Narsingh Verma, Sandeep Kumar Gupta, Sayali Patil, Shashank Tiwari, Ashok Kumar Mishra. Effects of ashwagandha ( Withania somnifera) standardized root extract on physical endurance and VO 2max in healthy adults performing resistance training: an eight-week, prospective, randomized, double-blind, placebo-controlled study. 2024 Apr 8:12:335.

Withania has a long history of use in Ayurvedic medicine and has since gained a reputation in the West for its adaptogenic properties. A growing demand for safe and effective herbal support for the improvement of endurance and strength performance among athletes, including recreational athletes, has cast a spotlight on Withania as a candidate to improve vigour, strength and stamina in such individuals.

Can Withania Enhance Physical Performance?

An eight-week, randomised, double-blind, placebo-controlled study investigated the effects of 300 mg standardised Withania root extract (>5% withanolides), taken twice daily as capsules with milk or water, on muscle size, strength and cardiorespiratory endurance following resistance training. Eighty healthy male and female participants aged 18 to 45 years who engaged in regular physical activity participated in this study. They were evenly allocated to Withania and placebo groups. All participants performed eight weeks of resistance training every alternate day with one day of complete rest per week. Study outcomes included muscle strength (one repetition maximum [1RM] bench press and leg extension), muscle size (circumference of arm, chest and upper thigh) and cardiorespiratory endurance (VO_2max), assessed at baseline and after eight weeks. Analysis of covariance (ANCOVA) was used to estimate adjusted differences based on sex, body mass index (BMI) and chest circumference at baseline.

The Results

In total, 37 participants from the Withania group and 36 from the placebo group completed the study (others excluded due to poor treatment compliance). The Withania group saw greater improvements in bench press (males effect size [ES] 0.91 p=0.0084; females ES 1.56 p=0.0005; total ES 1.14 p<0.0001), leg press (males 1.22 p=0.0049; females 0.63 p=0.018; total ES 1.11 p=0.0005) and endurance (males p<0.0001; females p<0.0001) compared to placebo. A within-group analysis in the Withania group demonstrated a significant (p<0.0001) increase of 23.5% and 22.8% in 1RM bench press and an increase of 15% and 9.9% in 1RM leg press over time and in both male and female participants, respectively. As for VO_2max, in the Withania group, a statistically significant 9.5% and 7% increase was observed over time in both males (p<0.0001) and females (p<0.0001), respectively.

At the end of the study, there was a significant increase in both chest (total p=0.019) and arm (total p<0.0001) but not thigh circumference in the Withania group, as compared to the placebo group. Improvements in muscle girth for chest (males p<0.0001; females p<0.0001), arm (males p<0.0001; females p<0.0001) and thigh (males p=0.0003; females p<0.0001) were seen in both male and female participants within the Withania group. This is important to acknowledge since data on training in females is scarce.

Was it Safe?

No adverse events were reported in the study. The authors acknowledged their oversight in failing to anticipate data loss due to loss to follow-up; and regarded milk consumption as a limitation, as milk may enhance protein synthesis and could have affected some of the parameters of interest. In addition, Withania’s impact on stress and sleep were not measured in this study nor was food intake, although participants were instructed not to change and follow the specified diet for the duration of the study. Extrapolating these findings to other groups for longer durations should be done with caution. Future studies should include a comprehensive dietary analysis participants' daily calorie and protein consumption, as well as a longer-term follow-up with diverse populations.

The Final Verdict

Eight weeks of Withania root extract supplementation along with resistance training can effectively enhance muscle strength, growth and endurance in resistance-trained male and female participants.