The rate of demand for energy in the body determines whether the body will use aerobic or anaerobic cellular respiration. Each process has different end products. The end product atp contributes to energy transfers in the cells by releasing energy when it is needed. Isabella is competing in the 50-meter freestyle and needs fast energy production for about 40 seconds. Tyler is running a half marathon and needs slow and steady energy production for almost two hours. Drag the terms to the correct athlete based on which metabolic pathway their muscle cells will utilize for energy production in their races.