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Fitness Theory and Practice. CrossFit's rationale & foundations. Who is fit? What is fitness?

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Old 07-03-2008, 12:34 AM   #1
Sam Ser
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power output, or total work?

question for the gurus here:

which is more important in the crosfit approach to fitness, power output, or total work?

here's an example:

according to the output calculator at performance menu/catalyst athletics (thank you, guys!), i calculated total work and power output for two different single set max bench presses.

one set was 15 reps with the equivalent of my bodyweight, the other 10 reps with a heavier weight. my total work was slightly higher with the lighter weight, while my power output was slightly higher with the heavier weight.

what should i make of this?

i understand that the idea is to move more weight across a greater distance in less time. (in this case, more weight over a fixed distance in less time.) but if that's the definition of work, then why was my total work LESS when i moved more weight in less time?

and which would be preferrable, 15 reps at weight X, or 10 reps at weight Y?

(by the way: i also computed my 1 RM and found that, not only was the total work abysmally less than the total work for my 15-rep set with my bodyweight (no surprise there), but my power output was significantly less, too. this makes me think that, although testing maximal strength is cool, and taxing in a unique way, it isn't a very good workout. )

thanks in advance for your input.
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Old 07-03-2008, 11:29 AM   #2
Sam Ser
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Re: power output, or total work?

wow... NO ONE has any thoughts on this?




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Old 07-03-2008, 11:37 AM   #3
George Mounce
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Re: power output, or total work?

Work, in less time = more power.

Power production is what CrossFit is about. Take the pull-up for example. You can do 30 dead-hangs in X time, or you can do 30 kipping pull-ups in Y time and everyone I know of will have a Y time that is substantially less than X.

Therefore you are doing the same work (BW movement from point A to B, with said force), but the time is smaller, its more power.

You are just playing around with the equation P = (FxD)/T. You are purposely messing with just the F. The really dependent variable is T though when talking power production.
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Old 07-03-2008, 11:51 AM   #4
Jared Ashley
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Re: power output, or total work?

I don't think the power vs. work argument really applies to a single set... all that matters in that context is weight & reps. Even then, it depends on goals. High strength goals, you'll want higher weight, endurance goals you'll want more reps (duh).

Anyway, the power output vs. total work is applicalble to the metcon workouts only. And the answer is: you need a high capacity of both, with power output being more important. Something like "fran" or "helen" or "run 5k" is all about power... you're always going to do the same amount of work, and you're trying to do it in less time, and therefore higher average power. Something like "cindy" or "mary" is actually both... the more rounds you do, the more work you did, but in the same amount of time, so power is increased also. So power is ALWAYS important. Every now and then you need to do a ton of total work too... hence the occasional hellish workout like "murph" or "eva", where your power output can't get too high, 'cause you've gotta maintain it for the better part of an hour!

Oh, and to explain your math questions... the actual calculation goes like this:

Work = force * distance. Therefore:

10 reps of 135 lbs, say you move the bar 1 foot = 1350 ft lbs of work
15 reps of 120 lbs, same 1 foot = 1800 ft lbs of work

Power = work/time or (force * distance)/time. Therefore:

Say in both cases you took 2 seconds per rep:

1350 ft lbs/20 seconds = 67.5 ft lbs/sec (and yes, there is a conversion from this unit to horsepower or watts)
1800 ft lbs/30 seconds = 60 ft lbs/sec

on 15 reps of lighter weight, work is greater because you did a lot of reps, but power is less because it took you so much longer. If you can bust the 15 out fast enough, you could get the power to be greater.

But really, none of that matters... power output and work output doesn't truly become relevant until you're talking about several minutes (or at least 2-3 minutes). To say you output 1 horsepower for 1 rep on an olympic lift is meaningless... it's for like 1/2 second. But if you can say you maintained 1/4 horsepower for 10 minutes; THAT is something!
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Old 07-03-2008, 12:11 PM   #5
Phillip Garrison
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Re: power output, or total work?

What's more important to you as an athlete?
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Old 07-03-2008, 12:25 PM   #6
Phillip Garrison
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Re: power output, or total work?

Quote:
Originally Posted by George Mounce View Post
Work, in less time = more power.

