Sleep is it important?

The question is how much does sleep effect muscle hypertrophy and strength? And can this be offset by perfect nutrition?

So first we need to know the conditions required for muscle hypertrophy to occur. There are three mechanisms of hypertrophy. Mechanical tension, metabolic stress and muscle damage. Mechanical tension means muscular force. Mechanical tension is higher with heavier loads as the muscles can contract with more force against a heavy load. Metabolic stress = the pump this happens when the muscle is kept under tension for a period of time and is a result of restricted venous return, so the blood pools in the muscle giving it that pumped full look. Muscle damage occurs with an increase in the volume of your traditional training. Too much and you will be overly sore. The best hypertrophy programs ensure that none of these are left out of the program depending on the phase or the block which you are currently in. We also need to ensure we are in a calorie surplus as we need to extra calories to allow our body to build to build the new tissue. After this it comes down to rest we must time our sessions in such a fashion that we allow adequate recovery between sessions so that the muscle can recover and rebuild. But we don't want to wait too long or detraining can occur, and we could lose the muscle tissue we worked hard to build. Writing a good hypertrophy program is a delicate balancing act between using the correct process depending on where you are in your yearly cycle, the degree of surplus and the frequency of the training sessions.

Now I attempted to keep this as short as possible but in order to know precisely how sleep effects muscle hypertrophy and performance we need to take a more detailed look into what hypertrophy is and what happens on a deeper level.

What is Muscular Hypertrophy?

Muscular hypertrophy is an increase in the cross-sectional area of a muscle. The increase is a result of sarcoplasmic hypertrophy caused by increases of sarcoplasmic fluid with the muscle cell and myofibril hypertrophy and increases in actual actin and myosin contractile proteins.

The Physiology of Skeletal Muscle Hypertrophy

Satellite Cells

Satellite cells function to facilitate growth, maintenance and repair of damaged muscle tissue. These cells are called satellite cells because where they are located. Satellite cells are located on the outer surface of the muscle fibre, (a bit like a satellite in the outer atmosphere ).

Usually, these cells are dormant, but they become activated when the muscle fibre's become subject to trauma, damage or injury which is exactly what's happening when you push them past their current threshold during resistance training. The satellite cells then multiply, and the daughter cells are drawn to the damaged muscle site. They then fuse to the existing muscle fibre, donating their nuclei to the fibre, which helps to regenerate the muscle fibre. It is important to emphasise the point that this process is not creating more skeletal muscle fibres, but increasing the size and number of contractile proteins within the muscle fibre. This satellite cell activation and proliferation period last up to 48 hours after the trauma or shock from the resistance training session stimulus.


Resistance exercise causes trauma to skeletal muscle. This trauma causes the immune system to respond with a complex sequence of immune reactions leading to inflammation. The purpose of the inflammation response is to contain the damage, repair the damage, and clean up the injured area of waste products. In response to the trauma, macrophages move to the site and secrete cytokines, growth factors and other substances. Cytokines are responsible for protein breakdown and removal of damaged muscle tissue

Growth Factors

Growth factors are highly specific proteins, which include hormones and cytokines. Growth factors stimulate the division and differentiation of a particular type of cell. Regarding skeletal muscle hypertrophy, growth factors of specific interest include insulin-like growth factor (IGF), fibroblast growth factor (FGF), and hepatocyte growth factor (HGF). These growth factors work in conjunction with each other to cause skeletal muscle hypertrophy.

Insulin-Like Growth Factor

IGF is a hormone that is secreted by skeletal muscle. It regulates insulin metabolism and stimulates protein synthesis. There are two forms, IGF-I, which causes proliferation and differentiation of satellite cells, and IGF-II, which is responsible for the proliferation of satellite cells. In response to progressive overload resistance exercise, IGF-I levels are substantially elevated, resulting in skeletal muscle hypertrophy.

Fibroblast Growth Factor

FGF is stored in skeletal muscle. FGF has nine forms, five of which cause proliferation and differentiation of satellite cells, leading to skeletal muscle hypertrophy. The amount of FGF released by the skeletal muscle is proportional to the degree of muscle trauma or injury.

