Influence Of The Ipsilateral Eccentric Contraction Training On Force Fluctuation In The Untrained Contralateral Limb

Abstract

Unilateral muscle training has effects on the untrained contralateral homologous muscle ("cross-education"). Greater "cross-education" has been evaluated by the change of maximal strength in untrained limb following eccentric contraction training than concentric contraction training. Possible causes of "cross-education" are neural adaptations. If so, it is expectable that not only the increase of maximal strength but also the improvement of submaximal muscle performance enhance, but the latter has not been evaluated following eccentric contraction training than concentric contraction training. PURPOSE: To examine the effect of eccentric contraction training (ECCT) and concentric contractioin training (CONT) on the force fluctuations (FF) during submaximal isometric contraction in elbow flexors. METHODS: Ten participants were randomly assigned to ECCT (n = 5) and CONT (n = 5) group. Forces were recorded by using the load cell (LUR-A-2kNSA1, KYOWA) during maximal voluntary isometric contraction (MVC) and submaximal isometric contractions at 10, 30, 50 and 80%MVC force level of before and after training in right and left elbow flexors. ECCT and CONT were performed to extend/flex the right cubital joint from maximal flexion/extension to extension/flexion using the dumbbell where the weight corresponding about 45-60%MVC force of pre-training. Trainings were consisted of 6 sets of 10 repetitions in a day, 3 times per wk for 3wk. FF was calculated as follows; SD/mean force × 100. Comparisons of FF between pre- and post-training at each contraction level in both arms were made using paired-t test. Statistical significance level was set at p < 0.05. RESULTS: MVC force of left arm was increased in CONT group, but not significantly. Left arm MVC force was significantly increased in ECCT group (109.2 ± 4.8%pre-training, p < 0.05). FF of left arm at 50%MVC force level in ECCT group was significantly decreased (pre-training; 1.9 ± 0.2%, post-training; 1.5 ± 0.1%, p <0.05). FF at the other force levels in left arm and all force levels in right arm did not change significantly. CONCLUSION: ECCT induced significant increase of MVC force and decrease of FF during submaximal isometric contraction in left arm. Decrease of FF in the untrained arm may occur selectively depending on the load used in the trained arm.