Core body temperature in exercise and sports
What you need to know
Core body temperature is more than just a number—it’s a vital sign that reflects your body’s ability to adapt to physical stress. Your body’s core temperature plays a critical role in your performance and safety. Understanding how your body regulates temperature during exercise and what happens when it deviates too far from the ideal range can help you optimize performance and avoid dangerous complications.
Core Body Temperature
Core body temperature reflects the temperature of your internal organs, such as the heart, brain, and muscles. The average is about 98.6°F (37°C), but during exercise, it naturally rises as your muscles generate heat.
The body relies on thermoregulation to maintain a stable temperature. This is vital for ensuring optimal muscle function, enzyme activity, and cardiovascular performance. However, prolonged or intense physical activity, especially in extreme environments, can overwhelm these regulatory systems.
How Exercise Affects Core Body Temperature
When you exercise, your muscles produce heat as a byproduct of energy consumption. This can cause your core temperature to rise rapidly. To counteract this, the body activates cooling mechanisms such as:
Sweating: Sweat evaporates from the skin’s surface, dissipating heat.
Increased blood flow to the skin: Blood vessels dilate (vasodilation) to transfer heat from the core to the skin.
Elevated heart rate: This helps circulate warm blood to the skin for cooling.
While these mechanisms are effective, they have limits. Factors like high humidity, dehydration, or inadequate acclimatization can impair your ability to cool down, leading to overheating.
Core Body Temperature at Different Stages of Exercise
Optimal Range
97°F–99°F (36.1°C–37.2°C)
Performance: This range supports peak physical performance. Muscles contract efficiently, and energy systems operate at their best.
Cooling Mechanisms: Minimal activation, as the body is in homeostasis.
Elevated Temperature
99°F–101°F (37.2°C–38.3°C)
Performance Impact: Increased heart rate and sweating. You may start to feel warm but can generally maintain activity.
Cooling Mechanisms: Sweating intensifies, and blood flow to the skin increases.
Key Tips: Stay hydrated and take short breaks to prevent further overheating.
Mild Hyperthermia
101°F–104°F (38.3°C–40°C)
Performance Impact: Fatigue, reduced endurance, and potential muscle cramping.
Cooling Mechanisms: Sweating may be at its peak, but dehydration can impair effectiveness.
Risk: Heat exhaustion becomes a concern, characterized by dizziness, nausea, and heavy sweating.
Key Tips: Take immediate cooling measures, such as drinking fluids, using fans, or finding shade.
Dangerous Hyperthermia
Above 104°F (40°C)
Performance Impact: Rapid deterioration. Confusion, disorientation, or even unconsciousness may occur.
Cooling Mechanisms: May fail as dehydration and electrolyte loss hinder sweat production.
Risk: Heatstroke, which is life-threatening, with potential for organ damage or death.
Key Tips: Stop all activity immediately, apply ice packs to major arteries (neck, armpits, groin), and seek emergency medical help.
Core Temperature in Cold Weather Exercise
While overheating is a common concern, exercising in cold weather presents a different challenge. The body’s core temperature can drop if heat production from exercise doesn’t match heat loss to the environment.
Optimal Range: Layer appropriately to trap body heat while avoiding excessive sweating, which can lead to faster cooling once you stop moving.
Risk of Hypothermia: If core temperature drops below 95°F (35°C), shivering, reduced motor skills, and confusion can set in.