Why do we get hot when we exercise?

It’s your body’s way of regulating your core temperature, preventing you from overheating. Your muscles heat up as they expend energy during exertion. When this happens, your skin begins to sweat, causing your body to cool down. The spike in your body heat also alerts your brain to ensure your body remains at the normal core temperature of 98.6 degrees Fahrenheit (or 37 degrees Celsius).