Summary:
- 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.
Hypertrophy
- 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.
- Norepinephrine
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.
Sources and links:
- FoundMyFitness – Sauna (link to website)
- FoundMyFitness — Jari Laukkanen (link to summary)
- Wikipedia