First: 4 months, why are you entangled in these problems? The subtle changes of the fitness crowd itself are very complicated. Seasons, spirits and your current nutritional supply may all affect your dimensions at that time. Maybe you took some nutritional supplements or something.

Second: the growth of muscle dimension is in (years). You should make rapid progress in just four months, but the degree of muscle division and the density of muscle fibers are unstable. Obviously, you won't move up and down after going through the bottleneck period of 1 year.

Thirdly, the next day or even the fourth day is the best time to recover muscle mass under the condition of adequate diet and sleep after intensive training. The process of muscle growth recovery is that blood is sent to protein to repair torn muscle fibers, thus growing new muscle fibers. So when you recover, you are also in a state of semi-congestion. When muscle tissue no longer hurts or recovers, the dimension (normal) will decrease.

Fourth, the above content is entirely personal. I have been exercising for two years.