Cold weather often puts an underestimated strain on endurance athletes, especially if the body temperature drops before exercising. Here are the most important findings and tips.

Human efficiency is similar to a car engine: much of our energy is released in the form of heat. This is why athletes often find cold weather to be secondary, because they quickly get warm again due to intensive training. However, new research from the Journal of Applied Physiology shows that cold weather can significantly affect endurance performance – especially if the core body temperature is already lowered before exercising.

Overview of study results

The study compared four conditions, including a thermoneutral environment (22 °C) and three cold scenarios at 0 °C. In cold conditions, the subjects' skin temperature was lowered, in some cases the core body temperature by 0.5 or 1.0 °C, before pedalling to exhaustion at 70 percent of their maximum VO2 power. The results showed that performance decreased dramatically as the core temperature dropped: cooling the skin alone reduced endurance capacity by about 30 percent, reducing the core body temperature accounted for another 30 to 40 percent.

Why cold reduces performance

Several factors result in reduced performance:

1. Vasoconstriction: Cold conditions constrict the blood vessels, causing less oxygen to reach the muscles.
2. Energy loss due to shaking: Shaking increases energy consumption, draws resources away from the actual movement and makes muscle coordination more difficult.
3. Chemical restrictions: Cold weather affects oxygen binding in the blood and makes oxygen transport more difficult.

Interestingly, the core body temperature in the hypothermal tests barely increased despite maximum effort. The flow of blood to the muscles seems to transport the cold blood back to the core, so that the body doesn't produce sufficient heat.

Mental impact and motivation

The cold affected not only the physiology, but also the mental state of the subjects. Their motivation was lower prior to the start of the tests, and the perceived effort was higher at the beginning of the exercise. Despite these differences, all participants achieved the same maximum subjective effort at the end of the test (Borg 20).

Practical consequences

The study clearly shows that not only the ambient temperature during training or racing is decisive, but also the baseline situation. Skin and core temperature significantly affect performance. Those who spend a long time in the cold before exercising or before a race risk significantly reduced performance. For winter sports enthusiasts and runners, this means keeping warm until you start. Taking appropriate measures such as wearing insulating layers of clothing – such as clothes that can be quickly removed – are essential for maintaining an optimal core body temperature.

And in summer?

It's exactly the opposite in hot summer conditions. The body then needs to use more energy for cooling in order to keep the core body temperature at 37 degrees. This means less energy for exercise and, accordingly, a reduction in performance due to many factors such as reduced cardiac output, fluid loss and decreased nutrient transport due to redistribution of the blood to the body’s surface or a regulatory mechanism in the brain. Precooling (e.g. an ice bath, cold vest) and percooling (e.g. cold drinks, cooling collar) are particularly effective. The longer the workout, the more important this is. 

Studies have shown that it is possible to adapt to high temperatures. Precooling and percooling should be used to get the last percent out of your performance when it really matters.