Lower extremity muscle hypertrophy in response to resistance training in older adults: Systematic review, meta-analysis, and meta-regression of randomized controlled trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 39579806 · doi:10.1016/j.exger.2024.112639
What was done
A systematic review and random-effects meta-analysis of randomized controlled trials was conducted using PubMed, Embase, and Scopus to evaluate the effects of supervised resistance training on knee extensor hypertrophy in adults aged 65 years and older. Outcomes evaluated were muscle size, fiber area, and leg lean mass (LLM), reported as standardized mean differences (SMD) or raw mean differences (RMD). Meta-regression was used to analyze the influence of age, weekly sets, and intervention duration.
What was found
Thirty-two studies were included in the review and 28 were meta-analyzed. Resistance training led to significant increases in muscle size (SMD = 0.34; 95% CI: 0.16 to 0.52; p < 0.001), quadriceps femoris size (95% CI: 0.20 to 0.69; p < 0.001), and fiber area (SMD = 0.54; 95% CI: 0.24 to 0.84; p < 0.001). No significant effect was detected for leg lean mass (RMD = 0.22; 95% CI: -0.22 to 0.66; p = 0.321). Meta-regression found a significant effect of intervention duration on type II fiber area (p = 0.034), but no significant effect of age or weekly sets on any outcome.
Why it matters
This review shows that adults 65 years and older can achieve skeletal muscle hypertrophy at both the whole-muscle and muscle fiber levels with resistance training. It also suggests that gross leg lean mass measurements may not adequately capture localized muscle growth.
Limits
The abstract does not report the total participant count across studies, training intensities, or adherence rates. Measures of whole-leg lean mass failed to reflect the hypertrophic changes observed directly in muscle imaging and biopsy specimens.