Effects of six weeks of resistance exercise with reciprocal contractions on knee extensors neuromuscular performance: Randomized controlled trial

BACKGROUND: Studies have shown that reciprocal exercise using a pre-activation of antagonist muscles may increase the agonist neuromuscular performance. OBJECTIVE: To compare the efficiency of two modalities of resistance training (with and without antagonist muscle preactivation) during a six week program on knee extension neuromuscular performance of healthy men. METHODS: Forty-nine men were randomly assigned into two groups: 1) reciprocal training: REC - one concentric knee flexion immediately followed by one concentric knee extension, and 2) control: CON - one concentric knee extension exercise, without pre-activation. Both training modes were characterized by three sets of 10 repetitions at 60 degrees/s, 2 days/week. Knee extensor peak moment (PM), load range (LR), electromyographic activity (EMG) of the vastus medialis (VM), rectus femoris (RF), and biceps femoris (BF) co-activation were assessed pre and post 6 weeks of training. A 2 x 2 mixed factor ANOVA was applied to evaluate differences between variables. RESULTS: Significant increases were found for PM between pre and post-evaluations for both groups. In relation to VM and RF activation, co-activation (BF/VM and BF/RF) and LR, no significant differences between groups and moments were found. CONCLUSION: In view of the results further research is indicated in order to examine the utility of longer programs in positively affecting antagonist muscle co-activation as well as in elucidating its clinical effects in individuals with musculoskeletal dysfunction.