Time Under Load (TUL) is the terminology used to describe how long your muscles are working for during an exercise set or workout. For example; if I were to perform 60 seconds of slow, controlled push ups my time-under-load for the set would be 60 seconds. If I were to perform a second set for 30 seconds my total time-under-load would be 90 seconds. Simple right?
Measuring exercises by time-under-load as opposed to the traditional method of counting repetitions offers a number of advantages. First of all you are less inclined to stop an exercise when you reach a predetermined number of reps. Secondly you are less likely to rush repetitions in the quest for higher scores. It is much easier to score higher rep totals by rapidly bouncing through exercises using little muscular effort and a lot of momentum but this is not a productive use of your time and heightens the risk of injury.
What are the ideal time-under-load ranges? As yet there doesn’t appear to be a definitive answer and likely varies from individual to individual depending on muscle fibre type. However if time-under-load is too short you won’t fatigue as many muscle fibers. If time-under-load is too long you run the risk of boredom and really unpleasant levels of discomfort.
Of course, like counting repetitions, time-under-load can be gamed. If you pause in the easy position of an exercise (like the top of a push up) you will accumulate seconds without accumulating any meaningful work. Watch out for this as its easily done when your muscles are screaming!
In The Gymless Training System I recommend using exercises and resistances which you can perform for a minimum of 30 seconds and a maximum of 120 seconds with the sweet spot likely between 60 and 90 seconds for most people. If you fall outside these end-ranges try to make the exercises easier or harder respectively.
The downside to using time-under-load as your barometer is it’s a bit trickier to monitor than simply counting reps. A cheap digital wristwatch started at the onset of an exercise and quickly checked at the end provides a reasonable solution! If this is still a hassle you can always revert back to counting reps instead. Ultimately progress is what’s important, not how you measure it.