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 (VO 2 max), 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; VO 2 max: 9.99 vs. 6.64 mL/kg/min; p < 0.001), and sustained till day 91 (1-RM: 15.31 vs. 7.33 kg; VO 2 max: 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 .