Six tips from the experts to keep cool during summer workouts
To work out in the heat, you need to acclimatise, cool your body, and drink water before, during and after exercise, say leaders in the sports medicine field
Sticky, sweaty and energy-sapping: that pretty much sums up exercising in the summer. But sweating is unavoidable; it's the body's way of cooling off when its core temperature gets too high. It helps us survive the heat.
This automatic, involuntary temperature-regulation process (called thermoregulation) to maintain a stable core body temperature of about 37 degrees Celsius is orchestrated by the hypothalamus in the brain. It's based on a negative feedback loop sensitive to sensory information that detects heat gained by the body and heat lost to the environment.
As the temperature rises and body temperature is elevated (called hyperthermia), heat loss mechanisms are activated, such as increasing cardiac output, widening of the skin's blood vessels (which decreases blood pressure) and the initiation of the sweating response.
Sweating increases as the core body temperature rises to 39 degrees, when maximal sweat rates are achieved. While the body can tolerate small changes of two to three degrees, a critically high body temperature can cause cramps, exhaustion and, in severe cases, life-threatening heat stroke.
To help athletes sustain and/or enhance performance and to minimise the risk of heat illness from exertion, an international team of sport scientists published detailed recommendations last month for prolonged sporting activities in hot ambient conditions.
Appearing in the peer-reviewed , the report is the result of a meeting of the experts in March last year at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar, where they reviewed and discussed training and competing in the heat.
Here are six tips from the experts to keep cool during summer workouts.
The most important thing you can do to reduce physiological strain and optimise performance in sizzling conditions is to acclimatise, say the experts. This should involve repeated exercise in hot weather lasting at least 60 minutes a day over one to two weeks.
Heat acclimatisation improves the body's ability to control body temperature, sweating and blood flow through the skin. It also expands blood volume, allowing the heart to pump more blood to muscles, organs and the skin as needed.
Within the first few days of acclimatisation, your body will show signs of adaptation: decreases in heart rate, skin and rectal temperature, and increases in sweat rate and work capacity. However, the experts say the main physiological adaptations are not complete until about a week later.
"Ideally, the heat acclimatisation period should pass two weeks in order to maximise all benefits," they say. The fitter you are, the more quickly you'll adapt.
You should begin a workout or race in a euhydrated state, meaning with a normal body water content.
"Resting and well-fed humans are generally well hydrated," say the experts, "and the typical variance in day-to-day total body water fluctuates from 0.2 per cent to 0.7 per cent of body mass." For a 60kg person, that means 1.2kg to 4.2kg of total body water.
Every two to three hours before exercising in the heat, the experts advise drinking about 6ml of fluid per kilogram of bodyweight. For a 60kg person, this means about 360ml of fluid.
You can tell how hydrated you are by monitoring the colour of your urine. If you're properly hydrated, it should be very pale yellow. Urine that is dark yellow or tan indicates greater dehydration.
During intense prolonged exercise in the heat, body water mass losses should be minimised - without increasing body weight - to reduce physiological strain and help to preserve optimal performance, the experts say.
Sweat rates during exercise in the heat vary dramatically depending on one's metabolic rate, environmental conditions and heat acclimatisation status. Typically, athletes performing vigorous exercises in hot environments have a sweat rate of between one and 1.5 litres per hour, although certain people can sweat more than 2.5 litres per hour.
Training in the heat also increases your daily sodium (salt) requirements, the experts say. Sodium supplementation might therefore also be needed during exercise, especially for heavy and "salty" sweaters.
Sodium is the main electrolyte lost when you sweat. If too much is lost and not replaced, muscles may cramp.
If your workout lasts longer than an hour, the experts advise consuming a solution containing 0.5 gram to 0.7 gram of sodium per litre. Pocari Sweat sports drink, for example, has 0.49 gram of sodium per litre.
If you're experiencing muscle cramps, the experts suggest increasing sodium supplementation to 1.5 grams per litre of fluid.
"People who sweat heavily may also deliberately increase sodium intake prior to and following hot-weather training and when they compete to maintain sodium balance," they say.
They also advise including 30 grams to 60 grams per hour of carbohydrates in your hydration regimen for exercise lasting longer than an hour, and up to 90 grams per hour for events lasting more than 2½ hours. This can be done through a combination of fluids and solid foods.
Adequately rehydrating after exercise in the heat, by providing plenty of fluids with meals, is essential to optimise recovery, say the experts. If aggressive and rapid replenishment is needed, consume fluids and electrolytes to offset 100 to 150 per cent of the mass you lost within one hour of ending your workout.
Recovery hydration regimens should include sodium, carbohydrates and protein. This is because exercising in the heat increases carbohydrate metabolism.
A drink containing protein might help restore fluid balance after exercise better than a standard carbohydrate-electrolyte sport drink, the experts say. Combining protein (0.2 gram to 0.4 gram per kilogram of body weight per hour) with carbohydrate (0.8g per kilogram of body weight per hour) can also maximise protein synthesis rates.
Chocolate milk, for example, is an ideal recovery drink. It has a carbohydrate-to-protein ratio of 4:1, as well as sodium.
You can cool yourself externally by using iced garments, towels, water immersion or fanning, or internally via cold fluids or ice slurries.
Skin cooling will reduce cardiovascular strain while exercising in the heat, while whole-body cooling can reduce organ and skeletal muscle temperatures.
Immersing your entire body in cold water for 30 minutes at a temperature of 22 to 30 degrees, or immersing body parts such as legs at lower temperatures (10 to 18 degrees), has been shown to be effective.
However, cooling of the muscles will decrease nerve conduction and muscle contraction velocities, and athletes might therefore need to warm up again before a workout or race.
Cold fluids can potentially enhance your endurance performance if you drink it before, but not during, exercise, the experts say.
It's suggested that the downside of ingesting cold fluids during exercise might be a reduction in sweating and, therefore, skin surface evaporation, due to the activation of thermoreceptors, which are probably located in the abdominal area.
