Effects of very short rest periods on hormonal responses to resistance exercise in men.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 20555276 · doi:10.1519/JSC.0b013e3181ddb265
What was done
Ten experienced resistance-trained men (mean age 20.37 ± 2.24 years, body mass 65.5 ± 26.70 kg) completed three resistance exercise sessions in a randomized crossover design with inter-set rest intervals of 60 seconds (P60), 90 seconds (P90), or 120 seconds (P120). Each session consisted of 4 sets of squat and bench press to failure at 85% of 1-repetition maximum. Blood draws were collected pre-exercise (T0), immediately post-exercise (T1), and 30 minutes post-exercise (T30) to measure serum growth hormone, testosterone, and blood lactate.
What was found
Immediately post-exercise (T1), serum growth hormone concentration was significantly higher in P60 (64%) compared with P120. Serum testosterone concentrations at T1 were significantly higher in P120 (65%) and P90 (76%) compared with P60 (p <= 0.05). Blood lactate concentrations increased significantly at T1 across all three conditions without significant between-protocol differences. Training volume was numerically greater with P90 and P120 than P60, but this difference was not statistically significant.
Why it matters
This study shows that inter-set rest duration differentially alters acute endocrine responses, with shorter rest favoring immediate growth hormone release and longer rest favoring testosterone elevations.
Limits
The sample size was small (n = 10) and limited to young, trained men. The study assessed only acute hormonal changes up to 30 minutes post-exercise, without evaluating muscle protein synthesis, chronic muscle hypertrophy, or strength outcomes.
Cited by
- contradicts Shorter rest intervals between sets promote greater acute post-exercise elevations in growth hormone, testosterone, and IGF-1.