It is common to observe bilateral strength deficit during the vertical jump. This is characterized by lower strength produced during bilateral contractions, when compared to the sum of the unilateral contractions of similar muscles. There is not much scientific knowledge about the effect of unilateral fatigue on bilateral activities. The aim of this study was to investigate the effect of unilateral fatigue on bilateral deficit performance during bipedal vertical jump. Ten sedentary young adults unilaterally fatigued each lower limb and performed vertical jumps (bipedal and unipedal). We measured the vertical ground reaction force and myoelectrical activity to each lower limb and conditions (pre-fatigue, fatigue of the dominant limb (FD) and non dominant limb (FND)) were measured. Differences between tasks and conditions only on the pre-fatigue (p=0.030) were observed. Differences were observed for the bipedal vertical jump between pre-fatigue and FD (p=0.005), and unipedal vertical jump between pre-fatigue and FD (p<0.001) and FND (p<0.001). We only observed change on the performance of bipedal vertical jump during the FD condition. We observed a trend to the asymmetry index decrease for the muscular action of the fatigued contralateral lower limb by electromyography. The results suggest that there is a common command where the nervous system considers the muscles simultaneously activated as a unit, except in conditions of unilateral lower limb fatigue.
fatigue; countermovement jump; bilateral strength deficit
