T Nation

time under tension

I have been thinking about this for the past few days. What is the difference between a set of 6 reps that takes 40 seconds and a set of 10 reps that takes 40 seconds? Or even a set of 4 reps that takes 40 seconds and a set of 12 reps that takes 40 seconds? Is there really that much difference since they are all in the hypertrophy range?

…crunches some numbers…okay, so here’s what I came up with: if you’re using the same poundage (for all scenarios), there are only going to be slight differences.
For example, let’s say that the barbell you’re using is 120 pounds.
a.) you lift it 6 times in 40 seconds, or an average of 1 rep every 6.6 seconds. For simplicity, lets take away the .6 (assume a pause at mid-motion), and assume you have equal concentric and eccentric tempos. Thus:
3 sec. concentr. + 3 sec. ecc. + .6 sec pause = 6.6 seconds per rep. Over the course of 6 reps, that equals to 18 seconds of stress to your muscles both concentrically and eccentrically. (and of course, the weight is 120 pounds).
b.) Now if you lift the same barbell for 10 reps in 40 seconds, that gives you an average of 4 seconds per repetition. For consistency, we must subtract .6 sec. for the pause at midrange. Thus you have 3.4 sec. per rep or 1.7 sec. for both conc. and ecc. Over ten repetitions, this equals out to 17 seconds of both ecc.and conc. stress (or 1 second less of tension than in the first scenario).
c.) Now it becomes apparent that there is a slight difference in the lenght of time the muscles will be under tension. That is because I (mistakenly perhaps) assigned an arbitrary .6 seconds to the pause at midrange. Obviously (to me now), the fewer reps that are performed, the less the .6 will be called into play. (I initially did that because I did not have a calculator until just now).
d.) when compared without the influence of the pause at midrange, time under tension for both concentric and eccentric will be pretty much equal at around 20 seconds. and as such, the load-stress will be the same for every protocol as long as the same weight is used.
If a different weight is used for each protocol, of course then everything changes. And the properties and effects of other factors such as momentum must be considered…a faster rep count requires increased speed of movement which = increased momentum which can reduce muscular stress. I apologize for my “stream of consciousness” post, and especially to all who have read the whole thing…I just thought it was interesting.