Effects of Ashwagandha (Withania somnifera) on Physical Performance: Systematic Review and Bayesian Meta-Analysis

Systematic review with Bayesian meta-analysis of randomized and some non-randomized trials in healthy adults with varying training status, including untrained, recreationally active, and strength-trained participants. Thirteen studies met review criteria and 12 were included in the quantitative analysis, with 615 healthy adults represented across the studies analyzed.

Ashwagandha (Withania somnifera) was given orally in a wide range of regimens across included trials, most commonly 120 to 1250 mg/day for 28 days to 12 weeks. Formulations included root extract products such as KSM-66, Sensoril, Shoden/ARLE Shoden, and aqueous root extract preparations, typically compared with placebo.

Ashwagandha showed a beneficial overall effect on physical performance outcomes versus placebo. For strength and power, the pooled effect was d unb = 0.68 (95% CI 0.40 to 0.95) and the Bayesian estimate was mu = 0.67 (95% CrI 0.28 to 1.04). For cardiorespiratory fitness, the exploratory pooled effect was d unb = 1.37 (95% CI 0.26 to 2.48), and after excluding an outlier it was d unb = 1.85 (95% CI 1.40 to 2.31). For fatigue and recovery, the pooled effect favored Ashwagandha with d unb = -1.17 (95% CI -3.01 to -1.049) and Bayesian mu = -1.18 (95% CrI -1.70 to -0.63), where negative values indicate less fatigue and better recovery. The authors concluded that the probability of a beneficial effect on physical performance is very high.

The evidence base was small and heterogeneous, with only 13 eligible studies and 12 contributing to meta-analysis. Trials used different populations, durations, doses, and Ashwagandha formulations, and some outcomes required outlier handling or exploratory analyses. The authors noted that more comparable research in exercisers and athletes is needed to obtain a more stable estimate of the true effect.