No abstract

Achilles tendon (AT) compliance can affect the generation and transmission of triceps surae muscle forces, and thus has important biomechanical consequences for walking performance. However, the uniarticular soleus (SOL) and the biarticular (GAS) function differently during walking, with in vivo evidence suggesting that their associated fascicles and tendinous structures exhibit unique kinematics during walking. Given the strong association between muscle fiber length, velocity and force production, we conjectured that SOL and GAS mechanics and energetic behavior would respond differently to altered AT compliance. To test this, we characterized GAS and SOL muscle and tendon mechanics and energetics due to systematic changes in tendon compliance using musculoskeletal simulations of walking. Increased tendon compliance enlarged GAS and SOL tendon excursions, shortened fiber operation lengths and affected muscle excitation patterns. For both muscles, an optimal tendon compliance (tendon strains of approximately 5% with maximum isometric force) existed that minimized metabolic energy consumption. However, GAS muscle-tendon mechanics and energetics were significantly more sensitive to changes in tendon compliance than were those for SOL. In addition, GAS was not able to return stored tendon energy during push-off as effectively as SOL, particularly for larger values of tendon compliance. These fundamental differences between GAS and SOL sensitivity to altered tendon compliance seem to arise from the biarticular nature of GAS. These insights are potentially important for understanding the functional consequences of altered Achilles tendon compliance due to aging, injury, or disease.

The aim of this study was to investigate the effects of unilateral and bilateral fatigue on both postural and power bipedal tasks. Ten healthy subjects performed two tasks: bipedal quiet standing and a maximal bipedal counter-movement jumping before and after unilateral (with either the dominant or nondominant lower limb) and bilateral (with both lower limbs) fatigue. We employed two force plates (one under each lower limb) to measure the ground reaction forces and center of pressure produced by subjects during the tasks. To quantify the postural sway during quiet standing, we calculated the resultant center of pressure (COP) speed and COP area of sway, as well as the mean weight distribution between lower limbs. To quantify the performance during the countermovement jumping, we calculated the jump height and the peak force of each lower limb. We observed that both unilateral and bilateral fatigue affected the performance of maximal voluntary jumping and standing tasks and that the effects of unilateral and bilateral fatigue were stronger in the dominant limb than in the nondominant limb during bipedal tasks. We conclude that unilateral neuromuscular fatigue affects both postural and power tasks negatively.

Abstract-It is unclear whether athletes change their postural control over the course of a full sport season, or become more asymmetrical with respect to their neuromuscular performance over the same period. The aim of this study was to investigate the effects of a full sport season on the postural control of team handball elite athletes. Ten healthy, elite male team handball players performed bipodal standing (BP) and right and left unipodal standing (UP) during 30s. We used the RMS and speed of the center of pressure to describe postural sway. For the BP task, the sway was lower at the end of the season (p<0.005). For the UP tasks, the sway was lower at the end of the season only for the non-dominant limb (p<0.001). Differences between limbs were observed only at the end of the season (p<0.03). In conclusion, a full team handball season did not lead to deterioration of the athletes' postural control, but by the end of the season, the athletes were more asymmetrical.Keywords: exercise performance, biomechanics, motor control, postural stability, stabilometry, physical performanceResumo-"Efeitos da temporada completa em parâmetros estabilométricos em atletas de handebol de elite." Não é claro na literatura científica se atletas mudam seu controle postural ao longo de uma temporada esportiva, ou mesmo se tornam mais assimétricos em relação ao seu desempenho neuromuscular durante o mesmo período. O objetivo deste estudo foi investigar os efeitos de uma temporada esportiva completa no controle postural de atletas de elite do handebol. Dez jogadores de elite de handebol, saudáveis, realizaram a tarefa de postura ereta quieta bipodal (BP) e unipodal direito e esquerdo durante 30 segundos. Foi utilizada a RMS e a velocidade do centro de pressão para descrever a oscilação postural. Para a tarefa de BP, a oscilação foi menor após a temporada esportiva (p < 0,005). Para as tarefas unipodais, a oscilação foi menor após temporada esportiva apenas para o membro não dominante (p < 0,001). Apenas após a temporada, foram observadas diferenças entre os membros (p < 0,03). Em conclusão, uma temporada esportiva para o handebol não levou à deterioração do controle postural dos atletas, entretanto no final da temporada, os atletas apresentaram-se mais assimétricos.Palavras-chave: desempenho do exercício, biomecânica, controle motor, estabilidade postural, desempenho físico Resumen-"Efectos de la temporada completa en parámetros estabilométricos en atletas de balonmano de élite." No está claro en la literatura científica si los atletas cambian su control postural a lo largo de una temporada deportiva o incluso si llegan a ser más asimétricas en relación con su rendimiento neuromuscular durante el mismo período. El objetivo de este estudio fue investigar los efectos de una temporada deportiva completa en control postural de deportistas de elite de balonmano. Diez jugadores de balonmano de élite, sanos, llevaron a cabo la tarea de la tranquilidad de la postura de pie bipodal (BP) y unipodal izquierda y derecha durante 30 segundos. RMS...