Start easy and add a little weight each workout, or if you're doing bodyweight, vary your reps from workout to workout and try to finish each workout faster than the last. (nerdfitness.com)
But what exactly is «under control,» especially knowing what we do about the importance of varying rep speeds. (muscleandperformance.com)
Even varying reps, intensity, rest periods and style, you may find yourself just going through the motions and not enjoying your workouts the way you did before the novelty wore off. (fitnessrxwomen.com)