Power production is what CrossFit is about. Take the pull-up for example. You can do 30 dead-hangs in X time, or you can do 30 kipping pull-ups in Y time and everyone I know of will have a Y time that is substantially less than X.

Therefore you are doing the same work (BW movement from point A to B, with said force), but the time is smaller, its more power.

You are just playing around with the equation P = (FxD)/T. You are purposely messing with just the F. The really dependent variable is T though when talking power production.
Except F=MA
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Old 07-03-2008, 09:15 PM   #7
Sam Ser
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Re: power output, or total work?

Quote:
Originally Posted by Jared Ashley View Post
I don't think the power vs. work argument really applies to a single set... all that matters in that context is weight & reps. Even then, it depends on goals. High strength goals, you'll want higher weight, endurance goals you'll want more reps (duh).

Anyway, the power output vs. total work is applicalble to the metcon workouts only. And the answer is: you need a high capacity of both, with power output being more important. Something like "fran" or "helen" or "run 5k" is all about power... you're always going to do the same amount of work, and you're trying to do it in less time, and therefore higher average power. Something like "cindy" or "mary" is actually both... the more rounds you do, the more work you did, but in the same amount of time, so power is increased also. So power is ALWAYS important. Every now and then you need to do a ton of total work too... hence the occasional hellish workout like "murph" or "eva", where your power output can't get too high, 'cause you've gotta maintain it for the better part of an hour!

Oh, and to explain your math questions... the actual calculation goes like this:

Work = force * distance. Therefore:

10 reps of 135 lbs, say you move the bar 1 foot = 1350 ft lbs of work
15 reps of 120 lbs, same 1 foot = 1800 ft lbs of work

Power = work/time or (force * distance)/time. Therefore:

Say in both cases you took 2 seconds per rep:

1350 ft lbs/20 seconds = 67.5 ft lbs/sec (and yes, there is a conversion from this unit to horsepower or watts)
1800 ft lbs/30 seconds = 60 ft lbs/sec

on 15 reps of lighter weight, work is greater because you did a lot of reps, but power is less because it took you so much longer. If you can bust the 15 out fast enough, you could get the power to be greater.

But really, none of that matters... power output and work output doesn't truly become relevant until you're talking about several minutes (or at least 2-3 minutes). To say you output 1 horsepower for 1 rep on an olympic lift is meaningless... it's for like 1/2 second. But if you can say you maintained 1/4 horsepower for 10 minutes; THAT is something!

thanks, jared. some good points.

i did calculate fran, using different weights and different times. time -- that is, speed -- proved to be the most significant factor in power output. fast, i realize now, really IS fit.

the interesting thing for me to see was that the use of lighter weights, by enabling more speed, allows for morepower output. when i first saw the rep ranges that are most common in crossfit workouts, i was concerned about strength (!). but, after years of swallowing the idea about needing more and more poundage in slow, isolation lifts, i'm coming around to the idea that moving lower weights faster is a path to strength.

of course, you have to push your limits in endurance and maximal strength efforts, too. but i see how the move-fast-for-several-minutes system works.
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Old 07-04-2008, 10:20 AM   #8
Shane Skowron
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Re: power output, or total work?

Unless I am misinterpreting your question, total work is completely useless for nearly all Crossfit contexts. Total work can be essentially understood as volume. And everyone knows that increased volume does not equal increased fitness.

Take "Fran" as an example. If you do Fran as rx'd in 5:00, you have a high power output. If you do Fran twice, but you take a leisurely 30:00, you had a higher total work output. But of course, your power output is significantly reduced. It's not hard to judge which workout was better.

Total work only matters when the power remains the same. Two Frans in 10:00 is impressive because you do double the work at a constant power rating.
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Old 09-04-2012, 09:28 AM   #9
Jon Gray
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Re: power output, or total work?

I'm considering restructuring my workouts so that "work" is not the number of reps for a particular weight but rather foot/lbs or work. Then I would adjust the weight and reps based upon optimal power output.
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Old 09-04-2012, 09:31 AM   #10
Eric Shuty
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Re: power output, or total work?

Some of you are totally overthinking this whole fitness thing....
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