Physical activity gives an outlet to stress, and people used to get way more of it. Stress and physical effort are supposed to go hand-in-hand; you feel stresse

Physical activity gives an outlet to stress, and people used to get way more of it. Stress and physical effort are supposed to go hand-in-hand; you feel stressed, which gives you a boost of adrenaline, which you need to physically fight back whatever caused the stress. When the physical component is missing, the stress just lingers and wreaks havoc on your body.