People often discuss the importance of removing, or “flushing out,” lactic acid from the blood after intense exercise to ...

Lactic acid has long been vilified, but new research shows that it doesn't impair muscle function. In fact, it might actually be good for you.

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.

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.