How does this work?  Here’s the science!  In response to heat, the body will quite quickly respond by increasing blood volume.  One study showed an increase of 17% from just 4 sauna sessions. This in itself will benefit training and racing in the heat as the extra blood volume will help with body cooling.

However, the real benefit happens in the following adaptation.  Your body likes to keep a consistent hematocrit level in your blood.  Hematocrit is the % of red blood cells in your blood – these cells are the ones that carry oxygen to your muscles.  So when your blood volume increases, your kidneys senses the drop in hematocrit and produces more (natural) EPO to restore the red blood cell concentration. Once this has returned to its baseline then you’ve ended up with more red blood cells in your blood – and hence a higher ability to transport oxygen to your muscles.

Before you do any heat training, safety is paramount; it can be dangerous.  I would always start with shorter and less hot sessions before increasing.  Always have someone else with you.  Stay hydrated and monitor your heart rate.  If you have any underlying heart conditions then do not do it.

The best way to do it is with a hot tub.  You can control the temperature (start low and then no more than 40^OC) and the temperature can be constant.  You can use a sauna, however it is harder to control the temperature and if using a wet sauna then the amount of steam is a big factor.  You can use your bath at home, but the water can be hot enough to scald so be very careful.

Start with 1 or 2 sessions a week and then increase to 2 to 3.  10 minutes is fine to begin with and then you can increase to 20 mins once you know you can tolerate it.