Complex sentence: It is, however, a typical posture muscle dominated by slow-twitch red type 1 fibers, and is therefore susceptible to pathological shortening or contracture (especially in older people with a sedentary lifestyle) and requires regular stretching to maintain normal tone.
Split into simpler sentences: It is, however, a typical posture muscle dominated by slow-twitch red type 1 fibers. Therefore, it is susceptible to pathological shortening or contracture, especially in older people with a sedentary lifestyle, and requires regular stretching to maintain normal tone.