The term "time under tension" or TUT has been flying around the bodybuilding community for years. It's usually associated with the term "slow and controlled" when referring to rep speed.

But simply slowing your reps way down to increase TUT probably isn't the best way to do it. Adding more reps is.

Time under tension deals with set duration, not just rep duration. Slowing reps down or adding more reps can both increase the TUT of a set, but which is better? Let's take a look at a study that examined identical time under tension with different rep schemes and durations.

The Study

Twenty-two males with at least 6 months of training experience and the ability to bench at least bodyweight were recruited. After establishing 1RM, the subjects performed two protocols on separate days:

  1. Three sets of 12 reps at 60% of 1RM on Smith machine bench press, 3 minutes rest between sets. Rep duration was 3 seconds: 1.5 seconds eccentric and 1.5 seconds concentric (lowering and lifting phase of each rep).
  2. Three sets of 6 reps at 60% of 1RM on Smith machine bench press, 3 minutes rest between sets. Rep duration was 6 seconds: 3 seconds eccentric and 3 seconds concentric.

Total time under tension per set for each trial was 36 seconds.

EMG of the anterior deltoid, pec major, and triceps were recorded. Lactate values were assessed prior to exercise, 1 minute after each set, and every 3 minutes for 12 minutes following the final set.

The Results

  • EMG was higher during the protocol with shorter rep duration.
  • EMG was higher in all the muscles during the shorter rep duration protocol.
  • Lactate values were higher during that protocol as well after each set. They remained elevated for longer post workout too.

What This Means to You

The increased muscle activity during the shorter rep duration, along with the higher lactate values, show a clear winner in the time under tension battle. With TUT equal (36 seconds), doing more reps seems to be the winner via increased activation and greater lactate levels, indicating greater metabolic stress.

So instead of slowing down your reps in a workout to increase time under tension, simply add a few more reps with a faster rep speed.

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  1. Lacerda, LT, Martins-Costa, HC, Diniz, RCR, Lima, FV, Andrade, AGP, Tourino, FD, Bemben, MG, and Chagas, MH. Variations in repetition duration and repetition numbers influence muscular activation and blood lactate response in protocols equalized by time under tension. J Strength Cond Res 30(1): 251–258, 2016