When we rest immediately after completing an intense workout, our muscles will soon switch from

aerobic respiration to lactic acid fermentation
lactic acid fermentation to aerobic respiration
aerobic respiration to alcoholic fermentation
alcoholic fermentation to aerobic respiration

Explanation:

Aerobic respiration refers to the process of producing energy involving oxygen and it's the opposite of anabolic respiration (without oxygen). So, when your are doing some exercise you are in a aerobic respiration process to have enough energy.

But after you finish, muscle begin to rest using lactic acid fermentation, this helps muscles to recover. So, the amount of lactic acid depends on muscles conditions to affront stress, this is why people that don't often exercise, feel more pain after, that effect is due to lactic acid fermentation.

i think the miocene epoch spans the time from 23 million to 12 million years ago.

it will increase due to the time span