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The short-lived season Philadelphians call "Spring" appears to be over. Tomorrow, it's official: summer, with its stagnant humidity and oppressive heat, is here to stay. The high temperatures will certainly have an effect on your body - and will probably slow you down, but they don't have to stop you from exercising outside altogether. Understanding the physiological changes your body undergoes when working out in the heat can help you make smarter and safer decisions about continuing to do it.
When its ultra hot, your body's main concern is cooling itself down, which is does through perspiring. As sweat evaporates from the skin, it cools the body. (Think of the way rubbing alcohol feels cold on the skin as it quickly vaporizes.) Sweat's downside is that it reduces overall blood volume, forcing your heart to pick up its pace in order to do the same amount of work. On a hot day, you might feel your heart rate sky-rocketing for a task that normally feels easy.
A second method of regulating body temperature lies in blood redistribution. Your body directs more blood to the skin to dissipate heat (this is why your face gets so red), therefore less is available to the working muscles/organs. Reduced blood flow to exercising muscles is another reason why your normal workout intensity may feel compromised.
That's the nerdy scientific background on exercising in the heat - even Temple couldn't take the geek out me - but here is a user-friendly and practical checklist for how to handle these effects:
- Realize that you are not going to set any records in the heat. If you typically run a 9 minute mile with ease, don't be surprised when it feels nearly impossible on a hot day. Slow down. Respect that your body has a tremendous responsibility to regulate its temperature - your brain doesn't function at 105 degrees!
- Avoid exercising when the sun is higher in the sky, between 10am and 4pm.
- Wear synthetic clothing that wicks away sweat. Remember, sweat has to evaporate off of the body in order to cool it. Cotton clothing will soak up sweat and cling to you, leaving no room for this process.
- Wear light-colored clothing. White = good. Black and navy = bad.
- Stay hydrated. Plan your route around water fountains or carry a water bottle.
- Try to stay in shady areas.
- Don't be afraid to take breaks!