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Fitness & Health

16th Jul 2018

How heat affects your training and performance

Temperatures have soared in Britain, but that's no reason to let your workouts suffer

Alex Roberts

The UK is in the midst of a heatwave. Temperatures have generally exceeded 25 degrees for over a month, which places extra demands on your body

You still need to get your workouts in, but the heat can make training difficult. To get to grips with the warm weather, JOE spoke to Jim Pate, Senior Physiologist at the Centre for Health & Human Performance (CHHP).

JOE: How does heat affect variables of training such as the weight you can lift, the reps you perform and the intensity with which you exercise?

Jim: “A little bit of heat is not necessarily a bad thing. We know that ‘warming up’ before physical activity will help improve performance and mitigate the risk of injury. However, too much heat can negatively impact performance.

“Muscle function is impaired by excessive heat and dehydration or the loss of excess water from the body. Imagine your car engine overheating and running out of coolant at the same time. For exercise, this means less duration and less intensity from the same amount of effort. Additionally, fatigue, cramps, slowed reactions and loss of concentration are all associated with excess heat and a drop in performance.”

What are the effects of heat on your body?

“As a warm blood mammal, our body has an optimum operating temperature, 37 degrees. If our core body temperature deviates too much from 37C our ability to maintain homeostasis – to stay alive – is compromised.

“We have mechanisms to help us cope with environmental temperature stress. To deal with heat, we sweat. Evaporation of sweat from the surface of our skin helps dissipate excess body heat.

“In addition to environmental heat affecting our physiology, the higher the intensity of exercise, the more heat is produced. We do adjust to higher temperatures given time. Increased sweat rate and earlier onset of sweating both occur given time to acclimatise to a hot environment.”


What is an optimal strategy for hydration when it’s particularly hot?

“Water and salt loss during exercise is inevitable due to sweating. This loss is exacerbated with higher environmental temperature. Excess water loss leads to dehydration which also leads to a drop in exercise performance.

“The most sensible way to manage this is to drink more on hotter days. You also lose salts when you sweat so adding an electrolyte table to your water bottle or making sure your drink of choice contains them is also a good measure.

“When you drink, there is a maximum rate at which your bottle can absorb the water. A strategy of drinking little and often can be applied to help optimise usage without taking too much water onboard that is then just passed.”

JOE: The American College of Sports Medicine (ACSM) recommend 350-500ml fluid at least 2 hours prior to exercise.

Are there certain sports or different styles of training that require different approaches to heat management?

“Obviously, environment plays a big factor. Races like the Marathon des Sables of the Bad Water 135 through Death Valley pose significant heat challenge by location.

“Similarly, sports or activities in countries with hot climates do too. Adjusting the timing of competition and training sessions to avoid the heat is a good management strategy. Indoor air conditioned training facilities are another option when resources are available.”

Would you recommend any supplements for combating this stress?

“Water and electrolytes are crucial to combat dehydration and to maintain the ability to sweat and cool the body during exercise.”

Drinking Isotonic In Heat

What should our nutritional considerations be?

“Other than water and electrolytes, fuelling correctly before, during and after exercise is a key component performance management.

“More heat during exercise is an additional challenge. If your body is going to rise to and overcome it, you need to be in the best state possible to do so.”

Are there any key “rules” to put into practice?

“Plan ahead. Check the weather and make sure that you have the right equipment for the environment where you will be exercising. Be aware, if something really doesn’t feel right, stop exercising and find somewhere to cool off or at the very least slow down.”

Can your body adapt to hot climates?

“It is possible to heat acclimatise yourself. Exposure to higher than normal temperatures and exercising in heat stimulates your body to manage heat better.”

Social stresses can also negate your progress – read more on how weightlifting can help.