Nicolas Bideau

Energy Flow Analysis During the Tennis Serve Comparison Between Injured and Noninjured Tennis Players

Background: Energy flow has been hypothesized to be one of the most critical biomechanical concepts related to tennis performance and overuse injuries. However, the relationships among energy flow during the tennis serve, ball velocity, and overuse injuries have not been assessed. Purpose: To investigate the relationships among the quality and magnitude of energy flow, the ball velocity, and the peaks of upper limb joint kinetics and to compare the energy flow during the serve between injured and noninjured tennis players. Study Design: Case-control study; Level of evidence, 3. Methods: The serves of expert tennis players were recorded with an optoelectronic motion capture system. The forces and torques of the upper limb joints were calculated from the motion captures by use of inverse dynamics. The amount of mechanical energy generated, absorbed, and transferred was determined by use of a joint power analysis. Then the players were followed during 2 seasons to identify upper limb overuse injuries with a questionnaire. Finally, players were classified into 2 groups according to the questionnaire results: injured or noninjured. Results: Ball velocity increased and upper limb joint kinetics decreased with the quality of energy flow from the trunk to the hand + racket segment. Injured players showed a lower quality of energy flow through the upper limb kinetic chain, a lower ball velocity, and higher rates of energy absorbed by the shoulder and elbow compared with noninjured players. Conclusion: The findings of this study imply that improper energy flow during the tennis serve can decrease ball velocity, increase upper limb joint kinetics, and thus increase overuse injuries of the upper limb joints.

2D dynamical efficiency of a swimfin: a fluid–structure interaction approach

Recent literature has shown a great interest in evaluating the propulsive efficiency in order to enhance performances in fin swimming or development of biomimetic systems. Such problems appear to be complex for two reasons. On the one hand, for realistic undulatory motion, there is a strong interaction between the fluid and the moving fin. On the other hand, the deformable feature of the structure plays an important role on the dynamical response during the locomotion. A coupled fluid–structure interaction model is therefore necessary to quantify the energy transfer between the fin and the water and to evaluate the accurate propulsive force generated.

Spatiotemporal analysis of 3D kinematic asymmetry in professional cycling during an incremental test to exhaustion

ABSTRACT This study investigated the influence of an incremental exercise on bilateral asymmetry through the spatio-temporal evolution of 3D joint angular displacement, using the Normalized Symmetry Index () and cross-correlation methods. Twelve professional cyclists performed an incremental test to exhaustion, during which motion capture was used. Results revealed a decrease in range of motion between the first and last stages for twelve of the eighteen joint rotations, with the highest impact observed for right hip flexion/extension (61.8 ± 4.7° to 58.8 ± 4.1°, p < 0.05, ES = 0.68). For both stages, significant bilateral differences greater than 10° were observed for hip and knee flexion/extension (p < 0.05, ES>0.90) and ankle and hip internal/external rotation (p < 0.05, ES>0.25). Cross-correlation displayed the lowest pattern similarities for hip abduction/adduction and the highest similarities for knee flexion/extension, ankle plantarflexion/dorsiflexion and hip internal/external rotation. The cross-correlation method showed that the right leg was mostly ahead of time with respect to the left leg, a trend that was accentuated with power output increase. Instantaneous fluctuated up to 18% throughout the pedalling cycle, with different behaviour between the power and recovery phases. This study demonstrated the workload effects on side-to-side joint angular pattern similarity.