Photo: iStock.com/lzf
Summer means peak season for many endurance athletes: long rides, competitions, ambitious training blocks. At the same time, summer is the season when many most often overexert themselves. As a result, a pace that was easy in April suddenly feels like a race session at 32 degrees. Those who do not understand the cause risk overtraining, circulatory problems, or simply weeks of frustration.
During exertion, the muscles produce heat that must be dissipated through the skin. In cool temperatures, this works smoothly through sweat evaporation and heat radiation. However, if the outside temperature rises, especially in combination with high humidity, the temperature gradient between the skin and the environment decreases. The body has to send significantly more blood to the skin surface to get rid of heat at all.
This "competitive relationship" between skin and muscles for the available blood volume is called cardiovascular drift. Practically, this means: At the same wattage or running pace, the heart rate continuously increases during a session, even though the external load remains the same. Many athletes mistakenly interpret this as a loss of form – but it is a completely normal physiological reaction to heat.
A common reflex is to completely avoid hot sessions and only train early in the morning or late in the evening. Understandable in the short term, but in the long term a missed training stimulus. The body can significantly adapt to targeted heat exposure within ten to fourteen days: Blood plasma volume increases, the sweat rate becomes more efficient, electrolyte loss per liter of sweat decreases, and the core temperature at which the body begins to sweat also decreases. So if you are already competing in a race with expected high temperatures, you benefit from consciously completing individual, controlled sessions in the heat instead of completely avoiding them.
Important: These sessions should be short and moderate, not the most intense training session of the week. The goal during these "heat sessions" is physiological adaptation, not peak performance.
In addition to internal control, body temperature can also be actively influenced from the outside. Regularly pouring cold water over the head, neck, and arms directly supports temperature regulation in well-perfused, skin-close areas. The effect: The body has to invest less energy in heat dissipation itself, which noticeably saves energy for actual performance during long sessions. Those who are out in the heat should therefore not view this form of cooling as a nice additional measure, but as a fixed part of the race and training strategy.
As important as reduced intensity is on hot days – completely avoiding fast stimuli would be the wrong conclusion. Short, targeted exertions like sprints, accelerations, or short steep climbs keep the nervous system active and ensure that the legs remain fast and responsive despite the heat. The advantage of such short stimuli: They only briefly stress the circulatory system and temperature regulation but still provide the neuromuscular impulse that is missing in purely calm base training. One to two such short, intense sequences per week are usually enough to maintain agility throughout the summer.
Fluid needs vary greatly between athletes – sweat rates of less than half a liter to over two liters per hour are not uncommon. General drinking recommendations therefore fall short. More meaningful is a simple weighing test: Compare body weight before and after a one-hour session without fluid intake. The difference roughly corresponds to the hourly sweat loss and provides a realistic guideline for individual fluid intake.
For sessions over 60 to 90 minutes in the heat, plain water is often not enough. Sodium is the most important lost electrolyte and should be specifically supplemented during longer, sweat-inducing exertions to prevent muscle cramps and a drop in performance towards the end of the session.
After training, it is crucial to replenish empty stores as quickly as possible and balance fluid loss to initiate recovery.
In addition to cooling, pacing, and fluid intake, it is worth looking at the weekly structure. It makes sense to schedule the most intense session of the week in the cooler morning hours and distribute easy base sessions more flexibly throughout the day. Race simulations with high intensity should be shortened rather than completely canceled in extreme heat – for example, by shorter intervals with the same number of repetitions.
Heat does not change trainability itself, but the conditions under which training must take place. Those who understand that an increased pulse in the heat is normal, train specifically instead of randomly in the warmth, know their individual fluid needs, and smartly adjust their weekly structure do not lose form in the summer – but often lay the physiological foundation for stronger performances in the fall.
In summer, many train more intensively due to long days and a packed competition calendar, but underestimate that heat additionally stresses the nervous system and regeneration requires more attention. Ambitious athletes often make three typical mistakes.
After a long solo flight, Steffi Häberlin successfully defended her title from the previous year at the Swiss Championships at the end of June. The 28-year-old from Thurgau was active as a mountain biker from 2020 to 2024. With strong performances at the Tour de Romandie and the Tour de Suisse in the national team jersey, she drew attention to herself and received a professional contract with the Dutch team SD Worx.
After the recent spell of cold and wet weather, we’re now heading into a period of high temperatures. That can become quite challenging if you want to continue your training as usual or even take part in a race. We’ll show you what to look out for and share some effective strategies to stay cool.
