Heat Acclimation – Dr Jodie Moss

Heat is often debilitating for a runner. Heat cramp, heat exhaustion, dehydration, heat stroke, headaches and the desire just to stop are all very real problems.

As the summer season approaches, running in a hot climate is sometimes unavoidable, however, racing in a hot climate is relatively controllable as you will understand in advance the race, the environment and the expected temperatures one can expect.

Understanding the conditions of ones running and racing environment is crucial to make the best of all the hard training you have done. So, one needs to adapt and plan.

Heat acclimatisation takes place in a natural environment where one can specifically prepare in advance of a chosen race or project, ideally for 7-14 days before the event. For most of us though, the luxury of travelling for 14-days and having an acclimatisation holiday is not a realistic proposition.

This is where Heat Acclimation comes in. In simple terms, this is about providing heat stress in a controlled environment, typically a heat chamber, over a set period of time and sessions.

Dr Jodie Moss has specialised in heat acclimation and in the process, put her learning to real time use at the 2019 Marathon des Sables where she placed 8th woman.

Jodie at MDS

With Marathon des Sables approaching, it is timely to re-visit and gain a full understanding of what is required to acclimate to heat with an interview with Dr Jodie from July 2020.

Podcast HERE.

What is it about heat that makes running so difficult?

You are imposed upon by a different challenge. What happens is you create this metabolic heat by contracting your muscles. 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:

An increase in skin temperature is likely the one which is noticed first 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.

Perceptually:

We thermally perceive it to be a lot hotter.

You are more uncomfortable.

The feeling of needing to slow down and therefore performance is impacted.

Is heat acclimation as valid for the runner at the front, as well as the runner at the back?

In principal, yes. However, if we take Marathon des Sables as an example and the winner, Rachid El Morabity, he is a Moroccan, he lives in the environment in which the race takes place, therefore he is naturally acclimatising on all his training runs. Therefore, he has no need to acclimate artificially.

Highly trained individuals though, through training, 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 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.

Acclimate for the heat.

When is a good time to start adapting to heat and how?

It is a consideration for close to competition, typically in a period of 7 to 21-days. Adaptation from exposure diminishes rapidly, so, there is no need to do this too far away from the chosen event. 

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. However, very few have such a luxury and this is where acclimating as opposed to acclimatising steps in.

However, budget can be an issue, so it is possible to adapt via some simple home methods. Keep one’s training as planned, say by a coach, and then add layers of clothing while training. Have a hot bath after training. One can also consider Bikram Yoga and say saunas. But, and this is a big but, while some of these interventions will have some benefit, it is not something that can be recommended completely as it is harder to prescribe and measure.

We want heat adaptation and these adaptations only occur when there is sufficient thermal strain.

As an example, one could run for an hour with layers and build heat. Then immediately have a hot bath. Water has a greater density than air and the heat inside the body would be retained and most likely increase, this would stress the system. But, the issues arise with how long does one do this… Ultimately though, this is considerably better than nothing!

By far the best way, is environmental heat chamber.

Environmental Heat Chamber

The jury is still out on what is the optimal sessions for performance gain, however, five sessions would be considered fundamental over a period of 7 to 14-days. This period has shown results of a much 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. So, based on sweat rate, a longer period of time provides the best results.

 In regard to the sessions, they could be performed every 2-days, every other day, every day and some even do 2 sessions per day. But obviously time and budget is a huge factor.

It is also important to remember that these sessions take place close to competition, so, monitoring stress and recovery is equally important. 

In regard to session length, 60-minutes is usually adequate and this allows the body to get hot enough.

I get asked about adding a run pack and weight, for example, MDS is a self-sufficient race and a pack is required. On the start line, the minimum weight will be 8kg. But training with this in the heat is not necessary, but some insist as it provides security, comfort and a greater understanding of what the Sahara, as an example, may feel like. But this adds additional stress and the sessions are about heat adaptation.

The Protocol

Isothermic heat acclimation intervention is typical. We get you to exercise so that your core reaches a certain temperature. For this we use a rectal thermistor. This ensures that you meet the thermal stimulus, crucial for sessions like this.  

