Adam Mills sends some scientific explanations about cycling performance in the heat:
"As the summer settles in and the mercury routinely climbs towards the top of the thermometer, heat becomes a factor in racing and training. Many people write articles about what happens and many authors say the normal, "drink water and stay cool." But that doesn't really give the extreme conditions the respect that they deserve. When it feels like you're on the surface of the sun, what are some real and effective steps you can take to help you perform better than those around you in the heat? We'll talk about this and provide some insight on what happens based on the newest research driven in part to prepare athletes to compete in the extreme conditions seen at the Summer Olympic Games in Atlanta, Athens, and Beijing.
The limits of human capacity.
The need to be able to perform in hot and humid conditions is growing with the importance and competitiveness of sport. However, steps should be taken to account for the primary limiting factor to performance in heat: Core Temperature. The limit is 104F. As your core approaches this number, the brain becomes more and more focused on shutting down the body to prevent permanent damage. So instead of stubbornly trying to "beat" this number (and failing), efforts should be spent keeping the core temperature below this ceiling.
Physiological Reality of Training and Racing in Heat
The primary fallacy of training in the heat is that many athletes and even coaches assume that because one can not work at the same level for as long, that the Functional Threshold Power (FTP) of the athlete lowers in the middle of the summer. However, upon some critical thought, along with the new and current research, that line of logic while practically true, is not the case physiologically. This means that while your FTP in hot and humid conditions may be "low," normal physiological indicators of Lactate Threshold (note the difference in terms) show that you are, in fact, no longer training hard enough to "bump" your fitness. This becomes painfully obvious when traveling from a hot climate to a cool climate mid- late season as a "de-training" effect can and will occur unless...
From a training perspective, it is important to make adjustments to your training that allow you continue to meet the physiological demands of the sport at all levels and climates. This means that the same intensities and time at intensities are needed but in a manner that will not cause you to overheat.
Heat and Altitude, the Parallels
As we pour over the research here, the parallels begin to surface between heat and altitude:
Similar in that in order to become acclimatized, chronic prolonged exposure must occur. This means, for heat you will need 3 hours or more exposure over 5-12 consecutive days. There's no way around that.
Performance is not improved by racing and training in heat or at altitude. Many associate acclimating to training in the conditions. Just like Live High Train Low (LHTL) is the BEST way to use altitude, living in warm conditions and training in cool conditions is the best way to become accustomed to heat while minimizing the stress that heat places on your body.
Heat and altitude illness become easier to "catch" with each recurrence. Once you overdo it, you're taking a step backwards in your tolerance. Training until you become "too hot to continue" is NOT a good decision.
Heat and altitude lower your performance, albeit in different ways. Altitude is through a lowered partial pressure due to oxygen (pronounced, "less air up high"). Heat lowers performance by making the limiting factor how much core temperature you can tolerate. More power produced = more heat produced. More heat= more core temperature and higher core temperature= lower performance.
Both heat and altitude add physical stress to your body. However, unlike altitude, you can take a multitude of steps to lower and maintain core temperature even in hot conditions.
So as you pin a number or air up your tires, remember that heat and humidity will hurt your performance to some degree and are two forces you absolutely must respect. Have fun and stay safe.
Adam Mills, MSEd, RCEP
CEO, Senior Consultant