This will explain the concept of training with different rep ranges and their impact of muscle strength, growth and endurance. It will also incorporate the idea of time under tension (TUT) and its role in training. All of this pertains to individuals who are focusing on muscle growth rather than powerlifting or Olympic lifting. Rep ranges are typically broken down into three categories: strength, growth, and endurance. The number of reps is as follows: 1-6, 8-12, and 12-15+.