Beat the heat

How can you still perform at your best when the mercury rises? Read on for advice from Sarah Moseley, British Rowing Sport Scientist (Physiology)


Beat the heat (c) Jo Scales

Temperatures are set to rise and exercising when it’s more than 25°C may have a significant impact on how you feel and perform. So what can you do to ensure that you are best prepared to thrive in the summer heat?



Sweating plays an important role in cooling the body during exercise. Sweat rates can often exceed 1-2 litres/hour in the heat and, if fluids lost through sweating are not replaced sufficiently, then dehydration will occur. Even if you lose as little as 2% of your body weight in fluids, this can impair your ability to cool down and perform to your best.


What can you do?

Before exercise

Consume approximately 500ml of fluid every 2-3 hours before training or competition.

During exercise

Be prepared and ensure that you have sufficient fluid for outings.

Losses in body mass through sweating should be minimised by drinking little and often during an outing.

Sodium is the main electrolyte lost in sweat and should be replaced during prolonged sessions over an hour in the heat. Add a quarter of a teaspoon of table salt per litre to your drink, or additional salt with your food, to replace these losses and help fluid retention.

Be prepared and ensure that you have sufficient fluid for outings
After training

Weigh yourself before and after exercise to find your estimated sweat rate. This will determine how much you need to drink in order to replace lost fluids. Scroll down to 4 to see how to calculate your sweat rate.

Replace 120-150% of the body mass that you have lost in sweat within the first 1-2 hours of stopping exercise. One kg of body mass equates to one litre of fluid and should be replaced by drinks containing electrolytes, carbohydrates and protein ie. water, juice or milk.



In order to cope with an increase in temperature, your body will make some specific physiological changes to regulate its temperature and perform at its best. The most noticeable adaption is an improved ability to remove body heat through sweating. This is primarily achieved by an earlier onset of sweating and higher sweat rates. Appropriately planned, and targeted heat acclimatisation, can improve maximal and submaximal performance in hot and in temperate conditions. Maximal is where you train to your maximum and exhaustion; submaximal where you train below your maximum.

What can you do?

Safety first – build up your exposure

Build up exposures to the heat gradually to adapt to the new conditions. Keep your perceived effort easier when it’s hot and save your longer, or intense, outings for cooler times of the day.

Targeted heat sessions should last for at least an hour to induce sweating and increase body temperature.

Full acclimatisation can be achieved within two to three weeks, depending on the temperature, the frequency and duration of exercise.

Consider wearing extra layers during your cooler workouts to stimulate the effect of a warm environment or turn off the fans in your gym to minimise evaporative cooling through the air flow.



While targeted sessions in the heat may be beneficial, you should plan to cool off during key performances. Cooling strategies before, during and after exercise, have the potential to improve sweating, offsetting detrimental increases in body temperature.

What can you do?

1 – Avoid unnecessary exposure to the sun. Rig your boats and complete your warm up and cool down in the shade where possible.

2 – Wear sun cream (SPF 30+) to protect you – sunburn decreases cooling efficiency and can be detrimental to performance. The GB Rowing Team wore Green People organic sun cream at the World Cup 2 in Linz.

3 – Choose light coloured, and breathable, clothing.

4 – Lower your skin temperature by soaking a T-shirt in cold water and re-soak every 5-10 minutes.

5 – Use a fan, or your hand, to create a breeze to help your skin cool down.

6 – Place cooling towels or ice packs on your neck and on major muscle groups, or submerge your hands/arms/legs/ankles in cool water.

Take it further with the science

Heat acclimation improves exercise performance by Lorenzo S. et al. Journal of Applied Physiology, 2010 Oct; 109, pp1140-1147.
Consensus recommendations on training and competing in the heat by Racinais S. et al. Scandinavian Journal of Medicine & Science in Sports, 2015 June; 25, Suppl 1:6-19.



You can calculate your sweat rate in these easy steps:

1 – Go to the toilet. Weigh yourself before exercise, wearing minimal clothing.

2 – At your 60-minute training session consume fluid as normal. Wipe away sweat from skin and hair.

3 – Weigh yourself after exercise, again wearing minimal clothing. Record how much fluid you consume during exercise.

4 – Then calculate your (pre-session weight) – (post-session weight) + (fluid consumed) = sweat rate

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