ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive
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VERTICAL JUMP HEIGHT PREDICTION THROUGH THE ANALYSIS OF GROUND REACTION FORCES
Full text linkThis study aimed to perform a linear multivariate regression analysis of kinetics variables to predict the height obtained in the countermovement jump (CMJ). Twenty-nine men, physically active, performed 3 maximum CMJ with 1 minute of interval between each jump. Variables of force and velocity, such as peak force in the eccentric phase (r=0.405), peak velocity in the concentric phase (r=0.393), and peak of force (r=0.392), showed positive association with the jump height. The regression analysis showed that the combination of the variables explained 65% of the jump height, it also demonstrated that force and velocity are determinant for the performance of this task
ELECTROMECHANICAL DELAY AND ITS MECHANISMS ARE NOT IMPAIRED FOLLOWING ECCENTRIC EXERCISE
Full text linkThe aim of the present study was to assess the effect of exercise-induced muscle damage on both electrochemical and mechanical components involved in the electromechanical delay in the gastrocnemius medialis muscle. 15 healthy participants completed 10 sets of 30 maximal eccentric contractions of the plantar flexor muscles at a constant angular velocity of 45°.s-1. Delayed onset muscular soreness, maximal isometric torque, and electromechanical delay were measured before, 1h, and 48h following eccentric exercise. The present study revealed that the time required for both electrochemical and mechanical process involved in electromechanical delay are not impaired by exercise induced muscle damage. This study suggests that the long lasting reduction in force after eccentric exercise cannot be associated to an alteration of the force transmission efficiency
NEUROMUSCULAR PERFORMANCE OF DOLLYO CHAGUI: COMPARISON OF SUBELITE AND ELITE TAEKWONDO ATHLETES
Full text linkAiming to compare the execution time, linear and angular speeds, ground reaction force (GRF) and electromyographic (EMG) parameters between taekwondo athletes of two different standards, 8 elite and 8 subelite black belt taekwondo athletes performed eighteen round house kicks, in two randomized height (Head and Chest), with their dominant lower limb, combining maximum impact and speed, in a selective reaction time design. Kinematic were recorded through 3D kinemetry. Timing parameters and EMG cocontraction index were significantly lower in elite group, while peak of linear (toe and knee), angular speeds (knee and hip), and GRF were significantly higher in elite group. We conclude that reaction time, duration and velocity of kick and cocontraction could be useful in selecting top level taekwondo athletes and monitoring their training status
THE RELATIONSHIP BETWEEN NECK STRENGTH AND HEAD ACCELERATIONS IN A RUGBY TACKLE
Full text linkThe purpose of this study was to investigate the relationship between neck strength and head accelerations during a rugby tackle. Ten elite rugby players had their neck strength assessed and head accelerations tracked using a three dimensional motion analysis system during a rugby tackle. Higher levels of strength were related to lower head accelerations. Significant relationships were found between coronal plane accelerations and flexion and extension strength. The findings support those in the literature suggesting that increasing neck strength is a potential target to reduce sport concussions
LOAD CONDITION OF THE WRIST DURING THE FORWARD HANDSPRING, THE FORWARD HANDSPRING WITH ULNAR DEVIATED HAND POSITIONING AND THE BACKWARD HANDSPRING
Full text linkThe aim of this research was to deterime the loading conditions throughout the forward handspring, the forward handspring with ulnar deviated hand positioning and the backward handspring using an inverse dynamics approach based on simultaneously acquired kinetic and kinematic data. 14 gymnasts performed five of each movement. The range of motion (ROM) around the pronation/supination axis in the forward handspring with ulnar deviated hands was significantly higher than in the two other executions. The calculated moment acting on the wrist during backward handsprings exceeded the ones during the forward executions significantly. Due to the knowledge of the loading conditions, long-term damages can be estimated and minimized in such repetitively excessive motions
