When you come to a point where you can complete all 3 circuits easily, add just enough weight to reach failure at the same rep range and / or add one or two bodyweight movements to the end of this circuit. (fitnessandpower.com)
Training in the same rep range will eventually lead to plateaus. (fitnessandpower.com)
«If you constantly lift the same weights within the same rep range and same tempos (speed), your body will use less and less calories to perform the exercise,» says strength and conditioning coach Alice Round. (womenshealthandfitness.com.au)