July 17, 2018

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Heat acclimation can occur naturally as the weather warms up and we will have some physiological adaptations due to training in naturally warmer environments. But heat acclimation training can also deliberately simulated and used prior to competing in hotter conditions in order to prepare the body for the extra physiological strain (eg. Heat training for people from Melbourne prior to going competing in Hawaii Kona Ironman) or also used to gain physiological changes even if not competing in hotter conditions as the end game.

One of the exciting things about heat training is the speed at which we can see significant adaptations in the body. If done correctly, with 7-10 days we see:
– Increases blood plasma volume
– The fluid portion of the blood is increased assisiting in transporting O2 and nutrients and also assisting in continued sweating and cooling of the body
– Decreased heart rate during exercise at same intensity
the initial heat stress will mean the body has to work harder when first exposed to the heat, but within a week the body adapts to be able to reduce exertion at the same intensity
– Decreased Sweat sodium

This is really interesting and important as it shows that in order to maintain electrolyte balance, the body, recognising greater sweat losses n the heat, adapts to reserve the amount of sodium lost through sweat. To me this highlights the bodies’ preference to ensure blood sodium levels remain at normal levels. This also highlights the fact that we likely have very different sweat profiles during Winter and Summer depending on our training exposure

Earlier onset of sweating
Sweat is the most effective body cooling method we have whilst exercising. Sweating earlier and sweating more is an adaptation to maintain a cool body temperature. Again this may highlight different hydration needs during Summer and Winter

Increased blood flow to the skin
This is the mechanism by which we are able to produce sweat, which evaporates on the skin releasing heat and cooling our bodies

So we can expect to see some of the above adaptations occurring naturally as part of a structured Summer training program, but if we are to try to simulate hot conditions in order to help the body adapt and cope with the heat stress for a performance improvement some of the following points are worth considering which may ensure your exposure is enough to get the benefits.

Aim for Temperature > 36deg C and humidity > 50%
Note – this has been reported to be most effective in gaining the desired adaptations. It may be prudent to understand the environment you may compete in to further prepare yourself. For example the dry heat and low humidity in Kona is very different to high humidity of Far North Queensland.

7-14 days required

90-100mins per day (at least 10 days in a row) or 90mis every 3rd day of 30 day cycle may yield similar results

Exercise intensity in these sessions at approx. 50% VO2 Max i.e. the heat exposure will limit your output, but also the sessions are not necessarily about “flogging yourself”. The exposure, consistency and the duration present as the most important factors.

Heat acclimation studies have shown differences in how long the adaptations last for and vary from 10-28 after ceasing heat acclimation training, and so this may very well point to practical ideas like arriving two weeks prior to your event in a hotter climate to assist in acclimating. There are some fair arguments to also seeking ways to expose yourself to some consistent structures heat sessions further out from events, but also consider that the physiological adaptations to heat training all assist in a higher level of function and therefore may also increase performance even when not specifically competing in the heat.

Some takeaways for me in the hydration world are to consider that your sweat profile and therefore hydration and electrolyte replacement needs are likely to be markedly different in different seasons so consider this in planning. Preparing the body for specific climatic conditions is a no brainer, but do some further research into how to incorporate the exposures into your training cycle carefully. Monitor yourself and reflect upon your outputs and recovery when making any significant changes in your heat exposure.

Andy Garlick is the director of Sports Science and Lead Exercise Scientist at The Sweat Lab, Powered by SOS Hydration and advises athletes of all levels on matters of personalised hydration, sweat profiling and electrolyte balance in the pursuit of better performance and greater wellbeing.