Yes, these are the dog days of summer. The days Canadians long for in mid January. But now that they are here, somehow we find ourselves suffering in oppressive humidity and extreme temperatures.

But humidity can do more than make you feel tired, clammy and have a bad hair day. It can affect sports performances and just about any outdoor physical activity and how the body attempts to cool itself. When the air is saturated with water vapor, sweat from the body won’t evaporate as well as it would in lower humidity, and mostly just falls to the ground before it has a chance to cool the skin. Since the body doesn’t get any cooler, the body continues sweating. Not only can this increased demand on the thermoregulatory and cardiovascular systems of the human body potentially cause a decline in performance, this also leads to dangerous levels of dehydration because of it.

The human body uses evaporative cooling as the primary mechanism to regulate temperature. Since heat production during exercise can be as high as 15- 20 times that compared to rest, the body needs to find an efficient way to dissipate this heat and maintain a stable temperature between 36.5 and 37.5 °C.

A body that is working out in the heat and humidity can expect a typical sweat rate 1.0 – 2.5 litres per hour and in extreme temperatures and humidity, can expect rates of over 2.5 litres per hour. Developing some strategies to thermoregulate the body will decrease the risk of serious heat load.

• Stay hydrated. Increase volume intake into the body.

• If possible, take advantage of different times of the day to work out, in order to avoid high heat and humidity.

• Acclimate to the heat by regular exposure to hot environments.

• Consume adequate sodium.

• Minimize the amount of clothing worn so that it doesn’t produce an insulator effect on the skin.

The best way to know before you go is to learn about the Air Quality Heat Index (AQHI) and what it all means so that judgments and decisions on how to regulate the exercising body when the air quality is poor, can be made.

Visit these articles on air quality for more information.

Outdoor Exercise and Air Quality
Air Pollution and Exercise
SIRC Newsletter – Weather

For more information on heat and humidity, please visit SIRC.