Yesterday I participated in my first triathlon, a 50 mile race where I crashed and burned in the run. In fact most of the field crashed and burned in the run. It was so hot at Lake Heyburn that the run became more of a survival exercise than a race. The heat index was well over 100, and the course offered absolutely no shade for relief.
Through the 9 mile run, I averaged 13 minute per mile pace consisting of a lot of walking and very little running. My heart was racing when I tried to run, and when it wasn’t racing, I was feeling a strange pain in my flanks that had me somewhat concerned about my kidneys. Granted, that might have been from the 2000 meters of swimming and 40 hilly miles of cycling causing some muscle soreness, but when it’s that hot outside, I try to err on the side of caution.
At this point, you may be wondering why I would write an article about running in the heat. While I may not have my Hot Weather Running degree from Vermtech, I do have a lot of experience running in hot weather. During the Summer, I typically spend at least 2 days a week running midday in the Oklahoma heat. I routinely run sub-25 minute 5K’s in triple-digit weather, and I’ve been known to throw in 6.2 and 13.1 now and again. With what I learned yesterday, hopefully I can provide some insight beyond just hydrate and be careful.
Hydrate and Be Careful
Whaaaat? I said I would provide insight beyond hydrate and be careful, but I can’t just ignore the basics. If I failed to state the obvious, somebody might go out on a 20 miler without a single sip of water and then blame me when they wound up dead on the side of a trail. So since we’re here, let’s look at hydration and caution in depth.
Before you know how much and what to drink, you need to have a better idea of your sweat rate. While one person may only lose a few ounces in an hour of running, another person might drop a 2 liter with enough salt to supply the local Chinese restaurant for a few weeks. The only way I know to measure your sweat rate is to weigh yourself before and after exercise taking into account any hydration or elimination.
So far this Summer, my sweat rate has been absurd. Through a 30 minute run last week in a 107 degree heat index, I lost 3 pounds taking into account the 16 ounces of fluid I added back through hydration. That’s 6 pounds per hour if I continue at the same rate. In previous years, my sweat rate has been closer to 4 pounds per hour.
Since 1/2 a liter of fluid is around 1 lb, that means I need to drink around 3 liters/hour to replace all of the lost fluid. Needless to say, that’s absurd. My body couldn’t hope to process that much fluid in that short a time. And, that’s alright. Ending your run in a slight fluid deficit (3-4% body weight) is not going to affect your health or performance negatively. The goal is to avoid the level of dehydration that leads to fatigue, dizziness, and potentially other, more severe symptoms.
For a 1 hour run, a single, handheld 1/2 liter bottle would probably suffice. For 2 hours, I probably need 2 bottles. For 3 or more, I have to look at rehydrating at a much higher rate to avoid losing too much fluid.
But YOUR numbers will be different. You need to keep track of your fluid losses, come up with your own numbers, experiment, tweak, and go back out and try again. And when you’re out there running, look for these warning signs of a potential problem:
- Chills: The first symptom I experience when body temperature and/or hydration have gone off the rails are chills.
- Pit Stops: I don’t see this anywhere online, but it definitely happens to me. I almost never stop during a race, but when it’s hot and I get behind on fluids, I sometimes have to stop.
- Swollen Extremities: Did your wedding ring suddenly get really tight? Maybe you’re having trouble making a fist? If it’s hot, chances are you’re dehydrated, but this can also be a sign of hyponatremia so you have to think clearly before you take action. Hyponatremia is deadly so you have to make the right decision in this situation or get medical help.
- Dizziness: You’re too far gone. Stop running, cool off, and hydrate. Or, if you’re like that guy at my last triathlon, just keep moving forward and miraculously survive. Just don’t blame me if you take that route and end up dead.
- Cramping: It’s tough to come back from cramping, but as long as you’re not dizzy and not vomiting, you can try to work your way through the cramps.
- Fainting, Vomiting: Stop and get help.
Any Summer run you finish without a stop in the ER is a win. Check your ego at the door and be careful out there.
Adapt and Conquer
Like any other challenge in running, your body must have time to acclimate to the heat. It’s like running at higher altitude. Your body just needs some time to adapt to the new stress.
