Ashwagandha Science ashwagandhascience.org

Research summary

Ashwagandha, Strength and Endurance

Key takeaway

In one eight-week training trial, estimated cardiorespiratory endurance and arm and chest circumference favored ashwagandha. Between-group strength-change and thigh-circumference comparisons were not statistically significant; circumference is not a direct measure of muscle tissue.[1]

What these findings do not establish

The study randomized 80 adults and analyzed 73 after compliance exclusions; it used KSM-66 root extract, 300 mg twice daily for eight weeks alongside resistance training. Full-text Tables 3 and 4 do not support the abstract’s broad claim of greater strength improvement. Circumference measurements do not establish increased muscle tissue. This single trial does not establish effects without training, in other populations or with other preparations.[1]

Comparative changes in the training trial

In one randomized placebo-controlled trial of active adults undertaking resistance training, ashwagandha root extract was associated with greater improvements in estimated cardiorespiratory endurance and arm and chest circumference; bench-press and leg-extension strength changes and thigh circumference changes did not differ significantly between groups. The study randomized 80 adults and analyzed 73 after compliance exclusions; it used KSM-66 root extract, 300 mg twice daily for eight weeks alongside resistance training. Full-text Tables 3 and 4 do not support the abstract’s broad claim of greater strength improvement. Circumference measurements do not establish increased muscle tissue. This single trial does not establish effects without training, in other populations or with other preparations.[1]

Safety and medication context

NCCIH does not recommend ashwagandha for people with thyroid or autoimmune disorders or those who are about to have surgery. Discuss these conditions and any planned surgery with your healthcare professional before considering ashwagandha; supplement research does not justify changing prescribed care.[2]

Ashwagandha may interact with medicines for diabetes or high blood pressure, immunosuppressants, sedatives, anticonvulsants, and thyroid hormone medicines. Discuss possible interactions with your prescriber or pharmacist before use; do not stop, replace, or adjust prescribed medicines based on supplement information.[2]

References

  1. 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.. F1000Research. 2024. Randomized controlled trial View source →
  2. Ashwagandha: Usefulness and Safety. NIH National Center for Complementary and Integrative Health. Retrieved 2026-09-30. Government health fact sheet View source →

Read the concise FAQ answer

Use the FAQ when you want the direct answer first, then return here for the full evidence context.

Does ashwagandha build muscle?

The trial reported endurance and arm and chest circumference differences. Its full-text strength-change comparisons were not statistically significant, and circumference is not a direct measure of muscle tissue.

Read FAQ →

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