Effects of equivolume isometric training programs comprising medium or high resistance on muscle size and strength

Isometric unilateral elbow extension training was conducted for 10 weeks (3 times per week) on 12 young adult men to investigate the effects of equivolume exercise programs with different combinations of intensity and duration on the morphological and functional aspects of the triceps brachii muscle. One group of 6 subjects trained by developing maximal voluntary contraction (MVC) for 6 s per set with 12 sets per session (100%G), while the other group of 6 subjects trained at 60% of MVC for 30 s per set with 4 sets per session (60%G). Training significantly increased the muscle volume (V_m), fascicle pennation angle of the triceps brachii, and torque output during concentric and eccentric elbow extensions at three constant velocities of 0.52, 1.57, and 3.14 rad·s^-1 as well as under the training condition, with no significant differences in the relative gains between the two programs. However, 100%G showed significantly greater V_m than 60%G after training, when V_m before training was normalized. Thus, only 60%G significantly increased the ratio of torque to V_m developed in the eccentric actions at the three velocities and concentric action at 1.57 rad·s ^-1. The present results indicate that isometric training programs of medium resistance/long duration and high resistance/short duration produce different effects on V_m and dynamic strength relative to V _m, even if the training volume is equalized between the two protocols.