position of the shoulder during TST and ISW phase. Shoulder movement in coronal plane (Fig. 3.b) presents characteristic angular changes for normal gait in relation to abduction and adduction movement. The movement in this plane is smooth and is characterized by larger disparity of individual results than we can see in sagittal plane. This is the evidence of great variation in angular range in subjects. What is important is that entire movement in coronal plane takes place in abduction arrangement according to joint axis. From the beginning of the foot flat till the end of TST position the shoulder abducts. The range of movements (Fig. 3.c) vary significantly within subjects. That means a great disparity at the onset position of the shoulder and its rotation in transverse plane. After holding this position of peak flexion momentarily, the shoulder then extends throughout the swing phases.

Elbow angles All the time during walking the elbow stays at flexion position (Fig.4.a). Moving in the same direction as the shoulder, the elbow also goes through an corresponding arc of flexion and extension during each stride. At the onset of stance it flexes to a position of 30° however, never extends beyond 20° flexion. As a result, maximum flexion (56°) is achieved by the time of contralateral foot flat. Contralateral foot flat at the onset of pre-swing stimulates both the shoulder and elbow to reverse their motion toward extension. This motion continues throughout the swing period. The elbow reaches its maximally extended position of 20° flexion by mid swing (while the shoulder continued extending until its final posture of 7° extension is achieved as the ipsilateral heel contacts the floor once again). The total range of motion in this joint is 28±4°. Flexion and extension movements in sagittal plane are accompanied by rotation movements in horizontal plane (Fig.4.b). Their range is approximately 7°, whereas entire movement stays in interior rotation of the forearm. 5 Head angles Head angles relates to the body of walking subject, so called “Anatomy”. Head is bent anterior through the whole range of mean angular values. Its range of motion (just about 3°) characterizes significant disparity of the results in individuals as shown by the relatively large shaded area. Despite this variability among subjects, the patterns of gentle changes of head position are noticed. The head angles oscillate between 1.5 and 4.5° showing two peak deflections within each walking cycle (Fig. 5.a). Head movements in coronal plane characterize small angular changes (3°). At the onset of the stance head is near neutral position (Fig. 5.b). In MST the first movement we can observe is towards to the long axis of the body (approximately 1.5 ) and then the second one which lasts to the end of ISW is lateral tilting of head. At the end of swing phase (TSW) head is in neutral position again. The average total angular range in transverse plane is approximately 10°. At IC there is seen head position near to neutral (Fig. 5.c). The largest movement of head rotation is connected with TST, PSW phase and with the end of swing phase (TSW). During ISW and partly in MSW we have found very similar pattern of angular changes as the phases at the onset of the stance (the range of rotation achieves approximately 3°). Then the head rotates to the left to a position of 8° rotation.

Spine angles Spine angles (whole lumbar segment) is recorded in relation to the pelvis. Lumbar spine movements according to the pelvis in sagittal plane characterize small range of angular changes, approximately 3°. Simultaneously this part of spine is in flexed position according to the pelvis during the whole normalized gait cycle. We have found significant changes in LR, TST and TSW phases. Figure 6.a. presents two peaks of extension (minimal value of flexion) 40% and 90% gait cycle. It is worth to emphasize disparity of individual flexion lumbar spine position according to the pelvis. It results from the variability of physiological curve of analyzed spine unit. Figure 6.b. shows the trajectory of lumbar spine in coronal plane, which characterizes three basic angular changes. At IC this segment is in neutral position and then in LR it bends to the left according to vertical pelvis axis to a position of 6°. From the onset of MST to the end of stance phase in PSW there is seen spine movement to the left in the range of 12°. During the first part of TST lumbar spine is in neutral position according to the pelvis, that goes through 10% gait cycle. After toe-off, during ISW and MSW, spine is in neutral position again. At the end of swing phase TSW lumbar spine does not change its position according to the pelvis in coronal plane. Angular changes range during rotation is significant (approximately l2°) (Fig. 6.c).

