Slow vs. Fast Crunches

 OPENING ARGUMENTS  DEFENSE  Bodybuilders have always done reps in a slow and controlled manner, because it better works the target muscle rather than relying on momentum to “cheat” on the exercise. Therefore, crunches should be performed at a speed no faster than 2 seconds on the positive (concentric) reps and 2 seconds on the negative (eccentric) reps.
  PROSECUTION Fast reps (at a speed of 1 second or less on the positive) can