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THE REBOUND OF THE BODY USING RUNNING-SPECIFIC PROSTHESES IN UNILATERAL TRANSFEMORAL AMPUTEES
Get PDFAlthough the elastic bounce of the body is considered a prerequisite for running, the rebound strategy in individuals with lower extremity amputation is not well known. This study aims to investigate the rebound strategy at different running speeds in unilateral transfemoral amputees (uTFAs) wearing running-specific prostheses (RSPs). On an instrumented treadmill, eight uTFAs ran at incremental speeds (30%, 40%, 50%, 60%, 70%, and 80% of the average speed of their 100-m personal records). The rebound strategy of the unaffected and affected limbs is evaluated using the ratio of the natural frequency of the spring-mass system (fsist) to the step frequency (fstep). At all speeds, fsist/fstep in the unaffected limb is considerably greater than that in the affected one. The interlimb differences in fsist/fstep tended to increase with the speed. These results suggest that the rebound strategy is not the same for the unaffected and affected limbs in uTFAs across a range of speeds, and that uTFAs wearing RSPs perform bouncing steps using the alternate asymmetric rebound strategy (fstep \u3c fsist) through different limbs
INFLUENCE OF CALCULATION PARAMETERS ON NONLINEAR DYNAMICS MEASURES
Get PDFNonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent biomechanics studies. The aim of this study is to identify the range of time delay and embedding dimension values estimated for gait data, and how sensitive Lyapunov exponent and correlation dimension are to the range of these values. A participant walked at 3 km/h and ran at 9 km/h on a treadmill for 2 minutes. Lyaponuv exponent and correlation dimension were calculated based on a combination of the optimal and mean average time delay (TD) and embedding dimension (ED) for both angle and marker data. In the majority of literature, only one ED and TD is considered for LyE estimation, based on an average across data or values suggested in previous papers. However, the results of our study show that every angle or position, has an optimum ED and TD, and the use of these values affects the nonlinear dynamics values in non-trivial ways
SYNCHRONIZATION OF SPRINTING BETWEEN BLIND AND GUIDE SPRINTERS: A CASE STUDY
Get PDFThis study aimed to evaluate the magnitude of synchronization between blind and guide sprinters for elite and sub-elite pairs. Two pairs of male blind sprinters and their guide sprinters performed 60-m sprints during which ground reaction force and sprinting motion were recorded. Although flight time and propulsive force in sub-elite pair showed significant and moderate difference between the sprinters, there were trivial and small differences in variables between the sprinters of elite pair. Moreover, the correlation (r = 0.97 and 0.84) in the thigh angle in the sagittal plane between blind and guide sprinters was high with no phase shifting for the elite pair compared to the sub-elite pair during the initial acceleration phase. The results indicate that the magnitude of synchronization is likely high in an elite pair of blind and guide sprinter especially during the initial acceleration phase
MOVEMENT VARIABILITY IN THE SPINAL KINEMATICS OF FAST BOWLERS
Get PDFThe purpose of this study was to quantify the inter- and intra-individual spinal movement variability in a group of pre-elite and elite fast bowlers. Eleven pre-elite and elite level bowlers from the Otago region (New Zealand) took part in the study. Each bowler bowled two six-over spells, while being recorded by a 3D motion analysis system in two sessions, one week apart. Thorax and lumbopelvis segments were modelled and analysed. Between session changes in spine kinematics were greatest for lateral bending (p = .0001). Inter-individual variability was much greater than the average within-participant variability (more than double), highlighting the need for individual analyses of fast bowlers in the future. Inter- and intra-individual variability in spinal movement among a homogenous group of fast bowlers found in the current study will be important for designing future studies on cricket fast bowlers
USING COMPUTER VISION AND DEEP LEARNING METHODS TO CAPTURE SKELETON PUSH START PERFORMANCE CHARACTERISTICS
Get PDFThis study aimed to employ computer vision and deep learning methods in order to capture skeleton push start kinematics. Push start data were captured concurrently by a marker-based motion capture system and a custom markerless system. Very good levels of agreement were found between systems, particularly for spatial based variables (step length error 0.001 ± 0.012 m) while errors for temporal variables (ground contact time and flight time) were within 1.5 frames of the criterion measures. The computer vision based methods tested in this research provide a viable alternative to marker-based motion capture systems. Furthermore they can be deployed into challenging, real world environments to non-invasively capture data where traditional approaches would fail
DOES HIP CONTRACTURE EFFECT ANTERIOR PELVIC TILT CHANGES DURING SQUATTING?
