metabolism, so the rate a person's hair grows has more to do with his activity level. for people who keep a typical schedule, hair will grow slowest at night during sleep, when resting metabolism is at work.
hair on the rest of your body goes through this same process, but the whole cycle only lasts for a month or so. that's why body hair does not grow very long in length like the hair on your head does. here are some facts about follicles and your hair: you are born with all of the follicles you will ever have — about 5 million. 