037: Running in the Heat
May 24, 2018
Summer is coming! It’s important to be aware that heat and humidity can change running in many different ways. Down here in Florida, we understand the importance of dealing with heat and humidity, but this is important no matter where you live.
Let's review of what happens to body temperature when we exercise:
- Body temperature goes up so the body sweats to try to cool it body temp down
- Body cools down as the sweat evaporates from our skin
- Body also sends more blood to the skin to cool us down, but during exercise the blood is also being sent to our working muscles - this can lead to overheating
- Body can divert more blood to skin, but then not as much going to muscles, so muscles have to work harder to produce the same effort
Heat in a dry climate:
- Dry air evaporates sweat from your body almost as quickly as you’re producing it so you can become dehydrated much more quickly.
- As you become more and more dehydrated throughout a run, your heart needs to work harder to pump your blood because it’s becoming thicker (as you lose water)
- This is called cardiac drift: your heart rate increases over the course of a run even when the intensity stays the same.
- Heat and sun increase your core body temperature. As soon as you start getting too warm, running will feel much more difficult even if your pace is the same as usual.
Heat and humidity:
- The air is already super saturated with water, so less evaporation is occuring - the water/sweat stays on your skin
- Lack of evaporation of the sweat from your skin (because there is already so much moisture in the air) leads to decreased ability for the body to cool itself
- Body tries to compensate by sweating more to get the cooling effect, which can lead to increased dehydration
How heat and humidity can affect performance:
- Running pace is affected as temperature rises
- Ideal running temp is around 50 degrees. At 60 degrees, there is a 2-3% increase in running pace (so 8 mm is actually 8:12). At 80 degrees, pace is affected 12-15% so 8 mm is 9:06
- Humidity 60-90% can increase HR 10 bpm so an 8mm might feel like a 6mm
- Muscle cramps - dehydration and loss of electrolytes
- Symptoms include dizziness, fatigue, mental fog
- Heat exhaustion
- Dizziness, headache, nausea, cold/clammy skin, profuse sweating
- Core body temp above 104
- Heat stroke
- Core body temp over 105 deg
- Disorientation, clumsiness, confusion, poor balance, and a lack of sweating
- Immediate medical attention needed - need to cool body temp - cold bath, ice packs
Advantages of running in the heat:
- Body becomes more efficient at handling the heat
- Body can dissipate heat better - improving blood flow to muscles and skin
- Start sweating sooner to help keep core body temp low
- Sweat out less electrolytes
- Body produces more blood so it doesn’t have to share as much between skin and muscles
How to train in high heat and humidity:
- Stay hydrated - aim for 4-8 oz every 15-20 min
Run early or late, not in mid-day sun
Run in the shade
- Weigh yourself before and after a workout to see how much water weight you lost and then replace it 16 oz per 1 lb lost
Wear performance fabric and avoid cotton - choose moisture-wicking fabrics and lighter colors
Plan your run around water fountains (local parks) or stash water on your route
Wear visors to allow heat to dissipate through your head, instead of hats that can trap in the heat
Carry a small sponge with you to help absorb some of the sweat
Have a cold towel waiting for you at the end of the run
Run by effort, not by pace - Like we said, running feels harder in the heat so don’t worry so much about paces
- Plan your run ahead of time and pick routes that are tree-lined
- Concrete and asphalt absorb heat then transmit more heat back to you so consider trail running = More shaded and natural surfaces are cooler
Hope you enjoy it!! Let us know if you have any questions that you would like answered on our show!
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