Heat chamber acclimation

Last updated: 19-Oct-18

By Steve Diederich and Elisabet Barnes

A few years ago, heat chambers were the domain of experimental science that we believed only existed at NASA or were ancillaries to the Hadron collider. Well, it turns out that there are quite a few of these facilities now available and these have grown out of the developing understanding of sports science. With more runners travelling to extreme climates, we now have a new tool in our armoury to help our understanding of how we are likely to behave and react in in these conditions.

Are you interested in running in a polar, desert or jungle environment? No problem, the environmental chamber will emulate temperature and humidity to your requirements. This will enable you to test how your body responds, get an idea of how you are likely to perform, and most importantly, help you adapt so that you perform better. In this way, you can avoid the conditions in your destination race becoming a surprise or upset to you.

It was a call from Ash Wilmott at the University of Brighton’s Sport and Exercise Science Consultancy Unit that prompted me to organise a visit to their facility to better understand how this works. In advance of The Coastal Challenge in Costa Rica (TCC), I asked Elisabet Barnes (an experienced athlete and coach who has previously performed well in the TCC and won the ladies’ title at the Marathon des Sables in the Sahara) if she would be willing to trial the facility and give us her expert opinion.


The chamber has the air of a modern facility purpose built for hi-tech studies. We were welcomed by Ash and his team of four, who set to work on getting baseline measurements from Elisabeth – skin fold thickness for body fat percentage, resting heart rate, blood pressure, weight, height, hydration status via a urine test, and blood samples were taken, along with the weight / volume of fluids she was planning on consuming. 

These measurements were immediately pumped into the system that displayed all the metrics on a large monitor. The team also placed patches on Elisabet’s skin to measure sweat sodium level and she wore a heart rate monitor.


Lastly (a surprise to me!) was an “internal” thermometer that was discretely inserted in … well you know where. This is one of the most vital of the measurements required as it accurately measures body core temperature in real time, a key indicator in terms of how the external conditions and your own metabolic heat production are coping under the stress of exercise. It is critical to monitor changes in core temperature closely during the time in the chamber to ensure a temperature that is high enough to allow for adaptations to take place, yet low enough to avoid any potential dangerous symptoms associated with a heat-related illness.

Elisabet: I have run in several heat chambers and I was really impressed with the facilities at Brighton University. They have a large and advanced state-of-the-art facility and a very knowledgeable and friendly team. It is probably worth mentioning that under normal circumstances, for a series of heat acclimation sessions, you wouldn’t necessarily be taking all the above-mentioned measurements. This was due to research carried out by the Masters Students involved. The key ones normally used include changes in blood plasma volume, core temperature, heart rate and sweat rate.


Once the desired temperature and humidity had been quickly reached in the chamber, Elisabet was on the running machine and undergoing a regular physiological profile test for lactate threshold. This included measuring blood lactate, gas values of oxygen and carbon dioxide to measure how much metabolic heat she was producing and how much energy she was expending, and perceived level of exertion, heat sensation and heat comfort, along with monitoring of heart rate and core temperature every 3 minutes as speed was increased 0.8 km per stage. The session lasted about an hour with Elisabet being able to adjust her output to suit her comfort and personal ambition.


Elisabet – It is very interesting to relate the perceived effort and comfort to the actual measurements. For example, because I am used to pushing myself hard at times, and having a high pain threshold, I find that I am surprisingly comfortable even if my core temperature rises to near dangerous levels. This is useful for me to know because I know that I must pay close attention to body’s response in the “real” environment. You can learn to notice even the smallest of signs but it can also be useful to relate your core temperature and perception of effort to a specific heart rate. You can then use the heart rate monitor in the race to help pace yourself and stay in a “safe” zone. Once the core temperature rises above 39 degrees, unless you slow down, it won’t be long before it could hit 40 degrees and that is very dangerous and must be avoided.


Once out of the chamber – the team lead by Ash give a thorough debrief.

There are two main uses for a heat chamber as part of runner’s preparation. Firstly, the benefit is for you to understand the effect on your body and your performance in extreme temperatures and humidity, both in terms of how you feel as well as the empirical data reported that gives you the harsh reality of how your body responds to these conditions. Secondly, by being in this environment you are starting the process of resetting your body thermostat located towards the front of your brain in your hypothalamus. Dr Mike Stroud, one of the most respected experts in the body’s adaption to extreme conditions, explains that as humans we originate from the hotter climates of Africa and we are suited to re-adapting to hotter conditions with relative ease. Conventional wisdom says that the adaption timetable can be complete within two weeks with regular heat sessions, however you may be able to attain 75% of heart rate and core temperature adaptations in 4-7 days.


Elisabet – TOP TIPS, if your next event is in an extremely hot environment, such as in the Saharan Marathon des Sables, completing a series of heat chamber sessions before your race can really help you. Not only do you get the benefit of a series of physiological adaptations that will help you perform better, but you also get the psychological benefit of having experienced what that environment feels like. This can make you more confident and reduce any concerns you may have. It can also help you develop a pacing strategy for the race and you don’t go in blind. Additionally, you can test and find out what hydration and nutrition may or may not work and make tweaks. Personally, I would suggest completing 5-10 hours total in sessions of 60-90 minutes under the supervision of professionals. These sessions should be done in final three weeks before your event for acclimation purposes. It can be tempting to think that the hotter the chamber, the more effective the acclimation but this is not the case. Try to simulate the real environment as closely as possible (heat and humidity) and take guidance from the staff that run the facilities because they understand how to perform the sessions for maximum benefit. Also, don’t forget that you are normally tapering for your race when you perform these sessions so be sensible with the effort exerted as the main purpose is to adapt to heat, not exhaust yourself with really hard training sessions. For example, for a self-sufficient race, if you do all your sessions with a heavy backpack so close to the race you may not get the rest and taper you need to be optimally prepared.

Ash and the team at the University of Brighton have conducted research into the adaptations towards heat stress and completed twice daily sessions which showed similar responses to once daily as well as in ultra-runners preparing for the Marathon des Sables 2016 with 4 days of short term heat acclimation, this has since been published in the Journal of Sport Science and can be found here

University of Brighton
Mithras House
Lewes Road
01273 600900

To read more about Elisabet Barnes, visit her blog.

All images RunUltra.

"the benefit is for you to understand the effect on your body and your performance in extreme temperatures and humidity"

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