Exposure to heat can increase the amount of heat shock proteins (HSPs). These are specialized proteins which are protective and regenerative in nature. In particular, HSPs can deliver the following effects:

• Prevent oxidative stress in cells: HSPs are excellent scavengers of free radicals, which are notorious for damaging the structure of our DNA and paving the way for the development of cancers as well as accelerate muscle catabolism.
• They can repair structurally abnormal protein molecules: This is extremely important for bodybuilding as well as for general health. More correctly formed proteins translate to either more muscle or enhanced recovery. So, in effect, HSPs boost recovery.
• Heat shock proteins can shut down protein degradation: A natural process that occurs in cells is the breakdown of what the body deems "unnecessary" amino acids. If you're an athlete, amino acids are a precious commodity and you'd rather keep yours. Heat shock proteins can inhibit a pathway known as the ubiquitin-proteasome pathway (UPP), which preserves more aminos that can then be used for protein synthesis.

Muscle adaptation is an essential part of training progression. If a muscle group is unable to adapt to the stressors being placed upon it, it won't grow stronger or bigger.

During exercise, especially resistance training, HSPs are transiently elevated to facilitate the "chaperoning" of amino acids to the site of muscle damage to initiate recovery. Accumulation of amino acids to the local site of injury isn't merely sufficient for repair, as correct protein folding needs to occur as well. HSPs ensure the correct assembly of these amino acids into the appropriate protein, ultimately enhancing hypertrophy.

Now, don't go and subject yourself to marathon sauna sessions. Quick visits ranging from about 15-30 minutes are optimal. This practice is known as "intermittent hyperthermia" and it's been shown in studies to enhance growth of skeletal muscle.

The eccentric, the negative or lowering portion of a lift, is the most promising range for muscular growth, but many people just drop the bar without actively resisting the weight. In a study, intense eccentric exercise was able to boost HSPs by over 1000 percent, clearly showing how the muscular damage that occurred during the rep must've been massive. Followed up with intermittent hyperthermia, the way would be paved for muscle growth.

So, heat acclimation makes your body function better, both aerobically and anaerobically, as well as in removal of toxins. Coupled with the potential for increased muscle gains, sauna time should be a no-brainer.

1. Gjøvaag TF et al. Effect of concentric or eccentric weight training on the expression of heat shock proteins in m. biceps brachii of very well trained males. Eur J Appl Physiol. 2006 Mar;96(4):355-62. PubMed.
2. Selsby JT et al. Intermittent hyperthermia enhances skeletal muscle regrowth and attenuates oxidative damage following reloading. J Appl Physiol (1985). 2007 Apr;102(4):1702-7. PubMed.
3. Thompson HS et al. A single bout of eccentric exercise increases HSP27 and HSC/HSP70 in human skeletal muscle. Acta Physiol Scand. 2001 Feb;171(2):187-93. PubMed.