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time under tensionYou’ve heard me talk about the 10-12 rep range (particularly 12 reps) and what makes it so “magic”!  In case you missed it I relate it all back to what I feel is one of the most crucial (if not THE most crucial) components to ever adding a single ounce of new muscle…and that is the principle of time under tension.

With an average rep being performed over a time span of 4 seconds (1 second to explosively lift the weights up and 3 seconds to lower the weights under eccentric or negative control) multiplied by the number of reps (12) we have a total of 48 seconds under some sort of muscle tension.

Trust me…for those of you out there who have yet to time yourself in an average set of anything…this number can feel like an eternity when you start doing this. While it seems random and arbitrary it actually is not.


What’s The Best “Time Under Tension”?

Science has shown that somewhere between 45 and 60 seconds of time under tension per set is just what the doctor ordered to produce maximum muscle return on your gym time investment! BUT…It’s not ALWAYS THE BEST! What?!?  Why are you going to start confusing me now you ask??

Because as with everything else in life…like it or not, there usually are some shades of gray that find a way in between the black and white to confuse the picture a bit.  This is one of those times! You have to remember…the REAL reason why this 45-60 seconds appears to be the magic range for building muscle boils down to one simple thing and that is INTENSITY!

It’s damn hard to do this kind of set once…let alone multiple times during the workout.  So…what if you can’t do it (or at least do it with any kind of consistency and without sacrificing your intensity)?  Well…in that case you have to lower the reps and push twice as hard to complete them! Your body knows only the intensity that it perceives during the exercise.

Make it feel hard and you’ll be rewarded with pounds of hard earned muscle.  Make it feel like a walk in the park and you might as well have shifted your metabolism and muscle growth into park as well….since your efforts in the gym will be getting you nowhere….fast!


There’s More To It Than Just Intensity

So is that all?  Just the intensity that you have to focus on?  Almost.  There is one other component at stake here and that’s the activation of BOTH fast and slow twitch fibers during your sets.  As you may have heard at some point your muscles are made up of primarily two types of fibers…fast and slow twitch.

Your fast twitch fibers are responsible for heavy burst lifting and noticeable muscle growth while your slow twitch fibers are more endurance oriented and have the advantage of being more resilient and faster recoverers.

Sooooo…..8 reps, slightly more than 12 reps, seems to target these fast twitch fibers a bit more and in doing so, has the ability to push for new muscle growth a bit better, again….especially if it’s easier to provide the necessary high effort and intensity that is a prerequisite to any productive workout by doing 8 vs. attempting 12 less than best reps!

So all in all, while we hear all sorts of recommendations and everyone will have you believe that there is one and only one rep range that works for building muscle…I like to think that one size DOES NOT fit all.  Principles do however…and those principles are INTENSITY OF EFFORT and FAST TWITCH FIBER activation through explosive movements.

Whether you’re giving your best in 8 reps or 12…the most important thing is that you’re giving your best.  No need to define yourself as an “8 rep per set guy” or a “12 rep per set guy” or anything in between for that matter.  Instead, keep bringing it every time you hit the gym and on every set and instead you can just define yourself as the “ripped, muscular and defined guy” that’s adding new muscle every workout!

Stay Strong,


Have you ever found yourself confused as to how many sets and reps you should be performing for certain exercises to get the best results?  If you thought the answer was “the same for every one”, then you’d be guessing…and you’d be wrong!  Don’t guess anymore!  Come check out the AthLEAN-X Training System and have the sets, reps, and rest times on over 122 exercises spelled out for you.  All that’s left to do now is grow!

Jeff Cavaliere Headshot

Jeff Cavaliere M.S.P.T, CSCS

Jeff Cavaliere is a Physical Therapist, Strength Coach and creator of the ATHLEAN-X Training Programs and ATHLEAN-Rx Supplements. He has a Masters in Physical Therapy (MSPT) and has worked as Head Physical Therapist for the New York Mets, as well as training many elite professional athletes in Major League Baseball, NFL, MMA and professional wrestling. His programs produce “next level” achievements in muscle size, strength and performance for professional athletes and anyone looking to build a muscular athletic physique.

Read more about Jeff Cavaliere by clicking here

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