The easiest approach is to make sure you’re maintaining your running volume through the Spring warm-up. If it’s gradual, you may be able to adapt without any particularly difficult runs, but if it’s not gradual or you miss some training during the late Spring and early Summer, it may be more challenging.
This year, I’ve struggled to adapt after a cold, soggy May followed by a month off for vacation. When I resumed running in July, heat indexes were North of 100 degrees fahrenheit. My training pace fell from a high-7 average to high-8’s because of being forced to walk. After a month of more consistent training, I’m finally starting to feel better heat tolerance during midday runs.
Protect Your Skin
Unlike my training runs, my triathlon run took place after I had already been out in the sun for 3 hours. Even though I had used sunscreen, the trisuit I wore left part of my back, shoulders, and upper arms exposed. It also exposed more of my legs than normal. The result was a moderate sunburn in all of those areas.
It’s hard to find studies relating sunburn to endurance exercise, but I did manage to find one, Human Thermoregulatory Responses During Heat Exposure After Artificially Induced Sunburn. Unfortunately, the structure of the study did not mimic the kind of situation I experienced so it’s hard to draw too many conclusions, but one issue the study does demonstrate fairly conclusively is that you will produce less sweat from skin that is sunburned. It also demonstrates a higher rate of perceived exertion (RPE), but RPE is obviously completely subjective. I can’t imagine feeling better with a sunburn than without.
My guess is that there is more to sunburn than just sweat rate and RPE, but even if we just look at sweat rate, it’s clearly important to protect your skin. At extreme levels of heat, even a minor adjustment in cooling capacity can make a huge difference. Whether you prefer sunscreen or covering up with clothing, take the appropriate steps not to sunburn.
Delay the Inevitable
There are a variety of effective tactics to delay your body’s need to cope with the heat. It could be something simple like running with a non-insulated handheld filled with ice water. Even in the worst heat, your hand will still get too cold to hold the bottle for more than a few minutes at a time. Eventually, the ice will melt, and the water will warm up, but your body will have benefited from blood being circulated through the hand carrying the bottle.
A similar tactic I’ve used for long runs is filling my hydration pack bladder with ice water. How long it lasts will vary from pack to pack and bladder to bladder, but there’s a good chance you will get 45-60 minutes of cooling over your entire back. I’ve also heard of runners using ice gloves or various other clothing items dipped in ice water and/or filled with ice. If someone hasn’t invented a hat with a pocket for ice on the back of your neck, then there’s your billion dollar product idea for the day.
At the triathlon, the water stops were offering towels dipped in ice water. On my first lap, I didn’t take one, and I paid dearly for it. Had I taken that towel, I might have been able to run most of the first 5K loop. Instead, I found myself less than a half mile into the first 5K struggling with heat exhaustion. Once you’re in that kind of deficit, it’s hard to get it back, especially on a course with neither shade nor wind. During the 2nd lap, I found a towel and started using it to keep cold water on my neck. The water stops also started giving us cold bottles of water to carry instead of just handing off cups. The net result was a drastic improvement in my heat stress to the point that I ran more in the last lap than I did in the first lap.
Running in heat is hard. Delay the full impact of the heat on your body as long as possible with whatever combination of cooling approaches is suitable for your race or training run.
Dress for Success
When running in the heat, you really have two choices: (1) Cover up (2) Strip down.
If the sun is out with little chance of shade accompanied by high humidity, covering up may be your best option. It’s the approach you see taken by people who work in the heat across the globe, and it’s hard to imagine they’re wrong. The clothing will protect you from sunburn and keep your temperature down by keeping the sun off of your skin. The obvious negative is that clothing will reduce the amount of cooling through sweating and blocks any wind or breeze.
On the subject of clothing, it’s probably good to discuss color. In my own experience, lighter colors will help in extreme heat, but there is considerable debate on the topic. My recommendation is to try both light and dark colors and see which feels better to you. If there’s no difference as shown in some studies, go with what you think looks best. That said, a Google Images search for Badwater Ultramarathon gives a lot of white clothing. White might be good…
If there is any wind on the course or the humidity isn’t too high, stripping down may be a viable option. The more skin you can expose, the faster your body will cool through evaporating perspiration. That said, please don’t get nekkid and tell the cops I told you it was a good idea. You still need to keep all of the relevant bits appropriately contained.