6 In IC there is the largest rotation angle (6°), then there is movement in the right-side rotation, which achieves maximum at the end of TST (6°). In PSW left rotation movement is started and it is continued to the end of gait cycle where it reaches value of 6°. The shaded area, that presents disparity of the results in the subjects oscillates between 6-8°.

DISCUSSION

If we take into consideration the great role of passenger unit (HAT) in locomotion, it seems to us that this is the key issue, if we want to understand reciprocal influence on the particular segments of the body in relation with the whole biomechanism movement [6, 10]. Dysfunctions that results from pathological work of the lower extremities or pelvis are always reflected in compensatory work of the upper body unit. Besides the range of angular changes in all three planes that accompanies HAT can stay without any affective influence on the lower limb work [11,12].

Our considerations in this paper were focused on studying and better understanding the work mechanism of the upper limbs, trunk and head in able-bodied during gait with natural velocity. Subjects’ gait was analyzed by means of kinematic parameters of the gait. There were taken into account angular changes of shoulder and elbow joints, head and lumbar spine movements in all three planes: sagittal, coronal and transverse.

As there are not so many investigations in this field, the results of this study can become a very interesting characteristics of gait in the population of healthy people.

We can not find in Bober studies [4] the accurate data in reference to angular changes in all upper limb joints. He just noticed the reciprocal action of upper and lower extremities where integrated movements of the pelvic and shoulder girdle reflect particular phases of the gait. Although upper limb rotation movement is not a main condition of the proper gait, upper extremities however, take important part in total gait pattern. Based on preliminary observation of the rotation patterns of the upper limbs Murray [6,7] claims they are the most variable gait components. It is also confirmed by own studies.

Shoulder angles presents two-directional shoulder movement in all three planes. The change of movement direction becomes visible in the end of TST phase. The shoulder flexes from maximum extension at the onset with reciprocal abduction and interior rotation. In the second part of the cycle the shoulder extends throughout the swing phase and diminishes abduction and interior rotation (return to neutral position in transverse plane). 7 Phasing of arm motion during walking is quite distinct. At initial contact the ipsilateral arm is maximally extended at both the shoulder and elbow. Following a brief delay the shoulder progressively flexes. There is a greater delay at the onset of elbow flexion that may relate to the maximally extended position of 20° flexion. Movement at the elbow toward greater flexion begins in mid stance. Moving in the same direction as the shoulder, the elbow also goes through an equivalent arc of flexion and extension during each stride. All the time during walking the elbow stays at the flexion position. Contralateral foot flat at the onset of pre-swing stimulates both the shoulder and elbow to reverse their motion toward extension. This motion continues throughout the swing period. Cappozzo [1] described the head movements trajectories in all three planes on the base of the similar studies. The results of our investigation are the reflection of his outcomes. Head is bent anterior through the whole range of mean angular values. Head movement in coronal plane characterizes small angular change. These are only small oscillate movements. At the onset of the stance the head is near neutral position. The average total angular range in transverse plane is larger than in sagittal plane. The largest head rotation movement is connected with TST and PSW phase and at the end of swing phase. During ISW and partly in MSW we have found very similar angular changes to the phases at the onset of the stance. Lumbar spine segment is flexed according to pelvis during whole normalized walking cycle. According to the pelvis this part of the spine characterizes small range of angular changes in sagittal plane. Significant differentiation of the individuals’ flexion alignment results from differentiation within physiological curves of analyzed part. There is noticed a large range of disparity (3-17,5) in subjects. In coronal plane we have found movement towards to vertical axes of the pelvis and the rest of stance phase accompanies markedly movement to the right from pelvis axes. Simultaneously these movements are supported by rotation to the left. In swing phase we can see significant movement of lumbar segment toward the vertical pelvis axes in sagittal plane with right-side rotation of the whole segment. In sagittal plane we can notice smooth movement toward spine extension at the end of swing phase.

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