Effect of daily 3-s maximum voluntary isometric, concentric, or eccentric contraction on elbow flexor strength.

The present study compared a 3-s isometric maximal voluntary contraction (MVC), concentric MVC and eccentric MVC of the elbow flexors performed daily for 5 days a week for 4 weeks for changes in muscle strength and thickness. Young sedentary individuals were assigned to one of three training groups (n = 13 per group) that performed either 3-s isometric, concentric, or eccentric MVC once a day for 20 days, or to a control group (n = 10) that had measurements without training. The participants in the isometric group performed isometric MVC at 55° (0.96 rad) elbow flexion, and those in the concentric or eccentric group performed concentric MVC or eccentric MVC between 10° (0.17 rad) and 100° (1.75 rad) elbow flexion at 30°/s (0.52 rad/s) on an isokinetic dynamometer. MVC isometric torque at 20° (0.35 rad), 55° (0.96 rad), and 90° (1.57 rad) elbow flexion, MVC concentric and eccentric torque at 30°/s (0.52 rad/s) and 180°/s (3.14 rad/s), and muscle thickness (MT) of biceps brachii and brachialis were measured before and several days after the 20th exercise session. The control group did not show any changes. The eccentric group showed increases (p < 0.01) in isometric (three angle average: 10.2 ± 6.4%), concentric (two velocity average: 12.8 ± 9.6%), and eccentric MVC torque (12.2 ± 7.8%). An increase (p < 0.05) was limited for isometric MVC torque (6.3 ± 6.0%) in the concentric group, and for eccentric MVC torque (7.2 ± 4.4%) in the isometric group. No significant changes in MT were evident for all groups. Performing one 3-s MVC a day increased muscle strength, but eccentric MVC produced more potent effects than isometric or concentric MVC.

Greater effects by performing a small number of eccentric contractions daily than a larger number of them once a week.

Our previous study found that one maximal voluntary eccentric contraction (MVC-ECC) performed daily for 5 days a week for 4 weeks increased MVC-ECC, isometric (MVC-ISO), and concentric contraction (MVC-CON) torque of the elbow flexors more than 10%. The present study investigated the effects of six maximal voluntary eccentric contractions on the MVC torques and biceps brachii and brachialis muscle thickness (MT). Thirty-six healthy young adults were placed to one of the three groups (N = 12 per group); the 6 × 1 group that performed one set of six contractions once a week, the 6 × 5 group that performed one set of six contractions a day for 5 days a week, and the 30 × 1 group that performed five sets of six contractions a day in a week. The training duration was 4 weeks for all groups, and changes in MVC-ECC, MVC-CON and MVC-ISO torque, and MT before and after the 4-week training were compared among the groups. The 6 × 1 group did not show significant changes in muscle strength and MT. Significant (p < 0.05) increases in MVC-ECC (13.5 ± 11.5%), MVC-ISO (9.3 ± 5.5%), MVC-CON torque (11.1 ± 7.4%) were evident for the 6 × 5 group only, and increases in MT were found for the 6 × 5 (10.4 ± 4.4%) and 30 × 1 (8.0 ± 5.8%) groups without a significant difference. These results suggest that performing a small number of eccentric contractions 5 days a week is more effective for increasing muscle strength than performing a larger volume of eccentric contractions once a week. However, it appears that training volume is a factor for muscle hypertrophy in a short-term training.

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°-50°) twice a week for 5 weeks. The total training volume (dumbbell weight × 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.