When you try your first Power Factor routine you’ll run into a couple of elements you might not be used to.

Timed Sets

After many years of open minded (read: non-dogmatic) experimentation we have discovered the value of measuring the power output of a muscle group over 30 seconds of maximum exertion.

Instead of focusing on a 1-rep max, or a 3-rep max, it’s more motivating and productive to measure 30 seconds of output. That output is a product of the weight used and the number of reps completed in exactly 30 seconds.

So using 300 lbs but only completing 7 reps (Total = 300 lbs x 7 reps = 2,100 lbs) is a lower power output than using 250 lbs but getting 9 reps (Total = 250 lbs x 9 reps = 2,250 lbs). The latter is 7.1% more total weight in the same amount of time. Win!

Most people aren’t used to using timed sets. There are two outcomes you want to avoid:

A) You select a weight that is too heavy so that after perhaps 15 or 20 seconds you have to stop. When you stop your power output is 0 lbs/min and that gets averaged into your total. Of course after a brief rest and with time left on the clock you can still grab the heavy height and bang out a few more reps before the 30 seconds is up. But that zero period still hurts your total. So you want to avoid choosing a too heavy weight.

B) You select a weight that is too light so that after the 30 seconds is up you aren’t even tired and could easily keep going. That means you didn’t generate your peak power in those 30 seconds. So you want to avoid choosing a too light weight.

What’s the perfect weight? Well, it’s the weight that causes you to be completely fatigued and unable to continue – right at 29.9 seconds.

So how do you know what weight on today’s Lat Pulldowns will cause you to hit total failure at 29.9 seconds? And how do you know what weight will make you hit failure on Deadlifts at 29.9 seconds? And so on.

The honest answer is ‘you don’t.’ And neither does anyone else. The exact answer is unknowable.

But there is a way to calculate a very close approximation based on your known previous performance.

Full Range or Strong Range Partials?

The other element of Power Factor workouts that many people are not familiar with is using only strongest range reps. Of course, you can elect to use conventional, full range reps on every exercise. The calculations can be altered for that.

However, once again, many years of open minded experimentation have revealed considerable benefits to strength, mass, and size gains (not to mention reduced risk of injury) when lifting much heavier weights but in a reduced range.

At this time, we have no universal formula that can tell a person how to convert his known full-range weights into his likely strong-range weights. There’s no chart where a 45 year old male can see that his 135 lb 1-rep max in the Bench Press will convert to 225 lbs in his top quarter range. Or where a 55 year old female can do the same. And so on for every common exercise.

But such charts always work with averages anyway. And what we need are specifics. All that matters is exactly what YOU can handle for 30 seconds in your full or strongest range.

Workout Zero

I gave this workout the name ‘Zero’ so people would be comfortable with some stop and start experimentation and not feel like they were wrecking their workout with mistakes.

Workout Zero involves some quick and easy experimentation, a sort of deliberate mistake-making trial run.

  • For each exercise, simply select your best approximation of what you think you can handle for sustained reps lasting 30 seconds.
  • Set a countdown timer on your watch, phone, or ask someone to time you. (I use 40 seconds on my watch so I have 10 seconds to get my grip and breathing right.)
  • After a few seconds of lifting try to judge whether you chose a weight that is too heavy to keep going or too light to put you at muscular failure
  • If you think you have the wrong weight stop immediately. Increase or decrease the weight and wait two or three minutes before you try again.
  • At the end of 30 seconds of lifting write down the weight you used and the number of reps you completed.
  • Move on to the next exercise and repeat the above process.

From these measurements we can begin to create new goals for next time. When we have data from how your next workout went, it will inform us what new goals are within your reach.

For each exercise we end up with a graph that looks like the one below. The more data you accumulate, the more accurate the predictions of goal weights, goal reps, and target dates for workouts when you are adequately recovered.

If you want to know what power you are capable of on 10 consecutive workouts, you can try it here.


  • Jim Johann Jr

    Hey Pete,

    This was certainly a thought-provoking article and your argument/example of 300×7 vs 250×9 really got me thinking about your comment that “weight trumps repetitions” or something reasonably close to that. In looking back whenever I’ve read that comment, I’ve always assumed that more weight referred to weight on the bar, whereas I now think you mean total weight lifted over the 30 seconds. Personally, I would much rather do 300×7 then the 250×9, because I don’t track by 30 second intervals.
    In examining the chest power chart in going from 4400 to 7551 lbs in the 30 seconds, a guy could start with 200lb x 22 reps in 30 sec and over the 6 workouts/31 days build to 251.7 lb x 30 reps in 30 sec. These weight/rep numbers would accomplish the 4400 and 7551.
    Now for the 7551 number, this combination would also work…495lb x 15.25 reps. The cynic in me doesn’t really think someone who could only do 22 reps with 200 has a snowball’s chance of doing 495 for 15 reps a mere 31 days later, unless he was sandbagging big time…even using short range partials. And it would not be possible for someone using full ROM. I admit that if we’re just counting full reps (partial or other ranges), 495×15=7425, is short of 7551…but close enough maybe.
    Out of curiosity, do you have a preference on which path you use to get to 7551? It goes back to something else you’ve said (paraphrased immensely here), that while 800×1 and 100×8 are the same work, there is a huge difference on the body/muscles. I would think, following your statement, that in the above examples, the 7551s (allowing for the rather small 116 lb shortage) are NOT equal.
    I’m not trying to put you on the spot here, but I am curious if you have done any research/testing on this scenario/idea? I can certainly understand people who would prefer less weight on the bar for safety reasons, especially if they find keeping good, safe form almost impossible when racing the 30 second clock to get in that last rep at 29.9 seconds. My reason for asking is based on your access to all the folks you’ve worked with over the years and the workouts you’ve programmed and tracked…all I have is my own training numbers and my personal preference.

    Appreciate any further insight you may have on this topic.


  • Bent Nissen

    If I practice leg pressure in the Mass Gain Study, I have more than twice as much weight as normal exercise. On the other hand, it hurt in my knees (not in the leg muscles) over 14 days afterwards. It can’t be healthy.

  • Hi Jim. Thanks for the observations.
    1. The PF is always in lbs/min so when I guy does 200lb x 22 reps in 30 sec (half a minute) his PF is actually 8,800 lbs/min.
    2. I don’t have a preference for how a person increases his PF. We’re usually trying to increase the weight used, but it always comes down to finding that ‘sweet spot’ where a person does the right number of reps that takes him to honest, just-can’t-do-another-rep, failure at 29.9 seconds. And that combination is a moving target that’s different every workout, or should be if progress was made from the previous workout.
    3. Here’s three real-world examples of trainee’s Power Factor changes over 10 workouts, you can see that human variance is substantial: http://www.precisiontraining.com/age-64-8lbs-gained-in-10-workouts/