31 May 2016


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With summer about to hit the northern hemisphere, heat and humidity will start to play a role on how you perform in training and races. Living in Phoenix, AZ, certainly makes training in the heat harder than in most places, with temperatures well over 100F mid-day. Even if it’s “only” 90-100F, your body will tend to easily over-heat, your heart rate will greatly increase and fatigue will set in quicker. For the average person, the core temperature is 97F (36C) which means that if you are standing still at a higher air temperature, your body is already working harder to keep its core temp cooler. With movement, work to keep it cooler is exponential. When you fail to hydrate at the same rate you are losing fluids and sodium, you will have your body “red lining”. The longer the exercise, the more you will have to hydrate.

First of all, it would be important to have a coach that is sensitive to the fact that you will be training under [possible] extreme heat. By that, I mean a coach who knows that you should reduce your training volume, but not necessarily the intensity. Again, under the heat, your body will have to work harder to keep the core temperature lower, even if you are not moving. On the bike, wind or any breeze that may flow outdoors will help your body to lower its surface and core temperature, meaning you shouldn’t necessarily restrict your training to indoor sessions; it’s all about not over-heating.

In general, hydration is key to performance, but the higher your core temperature is means the more fluids you will be losing per hour. Therefore, you have to compensate for your losses the best you can. Research has shown that for the average person, on average humidity conditions, needs a range from 15oz to 30oz of fluids per hour. The longer the duration of the exercise, the more deficit you will have. It’s very, very hard to drink as much as you “sweat out”, very simply because your body can’t process the amount of fluid you would need. Also as a rule of thumb, you may use the reference of 300mg to 600mg per hour (Olympic to Ironman distance) of sodium needs. The higher the temperature, the more you need. The more body mass you have, the more you will need. The higher sweat rate you have, the more you will need. And so on. Realizing a sweat test may be a good idea if you think you are a “heavy sweater” and know exactly how much do you need per hour of effort.

Your best ally is common sense. It is important to be self-conscious if you are doing more harm than good at some point and if you see your heart rate going well above its normal for any given perceived effort. If this happens, it may be a good idea to pull the plug immediately and not do any more damage. Also for that reason you should always use a heart rate monitor during the summer, even if you don’t during the winter sessions. What you eat is also important for performance in the heat. You should prioritize foods that are easily processed by your body and high-on-water foods, such as fruits and veggies. Because when you eat highly processed foods or fried and high on fat, your body will have to work twice as hard to break down those foods. This in turns causes your body to spend even more energy and more of the already stored water.

Training in the heat, also means that your fluid needs AFTER and BEFORE training are much higher. Making sure you start the training session already well hydrated and replenish the fluid losses after training will not only improve performance, as it will help your body flush out toxins and improve overall recovery from hard sessions. A good way to know how much fluids you have to make up for after training is to weigh yourself before and after the session. Over 80% of the “weigh loss” you see on the after metric is fluid loss.

Training in the heat is especially hard for those that come from cold climates due to natural acclimatization. However, training your body to deal with a lot of fluids on those cold climates will massively help your body’s efficiency to deal with it on hot weather. So if you train year round in the cold and are preparing for a race or a long period of training in the heat, practicing drinking a LOT will contribute massively to how you are able to perform under extreme conditions. In well over 90% of the cases, it’s almost impossible to over drink and very common to under drink.