Turning up the heat around exercise physiology

Professor Jim Cotter explains how studying the human body under extreme conditions may hold the key to understanding how our bodies keep us safe during exercise.

With the promise of a trip to Antarctica - Jim happily signed up for another two years of postgraduate study. Ironically, the trip never happened, but Jim became fascinated with the area of exercise and environmental physiology, eventually leading on to a PhD in heat stress physiology.

Twenty five years later - his research has taken him around the globe, from investigating the effects of acute and chronic hypoxia at Everest Base Camp, to understanding how different environments affect the body, in Greenland, Beijing and Northern Australia.

Now as a Professor and lecturer at the University of Otago, Dr. Cotter’s research is focused on understanding people’s physiological responses to exercise and the environment. He looks at how our bodies respond acutely and chronically to these stresses. 'One thing I find particularly interesting is exercising in extreme environments, because often that compounds the effects of exercise. Environments we are particularly interested in are hot, cold, at altitude, and the effects of dehydration. All of these impact the human physiology in a very integrated way, across multiple systems.'

Exercise and Environmental Physiologist, Professor Jim Cotter from the University of Otago.

The words extreme and exercise in the same sentence are enough to give most people heart palpitations. So why is Jim so interested in exercise in extreme environments?

Well there’s the obvious benefits of helping with weight loss and reducing your risk of chronic diseases such as type 2 diabetes and high blood pressure, and let’s not forget about the positive effects on your mood - that release of endorphins is enough to make anyone addicted! While these are some of the physical things we see and feel as a result of exercise, Jim is more interested in understanding what is happening within our body while we exercise.

'One of the most interesting things about exercise, is that it contains various different stressors like; energetic stress, dehydration (osmotic and volume) stress, heat stress, mechanical stress, acidotic or pH regulatory stress, and hypoxic stress.' Your body has to deal with all of these different stressors simultaneously in order to maintain homeostasis - a physiological equilibrium within your body.

'This makes exercise the single most powerful complex stressor your body can undergo.'

At a very basic level, your body deals with these stressors by using receptors that can detect changes in the body, for example, an increase in body temperature. This information is then detected within and outside the brain, then integrated, which will make physiological or behavioral adjustments accordingly, e.g. make you sweat more. On top of this, the environment where you exercise can have compounding effects to these already present stressors. For example, in hot and humid conditions, the off load of excess body heat through sweating becomes harder - making the overall experience more difficult than if that person were to complete the same exercise in a cooler, less humid environment.

Supplementing exercise with environmental stress

Interestingly, Jim tells us, 'because exercise shares many of its stressors with the environment, environmental stressors can be used as a substitute or supplement for exercise.' This is especially important for people who can’t exercise due to an illness or injury. On the flip side - 'athletes can consider boosting the stress of exercise by deliberately exercising in those environments with the aim of enhancing their fitness.' 

You may have experienced this yourself if you have used saunas and ice baths, or even tried hot yoga. The added environmental stress changes what would normally be a low exertion activity, into one that can leave you feeling physically fatigued. One of Dr. Cotter’s research goals is to understand to what extent stressful environments compare with those within exercise conditioning, and potentially supplement or replace those where appropriate.

An integrated approach to understanding exercise

Another focus for his group is understanding which of these stressors are important, and which are upstream of others. 'If we know the role and relative importance of individual stressors, it will help us to understand what exercise actually IS and why certain types, durations, and intensities of exercise are more or less effective, and for whom.'

Understanding the complexity and integrated responses happening within the body under different exercising conditions, requires multiple physiological parameters to be measured from volunteer participants at any given time. For example, in one experiment, they might want to look at how humans respond to changes in temperature whilst doing an aerobic activity such as pedaling on a bike. This might require the team to pull in 16-20 raw signals measuring body temperature, metabolismrespiratory pressures, sweat rate, blood pressure and its flow to different organs, as well as oxygenation of muscles and the brain.

The signals are amplified using a Bio Amp or Bridge Amp and processed using a PowerLab data acquisition system. By collecting multiple physiological signals simultaneously, and analyzing the data all in one place (LabChart), they can get an understanding for how the body responds and adapts to different stressors like heat.

Get up, get out, get active!

Jim explains how nowadays, we are continuously bombarded with information through the media deeming exercise in particular environments as unsafe. 'We have this rhetoric and public belief that an extreme environment is something out there, with people climbing and diving, or running across deserts and ice caps. We regard outdoor/adventurous people as endangering, or as risk takers.'

'However, we have the physiological mechanisms to acutely, behaviorally and adaptively deal with these environments through natural exposure but the more time we spend disengaged from these environments, the more ‘unsafe’ they will become. The constructed environment – which is increasingly devoid of natural stressors, is undetectable and transiently safe but thereby insidious and chronically unsafe.'

With sedentary lifestyles becoming the norm, Jim hopes his research will give us a better understanding and appreciation for exercise and our body’s capabilities, because at the end of the day, exercise is one of the best things we can do for ourselves, and guess what - it’s free!

Related Research:

Professor Trevor Day: Taking physiology to new heights - Creative approaches in high altitude research

Professor Damian Bailey: How exercise turns back the clock on your aging brain and The best exercises to boost blood flow to your brain

25 Jun 2019

By Mel Knottenbelt

Scientific Writer


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