Don’t sweat it! How exposure to heat affects your health and wellness, and how best to protect yourself

Posted on Thursday, July 26, 2018

Hot summer day

How exposure to heat affects your health and wellness, and how best to protect yourself

University of Ottawa professor Glen Kenny and his team study the effects of heat exposure on the body. We asked him some questions about his findings and what to do to protect ourselves.

Professor Glen Kenny

Tell us about your research.

We try to understand how to better protect individuals when they’re exposed to heat, at rest or while performing physical activity. Our lab has the world’s only calorimeter, a machine that measures very precisely how much heat the body can lose through the transfer of heat to the surroundings and the evaporation of sweat. Understanding a person’s ability to lose heat during rest or physical activity as function of the level of heat stress can provide valuable insights into how a person may tolerate the heat.

What have you learned?

We know that the ability to tolerate heat varies from person to person, from hour to hour and from day to day. In fact, many things influence it: age, general health, fitness, amount of time exposed to a hot environment, taking medication and many other factors, including the amount of sleep you had last night!

Who is at risk of heat-related illness?

Everyone is at risk!  However, the elderly, people with chronic health conditions and children are the most vulnerable.  People doing any kind of physical activity in the heat, including workers, are equally at risk of developing a heat-related injury, which includes heat exhaustion, heat cramps and heat stroke.  Heat exhaustion is one of the most common types of heat-related injury.  It can be accompanied by profuse sweating as well as changes in mental status (poor judgment, irritability), dizziness, nausea and headaches. It can also be associated with significant water or sodium depletion.  Left untreated, heat exhaustion can progress to life-threatening heatstroke.

What happens as we age?

As we get older, the body’s response to heat is impaired.  This response occurs in adults as young as 40 years of age and is worse in individuals with chronic health conditions such as type 2 diabetes.  In these individuals, heat tolerance is reduced as the body is less able to cool itself via the evaporation of sweat, placing them at increased risk of heat-induced illnesses or death during rest or physical activity in the heat. Thirst sensation also decreases with age, which can further impact heat loss. 

Are certain people at greater risk of heat-related injury during a heat wave?

In the absence of adequate protective measures (use of fans, air conditioning, etc.), a continuous exposure to high temperature conditions can lead to heat-related injuries in all individuals, and in extreme situations, death in the most vulnerable individuals.  The risk is even greater when we are exposed to hot and humid conditions.  Even short periods of heat exposure can reduce a person’s functional ability, quality of life (including sleep quality) and comfort.  Furthermore, exposure to heat can aggravate existing health conditions such cardiovascular and respiratory diseases. 

So how can we protect ourselves during a heat wave?

  • Take regular cool showers or baths, but not too cold, to avoid shocking the system.
  • Hydrate regularly.
  • Put cool damp towels on your neck, armpits and groin area.
  • Head for the basement — it’s cooler there.
  • Get some rest! Sleep improves your ability to handle the heat.


Why are people at greater risk of heat-related injury when performing physical activity?

Workers, as well as the general population, commonly experience hyperthermia — that’s when your body temperature rises to levels higher than normal — while performing leisure or work activities.  

During physical activity, the body produces heat. When combined with the heat gained from the environment, which occurs when air temperature exceeds skin temperature, it must produce more sweat to offset this heat gain, to prevent a dangerous rise in core temperature.  Under these conditions, the evaporation of sweat is the only way the body can lose heat.  If the sweat drips off the body, it is not providing any cooling.


How can we protect workers?

Our most recent research is focused on middle-aged and older workers exposed to heat in the workplace.To protect workers, industry commonly employs work/rest allocations to help prevent a dangerous increase in body temperature.  However, the guidelines that are currently used to determine these work/rest allocations do not consider key factors that can affect the body’s ability to dissipate heat, such as age, sex, the presence of chronic disease and other factors.  Moreover, they do not consider factors such as hydration, sleep, duration of the work shift and number of consecutive days of work, which can affect the day-to-day response to the heat. 

Workers can be exposed to extreme heat for eight to 10 hours a day, five to seven days a week, and the effects can be very detrimental. Unlike athletes, workers do not generally get time to recover between hard workdays. Consequently, they experience a gradual decline in their ability to lose heat and are in a greater state of dehydration and fatigue.  

If you are going to work in the heat, especially over consecutives days, just remember that your body may be less able to handle the heat with each passing day.  To ensure you remain safe, follow these few tips:   

  • Get well rested.  Make sure you get a full night’s sleep. 
  • Eat a well-balanced meal (keep your energy up) and hydrate regularly.
  • When performing physical activity, listen to your body and pace yourself.
  • Take frequent breaks. Sit in a shaded, well-ventilated area. 
  • When possible, stay away from direct heat sources (vehicle engines, sun, other).
  • Use the buddy system! Keep an eye on your colleagues.
  • Rotate crew members frequently.  Share the load and keep cool.
  • If you don’t feel well, don’t wait.  Alert your crew/manager and/or seek immediate medical attention.

Kenny and his team are continuing to find new ways to protect our health and wellness during heat exposure. As a first and important step, they are developing heat exposure limits for high-risk ambient and physical activity conditions that take into account age, sex, state of health and others factors that affect a person’s heat tolerance.  They are developing heat protection measures and strategies to prevent excessive heat strain during hot weather, both short-term (such as heat advisories, maximum indoor temperature standards, work/exercise exposure limits) and long-term (such as heat adaptation strategies for heat vulnerable individuals or groups). Additionally, they have begun to test monitoring systems to provide real-time protection from excessive heat strain, to safeguard the health and wellness of heat vulnerable people. 


For more information:

Véronique Vallée
Media Relations Officer
Cell: 613-863-7221



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