Efficacy and safety of a sustained release ashwagandha root extract capsules on muscle strength and cardiorespiratory endurance in recreationally active individuals: a randomized, double-blind, placebo-controlled trial.

INTRODUCTION: Previous studies suggest that conventional Ashwagandha (Withania somnifera) root extracts may improve physical performance in both athletic and non-athletic populations. However, evidence on sustained-release ashwagandha formulations is lacking. This randomized double-blind, placebo-controlled trial evaluated the safety and efficacy of sustained-release ashwagandha root extract (AshwaSR) 300 mg in improving muscle strength in recreationally active healthy individuals. METHODS: Eligible participants aged 25-50 years received AshwaSR 300 mg or placebo capsules once daily for 90 days. Changes in one-repetition maximum (1-RM) bench press, maximal oxygen uptake (VO2max), serum testosterone, creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations, and quality of life (QoL using SF-12 questionnaire) from baseline till study end were evaluated. RESULTS: Of 84 enrolled participants, 83 completed the study (AshwaSR, n = 41; Placebo, n = 42). Compared with placebo, participants receiving AshwaSR demonstrated significantly greater improvements in muscle strength and cardiorespiratory endurance starting from day 30 (1-RM: 4.69 vs. 2.23 kg; VO2max: 9.99 vs. 6.64 mL/kg/min; p < 0.001), and sustained till day 91 (1-RM: 15.31 vs. 7.33 kg; VO2max: 30.56 vs. 18.14 mL/kg/min; p < 0.001). In the AshwaSR group, total testosterone levels significantly increased from baseline to day 90 among men (mean increase = 121.43 ng/dL; p = 0.024); while the improvement in testosterone levels among women was non-significant (13.34 ng/dL; p = 0.545) and remained within normal reference ranges. The mean changes for total testosterone were similar between AshwaSR and placebo groups (p > 0.05). AshwaSR group reported significantly improved quality of life at day 91 compared to placebo group (Mental component: 7.72 vs. - 4.66; p < 0.001; Physical component: 5.23 vs. - 1.91; p < 0.001). Reported adverse events in both groups were mild and transient in nature. CONCLUSION: Three-months supplementation with AshwaSR 300 mg/day was safe and effective in improving muscular strength, cardiorespiratory endurance, and overall wellbeing in recreationally active healthy adults. CLINICAL TRIAL REGISTRATION: CTRI/2025/04/084383, https://ctri.nic.in.