Most people do exercise wrong. Either too much or too little. The body was designed to walk daily for the purpose of finding or hunting food. It wasn't designed to sit all day for weeks, and then suddenly go to the gym and run fast or lift huge heavy objects after weeks of atrophy. This is a recipe for injury and unhealthy tearing down of the body. The best way to avoid over doing it when trying to get back into shape is to use the Maffetone 180 heart rate formula: https://philmaffetone.com/180-formula/