Sumo-squat-with-kettlebell-jamie-watling

2. Train with challenging weights in the six-to-12 rep range

Adding lean muscle (called hypertrophy) is achieved with challenging weights in the rep range of six. Hypertrophy is the process of increasing the number of cells within an organ or tissue (such as muscle tissue), thereby increasing its overall size. If you train with higher reps, you surpass this stage and train your muscles for endurance rather than lean muscle gain.