We are entering the summer. The long-awaited Tour de France is coming, and that is a sign of sunny days on the bike. We can see riders excel when mercury is over 30C, and others fade surprisingly when the day before they had an excellent performance. That is heat, an ally for some, an enemy for others.
The Effects of Heat During Exercise
When riding in the heat, the human body is not able to exercise as hard as in temperate conditions. We have two main factors contributing to that decrease in performance: heat production and heat loss. When we pedal, a big part of the energy we produce is in the form of heat.
When not exercising in the heat, we can lose part of the heat generated via different methods (radiation, conduction, convection, and evaporation). If cold, we will heat the air around us and cool our core temperature. But, when hot, those heat-loss mechanisms don't work and we can't dissipate that heat, increasing the core temperature. Because of that, our performance drops.
This occurs due to physiological mechanisms (increased thermoregulatory demands, inflammation in the gut, less neuromuscular activation...), but also because of psychological mechanisms (less willingness to exercise).
A severe increase in temperature can cause serious issues, including heatstroke and death. So, what can you do to ensure you adequately train in the heat, being able to reach your targets and avoiding fatal consequences?
Analyse Your Circumstances
It's all about your context. You need to understand where you are at, what your history is, and what you can tolerate. First, identify in which conditions and context you will exercise. Is it a three-day vacation in a hot climate, or is it a race that you want to win? If you will only be out for a couple of days, with the aim of doing a few workouts so you don't lose fitness, you probably won't need to do anything specific besides riding early in the morning so you avoid high temperatures. If you want to perform in the heat, you need to work on it.
Assuming you want to lose as little performance as possible while riding in the heat, you will need to be able to deal well with heat. Now, if you have lived in Arizona your whole life and exercised in that environment, you probably won't need further adaptations. Contrarily, if you live in the north of Canada, where you reach 30C a couple of times a year, your approach should be completely different, as you need an adaptation protocol.
The Adaptation Protocol
A factor to consider when planning an adaptation protocol is your actual fitness. With good aerobic fitness, core temperatures are lower at normal conditions and heat can be dissipated more efficiently. On the other hand, if you are new to the sport, if you haven't been doing much training during the winter, or if you are a sprinter that doesn't have a very good aerobic fitness, you will need to emphasize more on the heat training in order to have a great heat dissipating ability.
When adapting to heat, core temperature decreases, plasma volume increases, you start sweating earlier and that sweat is more dilute, losing fewer electrolytes, all of these leading to greater cooling capacity.
In order to choose your protocol, consider two factors: what kind of protocol you do and how long to do it. The main stimulus to drive the adaptations is increasing core temperature and forcing a high amount of sweat. Here you may consider what facilities you have: do you live in a hot environment? Do you own an indoor trainer? Do you have access to a stationary bike?
If you live in a hot environment, try getting as hot as possible: go out in the middle hours of the day, try finding climbs so you go slower and get hotter... However, if you don't have that luxury, you can do it in your basement. Hop on the trainer, turn the fan off, and do everything you need to increase the temperature (turn the heater on, put the trainer in the bathroom with hot water running...). And, if you don't own a trainer, try borrowing one from a friend or exercising in a gym with a stationary bike.
The duration of the workouts should be around 60-90 minutes, without the need of going hard (go hard enough to sweat heavily). Regarding the duration of the protocol, about 2 weeks is the sweet spot, but if you are really fit you could adapt in just one week. So, 4 workouts per week in the heat for one week if you are fit, or two weeks if you are not so fit, will put you in a good place to tolerate the heat.
Though, remember to build it up: start with shorter and easier sessions, and finish it with longer and harder ones. Remember keeping it close to when you want to perform in the heat, as little as 3 days could decrease the improvements from all the hard work and sweat.
Cooling in the Heat
Once you are in the environment, you still need to keep yourself as cool as possible in order to perform at your potential. If you are not looking for maximum performance, follow the general guidelines: hydrate yourself well and add some electrolytes to improve rehydration. You can calculate your sweat loss and electrolyte loss, and tailor your drink to suit your specific needs.
If you are trying to maximize performance, you should consider further cooling methods. Always try staying as cool as possible before exercise. In order to do so, you could use an ice vest to cool yourself prior to riding. However, don't cool the legs, as this would impair the benefits from the warm up. If your event is a race where sprinting is key (track racing, BMX...) don't cool yourself, as this will impair your sprinting performance.
On the other hand, if your event is really long, cooling prior to the event won't give you much of a benefit. You should consider cooling if your event is between 10 and 60 minutes. Additionally, putting an ice sock underneath the jersey in the neck are could help cooling you during exercise. If it is a multi-day event, try cooling yourself as early as possible to improve recovery, and consider avoiding a warm down, as this will delay the cooling and add more heat.
How You Should Train in the Heat
As seen, how someone should face heat is very dependant on his goals, history and circumstances. If you will experience heat for a couple of days and just want to do a couple of workouts, adjusting the time of the ride to the temperature will help you deal with it. On the other hand, if you want to perform on a given day in the heat, an adaptation protocol and cooling strategies are needed to get the most out of yourself. But, if you just want to keep training during the summer months, with the consequent heat, try building things slowly.
Consider what your history is, how you deal with heat, and plan accordingly. If you don't deal well with it, but, you need to keep training, apply an adaptation protocol, lowering your targets for the workouts and building gradually (start with just easy rides in the heat, doing the harder workouts early in the morning).
Heat is an additional stress, and, if you are not adapted, you will run into problems if you keep training as you were in cooler conditions. So, look at your situation, adapt the training to your needs and abilities, and don't forget the basics: listen to your body and hydrate.
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