International Journal of Sports Medicine· 2026Q1
Time course of muscle hypertrophy with and without progressive overload
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- Q1SCImago
- 2026year
Short summary
Progressive overload (PROG) led to a greater increase in muscle cross-sectional area (mCSA) between weeks 9-12 of training compared to training without overload progression (N-PROG), with both protocols showing similar gains up to week 9. The PROG group also maintained higher relative effort (lower RIR) throughout the 12-week study.
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Key points
- Both progressive overload (PROG) and non-progressive overload (N-PROG) resistance training increased muscle cross-sectional area (mCSA) over 12 weeks.
- The increase in mCSA from sessions 18 to 24 was significantly greater in the PROG group (1.22 cm² difference) compared to the N-PROG group.
- The PROG protocol maintained higher relative effort, indicated by lower repetitions-in-reserve (RIR) at later training sessions.
- Overall volume load and perceived exertion were higher in the PROG group.
AI-generated from the title and abstract; the full text is not read.
Abstract
To compare the time course of muscle hypertrophy during resistance training with progressive overload (PROG) or without overload progression (N-PROG), 31 healthy untrained young adults completed a randomized within-subject trial. Each participant trained one leg with PROG and the contralateral leg with N-PROG using unilateral knee extension (3x10–12 repetitions, twice weekly for 12 weeks). Load was progressively adjusted in PROG and kept constant in N-PROG. Muscle cross-sectional area (mCSA) was assessed at Pre and after sessions 6, 12, 18, and 24. A protocol×time interaction was observed for mCSA (p=0.002). Both protocols increased mCSA from Pre to S24 (PROG: 3.36±1.94 cm²; N-PROG: 2.67±1.86 cm²), with no significant between-protocol differences in mCSA at the individual assessment time points. However, the increase in mCSA from S18 to S24 was greater in PROG than in N-PROG (between-protocol difference in change: 1.22 cm², 95% CI 0.59 to 1.84; p<0.001). Repetitions in reserve (RIR) was 0.47±0.61 at S1 and 0.20±0.37 at S24 in PROG, and 1.50±1.11 and 4.08±1.94, respectively, in N-PROG. Overall volume load and perceived exertion were greater in PROG (p<0.001). The PROG protocol maintained high relative effort, and the greater increase in mCSA compared with N-PROG was observed specifically from S18 to S24.
The authors' abstract, as published at the source. International Journal of Sports Medicine, 2026 · DOI ↗
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Field: Orthopedics and Sports Medicine
Orthopedics and Sports MedicineMedicine