Short inter-set rest blunts resistance exercise-induced increases in myofibrillar protein synthesis and intracellular signalling in young males.

Plain-language summary

This study set out to see whether shorter rest periods between sets of resistance exercise boost muscle growth signals more than longer rests. Sixteen young men did leg exercises at 75% of their max strength, with either 1-minute or 5-minute rests between sets, then had muscle biopsies to measure protein synthesis and growth signals. While both groups saw a rise in muscle protein synthesis after exercise, the 5-minute rest group had a much larger increase (152% vs. 76%) in the first few hours, along with better activation of key growth pathways, despite the shorter rest group showing higher testosterone and lactate levels.

Key findings

• 5-minute rests between sets led to a 152% rise in muscle protein synthesis in the first 4 hours post-workout, vs. 76% with 1-minute rests.
• Key muscle growth signals (p70S6K, rpS6) were stronger with 5-minute rests.
• Shorter rests raised post-workout testosterone and lactate more but blunted growth signals.
• By 24-28 hours, protein synthesis rates evened out between groups.