Effects of an Aqueous Extract of Withania somnifera on Strength Training Adaptations and Recovery: The STAR Trial

Withania somnifera (Ashwagandha) is an Ayurvedic herb categorized as having rasayana (rejuvenator), longevity, and revitalizing properties. Sensoril (R) is a standardized aqueous extract of the roots and leaves of Withania somnifera. Purpose: To examine the impact of Sensoril (R) supplementation on strength training adaptations. Methods: Recreationally active men (26.5 +/- 6.4 years, 181 +/- 6.8 cm, 86.9 +/- 12.5 kg, 24.5 +/- 6.6% fat) were randomized in a double-blind fashion to placebo (PLA, n = 19) or 500 mg/d Sensoril (R) (S500, n = 19). Body composition (DEXA), muscular strength, power, and endurance, 7.5 km cycling time trial, and clinical blood chemistries were measured at baseline and after 12 weeks of supplementation and training. Subjects were required to maintain their normal dietary habits and to follow a specific, progressive overload resistance-training program (4-day/week, upper body/lower body split). 2 x 2 mixed factorial ANOVA was used for analysis and statistical significance was set a priori at p <= 0.05. Results: Gains in 1-RM squat (S500: +19.1 +/- 13.0 kg vs. PLA +10.0 +/- 6.2 kg, p = 0.009) and bench press (S500: +12.8 +/- 8.2 kg vs. PLA: +8.0 +/- 6.0 kg, p = 0.048) were significantly greater in S500. Changes in DEXA-derived android/gynoid ratio (S500: +0.0 +/- 0.14 vs. PLA: +0.09 +/- 0.1, p = 0.03) also favored S500. No other between-group differences were found for body composition, visual analog scales for recovery and affect, or systemic hemodynamics, however, only the S500 group experienced statistically significant improvements in average squat power, peak bench press power, 7.5 km time trial performance, and perceived recovery scores. Clinical chemistry analysis indicated a slight polycythemia effect in PLA, with no other statistical or clinically relevant changes being noted. Conclusions: A 500 mg dose of an aqueous extract of Ashwagandha improves upper and lower-body strength, supports a favorable distribution of body mass, and was well tolerated clinically in recreationally active men over a 12-week resistance training and supplementation period.