In the simplest terms time under tension, or TUT for short, is the length of time a muscle is under tension during a set, or rather the amount of time it actually takes to finish a set. As it turns out, how long your force yourself to complete a rep has heavy implications.
Strength In Numbers
Experts tend to agree that in the area of strength gains, the optimal time for a given set lies somewhere between 4-2- seconds from time of liftoff to the tick you rack the bar. Basically, TUT equals the sum of the amount of time (in seconds) for the descent and the ascent of the bar. So taking the squat as an example, it if takes 3 seconds to descend towards the floor and 2 seconds to explode back up to the start, that is obviously 5 seconds worth of rep time. A three-rep set at that pace would obviously be 15 seconds worth of TUT.
With this in mind, some experts argue that this TUT factor is equally as important as the rep range itself, which for strength, is between 1-6 reps. As a rule it is always important to remember that a rep is only as good as the corresponding weight. In other words, to enhance strength, you need to make sure that the weight is relatively heavy to fulfil that rep range. You can not select a light weight and simply stop at say, 5 reps, when indeed you could have done 12 reps. That would indicate that you have selected an inappropriate weight.
Though you know the relationship between rep ranges, training goals and muscle failure, you may be short-changing the role of TUT. It is fair to say that when it comes to numbers, we typically factor in sets reps per set and the rest time between those sets. But there is a deeper way to view all that work, and that is where TUT comes into play. It breaks down the category of “reps” into its own spectrum – seconds. A given rep range should be spread over time if possible. The goal is to o=hold a muscle under tension at a given weight for various periods of time. If you can do so, using the bet range of 1-6 reps, over the best time to enhance strength, 4-20 seconds, then big gains in strength are inevitable.
The idea here is to configure a strength scheme that optimises both elements, which would seemingly give you the nest of both worlds. You would be working within a rep range that recruits the fast-twitch muscle fibres most responsible for strength while also submerging that target muscle under tension within the optimal spectrum of seconds. When it comes to fast-twitch fibres, the heavier weight and low-moderate rep schemes call them into play with greater success than the high-rep sets do.
Time To Get Strong
One way you might want to begin using TUT is to consider that as your rep range increases, the total time it takes to complete a rep decreases and vice versa. In other words, if your reps are low, then you might want to increase the time of both the eccentric and concentric portions of the repetition. This is not the only way to incorporate TUT, but it is a good place to begin.
So if you were doing 6 reps, your seconds per rep would be much less (around 2-3 seconds) than say a set of 2 reps of 6 seconds per rep, for example. You basically multiply the number of reps by the total time it takes you to complete a rep, with the goal to remain anywhere between 4-20 seconds total, regardless.
Increasing the amount of time it takes to move a very heavy weight is a phenomenon that few athletes ever attempt. Since the weight is relatively constant, 1-6RM, you can adjust the time per rep from one set to the next or from week to week. The end goal, again, is to spread out the reps in time between 4-20 seconds per set, which means you can perform any number of reps and time elements.
Because of the freedom from which to choose TUT schemes, it is advisable to keep a journal to follow your progression. Doing so will ensure you expose different loads to various rep speeds and total set times and will help you decide which combinations work the best.