We measure body weight naked and this allows us to monitor fluid intake and sweat rate. We can test urine to look at hydration status too. This is all about making the client aware of hydration and levels. We also want the client to leave a session re-hydrated!

A treadmill or bicycle is used. Personally, I prefer the bike as it adds less impact to the body. It’s important to remember, these sessions are about heat adaptation, they are not training sessions. A 5-minute check will include hear rate, core temperature, skin temperature, perception of thermal environment, how hot does the client think it is? And finally, I will ask how comfortable the client is. Then, the exercise will begin.

We aim for a core of 38.5 degrees in each session. This is ideal for pseudo motor and thermo functions to be maximised. It ensures that we are always controlling and meeting a fixed criteria. 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. 

We typically see improvements by session 3. But it is important to have, say 10-minutes of each session fixed, that way we can monitor improvement and adaptation. We can gain the data here and then report back. Day 5 to day 7 will show the most improvement. So, 7-sessions.

Time can be an issue and some may prefer to squeeze two sessions per day and compress 7-days, say, into 3 or 4. This is possible and literature confirms this. Total exposure is more important than days.

Ideally, the last session would be 1 or 2-days before departure for the chosen race.

What problems can occur without acclimation and how does one mitigate it?

A runner will be faced with a physical and perceptual challenge that will have negative effects. They will be slower, frustrated, dehydrated and have a potential of heat stroke and ultimately they may not finish the race. If any of these elements are experienced, try to cool 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 face, head, forearms and neck will help a little.  

On a personal note:

I did not have the perfect race and that is what makes me keep signing up to race. My heat protocols were great but I compromised my training and I was surprised with 8th place. I had an amazing support system and I do have chronic heat exposure, I am also very good at getting rid of heat. I also sweat high. But I need to be careful on dehydration. I made a mistake with my pack trying to make it as light as possible but I compromised my pack integrity and this hurt my back. I look forward to going back, I hope in 2021.

Jodie with her medal.

Top 3 tips to get ready in regard to heat and training.

1. Have a heat protocol as outlined above.

2. Test all kit and nutrition, leave nothing to chance.

3. Do not panic. Trust the training you have done. Do not increase mileage and training in the light stages. Do not risk injury or illness. Be healthy.

Seeking shade at the 2021 MDS.

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Do you like it on your back? In your hand? Or around your waist?

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With temperatures rising and longer lighter days for many of us in Europe and North America, we can hopefully all get out and run more. But as we all know, or maybe we don’t, we need to consider several things when running in the heat:

  • It’s harder
  • You sweat more
  • You need more fluid

We need to adapt. So what happens when the mercury rises?

Question, do you prefer it:

  •  On your back?
  •  In your hand?
  •  Around your waist?

Of course I am talking about your method of hydration.

 

READ THE FULL ARTICLE ON RUNULTRA HERE

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Laurence Klein, top-10 tips for the Marathon des Sables

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Laurence Klein (FRA) is a triple winner of the Marathon des Sables; 2007, 2011 and 2012. In 2013, Laurence returned to the Sahara looking for a 4th crown. Running a strong and dominant race, Laurence looked invincible, however, on the long-day she suffered from the heat and was forced to withdraw from the race with dehydration opening the door for Meghan Hicks (USA) to take the lead and win the 28th edition of the race.

We can all learn and here, Laurence provides her top-10 tips for the MDS.

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1/ RUNNING IN THE SAND

“Though sand is omnipresent along the Marathon des Sables course, you don’t just run in dunes. You also traverse stony zones, lunar landscapes and djebels. It’s important not to forget that detail in your preparation… To avoid getting tired, it’s also important to read the terrain you’re not used to. On large dunes for example, it’s best to run along the ridges and try to carve out your own wake so that you don’t sink into the sand as much. On the dunettes however, it’s easier to run in the tracks left by other competitors so as to use their footsteps like stairs. Finally, in the “fesh-fesh” (fine sand that looks like solid ground but behaves like soft mud), you really have to try to be as light on your feet as possible when you run.”

