system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why "no excercise = tiredness" but "excercising = energy"
gpt
Simply put, the more active you are the more mitochondria your body produces. It's like a domino effect. The more you exercise, the body makes more mitochondria to make more energy. Just reply if you need a more in-depth answer.