Unlocking Muscle Growth: How Exercise Influences Hormones

Hormones are signals the body uses to communicate to maintain homeostasis. The endocrine system is based on hormones binding to receptors to communicate. Today we will discuss various hormones and what they communicate, as well as how they can be affected by exercise and lifestyle.

General Adaptation Syndrome

• The adrenal gland responds to stress in three stages.
  • Alarm→Resistance→Exhaustion
  • Stress disturbs homeostasis and stimulates the body to adapt. The body enters the resistance stage releasing hormones to adapt. If the stress is exercise, the result is a training adaptation such as hypertrophy with the release of hormones such as testosterone. Sports scientists use this principle to progressively overload activity to control adaptation.
  • Too much stress without recovery or proper nutrition may lead to overtraining and injury.
• Exercise can signal the growth of strength, muscle, and connective tissue.
  • Training variables such as intensity, sets, rest, and exercise selection can change hormonal responses.

Muscle as the Target of Hormones

• When we exercise, muscle is damaged causing inflammation, marking muscle for repair. Hormonal interactions with muscle fibers stimulate the growth of new proteins and repair.
• Anabolic hormones 
  • Hormones that signal for the building of tissue. Block catabolic hormone messages from cortisol and progesterone which function to break down tissue.
  • Insulin, testosterone, and growth hormone are all examples of anabolic hormones.
• Catabolic hormones
  • Hormones that strive to break down tissues to provide for immediate energy needs. These hormones block the building of tissue and are released with stress.
  • Cortisol, progesterone, epinephrine, and norepinephrine are all examples of catabolic hormones.

Hormone Basics

• Lock and key theory
  • The theory states there is one hormone and one receptor. Hormones can only have a biological effect if a receptor is bound to a target tissue. Receptors can be found on the cell membrane which is acted on by polypeptide hormones or inside the cell cytosol which is bound by steroid and thyroid hormones.
• Downregulation
  • The inability of a hormone to interact with a receptor due to decreased sensitivity or removal of binding sites.
  • For instance, once a muscle is stimulated to grow by a hormone, the introduction of more of that hormone will yield diminishing returns due to decreased sensitivity, or fewer binding sites.
• Upregulation
  • With a stressor such as an exercise, sensitivity, and receptor number can increase as a result of the stimuli. This can be seen in diabetes 2 with increased insulin sensitivity with exercise.

Steroid Hormones

• These are fat-soluble and pass through the cell membrane to act on a receptor inside the cell. Inside, the hormone binds a receptor to form a hormone-receptor complex (HRC)
  • HRC moves to the nucleus to stimulate the DNA to create a copy of the desired protein with messenger RNA. This copy is moved to a ribosome which creates the protein for use. This is how a hormone can change the body’s composition.
• Cortisol 
  • Cortisol is a catabolic hormone that is released from the adrenal cortex in response to stressors. Signals for carbohydrate metabolism and controls glycogen in the muscle.
    • If glycogen is low, proteins will be catabolized to produce energy to maintain blood glucose. This causes the inhibition of protein synthesis and suppression of the immune system. 
      • When we were running away from predators or chasing our own prey, it was important to mobilize glucose in the blood for instant energy, at the expense of long-term health.
  • Cortisol is highly circadian and thus concentration is high earlier in the day and decreases throughout the day.
  • Cortisol’s Response to Exercise
    • Increases acutely in response to inflammation which contributes to the remodeling of muscle and the maintenance of blood glucose. This is because when you train, you damage muscle fibers and cortisol may clean away the damaged fibers to prepare for new proteins.
    • Adaptation to training disinhibits cortisol at the testis allowing testosterone to maintain comparative influence.
    • High-volume short rest results in increased cortisol.
      • Chronic cortisol may cause catabolic effects and Cushing’s syndrome. 
• Testosterone 
  • Testosterone is an anabolic hormone that promotes the building of proteins.
    • Circulating testosterone means nothing unless the hormone can find a receptor. Resting levels may be a marker of motor unit activation, metabolic demand, and receptor binding.
    • Testosterone can stimulate growth hormone from the pituitary which can increase protein synthesis of muscle. Growth hormone may aid in testosterone’s anabolic impact.
    • Testosterone can also bind to neuronal receptors to increase the neurotransmitters that are released, leading to increased force production.
  • Testosterone’s Response to Exercise
    • Perform High-Intensity Interval Training (HIIT)
      • Repeated high-intensity exercise bouts with brief recovery periods. Example: 2-minute run at 95% VO2 max with 2 min walk & jog recovery for 8 repetitions.
      • This exercise is normally catabolic, and testosterone may maintain protein synthesis so we do not lose muscle.
      • Oxidative stress may decrease muscle fiber size to optimize oxygen transport into the cell during HIIT training.
    • Perform resistance exercise
      • Implement large, multi-joint, compound movements such as deadlifts, power cleaning, and squats.
      • The load should be a heavy resistance of 85-95% of 1RM.
      • The volume should be high. For example, 6 sets of 10 reps at 80% of 1RM.
      • Short Rest intervals of 30 sec to 1 min
      • 2 or more years of resistance training experience
    • Testosterone may develop the nervous system in long-term training.
      • Augmenting the neural adaptations that occur for strength and power improvements.
    • Testosterone demographics
      • Younger men below 30 had higher free testosterone after a workout than older men.
      • • • Testosterone in women is 15-20 times less test than in men. A small but significant increase in serum testosterone increase was found in women after 6 sets of 10-rep squats.

