Complex sentence: There are rules that the Drill Instructors must follow for the safety of the recruits including the total length of time and the types of exercises that are done so that each muscle group is not over worked.
Split into simpler sentences: There are rules that the Drill Instructors must follow for the safety of the recruits. The rules include the total length of time and the types of exercises that are done so that each muscle group is not over worked.