Fifteen years ago I published my first peer-reviewed scientific paper with my good friend, the late Dr Gordon Sleivert (Gill N, Sleivert G. Effect of daily versus intermittent exposure on heat acclimation.  Aviation, Space and Environmental Medicine.  2001; 72:385:390).  Today the role heat plays in health and fitness is still a common topic of conversation.  Indeed, there seems to be a little bit of trend to use heat exposure to attenuate cardiovascular adaptations.  Such is the trend that the Welsh and English Rugby teams spent time in the likes of Dubai while preparing for the 2015 Rugby World Cup.  Interesting.

This specific use of heat has recently be referred to as "hyperthermic conditioning" which describes the use of heat stress to provide various physiological benefits to humans.  The most interesting and informative description of "hyperthermic conditioning" I have found is by Dr Rhonda Patrick (https://www.youtube.com/watch?v=aHOlM-wlNjM).  In her video she discusses how exposure to heat stress though the use of sauna can cause adaptations that increase athletic endurance.  This MAY occur through various physiological mechanisms such as increased plasma volume and increased blood flow to the heart and muscles.  In addition muscle mass MAY be increased by the elevation of heat shock proteins and growth hormone. 

What does this mean?  Can it really be that easy?  So does this mean you can go and sit in a sauna for 20-25mins and then not have to go for a run, a bike ride or a walk to get healthy and/or fit? 

In my opinion the answer is a big fat NO!  The use of sauna, and even spa pools, needs to be used just like any other form of health and fitness modality.   The addition of sauna and spa to your lifestyle and fitness plan should definitely be considered but it should always come back to your specific and individual needs. 

I think that using sauna and spa to produce a passive physiological stress, to increase sweat rate, to warm muscles and joints is AMAZING for those of us getting older and needing to look after our bodies a bit better.  If we can get some physiological stress and adaptation without pounding the pavement so much then that has to be a positive.

As an athlete will sitting in a sauna make you a better cyclist?  Will it help you run a marathon quicker?  It will depend on what it is you are needing to improve.  

When preparing for Ironman I will try to fit in a sauna 2x a week but not so I have to swim, bike and run less.......but to add another "passive" form of stress that MIGHT help me but more importantly I see it as an opportunity to work on my flexibility and recovery of tight muscles. I stretch and relax in the heat.  Great for my aging carcus! 

Don't underestimate the PHYSIOLOGICAL STRESS sitting in a Sauna for 20mins produces.  Yes it will get easier, yes it will be less stressful but there is fatigue associated with the body trying to keep core temperature below critical 40+ degrees!  Graduate your exposure and drink plenty of water before, during and after.