Cross-education effect observed in voluntary and electromyostimulation strength training

This study investigated the effects of four weeks of unilateral electromyostimulation(EMS) versus isometric strength training(IM), on knee extension strength of contralateral limb in previously untrained young adults. Subjects performed (IM, n=10) or evoked (EMS, n=10) 40 isometric knee extensions, at an intensity of 65% of maximum voluntary contraction force, three times per week, for four weeks. Pre and post training, both legs were tested for maximum voluntary strength on an isokinetic dynamometer, at 0 deg/s (isometric), 60 and 180 deg/s velocities. The results showed that the EMS and IM training were equally effective to improve strength in these subjects. Both types of training induced a significant cross-education effect in the untrained limb in voluntary isometric strength, but not in the isokinetic torque. The mechanisms underlying this phenomenon require further study.