After the 2018 Ironman Boulder, the biggest complaint I heard from athletes was the heat and its relation to a high DNF rate. We are all aware that heavy exercise in high temperatures can lead to medical emergencies such as heat stroke, but so many tend to brush this off as something that could happen but certainly won’t happen to them.
So instead of focusing on heat illness, I’d like to discuss a heat-related issue that should catch any athlete’s attention: Yes, if your body overheats, your performance will be diminished and you will not be able to race at your full potential. Consider this athlete's story.
Ironman Boulder second-timer Andrea Greger hit the start line prepared to annihilate her previous course time. The day started off well with a 15-minute PR on the swim leg, but by mile 30 of the bike, she knew she was in trouble. It was hot, she couldn’t eat and her pace suddenly slowed. After stopping three times to vomit, Andrea considered pulling from the race. With encouragement from teammates, she kept pedaling, finishing well behind her target pace.
As she started the marathon it quickly became clear that running wasn’t an option. No cooling effort could bring her core temperature down, and she vomited five more times. Although the task felt monumental, Andrea was determined not to quit and continued to march her way toward the finish.
“I remember at mile 25 of the run, a lady told me I was almost there, and I wanted to kill her!" she said. "It was another 20 minutes.”
Although it wasn’t the race she expected, Andrea learned a lot that day — about herself, about racing, and about the toll of heat.
Negative Effects of Heat on Performance
First, a quick physiology refresher. One of blood’s primary jobs during exercise is to carry oxygen to muscles. To cool the body, blood flow is shifted from muscles to the skin in an effort to dump heat. This process makes blood more difficult to pump to muscles to perform their work. The metabolic system used for muscle-fueling must then shift from aerobic to anaerobic metabolism, and VO2Max will be reduced.
In short, an athlete’s low-effort, sustainable-for-hours pace now has an expiration date closer to that of a hard tempo or threshold effort. The body burns through glycogen faster than you can process it in a race, so when it’s out, it becomes very difficult to continue. This is the dreaded bonk that can drastically slow pace, make racing miserable and lead to a DNF. And let’s not forget that heat illness is an issue and a serious risk.
To sum up, heat can lead to:
Wasted energy: When the body gets too hot, you sweat excessively. The energy spent running your cooling system on overdrive is energy that could be spent elsewhere.
Stomach issues and gastric distress: To dissipate extra heat, your body will increase blood flow to your skin as a cooling process, and decrease blood flow to your GI track. This shift away from the gut can lead to the dreaded stomach issues faced by many endurance athletes.
Decreased muscle endurance and cramping: Cramping occurs and muscle endurance is decreased because the body will burn through its limited glycogen stores more quickly with less oxygen available for metabolic processes.
Fortunately we are not doomed when the weekly forecast is showing temperatures in the 90s or higher. You can help minimize the slowing of pace through heat acclimation training, though it is important to be realistic about your heat acclimation and adjust pace accordingly. “Pushing through” is likely race mismanagement and can lead to disappointing results or, more likely, to a dreaded DNF.
Age-group athlete Michael Stanley said that including hot yoga as part of his training regime helped him in his heat acclimation efforts.
“That was a big help in preparing for the heat. I also scheduled rides and runs in the middle of the day to help prepare my body for the heat," he said. "All in all I had a great day at Boulder, and though it was hot, I felt I was well prepared for the day.”
How heat acclimation works
- With consistent exposure, your body begins to sweat at a lower temperature but will expend less loss of the electrolytes contained in sweat. Additionally, the body becomes better able to absorb liquid and calories in the heat.
- It takes just seven to 10 days to build heat acclimation, but only five to seven days to lose it. Once acclimation has occurred, maintain it by two short heat training sessions per week.
Heat acclimation in training
- Doing long or hard training sessions in the heat of the day can jeopardize the integrity of the workout by not allowing the body to perform at its full potential, but active recovery or shorter sessions can help the body adjust to the heat.
- Outside of training, avoid overly cooled environments, but don’t allow your body to get too hot either. You want your body to become accustomed to the heat without zapping your energy.
Heat acclimation in the sauna or steam room
- Two weeks prior to an event, begin doing “intervals” in the sauna (or steam room if preparing for humidity).
- On the first day, sit in the sauna for two to five minutes. Step out and cool down for several minutes, taking a cold shower if possible. Go into the sauna again for a few minutes less than the first time.
- Repeat this process for seven to 10 days, gradually increasing the intervals each time.
- Make sure to hydrate, consuming your normal electrolytes while in the sauna or steam room.
- While this is a great way to prepare your body for racing in the heat, do so at your own risk, and listen to your body. You do not want to end up unconscious on the sauna floor!
Race-day cooling methods
Start using cooling techniques before you are overheated.
Douse body with water: This will aid in evaporative cooling so that the cooling process isn’t relying 100 percent on sweat. This is easier on the body, preventing it from spending so much energy on sweating as a cooling mechanism.
Cooling fabrics: Try cloth ice-rolls around neck or a white hat, filled with ice at aid stations.
Fluid and electrolyte replacement: Using your calculated sweat rate, plan your hydration strategy appropriately. You will also want to experiment with electrolyte supplementation to find the correct balance for you.
You'll find your own race-day cooling techniques, but consider this advice from Ironman first-timer Jeff Bosch, who refilled or topped-off bottles at every aid station on the bike course and sprayed himself with any leftover water that wouldn't fit in the bottles. He also sprayed himself mid-ride, especially before descents and faster sections where the passing air would be effective in assisting evaporative cooling.
“I think it’s best to take the time to get extra water on the bike. It seems much like nutrition: if you get behind in cooling you can never seem to catch up," he said.
Sage Maaranen is the owner of Sage Training Multisport, a company assisting athletes of all levels to reach optimal performance or first-timer goals while maintaining a balanced life. An athlete herself, Sage hopes to invite camaraderie on this shared adventure and advocate for populations traditionally excluded from triathlon- namely women, minority youth, and LGBT athletes. Sage is a collegiate cycling coach and individual triathlon coach certified by USA Triathlon, USA Cycling and United States Masters Swimming. For more information, visit http://www.sagetrainingmultisport.com/ or contact her at email@example.com.
The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.