Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial.
Level 2 - randomized trial
Individual randomized, double-blind, placebo-controlled trial
PubMed 26609282 · doi:10.1186/s12970-015-0104-9
What was done
An 8-week, prospective, double-blind, randomized controlled trial evaluated the effects of Withania somnifera (ashwagandha) root extract on muscle mass, strength, and recovery in 57 healthy men (aged 18–50 years) with little resistance training experience. Participants were randomized to receive either 300 mg of ashwagandha root extract twice daily (n = 29) or a starch placebo twice daily (n = 28) while undergoing a resistance training program. The primary outcome was muscle strength (1-RM bench press and leg extension). Secondary outcomes included muscle size (arm cross-sectional area and chest circumference), body composition (body fat percentage), serum testosterone, and muscle recovery (serum creatine kinase).
What was found
Compared to placebo, the ashwagandha group demonstrated: - Significantly greater 1-RM bench press gains: 46.0 kg (95% CI: 36.6, 55.5) vs. 26.4 kg (95% CI: 19.5, 33.3; p = 0.001). - Significantly greater 1-RM leg extension gains: 14.5 kg (95% CI: 10.8, 18.2) vs. 9.8 kg (95% CI: 7.2, 12.3; p = 0.04). - Greater muscle size increases at the arm (8.6 cm², 95% CI: 6.9, 10.8 vs. 5.3 cm², 95% CI: 3.3, 7.2; p = 0.01) and chest (3.3 cm, 95% CI: 2.6, 4.1 vs. 1.4 cm, 95% CI: 0.8, 2.0; p < 0.001). - Greater increase in serum testosterone: 96.2 ng/dL (95% CI: 54.7, 137.5) vs. 18.0 ng/dL (95% CI: -15.8, 51.8; p = 0.004). - Greater reduction in body fat percentage: 3.5% (95% CI: 2.0%, 4.9%) vs. 1.5% (95% CI: 0.4%, 2.6%; p = 0.03). - Significant differences in post-training serum creatine kinase levels (Placebo: 1307.5 U/L, 95% CI: 1202.8, 1412.1 vs. Ashwagandha: 1462.6 U/L, 95% CI: 1366.2, 1559.1; p = 0.03), reported as stabilization of exercise-induced muscle damage.
Why it matters
This study provides randomized controlled trial evidence that ashwagandha supplementation may augment muscle hypertrophy, strength development, and endocrine response during the initial weeks of a resistance training regimen in untrained men.
Limits
The sample size was modest (57 participants) and restricted entirely to untrained adult males, precluding generalization to women, trained athletes, or older demographics. The trial duration was limited to 8 weeks, leaving long-term efficacy and safety unassessed. Dietary intake and baseline nutritional status were not detailed in the abstract.
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