Get PDFThe purpose of this study was to examine possible effects of hip flexor contractures on changes in pelvic anterior tilt during the squat. Twenty recreationally active subjects were evaluated for hip contracture using the Modified Thomas test. Eight subjects were found to have iliopsoas contracture and twelve were found to have rectus femoris contracture. A 2x8 mixed-model repeated measures ANOVA was completed between the positive and negative hip contracture groups for both the iliopsoas and rectus femoris results. No significant differences were found between the hip contracture groups for the iliopsoas (p=.90) or the rectus femoris (p=.18). These results indicate the Modified Thomas test results about hip contracture do not have an effect on changes in pelvic motion during the squat
THE EFFECT OF REPRESENTATIVE TASK DESIGN ON GROUND REACTION FORCES PRODUCED BY ADOLESCENT RUGBY PLAYERS
Get PDFOur primary aim in this study was to investigate differences in the ground reaction forces (GRFs) produced when adolescent rugby players performed match-reflective tasks of increasing degrees of representativeness. Fourteen male players performed three tasks; a straight jog, an anticipated cut and an unanticipated cut. These tasks were performed in four different conditions; landing with their dominant or non-dominant leg, while carrying or not carrying a rugby ball. Greater GRFs were recorded during both the weight acceptance and late push-off phases of the cutting tasks compared with the straight jog and during the push-off phase when the direction of the cut was anticipated. Carrying a ball, however, did not affect the GRFs recorded. These findings highlight the importance of employing representative task design when assessing performance and designing practice
ROAD TO LAB: COBBLESTONE CYCLING VIBRATIONS TRANSFERRED TO THE LAB
Get PDFThe purpose of the study was to provide vibration recommendations for laboratory-based cycling interventions derived from field tests on cobblestones. For that purpose, the vertical accelerations of the front and rear dropouts (points of wheel fixation at the frame) of the bike frame were recorded, with five experienced cyclists riding on cobblestones at different velocities. Lab vibration recommendations are based on the median frequency (34.6 ± 1.2 – 45.6 ± 0.5 Hz), rms of acceleration (5.5 ± 0.3 - 10.2 ± 0.6 g) , peak acceleration (48.5 ± 3.8 g) , mean amplitude (3.6 ± 4.3 – 5.0 ± 6.4 mm) and peak amplitude (69.7 ± 23.4 mm) of the dropouts. For a lab-based approach with vibration plates, the vibration stimulus should be applied (I) to the rear and front dropout, (II) with two different frequencies used for front (36 - 46 Hz) and rear (32 - 39 Hz) (III) and a mean vertical amplitude of 4 mm. The parameters presented provide the basis for vibration-related material testing, motion analysis or physiological performance testing in cycling
INFLUENCE OF COORDINATIVE MOTOR ABILITY ON LOWER LIMB KINEMATICS IN YOUNG FOOTBALL PLAYERS: INJURY PREVENTION THROUGH WEARABLE INERTIAL SENSORS
Get PDFThe aim of the present study was to evaluate, during ordinary training, the lower limb kinematics in young football players, and to verify if the kinematic patterns are influenced by coordinative motor abilities. Fourteen healthy players (10y ± 2m) were enrolled. Each player performed two activities: a pre-defined path with typical movements of football training and matches; the Harre test to evaluated children’s coordinative motor ability. Wearable inertial sensors were used to assess lower limb joint kinematics and accelerations. Based on Harre test, players were divided into two groups, more coordinated and less coordinated. During all tasks performed, less coordinated players showed stiffer kinematic strategies and greater limb asymmetry, which are potentially risky patterns for non-contact (e.g. Anterior Cruciate Ligament) injury. Quantitative analysis on the field could contribute to deepening the biomechanical understanding of players’ motion and injury risk
SEX-BASED ANALYSIS OF SPRINT ACCELERATION
Get PDFThis study assessed a variety of kinetic, spatial, and temporal variables during the early acceleration phase of sprinting for both men and women (N = 20) during standing and sprinter position starts. Forces, step distance, time, and velocity measured from the first four steps of each start via force platforms were compared across start, step, and sex via ANCOVA while removing the effect of height or weight. Velocity increased from step 1 to steps 2 and 3; while overall velocity was lower for women and the standing start (p \u3c 0.05). There were interactions of start * sex for horizontal force, ratio of horizontal to vertical force, overall velocity, and overall time (p \u3c 0.05). Men’s performance tended to be more negatively affected when using the standing start than women’s performance