A lower core temperature offers several key advantages for endurance athletes, especially during prolonged physical exertion.
In an earlier blog (Chapter 1) we already saw that the optimal temperature for a marathon runner is 6.2°C (43°F) for men and 6.8°C (44°F) for women. And that performance decreases with every degree the temperature rises (when temperatures are around 26°C (79°F) the performance decreases by 17.7% for men and 12.4% for women).
We also saw that for every degree your body’s internal temperature rises, your heart rate increases by about 10 beats per minute. That natural reaction places added strain and stress on your heart. (*6)
It has also been shown that muscle power output, is reduced by elevations in core temperature. (*11)
So, cooling your body, also in cool temperatures, makes sense. (*2)
There are many other advantages of a lower core temperature during endurance exercise:
Core cooling reduces sweat rate and helps retain fluid balance, which is crucial for endurance athletes. The study demonstrated that reducing body temperature before or during exercise can decrease the demand for sweating as a cooling mechanism, conserving hydration levels under heat stress. This helps athletes sustain performance and avoid dehydration-related problems. (*55)
High temperatures affect gastrointestinal (GI) function (digestive function) during prolonged exercise. The study found that elevated core temperatures reduce blood flow to the digestive system, leading to GI discomfort (digestive problems) and impaired nutrient absorption. Maintaining a lower core temperature helps ensure adequate blood flow to the digestive organs (like stomach, intestines), thereby improving nutrient uptake and reducing the risk of GI issues during long endurance exercise. (*56)
Higher core temperatures increase the rate of carbohydrate metabolism and lactate production, while cooler conditions encourage fat oxidation, sparing glycogen stores. This helps endurance athletes by reducing the frequency of carbohydrate intake needed to sustain energy, improving endurance over long distances. (*57)
Cooling during exercise could preserve muscle function, increasing power output stability by up to 15% over a control group without cooling. This effect was particularly noted in intense cycling trials, where core temperature had a direct impact on muscle performance (*58)
In conclusion: cooling strategies, particularly those that result in lower core temperature, are effective for improving endurance performance and comfort. This is attributed to the delayed onset of fatigue, improved hydration, and optimized nutrient absorption during endurance activities.