Marathon des Sables – The Legendary will soon be here and now is the perfect time to make sure that you plan for a series of protocols to acclimate to heat and the stress of heat before arriving in Morocco.

In simple terms, you need to impose heat stress on the body that will simulate the conditions you will race in when in the Sahara.

Acclimation to heat should be done close to competition, ideally sub 21-days and ideally in the final 14 and 7-days. Statistics show that 5-sessions (or more) offer a more fulfilled adaptation. The pseudo motor function (sweat rate) takes a little longer to occur, but all the other measurements, cardiovascular and lowering core body temp occurs quite rapidly. However, 5-10 sessions will allow even greater adaption, and provides better results in particular with sweat rate.

Now of course, if one is fortunate with time, the best scenario is to travel to the race location and adapt naturally in the environment of the race. Reality is though, few of us have this option and we must therefore simulate the stress of heat. The most obvious and effective protocols take place in an environmental heat chamber. Sessions could be performed every 2-days in a 14-day window. Adaptation from exposure diminishes rapidly, so, there is no need to do this too far away from the chosen event. 

Expense can be an issue and therefore there are other possibilities. Keep training as planned and add layers of clothing while training. Post training, when already hot from the stresses of a run, you could then take a hot bath which will raise core temperature. One can also consider Bikram Yoga and use saunas. The reality is though, while some of these interventions will have some benefit, and most certainly, they are better than nothing, it is not something that can be recommended completely as it is harder to prescribe and measure.

Environmental heat chamber

Environmental heat chamber is controlled and measured and in addition is monitored by a professional who gradually controls and analyses the stimulus to ensure maximum benefit and importantly, safety. In regard to session length, sub 60-minutes is usually adequate and this allows the body to get hot enough.

The use of a rectal thermometer is used to ensure that you reach the required thermal stimulus. Body weight is measured when naked and then this figure is used to measure fluid intake and sweat rate. Urine tests may be done to look at hydration status. It’s important that a client leaves re-hydrated after a session.

It’s important to remember, these sessions are about heat adaptation, they are not training sessions. A treadmill or bicycle is used and many testers prefer the bike as it adds less impact to the body and fatigue.

A 5-minute check will include heart rate, core temperature, skin temperature, perception of thermal environment, how hot does the client think it is? And finally, the tester usually asks how comfortable the client is. Then, the protocol will begin.

The target is a core temperature of 38.5 degrees in each session, which is ideal for pseudo motor and thermo functions to be maximised. Measuring the thermal strain is key. It usually takes about 30-minutes to get to 38.5 degrees depending on the individual. But external factors do have an impact. The session is about controlling and meeting a fixed criteria.

The first two sessions are often a challenge and then by session three, improvements can be noticed with the greatest improvement coming after day five with seven sessions being a great target to work towards. Total exposure is more important than days, so, if challenged for time, it is possible to do two tests per day, say AM and PM. As stressed above, the optimal time window is in the 14-days counting down to the event or race.

Loughborough Sport in the UK offer specific heat acclimation – book HERE

Do you need to acclimate to heat?

All runners in the Sahara will be faced with physical and perceptual challenges that will have negative effects on performance if not acclimated.

They will be slower, frustrated, dehydrated and have a potential of heat stroke and ultimately they may not finish the race.

Acclimating to heat pre-race prepares the body for the challenge to come!

When in the race, if you experience negative effects of heat, is there anything that can be done?

Yes, slow down, try to cool down as much as possible, seek shade at aid stations, rest and allow the core to lower. Hydrate and use spare water to provide a perceptual cooling: water on your face, head, forearms and neck will help a little with this.

Conclusion:

When one runs, you use muscle mass and this generates heat. When you then exercise in a hot environment, particularly if it is greater than skin temperature, then this makes it very difficult to get rid of heat. Humans are not the most efficient mechanically, so this energy from contracting muscles, potentially around 20 to 30% of the mechanical energy being made is converted to chemical energy, that means 70%, maybe even more, needs to be eradicated in the environment. If the environment is hot, for example, the Sahara, a challenge is imposed to eradicate the heat and what often happens is is that the heat is stored and one feels hotter and this then has a cascade effect of issues and problems, physiologically and perceptually.

Physiologically there is an increase in skin temperature as it is directly impacted upon by the environment. There will be an increased demand for blood flow that needs to go to muscle to provide it with oxygen/ energy to run, but also there is a competition for blood flow to the skin. In order to thermo regulate, blood is competing with muscles and skin and that creates an impact on one’s cardiovascular system. Typically, heart rate will increase due to the increased workload sending blood to muscles and skin. Body core temperature will increase. Sweet rate will also increase and therefore the percentage of water loss will increase and the consequence of this is dehydration – a deficit in body water with onward complications.

Trained individuals can gain thermal adaptations, irrespective of environment. For example, if you are training everyday, particularly at a high percentage of VO2max, one will create heat and this will require a higher sweat rate and therefore adaptation takes place. But, interventions should be in place both acute and chronic, to minimise the effect of environment on performance. Environment, will always have an impact on performance, no matter which athlete. So, make a plan now to adapt and acclimate in the final 14-days pre-race!

This article is based on a podcast (episode 191 of Talk Ultra) with Dr Jodie Moss PhD Sports Physiology, MSc Sports Nutrition.

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NEWS TWO Here

NEWS THREE Here

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