Heart Rate & The Heat

Aside from the obvious ‘be smart about it’ advice you hear when it comes to exercising in the summer, there are a few things to be mindful of. Especially when we get those couple of weeks here in Vancouver each year where the temp is pushing the high 30’s (or into the 40’s like we’ve just experienced here in June 2021!)

🫀Your heart has to work harder in the heat. The technical term for this is called Cardiovascular Drift. We see an increase in heart rate (HR) as there is increased demand on the heart due to the higher temperature & humidity. Not only is it pumping blood to your working muscles, but it’s also moving more blood to the skin to keep cool. To do both of these at once, overall blood flow needs to increase and our heart needs to beat faster to do so. We also see a slight drop in blood volume due to the water lost through sweat, so our heart again has to contract faster to compensate.

All of this to say, if you usually use your HR to monitor your exercise intensity, that goes out the window when the temperature skyrockets 😆

A better bet is to use Rating of Perceived Exertion (RPE). RPE is a subjective tool to monitor your intensity by how you’re feeling.

⚠️But most importantly, watch out for the signs of heat exhaustion, and worse, heat stroke. Maintain your fluid intake, use cooling towels, and be smart about the time that you’re going outside. Do you *really* need to be running or cycling in the middle of the day? Probably not. Go out earlier if you can!

Look out for your older and younger friends & family. Older adults (65+) may not recognize, and can’t tolerate sudden temperature changes as well as they used to. This is due to age related changes in skin and body mass which can affect thermal regulation.

Babies and children sweat less, which reduces their ability to cool down. Ensure you are providing lots of water, and a cool environment for them to play in.

Signs of heat exhaustion:

• Faint or dizzy
• Weak, rapid pulse
• Headache
• Profuse sweating
• Cool, clammy skin

Signs of heat stroke:

• Absence of sweating
• Hot, red, dry skin
• Confusion
• Pulsating headache
• High body temperature

⛔️Heat stroke is a life threatening medical emergency, dial 911 right away if you have any of these symptoms.