It's amazing to me that no matter how high the mercury goes, inevitably I will see someone outside running in the midday heat, 80's, 90's, 100 -- there's always someone out there pounding the sweltering pavement. For the record this kind of behavior does not show dedication to a fitness program, it shows a lack of intellgence.
As an exercise physiologist, I'm a big believer in the importance of working out consistently -- all year long. That said, EVERYONE (even the most fit among us) needs to drastically modify their workouts in extreme heat and humidity. Especially, when the weather first turns steamy and you're not acclimatized.
Heat illness is more than just feeling "a little uncomfortable" from the noon day rays -- it can literally be a matter of life and death. Heat illnesses range from the relatively harmless "heat cramps", to heat fatigue, to heat exhaustion to the potentially-fatal, heat stroke.
The body cools itself in two primary ways:
- By increasing blood flow to the skin so that heat is dissipated away from the body's core to the skin's surface.
- By increasing sweat production, so that the evaporation of sweat off the skin's surface can cool the body.
Heat (particularly with humidity) and exercise both compete with the body's ability to regulate body temperature within safe levels.
Exercise challenges the body by demanding blood for working muscles. So now your skeletal muscles are crying out for blood (for oxygen, nutrients and the removal of waste) at the same time your body is trying to keep you cool by bringing the blood to the skin's surface. On top of that, exercise generates its own heat which also needs to be removed from the body.
Humidity further exacerbates this problem, because if the air is already full of water vapor (as it is on a humid day) there is less room in the air to take up the sweat on your skin. So it just clings to you -- rather than cooling you as it evaporates.
And guess what? Your body is smarter than you are. Effectively your brain tells your body, "Hold on, Body -- apparently, we've got an idiot running in the noon day heat and humidity, let's shut her down before she overloads the system!" And you experience that as heat illness.
The signs of heat illness, include:
- Muscle cramps (particularly in the hands, feet or calves)
- Excessive thirst
- Drenching sweats with cold and clammy skin
- Feeling faint
- Slower heart rate
Signs of heat stroke (which is a medical emergency requiring immediate 911 assistance) include:
- Rapid heart beat
- Nausea and vomiting
- Hot, flushed dry skin
- Decreased sweating
- Decreased urination and/or blood in the urine
- High body temperature (104-106 degrees F)
- Loss of consciousness
- Shortness of breath
With heat illness (as with most things in life) an ounce of prevention is worth a pound of cure. So here are some tips for beating the heat -- before it beats you:
- Allow your body a chance to acclimatize to heat. It takes at least 4-7 days for your body to adjust to the change in temp and about 2 weeks to get used to working out in the heat.
- Drink plenty of water. Be sure to drink at least 4 oz. of water every 15-20 min. Don't rely on your thirst to let you know when you need water.
- Avoid alcohol. It dehydrates you.
- Add some salt to your food. Salt helps the body retain water.
- Workout smart. Exercise in the cooler times of day, either early AM or later PM when the sun's going down. Consider taking your normal outside workout indoors in the AC until the heat breaks, especially if you must workout at midday. Pace yourself. Do not expect to workout as hard as you normally would. It's not realistic -- or safe!
- Wear clothes that breath and wick moisture away from your body. Microfiber clothing such as Cool-Max, can really help draw your sweat towards your skin and allow it to evaporate more easily -- keeping you cooler. Cotton can get soggy and hold moisture against the skin -- impeding the evaporation process.
- Consider working out in the water. Swimming, water polo, water aerobics, even treading water are all good workouts that keep your core temperature down and can even be done in the heat of the day -- another great summertime alternative to pounding the pavement in the heat.
Geralyn Coopersmith is an exercise physiologist and certified personal trainer with over 20 years of professional experience. She is the Senior National Director of The Equinox Fitness Training Institute (EFTI) and the author of Fit and Female: The Perfect Fitness and Nutrition Game Plan for Your Unique Body Type. She has appeared on The Today Show, The Dr. Oz Show and The CBS Morning Show and she has been quoted in national magazines including: Elle, Shape, Self, Fitness, Health, More, Women's Health and many others.