Comparison between concentric-only, eccentric-only, and concentric-eccentric resistance training of the elbow flexors for their effects on muscle strength and hypertrophy

Purpose This study compared concentric-eccentric coupled (CON-ECC), concentric-only (CON), and eccentric-only (ECC) resistance training of the elbow flexors for their effects on muscle strength and hypertrophy. Methods Non-resistance-trained young adults were assigned to one of the four groups: CON-ECC (n = 14), CON (n = 14) and ECC (n = 14) training groups, and a control group (n = 11) that had measurements only. The training group participants performed dominant arm elbow flexor resistance training in extended elbow joint angles (0 degrees-50 degrees) twice a week for 5 weeks. The total training volume (dumbbell weight x number of contractions) in CON-ECC (5745 +/- 1020 kg) was double of that in CON (2930 +/- 859 kg) and ECC (3035 +/- 844 kg), because 3 sets of 10 contractions were performed for both directions in CON-ECC. Maximum voluntary isometric (MVC-ISO), concentric (MVC-CON), and eccentric contraction (MVC-ECC) torque of the elbow flexors and biceps brachii and brachialis muscle thickness (MT) were measured at baseline, and 3-9 days post-last training session. Results No significant changes in any measures were evident for the control group. The CON-ECC and ECC groups showed increases (P < 0.05) in MVC-ISO (12.0 +/- 15.7% and 11.3 +/- 10.8%, respectively) and MVC-ECC torque (12.5 +/- 18.3%, 16.2 +/- 11.0%) similarly. Increases in MVC-CON torque (P < 0.05) were evident for the CON-ECC (17.5 +/- 13.5%), CON (10.5 +/- 12.8%), and ECC (14.2 +/- 10.4%) groups without a significant difference among groups. MT increased (P < 0.01) after CON-ECC (10.6 +/- 5.4%) and ECC (9.7 +/- 7.2%) similarly, but not significantly after CON (2.5 +/- 4.8%). Conclusions ECC training increased muscle strength and thickness similarly to CON-ECC training, despite the half training volume, suggesting that concentric contractions contributed little to the training effects.