ESTIMATING STEP PARAMETERS USING PHOTOELECTRIC CELLS
Full text linkThe purpose of this study was to assess the OptoJumpTM photocell system (Microgate, Bolzano, Italy) in measuring step length and ground contact time during running. In two separate investigations, eight individuals repeatedly ran through a three metre section of OptoJumpTM track. Ground contact times were compared to concurrent force platform measures whereas step lengths were compared to physically measured lengths from foot imprints left in powder. Estimates of step length showed excellent validity with only 0.4% difference between methods and an intraclass correlation coefficient of 0.999. The OptoJumpTM systematically overestimated contact time with a mean bias of 2.7% compared to force platform measures. These results suggest that the OptoJumpTM can be effectively used to estimate step characteristics in real time
INFLUENCE OF CRANK LENGTH ON PEDALLING ECONOMY IN THE ACCELERATION PHASE IN TRACKCYCLING – A SINGLE CASE STUDY
Full text linkThe purpose of this study was to identify different effects of crank-length on cycling performance in track cycling. Two different crank lengths (162,5mm and 170mm) were used in a single-blind and balanced order at a wooden indoor cycling track. Saddle height and the position of the handlebar were kept constant during all trials. The subject was asked to complete 100m with maximum load with every crank length in each test session. To avoid test effects and effects from fatigue, the order of crank length was changed throughout all test sessions. Measured variables were torque (Nm), power output (W), Force (F), Cadence (rpm) and time (s). Results showed that force output stayed constant, while the 170mm condition had advantages in time, torque and power output due to the longer lever arm. Longer distances than 100m were not analysed
ADDING MASS TO THE SHOE DOES NOT AFFECT BALL VELOCITY IN A SOCCER PENALTY KICK
Full text linkThe aim of this study was to identify the optimum shoe mass that maximizes ball velocity in a soccer instep penalty kick. Two players performed 20–30 maximum-effort penalty kicks while wearing football shoes with lead weights attached to the base of the shoe (total mass: 0.26 – 0.81 kg). The kicks were recorded by a video camera at 100 Hz and a biomechanical analysis was conducted to obtain measures of ball projection velocity and kinematics of the kicking leg. We found that ball velocity was insensitive to shoe mass (at least for the range of shoe mass tested). An important contributing factor to the observed relationship was that the velocity of the kicking foot at ball impact decreased as the mass of the shoe increased. Our result indicates that players should not change their shoes before taking a penalty kick
EFFECTS OF SEAT POSITION ON THE JOINT MOMENTS OF THE LOWER EXTREMITIES DURING CYCLING IN THE ELDERLY
Full text linkThe purpose of this study was to quantify the joint moments of the lower extremities with different seat positions during cycling in elderly. Fifteen older adults performed cycling on a self-developed bicycle ergometer at three horizontal and three vertical seat positions. The pedals were instrumented with six-component load cells to measure pedal reaction forces; and a motion capture system was used to measure body segment kinematic data. Both data sets were used to calculate joint moments during a crank cycle. The results showed that seat positions affected joint moments significantly, especially the horizontal positions. A more posterior seat position led to a more balanced loading at the hip and knee, with less peak muscle loadings. The results will be helpful for cycle design and fitting for the elderly
A MECHANOMYOGRAPHIC ANALYSIS OF CONTRACTION TIME IN LUMBAR SPINE MUSCULATURE; CONTROL DATA
Full text linkMechanomyography (MMG) is an emerging diagnostic tool that investigates the contractile properties of human muscle tissues. This study investigated the contraction time (Tc) of localised muscles tissues within the lumbo-sacral spine in young, healthy participants (age: 20.92±2.02, BMI: 23.09±4.51, n=12). Analysis of 10 erector spinae muscle sites, as well as two over multifidus, found that muscle contraction time (Tc) was heterogeneous (p>0.05) and averaged 87.79ms. The data presented here represents control data for a future study into the diagnostic value of injury-related localised changes in Tc in chronic low back pain patients