Sixty-one-year-old Ballarat runner David Fraser’s weekly training regime includes four morning gym sessions and five trail runs ranging from 10 kilometres to 33 kilometres.
During summer, when temperatures rise, it is no different.
“Over summer, it would be rare to alter any of the routines. By keeping them the same, the body learns to adapt in all conditions, from very cold to extremely hot,” he says.
“The only time things would change is if there were lightning or very dangerous winds.”
While Fraser says he enjoys exercising in the heat and hasn’t experienced any serious side effects, citing occasional muscle cramps from sodium loss as his only issue, how safe is it to continue your normal exercise routine when it’s hot?
Exercising in the heat
Sam Chalmers, senior lecturer in human movement at Adelaide University, says that while the body has strategies to increase the rate of bodily heat loss during exercise in average temperatures, such as increasing an individual’s sweat rate and skin blood flow, “stressful sport and exercise in hot and humid conditions may mean that the body is unable to defend against substantial rises in core temperature. Exercise challenges the maintenance of our normal core temperature because it generates a huge amount of internal body heat while we are also combating heat gain from the hot external environment.
“This can mean comparatively minor symptoms such as headaches and feelings of faintness, through to more severe issues such as central nervous system dysfunction, loss of consciousness and organ damage,” he says.
It can also increase the risk of exertional heat illness, ranging from mild heat stress through to heat exhaustion and, in severe cases, potentially deadly heat stroke, says The Royal Australian College of General Practitioners President Dr Michael Wright.
“Symptoms of heat stress or heat exhaustion include dizziness, nausea, and fatigue. With more severe symptoms, such as if someone is confused, collapses, or stops sweating despite the heat and strain, those are signs of heat stroke, and they need emergency care.”
Who is more at risk?
Anyone can be affected by hot weather, but some people are more vulnerable and may become unwell at lower temperatures.
This includes adults over 65 years of age, pregnant women, children and babies, and people who don’t regulate heat as well, “such as those with chronic health conditions like heart, lung and kidney disease, and diabetes,” says Wright.
Exercising in a heatwave
A heatwave, which is usually defined as three or more days when the maximum and minimum temperatures are unusually high, can exacerbate the effects of high temperatures. In this scenario, Wright recommends avoiding outdoor exercise altogether.
“Sometimes skipping or postponing exercise is the safest option,” he says.
Sydney-based runner and exercise physiologist Veronika Larisova opts for early morning or late evening sessions to avoid the peak heat.
“I do alter my routine because I love being outdoors, but I don’t enjoy running in extreme heat in the middle of the day or early afternoon,” she says.
“Besides being uncomfortable, extreme heat places additional stress on the cardiovascular system and thermoregulation, so maintaining the exact same intensity, duration, or timing year-round isn’t always appropriate or safe.”
Larisova says that she also reduces the intensity of her workouts and changes the exercises she undertakes when temperatures are higher.
“When I only have time to exercise in my lunch break and the day is super hot, I usually swim laps at [Bondi] Icebergs or do a run-swim session at Clovelly,” she says.
“Consistency over time matters more than any single session.”
Can there be benefits of exercising in the heat?
While it may be best to avoid certain exercises in a heatwave, Chalmers says that, if undertaken safely, there can be benefits to exercising during the standalone days of warmer weather.
“Regular exercise in the heat will result in the process of heat acclimation, which is a set of physiological adaptations that increase tolerance to the heat,” he says.
“These can include increases in sweat rate, enhanced skin blood flow, greater body fluid volume, a lower heart rate for the same exercise intensity, and a general perception of feeling more comfortable in the heat.”
Not only has Fraser experienced this, but he says it has also been beneficial in other ways.
“My wife, who is a running coach, always told me that running in the heat was the equivalent of doing altitude training, the blood volume in your body increases, and your heart starts pumping more efficiently, which increases oxygen to your muscles,” he says.
“Your mental strength improves, and lastly, after finishing a run in the heat, dripping with sweat, you get a huge endorphin fix.”
Experts agree gradual exposure to warmer conditions may help your body acclimatise, but they warn against it during heatwaves.
How can you exercise safely in the heat?
If you choose to exercise in the heat, Sports Medicine Australia (SMA) chief executive officer Jamie Crain says planning and preparation are key to exercising safely.
“Drinking lots of water prior to exercising, that’s important to do, making sure you’ve got access to water during exercise, and of course, take breaks if you need it, ensure you have access to shelter or shade and adjust your clothing [to lightweight, breathable fabrics] as appropriate,” he says.
Crain suggests using the Sports Heat Tool – developed by SMA and the University of Sydney’s Heat and Health Research Centre – to assess heat-related risk factors for individuals during their respective sports.
“Internal heat production and the levels of clothing or protective equipment (which blocks heat loss) vary considerably by sport. The duration of exposure is also highly dependent on the sport,” explains Professor Ollie Jay, Academic Director, Heat and Health Research Centre.
“Our tool integrates all of these factors along with local weather information using a physiological model to estimate heat stress risk for 40-plus individual sports. ”
Chalmers also recommends the tool, as different sports have different risk profiles based on factors such as intensity and environment.
“More intense exercise and activities with less breaks are typically more risky than those where exercise intensity is lower and have more breaks,” he says.
“The heat risk tool can be used to inform decisions around when and how hard you might like to exercise and when additional cooling strategies might be required.”
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