How many repetitions should John aim for in each set of his weight training?

Focusing on 8-12 repetitions in each set of weight training is generally considered optimal for building muscle size and strength. This range is often referred to as the hypertrophy range, where the muscles experience enough tension and stress to stimulate growth. Training within this repetition range allows John to lift a moderate to heavy weight, which is essential for effective muscle engagement and can lead to strength gains along with increased muscle size.

Using lighter weights with higher repetitions, such as 15-20 or 25-30, typically emphasizes muscular endurance rather than building significant strength or muscle size. Conversely, performing only 2-4 repetitions generally focuses on building maximal strength and power, which may not align with John’s goal if he's primarily looking to improve his physique through muscle growth. Hence, targeting 8-12 repetitions strikes a balance that promotes both strength increases and a visually muscular physique.