A Feedback Controller pesign for a Biomechanical Model of the Press Handstand in Gymnastics

The purpose of this study was to design a PID based control system for a biomechanical model of the press handstand in gymnastics. The model was utilized to simulate a press handstand performance of a gymnast. A total of 10 simulations were performed using different controller parameters to achieve a decent result in joint kinematics which matches with the actual performance. The results of this study showed that maximum and minimum toque values can be used as proportional gain of a P controller. This PID based feedback control model can be developed and used for classification of the control parameters among press handstands performed on different apparatuses sudl as rings and parallel bars in gymnastics

SPHERE FITTING INTO VOLUMETRIC REPRESENTATIONS OF BASKETBALL THROWS

This study aims to provide an evaluation, through some simplifications, for the most forgiving throw positions in the game of basketball throughout the playing field. For each position, throws are modelled as differential equations and then solved numerically. Given a position in the playing field, velocity vectors of successful throws constitute a solid and we fit a maximal sphere into these solids to evaluate the error tolerance for each position. A contour graph for the volumes of maximal spheres was plotted for this evaluation

VOLUMETRIC EVALUATION OF BASKETBALL THROWS

This study aims to provide an evaluation, through some simplifications, for the most forgiving throw positions in basketball throughout the playing field. Throws are modeled as differential equations and then solved numerically. These numerical solutions are checked against major events such as backboard or rim collision, score etc. and continue (afler a bounce) or terminate accordingly. A volumetric approach have been undertaken to summarize these throws into a positional graph which is also presented

EFFECTS OF PATELLAR TENDON STRAP ON ELECTROMYOGRAPHIC ACTIVITY OF QUADRICEPS MUSCLES DURING DROP LANDING

The purpose of this study was to clarify how patellar tendon strap affects on electromyographic activity of quadriceps muscles during drop landing. Four healthy male athlete participants made three drop landings with/without strap and acceptable landing trials were analysed. There was a marginal delay for vastus lateralis onset timing for strapping condition and this may be one of the main contributions of strapping for decreasing knee pain during athletic activities

The effect of chalk on the finger-hold friction coefficient in rock climbing

International audienceThe main purpose of this study was to examine the effect of chalk on the friction coefficient between climber's fingers and two different rock types (sandstone and limestone). The secondary purpose was to investigate the effects of humidity and temperature on the friction coefficient and on the influence of chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed. Participants hung from holds which were fixed on a specially designed hang board. The inclination of the hang board was progressively increased until the climber's hand slipped from the holds. The angle of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient was calculated at the moment of slip. The results showed that there was a significant positive effect of chalk on the coefficient of friction (+18.7% on limestone and +21.6% on sandstone). Moreover sandstone had a higher coefficient of friction than limestone (+15.6% without chalk, +18.4% with chalk). These results confirmed climbers' belief that chalk enhances friction. However, no correlation with humidity/temperature and friction coefficient was noted which suggested that additional parameters should be considered in order to understand the effects of climate on finger friction in rock climbing

Effect of hold depth and grip technique on maximal finger forces in rock climbing

International audienceThe aim of this study was to understand how the commonly used climbing-specific grip techniques and hold depths influence the finger force capacities. Ten advanced climbers performed maximal voluntary force on four different hold depths (from 1 to 4 cm) and in two force directions (antero-posterior and vertical) using three grip techniques (slope, half crimp and full crimp). A specially designed platform instrumented with a 6-degrees-of-freedom (DoF) force/torque sensor was used to record force values. Results showed that the maximal vertical forces differed significantly according to the hold depth and the grip technique (ranged from 350.8 N to 575.7 N). The maximal vertical forces increased according to the hold depth but the form of this increase differed depending on grip technique. These results seemed to be more associated with finger-hold contact/interaction than with internal biomechanical factors. Similar results were revealed for antero-posterior forces (ranged from 69.9 N to 138.0 N) but, it was additionally noted that climbers have different hand-forearm posture strategies with slope and crimp grip techniques when applying antero-posterior forces. This point is important as it could influence the body position adopted during climbing according to the chosen grip technique. For trainers and designers, a polynomial regression model was proposed in order to predict the mean maximal force based on hold depth and adopted grip technique