Question

how muscular cramps are developed in human muscles during vigorous physical exercise​

Answer 1

Lactic acid develops in the lack of oxygen this causes muscle cramps. Is it clear?

Answer 2

due to lack of oxygen,glucose is broken down into lactic cid i.e. c3h6o3 and 2 molecules of ATP.

This lactic acid causes cramps and is slowly excreted after elimination cramps no longer remain