Physics question

[Jonathan Silverman]

Originally Posted by Tom Woodward

It logically follows that more mechanical work can be done for a longer period of time while guzzling less ATP by NOT maintaining ideal isometric contraction of the lower back in an exercise like high rep deadlifts. Interesting stuff....

You won't be able to more work though! Because of inevitable injury if your lumbar extension goes.

[Jared Ashley]

Originally Posted by Tom Woodward

Anyone intrigued by Jamie's post should check out this thread:

http://************.net/forum/showthread.php?t=5032 (not WFS due to language)

As Jamie says, isometric work generates zero work but requires energy consumption. This jives with Rip saying that more ATP is consumed while holding the erector spinae in ideal positioning than not, since that correct position for the lumbar is isometric. It logically follows that more mechanical work can be done for a longer period of time while guzzling less ATP by NOT maintaining ideal isometric contraction of the lower back in an exercise like high rep deadlifts. Interesting stuff....

hmm... I agree with mark's conclusion (intensity actually decreases when you bounce deads), but completely disagree with the reasoning behind it (a rather vague claim that the additional re-contraction of the erector spinae and the isometric hold somehow "burns more ATP"... maybe it's true, maybe not, but it's definately not a testable hypothesis). I'd say the REAL reason intensity decreases is that a substantial portion of the work (force * distance), is conserved during the bounce. At the bottom several inches of the pull, you're not generating 225 lbs of force, but some amount substantially less, therefore you're doing substantially less work.

More important is his *true* statement that the bounce is done to "increase the intensity with no attention paid to lumbar extention" and that that this is doing deadlifts WRONG. 225 is "light" for some, so they can get away with it, for awhile, without hurting themselves, but eventually it'll bite 'em in the a**!

[Barry Cooper]

I would disagree that an Iron Cross is zero "work". The work being done is creating an equal and opposite reaction to the force of gravity. If the amount you are "falling up" is equal to the amount you are falling down, you are in equilibrium. The analogy I would draw would be to a treadmill. Objectively, you stay in the same place. However, you are doing work.

For my two cents--and this has already been approximately said--the relationship is a ratio between the total power POSSIBLE in a given setup--given the limitations of the human body--and the amount actually generated. For someone who is weak, you could do a perfectly efficient 95 snatch. And for someone who is strong, you could do a really inefficient 200 lb. snatch. Paul Anderson's form, for example, was terrible, even though he was our last heavyweight O-lifting champ.

[Jamie J. Skibicki]

THe iron cross is zero mechanical work. Nothing is moving.

work = force x distance

distance = 0

work = 0


Also

work = change in energy
E = 1/2 mass * velocity^2

velocity = 0

E = 0

work = 0

[Jonathan Silverman]

I don't get it. Take Iron Cross, it is so hard. But it requires no work. I understand there is a neuromuscular component to this which is understated all the time. So it's about the coherence of the signal which has nothing to do with work.

anyway do muscles get bigger only because of the physics quantity of work? because it is an adaptation for better leverage. i refer to pg 83 of Starting Strength.

basically, getting big is about applying yourself as a lever a lot. i think the reasons gymnasts get ripped is because not bc they can do an iron cross but because they can do front levers and back levers.

[Jonathan Silverman]

imagine a definition of a strong mind using concepts of leverage.
wow...

[Lee Sybert]

Originally Posted by Jamie J. Skibicki

THe iron cross is zero mechanical work. Nothing is moving.

work = force x distance

distance = 0

work = 0


Also

work = change in energy
E = 1/2 mass * velocity^2

velocity = 0

E = 0

work = 0

But are you exerting engery, even with no motion involved. Your heart uses calories to beat and your body is moving something even though you don't see any external movement. Just a thought.

[Kurt Armbruster]

E=mv^2 is kinetic energy. There's no motion, so KE=0.

However, there's also the potential energy due to gravity one is fighting.

E=mass*acceleration due to gravity*height off the ground

[Jared Ashley]

Originally Posted by Lee Sybert

But are you exerting engery, even with no motion involved. Your heart uses calories to beat and your body is moving something even though you don't see any external movement. Just a thought.

Yes, you are most definately burning energy, that isn't up for debate.

Also, Jamie is correct that zero "work" is done. It's physics 101, and also cannot be debated.

The term "work," when applied to isometric loads, is completely irrelevant. Remember that although you aren't doing any work, you ARE producing tremendous FORCE... it's just that no matter how large the force, the distance it's applied over is zero, and therefore force * distance = 0.

Muscle is strengthened NOT by how much "work" it does, but rather by how much FORCE is produced.

Do the math, and you'll find that very little work is done in a starting strength workout when compared to say, "cindy". But SS will make you stronger than Cindy will because you're producing a whole lot more force.

[Jonathan Silverman]

Why are you producing force in an isometric hold when there is no acceleration?