Ashwagandha and Muscle Strength and Mass: What the Latest Meta-Analysis of 13 Trials Shows

Ashwagandha (Withania somnifera), also known as Indian ginseng, is one of the most extensively studied plant adaptogens — we cover it more broadly in our entry on ashwagandha, where we discuss its uses in the context of stress and sleep. Over the last decade, ashwagandha has also carved out a distinct, very prominent niche in sports supplementation, marketed as an agent supporting strength, muscle mass, and post-workout recovery in people who train with weights.

The problem with this popularity is that studies on ashwagandha and physical performance cover very different types of exercise — from resistance training, through sprinting, to long-distance aerobic effort — and results don't generalize equally across all these areas. The latest, most comprehensive meta-analysis to date allows this general picture to be broken down into parts and shows where the evidence is strongest, and where it's still far from certain — particularly in the area of strength and muscle mass that interests us here.

This result matters precisely because it breaks down the common, generalized claim "ashwagandha increases strength and muscle mass" into a more precise picture: the strongest and most consistently documented effect is for aerobic endurance, not maximal strength or muscle tissue gain, which are the main goals of most people reaching for this supplement in the context of resistance training.

The meta-analysis identifies exercise type as the strongest factor differentiating effect size, with a clear advantage for aerobic endurance over strength and power. A partial explanation may lie in the mechanism attributed to ashwagandha's adaptogenic action — easing the physiological stress response and a potential effect on parameters related to oxygen utilization and cardiorespiratory fitness, which have been studied more often and in a more standardized way than maximal strength or lean mass gain.

This doesn't mean ashwagandha has no potential in the context of resistance training — the meta-analysis clearly indicates that effects on strength were positive, just with less statistical certainty, likely due to fewer and less homogeneous studies evaluating this specific type of exercise compared with the better-studied aerobic endurance.

This distinction has direct implications for expectations: someone reaching for ashwagandha specifically hoping for gains in bench press strength or muscle mass is relying on the weaker part of the same data that looks considerably more convincing for runners or cyclists.

It's worth separating two different, often confused endpoints: muscle strength (e.g., maximum weight lifted in a given exercise) and muscle mass (growth of muscle tissue measured, e.g., by densitometry methods or limb circumference). The cited meta-analysis focused mainly on objective measures of exercise performance, including strength, and evidence directly concerning muscle mass gain remains sparse and scattered across fewer source studies than evidence on performance.

Earlier, individual clinical studies — not included in this specific meta-analysis, or forming only a small part of it — suggested a favorable effect of ashwagandha on strength gain and muscle circumference in men doing resistance training, but these results haven't yet been confirmed in a sufficiently large, consistent body of studies to speak of a well-established conclusion. This is an area where more well-designed, larger studies are needed before it can be considered more than a preliminary, promising signal.

Ashwagandha is one of the better-studied adaptogens in the context of physical performance, but this latest, most comprehensive meta-analysis mainly teaches caution against generalizations. "Ashwagandha improves sports performance" is too much of a simplification — a more accurate, honest summary would be "ashwagandha has its strongest evidence for aerobic endurance, and for muscle strength it remains a promising but still uncertain direction."