In frail community-dwelling older adults aged 65 and older, a 12-week protein supplementation intervention combined with supervised resistance training does not significantly improve leg press strength, appendicular lean mass, or physical performance compared to resistance training alone when analyzed across the entire population.

When older adults eat too little protein, their muscles don't get enough building blocks to grow stronger after exercise. Adding more protein helps only if they were eating very little before, because their muscles were not getting enough amino acids to turn on the signal that tells the body to build muscle. If they were already eating enough protein, extra protein does nothing because the signal is already fully turned on.