Flexi Says: Like all cells, muscle cells get chemical energy from breaking down glucose and other nutrient molecules in the process of cellular respiration. The chemical reactions that occur during cellular respiration are exothermic, meaning they release some energy as heat in addition to transferring chemical energy. When you exercise, your muscle cells need more energy than when you are at rest. The rate of cellular respiration in your muscle cells increases to meet this need. More heat is released as a result of increased cellular respiration. This heat is dispersed around your body by the circulatory system, and your overall body temperature increases.
