Phytoecdysteroids, particularly 20-hydroxyecdysone found in plants like Ajuga turkestanica and spinach, have been studied for their potential anabolic effects on muscle tissue. Several animal studies and a limited number of human trials suggest that phytoecdysteroids may enhance muscle protein synthesis and increase muscle mass or improve muscle tone. For example, a 2008 Journal of Steroid Biochemistry & Molecular Biology study found that ecdysterone increased muscle fiber size and grip strength in rats. Further, a 2019 randomized controlled trial published in Archives of Toxicology indicated that ecdysterone supplementation in humans led to greater increases in muscle mass and strength compared to placebo during resistance training.

The proposed mechanisms involve activation of the PI3K/Akt signaling pathway, which is crucial for muscle growth. However, the body of evidence remains limited, with relatively few high-quality human studies, small sample sizes, and short intervention durations. While some positive results have been observed, systematic reviews and regulatory agencies do not yet universally endorse phytoecdysteroids for muscle tone enhancement due to insufficient and heterogeneous data.

In summary, there is emerging scientific evidence supporting the use of phytoecdysteroids for improving muscle tone, but current research is not robust enough for strong clinical recommendations. More rigorous, large-scale human studies are needed to conclusively establish efficacy and safety.