Rapamycin May Blunt Exercise Gains in Older Adults, New Trial Finds
A new randomized controlled trial tested whether weekly rapamycin could enhance exercise benefits in older adults by leveraging the 'cycling hypothesis' — the idea that spacing doses around workouts preserves autophagy while allowing muscle adaptation. Forty sedentary adults aged 65–85 took 6 mg rapamycin or placebo weekly alongside a 13-week home exercise program. Both groups improved, but the placebo group consistently outperformed the rapamycin group across multiple fitness measures including chair-stand performance, six-minute walk distance, and grip strength. While the primary endpoint didn't reach statistical significance, two sensitivity analyses did favor placebo. Researchers believe rapamycin's ~62-hour half-life kept mTOR partially suppressed during training windows, undermining muscle adaptation despite the timed dosing strategy.