It takes around 28 days for the skin’s natural exfoliation cycle to finish, a process known as desquamation. While chemical exfoliants, like lactic acid, will aid the process, it still takes time.

Lactic acid build-up causes a burning sensation in your muscles during intense exercise. Lactic acid is not responsible for sore muscles the day after exercise, contrary to popular belief.

Using these workouts you’ll increase muscular and cardiovascular endurance, learn to maintain running mechanics at a faster ...

So you been sprinting, Lily? Just a bit of cramp? So that's the lactic acid building up. When an athlete does too much or runs too vigorously, not enough oxygen can be delivered to the muscles.