Effects of resistance training at different intensities of load on cross-education of muscle strength.

The objectives of this study were to 1) compare the extent of cross-transfer of muscle strength of high- versus low-load unilateral resistance training performed with external pacing of the movement (URTEP) and 2) compare the time course of the 2 approaches. Fifty subjects were randomized to 1 of the following 3 groups: G80 [2 sets at 80% and 2 sets at 40% of 1 repetition maximum (1RM), 1 concentric second and 3 eccentric seconds controlled by a metronome]; G40 (4 sets at 40% of 1RM, 1 s and 3 s controlled by a metronome); or control group. At week 1, the G80 increased the elbow flexion 1RM ( P  < 0.05) in contralateral arm. At week 4, both G80 and G40 increased the elbow flexion 1RM ( P  < 0.05) in contralateral arm. However, a greater 1RM gain was observed in the G80 than in the G40 ( P  < 0.05). Thus, although higher-load URTEP seems to enhance the cross-education effect when compared with lower-load URTEP, the cross-education of dynamic strength can be achieved in the 2 approaches after 4 weeks. Many patients would benefit from cross-education of muscle strength through URPEP, even those who are unable to exercise with high loads and in short periods of immobilization. Novelty: Unilateral resistance training promotes cross-education of dynamic muscle strength. However, higher-load resistance training enhances the effects of cross-education of muscle strength.