Ashwagandha, scientifically known as Withania somnifera, is an ancient adaptogenic herb used in Ayurvedic medicine. It is now popular in contemporary health and fitness communities due to its purported ability to enhance physical performance, manage stress, and influence muscle development. This interest has prompted scientific investigation into whether this supplement can truly contribute to measurable increases in physical size. This article examines the current scientific evidence regarding these claims of muscle hypertrophy.
The Direct Link to Muscle Hypertrophy
Clinical research suggests that Ashwagandha supplementation combined with resistance training provides significant gains in muscle size and strength compared to exercise alone. One double-blind, placebo-controlled study involving young men showed substantially greater improvements in the supplemented group. After eight weeks, the men taking Ashwagandha had an average increase of 8.6 cm² in arm muscle area, significantly higher than the 5.3 cm² increase seen in the placebo group.
This enhanced muscle growth was accompanied by a greater increase in strength performance. The Ashwagandha group experienced a greater increase in their bench press one-repetition maximum (1-RM) and leg extension strength compared to the placebo group. These findings indicate that the herb facilitates actual physical growth, or hypertrophy, in trained muscles, not just improved strength.
Another study documented that individuals taking 300 mg of Ashwagandha root extract twice daily for eight weeks saw notable enhancements in bench press strength. The supplemented group had a mean increase of 46.0 kg compared to 26.4 kg in the placebo group. This difference in measurable strength and size gains strongly supports the idea that the herb acts as a beneficial physiological aid during structured resistance training, leading to larger muscles.
Mechanism of Action: How Ashwagandha Supports Muscle Growth
The positive effects on muscle size and strength are attributed to Ashwagandha’s influence on several key physiological pathways. As an adaptogen, the herb helps the body manage stress by modulating the hypothalamic-pituitary-adrenal (HPA) axis. This action reduces the stress hormone cortisol, a catabolic hormone that breaks down muscle tissue. By lowering chronic cortisol levels, Ashwagandha helps shift the body into a more favorable anabolic, or muscle-building, state.
The supplement is also associated with supporting healthy testosterone levels, particularly in men. Testosterone is a primary anabolic hormone responsible for stimulating muscle protein synthesis, the process by which muscle fibers repair and grow larger. In studies involving men undergoing resistance training, Ashwagandha supplementation has been shown to increase total serum testosterone levels by approximately 15% to 17% compared to placebo groups. This hormonal support helps explain the greater strength and size increases observed.
Ashwagandha supports muscle growth by enhancing recovery after intense exercise. The root extract reduces markers of exercise-induced muscle damage, such as the enzyme creatine kinase, which leaks into the bloodstream when muscle fibers are damaged. By stabilizing these markers, the herb minimizes post-workout muscle breakdown and inflammation, allowing for faster repair and more consistent, high-quality training sessions. This enables athletes to train harder and more frequently, which are necessary conditions for greater hypertrophy.
Dosage, Timing, and Safety Considerations
For individuals using Ashwagandha to support muscle growth, research points to a standardized dosage range. Most clinical trials demonstrating significant effects have used a daily dose between 300 mg and 600 mg of a high-quality root extract. This daily amount is typically split into two doses to maintain consistent levels in the body, often taken morning and evening.
Consistency is more important than the exact timing relative to a workout; the herb should be taken daily for several weeks to see benefits. The extract should be standardized to contain a specific concentration of the active compounds, known as withanolides, to ensure potency. Specific branded extracts, such as KSM-66, are often used in research because they guarantee this standardization.
Ashwagandha is generally well-tolerated at recommended dosages, but some individuals may experience mild side effects. These can include digestive upset (diarrhea or nausea) and occasionally drowsiness or fatigue. If drowsiness occurs, it is best to take the full daily dose closer to bedtime.
There are certain contraindications where the herb should be avoided or used only under medical guidance. Due to its potential to modulate thyroid hormone levels, individuals with existing thyroid conditions should consult a healthcare provider. The herb is also not recommended for women who are pregnant or breastfeeding, and those with autoimmune disorders should exercise caution, as Ashwagandha may stimulate immune function.