Unilateral arm strength training improves contralateral peak force and rate of force development.

Neural adaptation following maximal strength training improves the ability to rapidly develop force. Unilateral strength training also leads to contralateral strength improvement, due to cross-over effects. However, adaptations in the rate of force development and peak force in the contralateral untrained arm after one-arm training have not been determined. Therefore, we aimed to detect contralateral effects of unilateral maximal strength training on rate of force development and peak force. Ten adult females enrolled in a 2-month strength training program focusing of maximal mobilization of force against near-maximal load in one arm, by attempting to move the given load as fast as possible. The other arm remained untrained. The training program did not induce any observable hypertrophy of any arms, as measured by anthropometry. Nevertheless, rate of force development improved in the trained arm during contractions against both submaximal and maximal loads by 40-60%. The untrained arm also improved rate of force development by the same magnitude. Peak force only improved during a maximal isometric contraction by 37% in the trained arm and 35% in the untrained arm. One repetition maximum improved by 79% in the trained arm and 9% in the untrained arm. Therefore, one-arm maximal strength training focusing on maximal mobilization of force increased rapid force development and one repetition maximal strength in the contralateral untrained arm. This suggests an increased central drive that also crosses over to the contralateral side.