Polypeptides/Peptide Hormones

• Made of many amino acids. Polypeptides are not fat soluble so they use secondary messengers on the cell membrane to communicate with cells.
• Insulin
  • Insulin binds to a receptor causing glucose transporters GLUT4 to move from cytosol to cell membrane to allow for glucose uptake into the cell.
• Growth Hormone
  • It is difficult to determine a direct cause-and-effect relationship with GH because it does so many functions and has many chemical structures.
    • However, there is a positive correlation between GH response and muscle fiber hypertrophy following 20 weeks of resistance training.
  • GH function
    • Decreased glucose use and glycogen creation. 
    • Increased amino acid transport, protein, cartilage, and collagen synthesis.
      • These anabolic properties make GH important for tissue healing, growth, and recovery.
    • Increased fatty acids, amino acids, and glucose availability.
      • GH results in conditions that promote tissue repair after exercises break down tissues.
      • The highest levels of growth hormone are known to be at night when we sleep, which is why 7-9 hours is so important.
    • Stimulates insulin-like growth factor I from the liver.
  • GH Response to Stress
    • GH is increased in response to hyperventilation and breath-holding.
      • An intensity threshold of stimuli must be reached to cause GH to be released.
        • For exercise, this means that a load that is too light will not stimulate the release of GH.
        • High loads, long duration of exercise, and lower rest periods yield the best response.
          • A 1-minute rest period between 3 sets of a 10 rep max had a good GH response.
    • Insulin-Like Growth Factors AKA somatomedins
      • GH stimulates the liver to release IGF-1.
        • TH and Testosterone also increase IGF synthesis
        • Travel in the blood with binding proteins and interact with receptors.
          • Nutrition and exercise have been shown to regulate IGF.
            • Pre-workout carbohydrate and protein intake correlated with higher IGF-1 release with exercise.
              • Caloric restriction may blunt IGF-1 release and cause a more catabolic environment.
            • At rest IGF-1 is mostly stored in fat cells with little in skeletal muscle, with mechanical stimulation of muscle cells, muscle releases IGF-1.

Amine hormone 

• Amines hormones are synthesized from the amino acid tyrosine.
• Catecholamines: Epinephrine & norepinephrine
  • Stimulate the fight or flight system. 
    • Increases heart rate, and cardiac output from the heart, and mobilizes glucose in the blood.
    • Improve calcium release in the muscle allowing for strength and power output.
    • Increase muscle blood flow by vasodilation
    • Norepinephrine also constricts blood vessels
  • Catecholamines and Exercise:
    • 3 sets for 10 reps at high intensity with 60-second rest were shown to increase catecholamines.
    • Resistance training has been shown to release epinephrine more during max effort.
    • Long-term stress or overtraining can cause renal exhaustion where catecholamines are depleted. Long-term cortisol can contribute to Cushing’s syndrome which is a cluster of symptoms such as cardiovascular disease and osteoporosis.  

Exercise And Hormones

• Hormones play a large part in growing size, power, and strength.  
• Anticipatory response
  • Hormones are released before exercise due to psychological anticipation.
• Mechanical stress
  • When larger motor units are recruited, the sensitivity and number of muscular receptors changes.
    • It has been found that 1-2 heavy resistance sessions can increase androgen receptors in muscle.
    • This means that testosterone will have an increased effect as a result of training. 
  • The hormonal response depends on the amount of tissue stimulated.
  • The repeated stimulus of hormones will desensitize the receptors after the genetic limit is reached.
    • With resistance training, the muscle cell will be stimulated to grow to a genetic size potential.
    • Continued stimulation will not yield the same growth as the same amount of hormone previously did.
  • Dosing exercise is important because a catabolic effect may occur with overtraining.
• Hormones in the blood
  • Hormones can be released into cells and blood with exercise. However, hormones in the blood are not a 1:1 marker of the status of cell change.
    • The impact is determined by the sensitivity of the receptor on the target tissue.
    • Or if a decreased hormone concentration is found in the blood, it may be due to higher uptake into tissue receptors.
    • This means the concentration of hormones in the blood cannot be examined alone to investigate the anabolic or catabolic environment.
• Endocrine System Adaptation
  • When one exercises, the endocrine system is trained and can adapt. The size of the glands, the creation and storage of hormones, and receptor sensitivity can all change.

TAKEAWAYS

• Train with large compound movements to grow.
  • The more muscle fibers involved in exercise, the greater stimulus. This is because of the principle of specificity, meaning only resisted muscle will adapt. 
    • Perform multi-joint compound movements such as squats and deadlifts at 85-95% 1rm for moderate to high volume over multiple sets of many exercises.
    • Short rest periods of 30-60 seconds have been shown to be the most effective for testosterone, however, resting for 1-3 minutes is okay to safely perform the movement.
  • How to Increase Growth Hormone?
    • Use high-intensity 10 RM heavy resistance for three sets of each exercise. Use short rest of 30-60 seconds. Pre-exercise nutrition of carbohydrates and protein before and after workouts will improve GH.
  • Adrenal hormone optimization
    • High volume, large muscle groups, with short rest. Allow for complete rest days in order to replenish the adrenals and prevent exhaustion.
    • Lower-volume workouts allow the adrenal gland to engage in active recovery.
• Anabolic and Catabolic Balance
  • The number of receptors bound with testosterone and insulin counters the binding of receptors of cortisol. The total of all factors inside the body will cause the resulting growth or destruction of muscle. 
  • Every action you take is a vote for an anabolic or catabolic environment.
    • Sleeping 7-9 hours.
      • Decreases cortisol and increased GH.
    • Perform resistance training.
      • Stimulate testosterone release and upregulation of sensitivity.
    • Minimize stress.
    • Eat sufficient calories and protein.
      • Nutrition
        • Ingesting carbohydrates and protein before a workout improves the androgen response. If you already have the nutrients in the blood ready to be used, there is less need to break down stores with catabolic hormones which may interfere with anabolism. 
        • 1 gram of protein per pound of body weight.
    • Minimize catabolic drugs like alcohol.

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