One of the great joys of the milder seasons is being able to take your workout outside. After a long winter of toiling under the iron in closed quarters, it’s nice to shake things up and head outdoors for a change of pace, whether it’s cycling, stair climbing, sprints, pickle ball, or just taking a set of kettlebells out to a secluded area and weight training under an oak tree.
In recent years, however, it seems like the milder days of spring get shorter in duration, while the dog days of summer start earlier, last longer and are much hotter. You don't have to take our word for it. Just look at the temperature records that are being set and reset everywhere from Arizona to Alaska.
Anyway, one question we often get here at ProSource is this: How hot is too hot to train outside? The answer isn't as simple as it seems. There is no universal temperature at which outdoor activities should be curtailed. Some people need to exercise with care when the mercury tops 75 degrees F; others can and do perform at peak capacity when the temperature is ten, fifteen or twenty degrees higher. (Although if it's 105 degrees F, maybe postpone that 5K.)
The factors involved include your overall fitness, your age, the activity in question, and how accustomed you are to outside physical exertion. (If you spend your days spreading asphalt for the highway authority, you've probably built up some acclimation to heat stress.)
So instead of watching the thermometer like a hawk, you need to know how your body reacts to heat, what the best practices are for supporting your body's response to heat stress are, and most importantly, what are the warning signs that are telling you it's time to stop.
Human beings are like the ultimate hothouse flowers. A few internal degrees below perfect body temperature and we begin to experience hypothermia, or freezing to death. A few degrees above and hyperthermia sets in. Hyperthermia occurs when your body generates and/or absorbs more heat than it can displace or release.
So your body is always heating itself. It is consuming fuel to produce and radiate heat. Staying warm is one of the conditions of staying alive. A normal human temperature, as we all know, is 98.6 degrees. But that's your internal temperature. The temperature on the surface of your skin is more like 90 degrees.
Once the heat outside your body exceeds the heat emanating from within, your body's stress response kicks in to make sure you don't overheat. Your body can dissipate heat through breathing and increasing blood flow to the skin, but the primary way that the body sheds heat to remain at stasis is through perspiration. Sweat glands secrete water, which cools the skin and then evaporates.
You're actually sweating pretty much all the time. If it's 40 degrees outside and you're wearing a cotton shirt, a sweater and a jacket, you're probably sweating. If it's 70 degrees outside and you're in direct sunlight, you're sweating again. If you're up on a stage, struggling through a speech, you'll sweat simply as a stress response. Most of the time, the amount of sweat is so small, we barely notice it. It appears on the surface of the skin as the thinnest sheen and evaporates immediately.
When the heat is on, however, we really start sweating. Copiously. In fact, during high-intensity exercise in modestly warm temperatures, you can lose as much as two liters of body water per hour, as your body works to cool off. You'll lose even more under more extreme heat conditions.
People react to heat differently in that some dissipate heat more efficiently. It may be genetics or they may simply be better acclimated to increased heat. But eventually everyone will begin to dehydrate. You're simply losing too much water at too swift a rate. As you lose moisture, you're also losing crucial salts called electrolytes, which support the chemical reactions necessary for fluid balance at the cellular level and also conduct electrical pulses in your body, allowing your muscles to contract.
Once your body's cooling system begins to be overwhelmed by outside factors -- high-intensity activity and ambient temperature -- hyperthermia begins to set in. This is simply defined as an abnormally high body temperature and it only takes a few degrees of temperature rise to manifest as a health emergency. A body temperature of more than 104°F is defined as severe hyperthermia.
How does hyperthermia progress? At first you'll probably notice increased redness of the skin and excessive sweating, followed by the onset of headache and muscle cramps. You may also experience mild nausea. Clearly, if any these latter symptoms appears, you need to stop exercising, get to a cooler location and drink water. Plenty of it. Spraying yourself with cold water will also help.
If you don't, heat exhaustion will begin to set in. Symptoms may include cognitive difficulty, mood changes, rapid pulse, tunnel vision, and dizziness. In the final stages, you may stop sweating entirely as you dehydrate fully and you may suddenly feel cold or experience goosebumps. You are now at the brink of losing consciousness. (Interestingly, people who are undergoing hypothermia, or freezing to death, have the opposite experience. In the final stages, they often feel unbearably warm and try to shed the clothing they're wearing.)
Happily, there are many strategies and safeguards we can employ to avoid this kind of dire, heat-related emergency. One, as we've said, is to simply be mindful of our body's interactions with excess heat.
The most important thing you can do is drink water during exercise. DO NOT wait until you are thirsty. You are losing body water at a swift rate while exercising in hot conditions, and your thirst response is almost certainly lagging behind. Shoot for about a liter of water per hour. The most water your body can absorb in an hour is about 1.5 liters. Drink water before, during and after exercise.
If you can, consume a sports drink that contains electrolytes like sodium, potassium and magnesium. These electrolytes, as we've said, help maintain fluid balance in the cell. Sodium, in particular, is essential for maintaining proper fluid levels. There is a reason for those ubiquitous bags of sunflower seeds in baseball dugouts on hot summer days. It isn't because sunflower seeds (or pumpkin seeds) are tasty. It's because they're covered with salt.
Dress correctly for the heat. Wear light comfortable clothing made of moisture-wicking material. Avoid cotton, which absorbs and holds sweat rather than letting it evaporate and carry away heat.
If you can, pick a shady place to exercise. Also workout with a partner. Symptoms that you might not notice in yourself can be easier to spot for someone else. And finally, don't overdo it. You're out there to increase your fitness and well-being, not end up in an emergency care unit. Be careful out there!
The articles featured herein are for informational purposes only and should not be construed as medical advice. Specific medical advice should only be obtained from a licensed health care professional. No liability is assumed by ProSource for any information herein.