Why when you run you make more carbon dioxide that when you sit still?

When you run, your muscles require more energy to sustain increased physical activity, leading to higher metabolic rates. This process, called cellular respiration, converts glucose and oxygen into energy, producing carbon dioxide as a byproduct. In contrast, when you sit still, your body's energy demands are lower, resulting in less carbon dioxide production. Thus, the intensity of exercise significantly elevates carbon dioxide output compared to a sedentary state.