Stress — Sauna


  • Sauna helps to induce hypertrophy (increase in size of muscle cells).
  • Oxidative stress (through exercise) is a source of protein degradation.
  • Heat acclimation reduces protein degradation (and stimulates hypertrophy) through:
    • Induction of heat shock proteins.
    • Induction of growth hormones.
    • Improved insulin sensitivity.
  • Positive impact on longevity, brain, endurance, red blood cells
  • Removes toxins.


  • Increase in the size of muscle cells.
  • Accompanying increase in strength.
  • Hypertrophy generally involves an increase in cell size rather than the number of cells.
  • At any given time your muscles are performing a balancing act between new protein synthesis and degradation of existing proteins.
  • Ratio of protein synthesis to protein degradation determines whether muscle cells grow or shrink.
    • Protein degradation occurs both during muscle use and disuse.

Oxidative Stress

  • Exercise triggers process of oxidative phosphorylation.
    • Mitochondria suck in oxygen to produce ATP.
  • By-product of this process is the generation of oxygen free radicals.
    • Superoxide and hydrogen peroxide (oxidative stress).
  • Major source of protein degradation.

Hypertrophy and heat acclimation

  • Heat acclimation reduces the amount of protein degradation.
  • Results in increase of net protein synthesis and, thus muscle hypertrophy.
  • Three ways:
    • Induction of heat shock proteins.
    • Robust induction of growth hormone.
    • Improved insulin sensitivity.

Heat shock proteins (HSP)

  • Induced by heat.
  • Example of hormesis (protective stress response).
  • Promotes the expression of a gene called heat shock factor 1.
  • HSPs:
    • Prevent damage by scavenging free radicals (oxidative stress reduction).
    • Support cellular antioxidant capacity through its effects on maintaining glutathione.
    • Repair misfolded, damaged proteins thereby ensuring proteins have their proper structure and function.

Induction of growth hormone

  • Increase in growth hormone, which leads to increase in IGF-1.
  • Two mechanisms by which IGF-1 promotes the growth of skeletal muscle:
    • Activation of the mTOR pathway, which is responsible for protein synthesis.
    • Activation of the Akt pathway, which inhibits protein degradation.
  • Major anabolic effects of growth hormone in skeletal muscle likely is second pathway: the inhibition of protein degradation (Akt pathway)

Increased insulin sensitivity

  • Insulin regulates glucose homeostasis.
    • Particularly by promoting the uptake of glucose into muscle and adipose tissue.
  • Insulin also plays a role in protein metabolism, albeit to a lesser degree than IGF-1.
  • Insulin regulates protein metabolism in skeletal muscle by the two following mechanisms:
    • Increases protein synthesis by stimulating the uptake of amino acids (particularly BCAAs).
    • It decreases protein degradation through inhibition of the proteasome.
      • Protein complex inside cells that is largely responsible for the degradation of most cellular proteins.
    • Major anabolic effects of insulin on skeletal muscle likely is second pathway: inhibition of protein degradation (proteasome).

Impact on longevity

  • Sauna associated with longevity by reducing all-cause mortality.
  • Higher levels of HSPs protects cells from a variety of cellular and environmental stressors.
  • Heat stress has also been shown to activate the longevity gene FOXO3.
  • FOXO3 increases the expression of many different genes that enable cells to deal with a variety of environmental and cellular stresses.

Impact on brain

  • Sauna induces activation of the sympathetic nervous system.
  • Also the hypothalamic-pituitary-adrenal (HPA) axis.
    • Norepinephrine
      • Helps with focus and attention.
    • Prolactin
      • Promotes myelin growth, which makes your brain function faster, which is key in repairing nerve cell damage.
    • Also shown to increase the expression of brain-derived neurotrophic factor (BDNF).
      • Increases the growth of new brain cells as well as the survival of existing neurons.
      • Modulates neuronal plasticity and long-term memory.
      • Ameliorates anxiety and depression.
    • Upregulates release of endorphins.
      • Heat stress causing the release of dynorphins.
      • In response, body upregulates endorphins.

Impact on endurance

  • Increases plasma volume and blood flow to the heart.
    • Reducing heart strain and lower heart rate for given workload.
  • Increases blood flow to the skeletal muscles.
    • Keeping them fueled with glucose, esterified fatty acids, and oxygen.
    • Reducing dependence on muscle glycogen stores (“hit the wall” later).
  • It improves thermoregulatory control.
    • Activating the sympathetic nervous system and increasing the blood flow to the skin and, thus the sweat rate.
    • Sweating occurs at a lower core temperature.

Impact on red blood cells

  • Heat acclimation boosts the RBC count through erythropoietin (EPO).
  • Body is trying to compensate for the corresponding rise in plasma volume.

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