Bilateral deficit between concentric and isometric muscle actions

The greater torque generation capacity of muscles when contracted alone than in combination with contralateral muscles, characterizes the bilateral limb deficit (BLD) phenomenon. Few studies have explored the BLD in dynamic movements, because isometric actions are considered ideal for evaluating strength. Therefore, the aim of this study was to compare BLD between isometric and concentric actions of the knee extensors. Eleven healthy young men (age=20.6 ± 1 yrs; weight=71.4 ± 6.4 kg; height =174.4 ± 7 cm) volunteered to participate. Initially, subjects visited the laboratory for familiarization with the test protocols. On two subsequent randomized days they performed a test protocol with either a unilateral (right and left limbs) or bilateral condition, with 48~h rest between. The test protocol was composed of five isokinetic concentric actions of the knee extensors at 60°/s and three isometric actions at a 60° angle of knee flexion. The greatest peak torque of the two conditions was used for analyses. Both muscle actions demonstrated greater values unilaterally (p< 0.05) than bilaterally and BLD values were not significantly different between them (p> 0.05). Therefore, if muscle torque production is greater unilaterally, athletes and coaches may utilize unilateral exercises to increase training loads.