When people who’ve never lifted weights before do leg exercises with either 20-second or 2-minute breaks between sets—while doing the same total amount of work—their thigh muscles grow about the same amount.
Scientific Claim
In untrained young men, 20-second and 2-minute inter-set rest intervals during volume-load-equated unilateral knee-extension resistance training over 10 weeks are associated with comparable increases in rectus femoris cross-sectional area (14.3% vs. 16.7%), suggesting rest duration may not be a critical variable for hypertrophy when total training volume is controlled.
Original Statement
“No significant differences were observed between conditions for the changes in cross-sectional area of the rectus femoris (SHORT = 14.3%; LONG = 16.7%; diff: 0.30 cm2 [95% CI − 0.77, 1.37]; P = 0.587)”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The study used a within-subject design with direct measurements (MRI) and reported precise effect sizes and confidence intervals. The language 'no significant differences were observed' is appropriate for the design and avoids causal inference.
Evidence from Studies
Supporting (1)
When two groups of guys did the same amount of leg work but rested for either 20 seconds or 2 minutes between sets, both groups grew their thigh muscles about the same amount — so how long you rest doesn’t seem to matter if you do the same total work.