This is a common question, which comes up several times a year in the Endurance Nation forums. Here’s the most recent iteration, with my response:
“The last time I trained in heat was last August if I recall correctly. I’m about to enter taper but I’m thinking that my priority should be running and biking in the heat, even if that means reduced duration and intensity.
Do we have guidelines about preparing to race in the heat? Does anyone have recommendations?
…the interesting question becomes whether to prioritize warm-weather running over workout quality. I’m inclined to run right after work tomorrow, for example, to begin to acclimatize…”
And my response:
Two key things to keep in mind about heat “acclimation”:
- No matter what you do, you’ll never feel as if 87F is the same as 62F
- No matter what you do, you’ll never be able to run (specifically; biking may be different) at the same speed in 87F as you do at 62 F. That’s not your goal. Your goal is to induce changes in your body’s physiology (sweating, blood volume, cardiac function, salt electrolyte management, etc) to enable you to perform at your best at maximum safe core temperature. That said, here is a summary of research on acclimation:
http://www.sportsci.org/encyc/heata…ccl.html#1
Here’s a paragraph from the above: “Most experts agree that intense physical training in a cool environment improves physiologic responses and speeds the process of heat acclimatization. During training in cool conditions, optimal physiologic adaptations may be achieved if strenuous interval training or continuous exercise, at an intensity above 50% of VO2max, is performed for 8-12 weeks. Maintenance of an elevated core body temperature appears to be the most important physiologic stimulus.”
Problem is, when training at intense levels in a hot environment, you get to (and above) that elevated core temperature sooner, and that limits you ability to keep working hard. You can use heart rate (HR) to help you determine how you’re doing relative to core temp. E.g., when doing faster intervals (TP, say, 5-8 minutes at a 10K pace), you want to run at the HR which you see when doing those intervals in an ideal environment (about 50F, no sun). Trying to do TP intervals at the same pace in 87F weather as you do when cooler will first raise your HR above that level, and you’re so close to your maximum HR that you can’t keep going at the same pace, so you’ll slow down, and not get the full benefit from the workout as to muscle fitness.
To your specific question: in my opinion (you can find differing expert opinion), do your key run workouts in cooler weather, to maximize fitness improvement. Do some less critical workouts in the heat, such as doing some bricks in the heat of the afternoon, or just a 20-30 minute jog in the heat after a morningswim. And use the sauna 20-30 minutes daily if possible to help with the physiologic changes you are trying to create.
If you simply MUST try to do some key running workouts in the heat, I opt for interval workouts rather than long steady runs. The biggest problem is with internal heat build-up. Once you get up to 102/3 or so, things start to deteriorate, and you must slow down or die. Doing intervals allows for recovery periods which enable the core temp to remain in the safe zone for the whole wko, even while doing maximum efforts at, say TP for 5-6 minutes.
Biking: usually, the bike is less of an issue, as it occurs in the morning, while it is still warming up, and you are moving +/- 20 mph, which has a wind chill factor with it. Unless you are doing a world class 100/200 meter sprint, you are not running that fast!