Acid Produced in the Body During Exercise

This page is the CodyCross answer for the clue below from Time for a check-up, Group 1711, Puzzle 3 (Defibrillator).

Question is: Acid Produced in the Body During Exercise

and the answer is: LACTIC

Word Meaning:

LACTIC — Of, relating to, or derived from milk.

Definitions from Wiktionary.