Postural ability reflects the athletic skill level of surfers.

This work analyses surfers' postural control and their use of visual information in static (stable) and dynamic (unstable) postures according to their level of competition. Two groups of healthy surfers were investigated: a group of local level surfers (LOC) (n = 8) and a group of national/international level surfers (NIN) (n = 9). Posture was assessed by measuring the centre of foot pressure with a force platform for 50 s with stable support and for 25 s with unstable support (sagittal or frontal plane). The tests were completed with the eyes open (the subjects looked at a fixed level target at a distance of 2 m) and closed (they kept their gaze in a straight-ahead direction). Results showed that the contribution of vision in postural maintenance, with unstable support was less important in the NIN surfers than in the LOC surfers and that the NIN surfers had better postural control than the LOC surfers. Firstly, the results suggest that expert surfers could shift the sensorimotor dominance from vision to proprioception for postural maintenance. Secondly, there is a relationship between the postural ability and the competition level of surfers. These observations are likely to induce new prospects of training for surfers.

Effects of knee and ankle muscle fatigue on postural control in the unipedal stance.

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.