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2/ AVOIDING BLISTERS

“Gaiters are essential in preventing sand from filtering through into your socks too much and causing large blisters. Those who are sensitive to them can also prepare their feet in the run- up to the event, by hardening them with special products or citric acid. On a personal level, I recommend choosing a suitable trail shoe, one or two sizes bigger than your usual town shoe, because feet tend to swell with the heat. Added to that, it goes without saying that when you have blisters, it immediately becomes a lot more painful to put your shoes back on with an additional layer of bandages if you’re already bordering on the limit of your shoe size.”

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3 / HYDRATE REGULARLY

“Dehydration is one of the biggest risks in the desert. It’s imperative you don’t forget this and force yourself to systematically drink the water offered by the organisation, taking small, regular sips during the race and in the evening when you get into the bivouac. During this event, you also loose a lot of salt. As such it’s essential you remember to take the salt tablets supplied by the organisation and plan a diet rich in mineral salts.”

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4/ PROTECT YOURSELF FROM THE SUN

“Avoid wearing dark clothing in the desert as it tends to retain heat. Instead, opt for light clothing and white caps, which reflect the light. It can also be very useful to keep a buff around the neck or the wrist, which you can moisten from time to time to freshen up and bring down your core temperature. The best thing is not to remove too much clothing, but not to wear too much either… and to protect oneself from the sun’s rays using a very good suncream.”

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5/ A LIGHT, BALANCED BAG

“When you pack your bag, don’t forget that you have to add to it the litre and a half of extra water supplied by the organisation throughout the event… As such a bag weighing around 7 kilos is ideal. You also need to think about correctly distributing the weight between the front pack and the backpack, so as to remain balanced and avoid placing all the bag’s weight on your kidneys. Personally, I recommend putting everything at the front that will be of use to you during the day, energy bars, water, roadmap, compass, salt tablets, etc. That way you don’t have to unpack your bag to retrieve something that’s located at the back.”

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6 / GET SOME REST

“It’s very important to get some good rest and sleep well. For this, don’t disregard the comfort of your sleeping bag and opt for a sleeping bag suited to temperatures of around zero. Indeed, even though it rarely gets cooler than that, the temperature range between day and night remains pretty significant and you can soon get cold. For the evening, the majority of runners use painters’ overalls, which keep out the cold and the wind, but you can also get very fine, very light technical clothing with long sleeves.”

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7/ EAT PROPERLY

“Whether you opt for freeze-dried meals or simpler food with a rice, pasta, couscous or mashed potato base, the most important thing is to have a good distribution between protein, which are used to repair the muscles that are in such heavy demand during exertion, carbohydrates, which enable you to quickly restore your energy and speed up the body, and fats, which are essential for the body to work efficiently; especially with this type of exertion where you dig deep into your store of fat. Similarly, don’t think twice about stepping up a little on the organisation’s requisite minimum daily dose of 2,000 calories a day.”

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8/ FINDING ONE’S BEARINGS

“Aside from some of the dunes, where you do need to know how to use a compass to keep on course, the risks of getting lost are virtually non-existent. Indeed the marking is very well done by the organisation throughout the course and there’s substantial monitoring of the runners by the race stewards. However that’s no reason not to learn to use a compass before taking off for Morocco!”

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9/ MANAGING ONE’S EFFORT

“The Marathon des Sables is a long race. As such you need to spread out your effort with the passing days and, most importantly, you mustn’t set off too quickly on the first leg. Instead take the time to adapt to the different terrains you will encounter. You should also think about saving your energy so that you aren’t too tired when it comes to the long stage on the 4th day. To do this, think about getting some good rest in the evening as soon as you return to the bivouac.”

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10/ LIFE IN THE BIVOUAC

“Life in the bivouac is very important. To really make the most of it, I advise you not to bring along your mobile phone so you can fully benefit from each and every moment. Indeed, a whole life and sense of solidarity takes shape within it… The runners are divided up into tents of eight people and they very quickly encourage and support one another and eat together… You have to learn to be generous within it and not get annoyed, remaining open to others. The MDS is a large family. There’s a big communion between the runners and you have to know how to respect that.”

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