압축 과정에 관한 문장 해석 부탁드려요

역학 책에 나온 문장인데 해석 부탁드립니다.
“When the compression process is non-quasi equilibrium, the molecules before the piston face cannot escape fast enough, forming a high pressure region in front of the piston. It takes more work to move the piston against this high pressure region.”