RESUMEN
The aim of this study was to compare the effects of acute muscle fatigue of the ankle and knee musculature on postural control by immediate measures after performing fatiguing tasks (POST condition). One group of subjects (n = 8) performed a fatiguing task by voluntary contractions of the triceps surae (group TRI) and the other (n = 9) performed a fatiguing task by voluntary contractions of the quadriceps femoris (group QUA). Each muscle group was exercised until the loss of maximal voluntary contraction torque reached 50% (isokinetic dynamometer). Posture was assessed by measuring the centre of foot pressure (COP) with a force platform during a test of unipedal quiet standing posture with eyes closed. Initially (in PRE condition), the mean COP velocity was not significantly different between group TRI and group QUA. In POST condition, the mean COP velocity increased more in group QUA than in group TRI. The postural control was more impaired by knee muscle fatigue than by ankle muscle fatigue.
Asunto(s)
Tobillo/fisiopatología , Fatiga/fisiopatología , Rodilla/fisiopatología , Postura/fisiología , Adulto , Humanos , MasculinoRESUMEN
The aim was to investigate the effects of fatigue induced by electrical stimulation superimposed onto voluntary muscular contractions on postural abilities and strategy (n=8). Two groups of subjects performed a fatiguing of the triceps surae, the first by voluntary muscular contractions (group VOL) and the second (n=8) by electrical stimulation superimposed onto voluntary muscle contractions (group VOL+ES). Balance was measured before and after the completion of both fatiguing tasks, by using a force platform which recorded centre of foot pressure (COP). Spatio-temporal COP parameters were used to evaluate the postural abilities, and a frequency analysis of the COP excursions (Fast Fourier Transform) was performed to estimate the postural strategy (low frequencies mostly account for visuo-vestibular regulation and high frequencies for proprioceptive regulation). In the post-fatigue condition, spatio-temporal COP parameters were not modified in either group. However, the frequency analysis showed that the high frequency band increased more in group VOL than in group VOL+ES. Calf-muscles fatigue did not impair postural control but it generated a change of the contribution of the proprioceptive information (myotatic loops) greater in group VOL than in group VOL+ES. Calf-muscles fatigue induced a modification of the postural strategy that may be exerted more strongly after voluntary muscular contractions than after electrical stimulation superimposed onto voluntary muscular contractions.
Asunto(s)
Extremidad Inferior/fisiología , Contracción Muscular/fisiología , Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Postura/fisiología , Adulto , Análisis de Varianza , Fenómenos Biomecánicos , Estimulación Eléctrica/métodos , Humanos , Masculino , Propiocepción/fisiología , Adulto JovenRESUMEN
OBJECTIVES: To examine whether sensorial manipulation affects subjects differently according to their postural performance and the strategies used. The literature showed that the level of competition of soccer players influences their postural performance and strategy. METHODS: Eight high-level (HL) professional soccer players and nine regional-level (RL) soccer players were tested (1) in a reference condition and (2) in a manipulated sensorial condition (MAN). The MAN condition consisted of perturbing the proprioceptive and exteroceptive information. For each postural condition, balance was assessed by measuring the centre of foot pressure using a force platform during a test of bipedal standing posture. RESULTS: The postural control was less perturbed in the HL than in the RL players in the two postural conditions. Moreover, the group-condition interaction showed that the postural control was less disturbed in the HL than in the RL players when the sensory information was manipulated. CONCLUSIONS: The HL soccer players probably possessed a better internal model of verticality than the RL players. Subjects who had a better postural control level were less disturbed by sensorial manipulation than the others in postural regulation.