DOMS is muscle soreness that occurs the day after an activity or workout. It is the result of a buildup of lactic acid in your muscles.

The pain is the worst 2-3 days after that exercise, then decreases, and that pain is normal after a new activity or increased intensity.

 PT Rob recommends doing gentle exercise during those days when you are sore, as it will increase blood flow to the muscle tissue, which will flush out the lactic acid, leading to less soreness.