Influence of Rest Interval Length on Acute Testosterone and Cortisol Responses to Volume-Load–Equated Total Body Hypertrophic and Strength Protocols

Abstract

We hypothesized that total body strength (S) and hypertrophic (H) resistance training (RT) protocols using relatively short rest interval (RI) lengths between sets will elicit significant acute increases in total testosterone (TT) and cortisol (C) in healthy young men. Six men, 26 (±2.4) years, completed 4 randomized RT sessions, after a control session (R). The S and H protocols were equated for volume load (sets × repetitions × load); S: 8 sets × 3 repetitions at 85% 1RM, H: 3 sets × 10 repetitions at 70% 1RM, for all exercises. The RI used 60 seconds (S60, H60) and 90 seconds (S90, H90). Blood was drawn preexercise (PRE), immediately postexercise (POST), 15 minutes postexercise (15 MIN), and 30 minutes postexercise (30 MIN). The H60 elicited significant increases in TT from PRE (7.32 ± 1.85 ng·ml) to POST (8.87 ± 1.83 ng·ml(-1)) (p < 0.01), 15 MIN (8.58 ± 2.15 ng·ml(-1)) (p < 0.01), and 30 MIN (8.28 ± 2.16 ng·ml(-1)) (p < 0.05). The H90 also elicited significant increases in TT from PRE (8.37 ± 1.93 ng·ml(-1)) to POST (9.90 ± 1.25 ng·ml(-1)) (p < 0.01) and 15 MIN (9.46 ± 1.27 ng·ml(-1)) (p < 0.05). The S60 elicited significant increases in TT from PRE (7.73 ± 1.88 ng·ml(-1)) to 15 MIN (8.35 ± 1.64 ng·ml(-1)) (p < 0.05), and S90 showed a notable (p < 0.10) difference in TT from PRE (7.96 ± 2.29 ng·ml(-1)) to POST (8.75 ± 2.45 ng·ml(-1)). All the protocols did not significantly increase C (p > 0.05). Using relatively short RI between RT sets augments the acute TT response to hypertrophic and strength schemes. Shortening RI within high-intensity strength RT may lead to concomitant enhancements in muscle strength and size over a longer period of training.