Here's a great new way to start a fight among fitness freaks:  jump on a site dedicated to "Getting Huge" or "Lifting Small Planets" or "Flipping Monster Truck Tires All Day!" and either espouse or reject everything to do with the "Time Under Tension" principle.  My, oh, my, the sparks will fly.  Prepare a new screen name in advance.

The "Time Under Tension" principle suggests that you've got to keep a muscle working for a certain amount of time in order to affect strength or size gains.  That is a set has to last a certain amount of time before enough microtrauma is caused in the muscles for them to grow and repair.  Some people say it's a few seconds, some people say don't waste your time with sets of less than 30 seconds.  Everyone states their opinion definitively and vehemently.  I know because I interviewed some very smart people about this idea a few weeks back and it was hell getting anyone to agree on anything except that lifting weights is sort of, kind of, under certain conditions, pretty good for you.

The advantage of getting to talk to many experts on a topic is that you can sift out the common themes, and here they are as far as T.U.T. goes.  I may not have my name on a hundred articles in YOUR DAD STILL HATES YOU EVEN THOUGH YOU'RE JACKED magazine, but I can give you the skinny on what those guys actually agree on, even though they don't always think they're agreeing, and it's this. 

Time Under Tension Matters!  Stop the press, it's true.  It does matter.  Here's why.  Let's say that one a good day, you can do exactly one pull-up.  That's the case with many of my clients when I see them for the first time.  Perhaps your instinct would be to do three sets of pull-ups to failure two or three times a week, meaning, three sets of one pull-up three times a week, in order to get better.  Why not?  That is, after all, more or less the format you take with just about every muscle group!  Work it hard multiple times, then let it rest a few days, and it grows.  

But you'd be wrong.  That kind of program pretty much ensures that you'll never get your sorry chin over that bar more than one time in a row from now till the Cubs win the series.  No:  the best way to get someone to do pull-ups is to do multiple sets of assisted pullups, generally in the 6-12 rep range.  Or--better yet--circle back to the pull-up bar every few minutes and do a single rep, completing ten to fifteen sets of your single pull-up over the course of a workout.  Pretty soon you'll have several reps under your belt at a time and you can start to do multiple sets of multiple reps.

I can't tell you exactly why that's true, but something's getting stimulated over the longer-term that isn't getting stimulated with the more abbreviated sets.  It's why Chad Waterbury recommends eight or ten sets when he's working with low-rep sets of two or three.  Whatever the magic number may be, those muscles need some T.U.T., and a few seconds just ain't gonna cut it. 

So what's the magic number, everyone asks?  Hard to say, exactly, but we can take a cue from the rep ranges that almost everyone recommends.  Some classics:  3 x 10.  4 x 8.  6 x 4.  5 x 5.  And some newer ones, fast becoming classics:  10 x 3.  8 x 3.  12 x 2.  What they all have in common, math whizzes, is a total rep range around 25-30.  This has been belabored in the books and mags for some time, but it seems like the optimal total time under tension for an exercise, assuming a rep tempo of ABOUT 4-5 seconds a rep, is two or two and a half minutes per exercise.  Not per set, mind you.  

I'm convinced that even high-intensity training, like the much-touted DoggCrapp system (hurrah!) at least comes close to these parameters as well, simply because the weight these people use is so prodigious that it's almost impossible to move at anything but a snail's pace:  rep tempo slows down, the concentric pause extends, and your one work set winds up taking far longer than that of a typical program.

People also argue that Olympic lifters violate the T.U.T. rule as well, despite the fact that they are, by and large, a pretty buff bunch.  But Olympic lifters also take a long concentric pause (holding the weight overhead, or in the clean position, for several seconds during each rep), and perform multiple sets of each rep.  The weight is only moving for a fraction of a second per rep--but the muscles are actually working from the moment the weight leaves the floor. 

Now:  I'm not giving you that number because I expect--or hope--you'll start watching the clock while you lift or anything inane like that.  I'm just saying that there seems to be an answer to this hotly-debated topic build in to most training programs, assuming, which I do, that these programs are well-thought out and road tested, or at the very least, built on those that are.