The influence of resistance exercise training prescription variables on skeletal muscle mass

Key points

1. 01Resistance training consistently increased muscle mass, strength, and physical function versus no exercise.
2. 02Heavier load (intensity) improved strength but did not clearly increase muscle size.
3. 03Higher training volume helped both strength and muscle growth, with hints of an inverted-U dose-response.
4. 04Weekly frequency mattered for strength when volume was not equated, but had little effect on muscle growth.
5. 05Many other variables (time of day, rest intervals, set configuration, periodization, training to failure) showed little or no measurable impact.

How it was conducted

Design

Umbrella review of systematic reviews and meta-analyses, PRISMA search, AMSTAR quality appraisal

Included reviews

44 reviews (5 systematic reviews, 2 meta-regressions, 35 meta-analyses, 1 network meta-analysis, 1 umbrella review)

Population

Healthy adults

Outcomes

Skeletal muscle mass (hypertrophy), strength, and physical function

Typical intervention

Resistance training programs averaging 6 to 24 weeks duration

What they found

• Hypertrophy with resistance training vs control in young women: SMD = 0.52; 95%CI: 0.20-0.78; p = 0.002.
• Hypertrophy with higher-intensity resistance training in older adults: SMD = 0.199; 95%CI: 0.046-0.343; p = 0.011.
• Load for hypertrophy showed no significant high vs low difference in a network meta-analysis (n = 747): SMD = 0.12; 95%CI: -0.06 to 0.29; p = 0.241; another review SMD = 0.03; 95%CI: -0.08 to 0.14; p = 0.56.
• Higher weekly training volume favored hypertrophy: SMD = 0.241; 95%CI: 0.026-0.457; p = 0.03; 10+ sets/week SMD = 0.520 vs <5 sets/week SMD = 0.307.
• Multiple sets beat a single set for hypertrophy: SMD = 0.11; 95%CI: 0.02-0.19; p = 0.016, with no added benefit from 4-6 vs 2-3 sets (p = 0.29).
• Strength gains with resistance training vs control: upper body SMD = 1.70; 95%CI: 1.28-2.13; lower body SMD = 1.40; 95%CI: 1.03-1.76; p < 0.001.
• Higher load improved strength: high vs low load SMD = 0.60; 95%CI: 0.38-0.82; moderate vs low SMD = 0.34; 95%CI: 0.05-0.62; another review high vs low SMD = 0.34; 95%CI: 0.15-0.52; p = 0.0003.
• Multiple sets beat a single set for strength: SMD = 0.26; p = 0.0001, with 4-6 sets not superior to 1 set (p = 0.17).
• Training to failure showed no clear advantage for strength: SMD = -0.09; p = 0.198, or for hypertrophy: SMD = 0.22; 95%CI: -0.11 to 0.55; p = 0.152.
• Time of day (morning vs evening) did not affect hypertrophy: SMD = 0.20; 95%CI: -0.40 to 0.40; p = 0.958.

Limitations

• Evidence on physical function was sparse, with only one review providing data.
• Effects of many prescription variables (periodization, inter-set rest, set configuration, set end point, contraction velocity) were rated as insufficient evidence.
• Findings synthesize heterogeneous reviews of differing methodological quality (AMSTAR scores ranged 2-10).
• Most included programs were short (6 to 24 weeks), limiting conclusions about long-term adaptation.

Why it matters

For patients

If your goal is to build muscle and get stronger, doing resistance training at all matters far more than fine-tuning the exact program.

For clinicians

Prioritize adequate weekly volume for both strength and size, and reserve heavier loads and higher frequency mainly for strength goals.

For readers

This pooled the best available reviews to show which training variables actually move the needle and which are largely interchangeable.