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Old 09-23-2009, 07:23 AM   #1
Louis Andre Pardo
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HELEN!!...and high school physics to measure Power improvement!

One of my favorite WODs! Came home yesterday and busted it out at lunch. In July I was in the worst shape of my life and getting back into CF and decided to also use CFE. On July 15th I did Helen in 13:45...I want to throw up just thinking of that performance. Well, after only two and a half months of training I just completed my fastest Helen yet...

Time: 9:08

Some quick physics and we can determine power increase... Power=Work/time. The Work (completing Helen) hasn't changed* but the time to complete that Work, and therefore Power, have changed. For the sake of simplicity I am not going to use units but just derive a percentage of Power change.

For the July performance I completed W (Work of Helen) in a t (time) of 825 seconds. For the sake of simplicity I am going to say the value of W is 825. I could use any value here but this just makes calculations easy as it conveniently gives me a baseline P (power) of 1, P=W/t = 825/825.
Using the same value for W and plugging in the new value for t we get P=825/548, P= 1.505. That would indicate a power increase of 50.5%

*Now, from a physics standpoint this is not accurate because W did actually change between July and yesterday. The fact is that I lost 6 lbs since the July performance. That means I need less F (force) to move my m (mass) across a fixed d (distance), W = F x d; therefore the amount of W performed yesterday was less than in July. Ultimately that means that the difference in performance cannot be entirely attributed to simply an increase of P but also a decrease in W.

From a practicle standpoint no one cares about the physics; they just see the 50.5% as a measure of performance increase (this can be said to be the true percentage increase of average velocity over a given distance as velocity = distance/time. Notice that unlike Work, distance did not change between the July and September performances). When runners compete they are all completing different W as their masses are different while they run across the same distance. People do not care about the amount of Work the runner completed as they cross the finish line; they care about who completed the task first and by how much. Regardless, we can probably find a way to reasonably account for the mass and Work differences and therefore Power difference.

The 6 lbs decrease in weight is equal to a 3.125% reduction in mass. Considering Work = mass x acceleration x distance, where any acceleration difference between July and September is negligable, we can reasonably assume for any task where I am moving my mass across a fixed distance, that the Work is decreased by the same 3.125%. This is a very safe assumption considering that a 55 lbs weight is added to one of the tasks of Helen, Kettle Bell Swings. This mass does not change, accounts for considerable movement distance and therefore it can be reasonably assumed that the percentage of Work decrease for the entire task of Helen is actually less than 3.125%.

Using the 3.125% reduction figure the work performed yesterday would be approximately 825 - (825 x 0.03125) = 799.218. Using this new work figure we can find a lower-end Power percentage improvement: P = 799.218 / 548 = 1.458.

These two calculations show a 45.8% to 50.5% increase in Power in less than 3 months!

Finally, a last measurement is how much faster I completed the task in September compared to July: (825 sec - 548 sec) / 825 sec = 33.57% reduction in time.

Either way, this is a huge performance improvement that I am very happy with.
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Old 09-23-2009, 08:09 AM   #2
Derek Robinson
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Re: HELEN!!...and high school physics to measure Power improvement!

Quote:
Originally Posted by Louis Andre Pardo View Post
One of my favorite WODs! Came home yesterday and busted it out at lunch. In July I was in the worst shape of my life and getting back into CF and decided to also use CFE. On July 15th I did Helen in 13:45...I want to throw up just thinking of that performance. Well, after only two and a half months of training I just completed my fastest Helen yet...

Time: 9:08

Some quick physics and we can determine power increase... Power=Work/time. The Work (completing Helen) hasn't changed* but the time to complete that Work, and therefore Power, have changed. For the sake of simplicity I am not going to use units but just derive a percentage of Power change.

For the July performance I completed W (Work of Helen) in a t (time) of 825 seconds. For the sake of simplicity I am going to say the value of W is 825. I could use any value here but this just makes calculations easy as it conveniently gives me a baseline P (power) of 1, P=W/t = 825/825.
Using the same value for W and plugging in the new value for t we get P=825/548, P= 1.505. That would indicate a power increase of 50.5%

*Now, from a physics standpoint this is not accurate because W did actually change between July and yesterday. The fact is that I lost 6 lbs since the July performance. That means I need less F (force) to move my m (mass) across a fixed d (distance), W = F x d; therefore the amount of W performed yesterday was less than in July. Ultimately that means that the difference in performance cannot be entirely attributed to simply an increase of P but also a decrease in W.

From a practicle standpoint no one cares about the physics; they just see the 50.5% as a measure of performance increase (this can be said to be the true percentage increase of average velocity over a given distance as velocity = distance/time. Notice that unlike Work, distance did not change between the July and September performances). When runners compete they are all completing different W as their masses are different while they run across the same distance. People do not care about the amount of Work the runner completed as they cross the finish line; they care about who completed the task first and by how much. Regardless, we can probably find a way to reasonably account for the mass and Work differences and therefore Power difference.

