This is a normal phenomenon.

If you don't exercise for a long time, sudden exercise will easily lead to excessive exercise, which will lead to excessive accumulation of lactic acid, which will cause muscle pain, and the pain will disappear after the excess lactic acid is excreted.

There are generally two ways to accelerate the elimination of lactic acid, one is to continue aerobic exercise, and the other is to fumigate with hot water.

I hope I can help you.