Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the practical application of health information. Nutrition. Exercise. Diet. Supplementation. I look at the science behind them, and let you know whether it’s something to consider or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
It finally happened the other day. The humidity returned together with high temperatures. We already had a stretch of gorgeous weather with highs in the 70s. lows in the 50s, and low humidity. Now, all you hear about on the weather is the Heat Index so it’s a good time to review the basics of working outside and exercising in the heat and humidity.
The phrase “it’s not the heat; it’s the humidity” has been around forever. What it means is the apparent heat impact on your skin. We cool our body by sweating when the apparent temperature gets too high. How high is that? It’s a personalized thing depending on fitness level, the number of actual sweat glands you have, age, and a number of other factors. Because this deals with working out doors in some capacity, we’ll consider the major factors in that area.
Clothing matters! In my opinion, this is not the time to be wearing body contouring Lycra or some other clothing that covers the skin tightly. Loose clothing that allows air to flow freelyover more skin area will be able to cool the body more effectively. While humidity with temperature is the point of this podcast, the wind can more effectively exchange the internal heat the body is trying to dissipate. It’s interesting. The wind that can reduce the ambient temperature in the winter, something we all know as wind chill, can have a positive effect in the summer. I prefer shirts that are made with nylon and have been treated to provide UVB protection. The shirts have a vent in the back and sides with a mesh inner lining that allows air to flow freely but that’s my preference. There are many suitable clothes to wear outdoor in the summer.
It's better to work in the shade if you’re doing yard work-- if you can. The trees on my property as well as my house provide natural barriers so that I can work all around the outdoors at some point during the day if I choose. If you’re going to walk, jog or run. Try to use trails that have a tree canopy to provide relief from direct sun. Spending a little time driving to a workout is worth the gas or electricity on the days with a high HI.
Fitness matters, even for working in the yard. If you’re a regular exerciser, you will have developed a better blood vessel supply to shunt the blood flow from the internal organs to the periphery to eliminate heat. Also, if you have built up heat adaptation through regular workouts in hotter conditions, that also helps to dissipate heat.
How hard should you work with a higher HI? It depends on the intensity of what you’re doing. If you’re kneeling while planting, picking weeds, and trimming plants, you can probably do that for several hours while taking breaks to maintain fluid levels. More about fluids later. When it comes to walking, jogging, or running, your fitness level will dictate how your body cools itself. I would expect that for the average workout, your time will increase as your body will be spending more energy trying to cool you as the HI increases. Unfortunately, there are no reliable charts or formulas to accurately calculate how much you should slow down The research just isn’t there yet. Just go with the flow and don’t overexert yourself as the HI rises.
Body fat also can impact work in the heat. It can take more energy to cool off which will further require a person to reduce effort in the heat. Some medications can also impact the ability to be active in the heat. In that case, or if you have a specific condition like diabetes or other diagnosed conditions, it’s best to talk with your physician for guidance. It may also be time to stay indoors during high heat indices.
I hate to make specific limits because we’re all individuals but here are general guidelines for being outdoors in the heat and humidity. When the combination of temperature and humidity reaches a HI greater than 85, curtail the intensity of your workouts outdoors by 20-30%. While it is dependent on humidity, a temperature of 82 with a humidity of 65%, that would create a heat index of 85. If the HI is above 90, unless you’ve regularly been training in those conditions, it may be time to either reduce your intensity by half or workout indoors. It can be just too dangerous for your health.
Let’s turn to fluids. It’s fairly simple in theory: the more you sweat, the more you need to replace. There are limits, however. Every year, there are some runners who drink too much water and get hyponatremia, the loss of electrolytes. It can happen to people doing heavy work in their yards as well like post hole digging or moving mulch around the yard.
It's best to switch to a sports drink with or without sugar. They almost all contain sodium and potassium, and more and more also contain magnesium and calcium. Sodium and potassium are critical to nerve function while calcium and magnesium are used in the nervous and muscular systems. Diluting the electrolytes with too much plain water can cause cramps and the loss of neural control. How much should you drink in the heat? When the HI is above 85, drink 4 ounces every 15 minutes. Can you intersperse drinks with caffeine like the cold coffee drinks that seems to be popular now? Yes. You don’t have to drink only sports drinks. Just mix it up to keep your cooling system working effectively.
What else should you do? Protect your skin by covering up exposed area is convenient but especially wear a hat, preferably with an extension to protect your neck. Also, wear sunscreen. For now, it has to be replaced on a regular basis as sweating can cause it to dissipate. But the FDA has recently approved a new ingredient called bemotrizinol (also known as BEMT or Tinosorb S). It has been used in Europe and Asia for over 20 years.
Why is it better? It covers a wide range of both UVA (aging/cancer-causing) and UVB (sunburn-causing) rays. It is more stable and doesn’t degrade as fast in the sun. It absorbs much better and should not leave the white chalky dust on the skin. The only real issue is that it isn’t available as of this recording. Look for it later in the summer of 2026.
That should get you ready for the summer heat and humidity. Maybe one more thing you can do? Get some extra sleep if you can. Spending time in the sun burns energy; you can probably use the sleep time to recover.
That’s all the time I have for this episode. If you like this podcast, please hit the share button and tell your friends and colleagues about it. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
