When it comes to building muscle and improving performance, resistance training and protein intake are rightly considered the primary drivers of progress. But one often-overlooked factor plays a key supporting role in the background: sleep. While it doesn’t directly trigger muscle growth, sleep — when paired with adequate nutrition — helps create the hormonal and recovery environment that allows muscle protein synthesis to occur efficiently, ultimately supporting long-term physical gains.

Understanding Protein Synthesis

Protein synthesis is the biological process through which cells build new proteins, which are essential for muscle repair and growth after exercise-induced damage. This process is stimulated by resistance training and supported by dietary protein intake, especially amino acids like leucine. However, for the body to maximise the benefits of this process, it requires optimal hormonal and physiological conditions — many of which are achieved during sleep.

Sleep: More Than Just Recovery

Sleep is divided into several stages, including REM (Rapid Eye Movement) and non-REM stages. The deep stages of non-REM sleep, particularly slow-wave sleep (SWS), are when the body enters a restorative mode. During these stages, the pituitary gland releases significant amounts of growth hormone which contributes to tissue repair and metabolic functions. While growth hormone doesn’t directly drive muscle protein synthesis in adults, it supports the broader recovery processes that help the body adapt to training over time.

Sleep also supports the regulation of other anabolic (muscle-building) hormones such as testosterone and insulin-like growth factor 1 (IGF-1). These hormones work synergistically to enhance the rate at which muscles recover and grow. On the flip side, sleep deprivation can elevate levels of cortisol, a catabolic hormone that breaks down muscle tissue and impairs recovery.

The Impact of Sleep on Muscle Gains

Research has consistently shown that poor sleep — in terms of both quantity and quality — can hinder muscle recovery and growth. A lack of sleep disrupts the hormonal environment necessary for protein synthesis. For example, studies have found chronic sleep restriction leads to sustained reductions of testosterone which can stall progress in muscle gain.

Furthermore, insufficient sleep can impair muscle coordination, reduce motivation to train and increase the risk of injury. All of these factors indirectly but significantly affect long-term progress in strength and hypertrophy.

Optimising Sleep for Better Results

For individuals serious about maximising muscle recovery and protein synthesis, here are some targeted strategies for optimising the anabolic effects of sleep:

  • Leverage the Post-Workout Sleep Window
    Training late in the day can disrupt sleep if cortisol remains elevated. To counter this, schedule workouts at least two to three hours before bed, or include a post-training cooldown routine that blends light stretching, breathwork or a short walk to normalise cortisol levels. These help downregulate the nervous system, preparing the body for high-quality sleep and efficient protein synthesis.
  • Consider a Protein-Rich Snack Before Bed
    Consuming 30-40g of protein 30–60 minutes before bed has been shown in multiple studies to support overnight muscle repair, particularly in resistance-trained individuals.
  • Track Heart Rate Variability (HRV) to Monitor Recovery Readiness
    Tools like WHOOP can help you understand whether your sleep is truly restorative. Higher HRV scores often indicate greater parasympathetic activity and systemic recovery, which may correlate with better readiness for training. Learn how you can optimise your heart rate variability with expert tips from Dr Sophie Bostock.
  • Establish a Consistent Sleep Schedule
    Individual needs vary between seven to nine hours, but what matters most is consistency and how you feel. Aim to follow a night-time and wake-up routine, even on weekends, and measure the amount you need based on you energy levels the day/s following.

While sleep does not directly drive muscle protein synthesis like resistance training and protein feeding do, it establishes the hormonal and neurological conditions needed for optimal recovery. Chronic sleep restriction disrupts this balance, impairing muscle repair, motivation and training performance. Training creates the stimulus, nutrition supplies the building blocks, but sleep provides the optimal environment for recovery and adaptation to occur.