Mark Allen: Training in Heat
If you are a triathlete, there will come a time when you must deal with heat. For most, it's on a daily basis during summer. For others it might be at a race far from home where the sun's intensity makes more than the competition heat up. Day to day heat requires some preventative maintenance to sustain your health and fitness. Race heat can be dealt with more easily. Both require attention to fluid and mineral replacement.
Day to Day Heat
The main challenge to training in heat is rehydrating. For many, It is almost impossible to replace fluids that get sweat out in training while you are working out. And the weather doesn't have to be extreme for a person to hit their maximum sweat rate. If the heat is hovering around 85F or higher you can hit that max sweat rate even at the low end of your aerobic heart rate zones! Absorption rates of fluids are around 30-40 oz/hour or about 1-1.5L/hour. Yet, the amount you lose can be
So here is the drill. Weigh yourself before you head out for a workout on a hot day. When you return home later weigh yourself again. The amount of weight difference is going to be almost completely from fluid lost through sweating and through exhaled air. Let's say the difference was five pounds. To replace that amount of fluid, you will need to drink 1.5 times the amount lost. So over the remainder of the day you would want to take in about 7.5 pounds of fluids. Keep in mind that your stomach can only absorb about two pounds of fluids per hour, so it will take some time to get it all back in. Humans are not like other animals that can go to the watering hole and down a massive amount of water and absorb it. A large part of what we drink passes through our bodies without being absorbed.
In all that sweat that you lost are going to be some key minerals that can also get depleted in heat. One is sodium, the other is magnesium. If either of these gets too low in our bodies performance drops. Low sodium can lead to a feeling of being overly fatigued, to muscle cramping, muscle weakness and headaches. Low magnesium can show up as muscle cramping also or as spontaneous muscle spasms. You may also experience your heart skipping beats, feeling disoriented, irritable or combative with low magnesium levels.
If you supplement magnesium, recommendations are around 300-400mg/day. Sodium recommendations are all over the board. In general, most people start to experience a fall off in performance after about three hours in heat if sodium is not replaced at a rate of about 350mg/hour. However, some people will need more than double this amount to stave off cramping. Regardless of what the recommendations are, consult with a trained professional in this area before starting with a regimen to supplement.
Racing in Heat
Keep in mind the general guidelines just mentioned on maximum fluid intake per hour and experiment with it in training so that you have a pretty good idea of how much you can drink per hour before you start to feel like your stomach is swimming in fluids. Also, test out sodium during long hot sessions to see what feels right for your body. We recommend you have a form of sodium that you can taste on your tongue. Suck on it until your body tells you that you have enough, then if there is any
left, you can spit it out. Swallowing a tablet will not allow this amount of fine-tuning to race sodium supplementation.
Preparing for racing in heat can be a challenge if you live in a climate that is significantly cooler than what you will encounter on race day. If this is the case for you, you can still acclimatize to heat before you go to your race by using multiple layers of clothing in training. As I entered my Ironman training I always wore one more layer of clothing than was necessary for the weather that I was going to be training in so that the microclimate next to my skin was hot and tropical regardless of what the outside temp and humidity was. This will provide you with some decent preparation for dealing with heat on a physiological level. Then if your race is a big priority and you have the luxury, try to get to the race site at least seven days in advance. It takes about seven days for your blood to go through the changes it does to help your body handle heat while exercising. After that amount of time, any further adaptation is psychological.
Then the final tidbit, limit alcohol consumption leading up to hot races or in the night before a key workout that will take place in heat. Alcohol consumption reduces your body's ability to deal with heat. So while a few beers or glasses of wine at night might be fun, if your workout in the heat the next day suffers because your body can't throw off the heat efficiently, the choice must be made. Which is most important at this time!
Off to the races!