How Sleep Builds or Destroys Your Muscle

Happy Labor Day! Hope you all are having a beautiful 3 day weekend out in the sun. Let’s talk about something I want you all to be more mindful of entering the new month.

Sleep: the most powerful recovery tool you have. It doesn’t come from the gym or the kitchen (although protein is the 1B to sleep’s 1A) but some of my clients say it's the hardest variable to improve upon. Let’s see if I can convince you to take it more seriously than “yeah I feel like I get enough.” 

Every time you train, you create small amounts of muscle damage. Repairing that damage is how you grow stronger and build muscle. The process is called muscle protein synthesis (MPS), and whether it works in your favor or not depends heavily on your hormones. Sleep is when those hormones align perfectly or fall apart if you’re not getting enough.

During deep sleep, your body enters one of its most anabolic, or muscle building, states. Testosterone peaks at night, especially in the first few hours of sleep, and it’s one of the main drivers of MPS. Without enough sleep, testosterone production falls. In fact, studies show that just one week of sleeping five hours a night can drop testosterone levels by 10–15%. That’s a huge difference when dealing with the limited amount of muscle we are able to build considering we all have stressful jobs, responsibilities, and overall lives. 

Growth hormone (HGH) is another hormone that promotes muscle growth and recovery that is released during deep sleep. HGH has many responsibilities: it stimulates tissue repair, mobilizes fat for energy, and supports recovery at the cellular level. Miss out on deep sleep, and those growth hormone pulses are blunted or missed entirely. That's muscle growth and fat loss you’re missing out on. 

On the other side is cortisol, your stress hormone. Cortisol isn’t bad in small doses, it rises in the morning to help you wake up, but insufficient sleep keeps cortisol elevated at night and throughout the day. Chronically high cortisol slows down MPS, speeds up muscle breakdown, and pushes your body toward storing fat instead of building muscle. The combination of low testosterone, reduced growth hormone, and high cortisol is the exact opposite hormonal environment you want if your goal is strength, performance, or physique changes.

Now, here’s where the amount of sleep really matters. Five hours of sleep is essentially a catabolic (muscle breakdown) state: testosterone and growth hormone suppressed, cortisol elevated. At six hours, things improve slightly, but your anabolic hormones are still significantly reduced. Seven hours is often the bare minimum where testosterone and growth hormone begin to normalize, giving your body a chance to recover. At eight hours, hormones line up optimally, testosterone is higher, growth hormone pulses are more consistent, and cortisol is well-controlled. Nine hours may not be necessary for everyone, but for athletes or people training hard multiple days per week, that extra hour can mean better recovery, performance, and resilience.

But here’s the catch: time in bed isn’t the same as time asleep. If you go to bed at 11 and set your alarm for 7, it feels like eight hours, but by the time you actually fall asleep, wake up during the night, and cycle through light sleep, you may only get six and a half. That difference matters. Six and a half hours of actual sleep looks hormonally a lot like six hours, not seven or eight. Most people overestimate their true sleep by 30–60 minutes, which is why so many think they’re “fine” on less sleep but wonder why progress stalls.

Of course, nutrition still matters and you can’t rebuild muscle without protein. But sleep determines how well your body uses that protein. That is when much of the protein you ate during the day is used to rebuild your muscle. If it doesn’t have that time, you won’t get as much repair as you were planning on getting. Ruh Roh Raggy. 

So people, if you want to maximize recovery, muscle growth, fat loss, and performance, protect your sleep. Get a true seven to nine hours, not just time in bed (this is an important difference), and prioritize sleep quality as much as training and nutrition. Because at the end of the day, muscles are broken down in the gym to be built back in the kitchen and while you sleep. They’re built in the hours of deep sleep that most people (myself included) aren’t getting enough of. 

GET IT!