Slow Tempo Beats Speed

The concept of "time under tension" (TUT) suggests that the duration a muscle is under strain during a set is a key factor for growth. Research indicates that for hypertrophy, a set duration of 20 to 70 seconds is effective, and individual reps lasting between two and eight seconds can maximize muscle growth. Exceedingly slow repetitions, such as those lasting longer than 10 seconds, may necessitate a reduction in weight to a point where it becomes less effective for hypertrophy. A critical component of time under tension is the eccentric phase of the lift, which is the controlled lowering of the weight. This phase, where the muscle lengthens under load, can create greater mechanical tension and microscopic damage compared to the concentric (lifting) phase. Some research suggests that this controlled stress during the eccentric portion is one of the most significant signals for the body to initiate repair and muscle growth. While a specific tempo can be a useful tool, many experts, including leading hypertrophy researcher Brad Schoenfeld, argue that mechanical tension—the actual force placed on the muscle—and overall effort are the primary drivers of muscle growth, not just the time spent lifting. The focus should be on challenging the muscles with a high level of effort, pushing sets close to or to the point of momentary muscular failure. Ultimately, the principle of progressive overload is fundamental for continuous improvement. This means gradually increasing the demands on the musculoskeletal system over time. This can be achieved not only by lifting heavier weights but also by increasing the number of repetitions or sets, or by manipulating training tempo to increase the total time under tension.