During the past week, I ran two races in 80+ degree temps, with high humidity under sunny skies. It was hot! In July we might, and perhaps should, expect that. Coincidentally I’ve been reading Alex Hutchinson’s Endure in which he probes various conditions elite athletes overcame to achieve new heights. Or if they miscalibrated, went over the edge. This book is a winner – Hutchinson has done his homework along with first-hand experience as a top middle distance runner. He was also an inside journalist on Nike’s attempt to break the 2-hour marathon in May 2017.
Considering the recent heat spell, the chapter on heat was relevant. I’ll paraphrase how Hutchinson describes it. When core temperature rises, blood shunts to the skin as a way of dissipating heat and cooling the body. This mechanism works up to a point but there’s a tradeoff – this shunting steals blood from internal organs. At the extreme, heatstroke makes an appearance. This is dangerous stuff. When core temperature rises above 106° the self-regulation process breaks down and external cooling (ice baths!) is needed immediately to avoid long-term damage. I thought back on an experience with my first car — a ’56 Chevy. It ran well but burned oil – about a quart every 150 miles. I was on a trip and missed checking the oil and suddenly smoke started coming through the steering wheel. I stopped, let it cool, and refilled the oil. It had plenty of water but parts of the engine needing lubricant had been compromised. The car started OK but never ran the same. While our bodies are designed to regenerate, there are limits. We may recall Alberto Salazar’s 1982 Duel in the Sun at the Boston Marathon. A dehydrated Salazar beat Dick Beardsley by 2 seconds, but collapsed and nearly died. Reports suggested his immune system was permanently compromised. He never ran as well again.
I then went to the Bible – Tim Noakes’ Lore of Running, the 921 page tome on everything you might want to know about running, in which he has a section on heat hazards. Suffice it to say, there is a gradation of risk from heat exposure with the continuum moving from a malaise tending to slow our pace to full-fledged heatstroke. Noakes describes, in some detail, how air temperature, humidity, wind, and the athletes’ sweating capacity are all relevant factors. Regarding the first two, you may have heard of the Wet Bulb Globe Temperature guidelines, the accepted index races use to cancel or suspend a race, and which results in a line graph showing moderate, high and very high risk from the combination of temperature and humidity. For example, the High Risk line intersects at 80° and 70% humidity and at 90°/30% and the Very High Risk line at 100°/30%, 90°/70%, and 85°/85%. Thus, humidity is a key contributor. When driving to a race our car thermometers show temp but not humidity. So we must be vigilant.
As to wind, recall your experience in front of a fan on a hot day or over you at night when trying to sleep in a room without AC. The ambient air temp is not cooler, but it feels cooler. By some accounts by as much as 10 degrees. We lose heat energy to passing air molecules but if the air is stagnate, that effect recedes. So on a hot day running into the wind is good even if it adds resistance.
The section on sweat capacity got into the weeds, but in essence Noakes notes individual differences plus the vital importance of acclimatization. Our bodies are better prepared in the fall for the heat after a summer of training in it.
Perhaps most interesting was Noakes’ conclusion that heat hazards are more prevalent in shorter race distances, say in the 5K to 10K range. He attributes this to trained athletes being able to expel heat better when in their aerobic zone, a place we stay for most of a longer race. It’s when we exceed this capacity, even for a short time, that we can expect trouble. Both Noakes and Hutchinson encourage hydration but agree this is not insurance against a heat event. Recall my ’56 Chevy had plenty of water!
My take away is we need to be smart. That on any particular day, we should account for the four factors: temp, humidity, wind, and conditioning, and adjust accordingly. Usually that means adjusting pace or time of day we run, but it might also mean running shorter and picking up our miles on a cooler day. Best on the hottest days to run with somebody or carry our phone. If we find ourselves succumbing to heat, immediate help is paramount.
Thankfully summer is here. Not long ago we were figuring out how much to layer. Enjoy these long, warm (sometimes hot!) days but be safe and stay cool!