Time Under Tension

TUT is often expressed using a 4-number notation that describes the duration of each phase of the rep. For example, 3-1-2-0 means: 3 seconds eccentric, 1 second pause in the lengthened position, 2 seconds concentric, 0 seconds pause at lockout. This notation lets you precisely program the stimulus you give to the muscle and makes sets reproducible and comparable over time.

For hypertrophy, a TUT between 30 and 70 seconds per set has historically been considered a useful reference. But be careful: TUT alone isn't a sufficient indicator. You can have a TUT of 60 seconds with a ridiculous weight and stimulate nothing. Mechanical tension is the product of force times time: you need both. An adequate TUT with a meaningful load is the optimal scenario. A high TUT with a weight that's too light is wasted work.

The most practical way to leverage TUT is to control the eccentric phase. Slowing the descent to 2-3 seconds increases TUT without having to drastically reduce the load. You don't need to count every second with a stopwatch: just keep a controlled, consistent rhythm. If you log your training, note the time of each set in addition to the rep count. Two sets of 10 reps can have very different TUTs, and therefore very different stimuli. It's a detail that separates training from training well.