So a wrestler cutting weight before a match is losing all muscle?
pretty much
Muscles are 70% water, they dont actually lose any fibres but they loose volume
The amount of muscle fibres you have are set at birth, you dont gain any extra when gaining size, the ones you have adapt and grow bigger
Hypertrophy isnt hyperplasia
Most top guys are just water bloated but the water is help in the muscle with the aid of insulin and glycogen
Hence how much they shrink once they stop.