Asymmetry of Force Fluctuation During Low Intensity Isometric Contraction in Leg Muscle

The purpose of this study was to investigate the asymmetry of force fluctuation in the leg muscles during isometric knee extension and flexion. Twenty healthy males (21±2 years) performed the maximal voluntary isometric contraction (MVC) in knee extensor and flexor. On the basis of MVC measurement, the subjects performed sustained isometric knee extension and flexion for 15s at levels corresponding to 10%, 20% and 30% MVC. The main findings of this study were: (1) a greater force fluctuation was found in the stronger MVC limb than in the weaker MVC limb at 30% MVC; (2) no difference was found in the force fluctuation between the stronger and weaker MVC limbs at 10% and 20% MVC; and (3) significant positive correlations were found between the target force values and the force fluctuation at each contraction intensity. These results suggest that: (1) asymmetry of force fluctuation increases with load, (2) asymmetry of the force fluctuation is observed at more than 30% MVC intensity; and (3) if the contraction intensity is same relatively loads (% MVC), force fluctuation is increase with absolute load (target force value). Force fluctuation influence the functional ability of an individual in controlling finger or limb movements in daily life. Further, asymmetry of force fluctuation might influence for more than 30% MVC of daily activities.