system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is it that people can easily walk many miles but standing still for 20 minutes makes you uncomfortable ?
gpt
To add to other answers, your calf muscles activate much more when walking than standing. Calf muscles are known as your "second heart" because they aid in delivering deoxygenated blood back up from the legs to the heart. So walking promotes better bloodflow throughout the body.