I have been introduced to the concept of time in tension over reps. Lots of workout stress number of reps done real fast so we can brag about how many we do. When we do them real fast form goes out the window along with full extension, control and benefits of gravity resistance. After an extended stretching series the pax was challenge to a series of the usual merkins squats lunges sit-ups leg lifts plank etc only this time to a s l o w count if 6 down and a s l o w 6 count up. There were only 5 reps of each exercise but it took a minute or more to do each one. The 5th rep of a merkin or a plank done this way started to feel really long. End result more muscles got used. Control and form just happened and a pumped up feeling afterwards assured a real workout just happened in 30 minutes of tension time.