Samuele Marcora

Does sleep really matter for muscle growth? Our new critical review, just pubbed-ahead-of-print in SCJ, takes a deep dive into the evidence linking sleep and muscle hypertrophy. Here’s what we found: Severe sleep deprivation can reduce muscle protein synthesis and negatively affect hormones, strength, and training performance. Moreover, observational research links both short and excessively long sleep with poorer muscle health and greater sarcopenia risk. But here’s the catch: there is surprisingly little direct evidence that habitual sleep duration actually affects resistance training-induced muscle growth. In fact, one of the few longitudinal studies found that sleeping ~1–2 hours less per night did not impair hypertrophy or strength gains over 5 weeks of resistance training in untrained men. So, while adequate sleep almost certainly plays an important role in supporting recovery and training quality, we currently cannot prescribe a specific amount as “optimal” for maximizing hypertrophy. A reasonable starting point appears to be ~7–9 hours per night. However, individual sleep needs likely vary considerably based on the interplay between genetic predispositions and lifestyle factors. Bottom line: The mechanisms suggest sleep matters, but we still need long-term controlled studies—especially in trained lifters—to determine how much it actually affects muscle growth. ovid.com/jnls/nsca-scj/fullt…