The 6 lbs decrease in weight is equal to a 3.125% reduction in mass. Considering Work = mass x acceleration x distance, where any acceleration difference between July and September is negligable, we can reasonably assume for any task where I am moving my mass across a fixed distance, that the Work is decreased by the same 3.125%. This is a very safe assumption considering that a 55 lbs weight is added to one of the tasks of Helen, Kettle Bell Swings. This mass does not change, accounts for considerable movement distance and therefore it can be reasonably assumed that the percentage of Work decrease for the entire task of Helen is actually less than 3.125%.

Using the 3.125% reduction figure the work performed yesterday would be approximately 825 - (825 x 0.03125) = 799.218. Using this new work figure we can find a lower-end Power percentage improvement: P = 799.218 / 548 = 1.458.

These two calculations show a 45.8% to 50.5% increase in Power in less than 3 months!

Finally, a last measurement is how much faster I completed the task in September compared to July: (825 sec - 548 sec) / 825 sec = 33.57% reduction in time.

Either way, this is a huge performance improvement that I am very happy with.

You may be the most intelligent Crossfit athlete on here !! Good work on the Helen. I am going to use that formula on some gains I have made to see what it shows.

Good Work.
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Old 09-23-2009, 08:31 AM   #3
Louis Andre Pardo
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Re: HELEN!!...and high school physics to measure Power improvement!

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Originally Posted by Derek Robinson View Post
You may be the most intelligent Crossfit athlete on here !! Good work on the Helen. I am going to use that formula on some gains I have made to see what it shows.

Good Work.
I think it has less to do with intelligence and more to do with boredom...thanks anyway.

A good one to measure would be Cindy. Time (t) doesnt change but Work (W) does.

Consider W = total reps. One round (5 pull ups, 10 push ups, 15 squats) equals 30 reps. So 16 rounds, for example, is equal to 480 units of work. If you went up to 20 rounds then you completed 600 unadjusted units of work (not adjusted for body weight variation).

Say your weight was 200lbs at the first test and it was 190lbs at the second test. Assuming the same distances covered (range of motion) we can reasonably say that each rep is equal to 5% less Work at 190lbs than at 200lbs.

So a baseline Power would be P=480/1200 sec = 0.40. Remember that this is unitless and will just be used to measure improvement percentage.

The new Power will be P=[600-(600 x 0.05)]/1200 sec = 0.475 (again, unitless). The difference or increase in Power would be 0.075/0.40 = .1875.
That would equate to 18.75% increase in Power.
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Old 09-26-2009, 01:18 AM   #4
David M Tillotson
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Re: HELEN!!...and high school physics to measure Power improvement!

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Originally Posted by Louis Andre Pardo View Post
From a practicle standpoint no one cares about the physics
Come on man, you gotta love physics.
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Old 09-26-2009, 10:52 AM   #5
John C Corona
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Re: HELEN!!...and high school physics to measure Power improvement!

Regarding Helen, it 'is' safe to assume the work decrease is less than the 3.125%, but not because the added 55# weight, but because your body weight doesn't move thru that large of a distance. I know your swing is probably a quarter squat, but your arms are travelling a larger distance, and their weight is almost nill. To get a more exact decrease in Work, you might have to know your times for each section of run, KB, and pullup. So if your runs are 2min, and your pullups are like 20 seconds, then total time actually moving your bodyweight is about 7min. 7/9.133 = .7664. So .7664 x 3.125% = 2.395%. So now you have 825 - (825x .02395) = 805.24. And 805.24 / 548 = 1.4694 or 46.9 %. If your runs and pullups are faster, then work decrease is even less, and power is a little more. If you think doing a KB swing uses more of your bodyweight, then power is a little less.

Also, my physics teacher would've had your head for refering to your weight as your mass. We know these are two totally different concepts. Your weight, or 'force' exerted on the ground due to gravity, is different from your actualy mass. I believe you know this and was using the term mass because everything else cancelled out.

Anyway, here's a cool power calculator for some movements (wfs):
http://www.performancemenu.com/resou...owerOutput.php
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Old 10-01-2009, 06:42 PM   #6
Jackson Harmer
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Re: HELEN!!...and high school physics to measure Power improvement!

Interesting numbers. I just did Helen for the first time today in 11:50. Tough workout. My time slowed dramatically on the final two pullup sets due to my hands being both too wet and too tired to hang on to the bar. Pullups after the swings was tough on my grip. I had to stop multiple times and start over because my tired and sweaty hands just slipped right off the bar. Have to glove up next time and I'll probably save at least 30 seconds.
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