Time under tensionTUT

Time under tension is how long a muscle is loaded during a set, usually calculated by multiplying reps by the tempo of each rep. It became popular as a way of arguing that how you lift matters as much as how much you lift.

There is something real underneath it. Deliberately rushing a set, particularly dropping the weight rather than controlling the lowering phase, removes a meaningful part of the stimulus, and controlled eccentrics are associated with better outcomes.

The version that has not held up is time under tension as a target to maximise. Studies manipulating tempo find that very slow reps reduce the load you can use and the total work you can do, and generally produce equal or worse hypertrophy than a normal controlled tempo. Longer is not better.

The more useful framing is that tension itself is the driver rather than the clock. Mechanical tension in the recruited fibres, sustained across enough hard sets per week, is what the evidence points to, and time is a rough proxy that breaks down at the extremes.

Comparing sets of different rep ranges by their time under tension is another common misuse. A set of 20 with light weight accumulates far more seconds than a heavy set of 5 and does not thereby produce more growth, because the tension in each rep differs enormously.

The practical residue is short and worth keeping: control the lowering phase over roughly one to three seconds, do not bounce or drop the weight, and stop counting.

In practice, count hard sets and progress load or reps, which our training volume calculator and double progression planner between them cover.