Hepatocyte Growth Factor

HGF is a cytokine with various cellular functions. Specific to skeletal muscle hypertrophy, HGF activates satellite cells.

Hormones in Skeletal Muscle Hypertrophy

Hormones are chemicals which organs secrete to initiate or regulate the activity of an organ or group of cells in another part of the body. It should be noted that hormone function is decidedly affected by nutritional status, foodstuff intake and lifestyle factors such as stress, sleep, and general health. The following hormones are of particular interest in skeletal muscle hypertrophy.

Growth Hormone

Growth hormone (GH) is a peptide hormone that stimulates IGF in skeletal muscle, promoting satellite cell activation, proliferation and differentiation.


Cortisol is a steroid hormone which is produced in the adrenal cortex of the kidney. It is a stress hormone, which stimulates gluconeogenesis, which is the formation of glucose from sources other than glucose, such as amino acids and free fatty acids.

Side note to those who follow a keto based diet. Your body has the trump card that is gluconeogenesis yep; it can create glucose from other substances like protein. Glucose is the primary energy source for the brain.

Cortisol also inhibits the use of glucose by most body cells. This can initiate protein catabolism (break down), thus freeing amino acids to be used to make different proteins, which may be necessary and critical in times of stress.

In terms of hypertrophy, an increase in cortisol is related to an increased rate of protein catabolism. Therefore, cortisol breaks down muscle proteins, inhibiting skeletal muscle hypertrophy.


Testosterone is an androgen or a male sex hormone. The primary physiological role of androgens is to promote the growth and development of male organs and characteristics. Testosterone affects the nervous system, skeletal muscle, bone marrow, skin, hair and the sex organs.

With skeletal muscle, testosterone, which is produced in significantly greater amounts in males, has an anabolic (muscle building) effect. This contributes to the gender differences observed in body weight and composition between men and women. Testosterone increases protein synthesis, which induces hypertrophy.

So we hit the gym perform some resistance training this causes trauma to the muscles we trained in the 24-72hr's post exercise the body begins its response to this trauma by via the process described above. Now in an attempt to adapt to this trauma, the body becomes a little stronger/resilient so if the same trauma occurs its equipt to deal with it without the need for a trauma response this repeated over time is what causes hypertrophy.

Now let's look at how sleep can affect this.

Sleep is essential for the cellular, organic and systemic functions of an organism, with its absence being potentially harmful to health and changing feeding behaviour, glucose regulation, blood pressure, cognitive processes and some hormonal axes. Among the hormonal changes, there is an increase in cortisol secretion, and a reduction in testosterone and Insulin-like Growth Factor 1as we just discussed the last thing that we want to do is increase cortisol as it initiates protein catabolism and decreases both testosterone and IGF-1 both of which are responsible for muscle hypertrophy. Consequently, we could say that a sleep debt decreases the activity of protein synthesis pathways and increases the activity of degradation pathways, favouring the loss of muscle mass and thus hindering muscle recovery and growth after damage induced by exercise

I was unable to find a study where sleep deprivation wasn't negatively associated with performance although there may be some ( please send me them I'd love to read them ) the overwhelming majority is going to suggest that depriving sleep won't improve the recovery and growth of muscle tissue following exercises induced damage.

However, sleep is the one thing that most people are unwilling to improve. They will eat the right foods. They will never miss training. However, a lot of people take sleep for granted. If you're trying to get stronger, leaner and more athletic, then you just cannot afford to miss this vital piece of the puzzle, or you are simply fighting a losing battle with yourself. Because of the way sleep debt effects hormal factors I would say it would be impossible to eat your way out of this problem.

My best advice is to work on ensuring the sleep you do get is maximised. Get off your phone you don't really need to see what your mate had for dinner or read another one of the 10,000 motivational quotes you have already seen today. Make sure your room is as dark as possible. Avoid caffeine post 4 pm trust me you don't need to be washing down your third scoop of pre-workout with a monster. If you still struggle to sleep just read one of my blogs it will either bore you into sleep, or you will learn something, that's a win-win in my opinion.

Want a training question answered? Just send me and email at or send us a DM on instagram.

If this benefited you in any way please share to help us grow and help more people.


Recent Posts

See All