Resistance exercise load does not determine training-mediated hypertrophic gains in young men.
Level 2 - randomized trial
Randomized controlled trial (within-subject design)
PubMed 22518835 · doi:10.1152/japplphysiol.00307.2012
What was done
Eighteen young men (mean age 21 ± 1 yr, BMI 22.6 ± 2.1 kg/m²) had their legs randomly assigned to two of three unilateral training conditions differing in intensity and volume: 30% of 1RM for 3 sets (30%-3), 80% of 1RM for 1 set (80%-1), or 80% of 1RM for 3 sets (80%-3). Subjects trained 3 times per week for 10 weeks. Outcomes included pre- and post-training muscle volume measured by magnetic resonance (MR) imaging, isotonic and isometric strength, and vastus lateralis biopsies pre-, post-training, and 1 hour following the first exercise bout to measure signaling protein phosphorylation.
What was found
MR-measured muscle volume increased significantly across conditions (P < 0.01) with no significant difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3 = 7.2 ± 1.9% (P = 0.18). Isotonic maximal strength gains did not differ between 80%-1 and 80%-3, but both were greater than 30%-3 (P = 0.04). Isometric strength gains were significant across groups with no between-condition differences (P = 0.92). Acute phosphorylation of p70S6K increased 1 hour post-exercise only in 80%-1 and 80%-3 conditions (P < 0.05). There was no correlation between phosphorylation of any signaling protein and hypertrophy.
Why it matters
This study demonstrates that lifting lighter loads to failure stimulates similar muscle hypertrophy as heavy loads, challenging the notion that heavy resistance is strictly necessary for muscle growth, though heavy loads remain superior for isotonic strength.
Limits
The sample was small (n = 18) and limited exclusively to young healthy men. The unilateral leg training model may not reflect whole-body multi-joint training responses, and the study was limited to 10 weeks of training.
Cited by
- supports A circa 2012 study by Stuart Phillips showed no difference in whole-muscle hypertrophy between 30% 1RM and 80% 1RM in untrained subjects performing leg extensions.