6-Weeks Resistance Training- And Retraining-Induced Muscle Hypertrophy And Strength Gains In Young Men

Abstract

It is known that resistance training-induced muscle hypertrophy and strength gains are larger during the early phases of training compared to the late phases of training adaptation. However, it is unknown whether the muscular adaptation of retraining following a short term detraining period would be similar to that occurring during the initial training phase. PURPOSE: To investigate the effects of high-intensity resistance training and retraining following a short term detraining period on muscle size and strength. METHODS: 14 previously untrained young men were divided into two training groups: continuous training (CTR, n=7) or training/detraining (DTR, n=7). The subjects participated in high-intensity bench press exercise training (75% of one repetition maximal, 1-RM), 3 days per week for 15 weeks. The CTR group performed continuously over a 15 week period while the DTR group had a 3 week detraining period between wk-7 and wk-9. MRI-measured triceps and pectorals major muscle cross-sectional area (CSA) and maximal dynamic (bench press 1RM) and isometric (elbow extension MVC) strength were measured before and at the end of wk-6, wk-9, and wk-15. RESULTS: After the initial 6 weeks of training, increases (p<0.01) in bench press 1-RM, elbow extension MVC and triceps and pectorals major muscle CSA were similar between the CTR (19%, 11%, 9% and 20%, respectively) and DTR (21%, 14%, 8% and 18%) groups. During the 3 weeks detraining, however, muscle CSA decreased (-3% ∼ -7%, p<0.05) but strength was maintained (-2% ∼ 1%) in the DTR group while muscle size (4∼5%, p<0.05) and strength (∼8%) continued to increase for the CTR group. In the DTR group, the increases in strength and muscle CSA were similar between the initial 6 weeks training and the 6 weeks of retraining (15%, 7%, 7% and 12% [n=5], respectively). On the other hand, training adaptation during the final 6 weeks for the CTR group (8%, 4%, 2% and 3% [n=5], respectively) was significantly lower (p<0.05) compared with the initial 6 weeks of training. As a result, improvements in muscle CSA and strength were similar between the CTR and DTR groups. CONCLUSIONS: Our results suggest that a short term detraining period does not inhibit muscle adaptations when compared to continuous training programs.