Lactic Acid is Produced in muscle cells from the reduction of pyruvate (under anaerobic conditions) to regenerate NAD+ so that glycolysis can continue. A rise in lactic acid usually accompanies an increase in physical activity.
Slow twitch is the type of muscle that contracts slowly and is fatigue resistant (marathon runner)
Fast twitch are muscle fibers that react quickly and fatigue quickly (track runner)
Anaerobic respiration requires 2ATP and doesn't require oxygen
Meanwhile, aerobic respiration requires oxygen and has 36-38 ATP
ATP (adenosine triphosphate) is the main energy source that cells use for most of their work