is it harder to lift the same weight when its more dense on the bar?
- 04-06-2009, 06:07 AM
is it harder to lift the same weight when its more dense on the bar?
Is it harder to lift the same weight when its more dense on the bar? what i mean is i got 363 above the knee x7 the other day with lots of 2.5kg weights on.Then today i used 385 with all bigger plates and i barely got it of the ground! Obviously its more weight but i expected better! Does anyone know what i mean by this?
- 04-06-2009, 06:27 AM
Weight is weight regardless of the number of plates used to accomplish this. If it was recent if could of been that your body is just exhausted and you weren't able to lift it. Diet and mood play a role in performance as well.
04-06-2009, 07:40 AM
i know where youre coming from . its a thought thats crossed my mind .my own thoughts are that the weight using smaller plates, is distributed further along the bar toward the end of it , and may put different stress level on the arms ( im talking bench press here) whereas using bigger plates the load is more toward the central part of the bar and is more direct. im trying to remember my physics here but failing. It could however be all in the mind.
04-06-2009, 08:07 AM
04-06-2009, 10:32 AM
Yes. A solid bar is harder to get a pull from(Dead) than a weak bending bar. Your body has an easier time easing into the weight than having to move the weight right from the go. Im not sure the exact physics of it, but i have felt the difference. Its not gorund breaking but i can vouch for a difference.
Edit: For bench press im unsure. I would imagine a bit easier but we are talking .00000000000001% prolly. Think of an arch. Arches are built to take stress off the center structure of a structure and split it to the outer bases. Imagine you are benching an arch when the bar bends. Taking stress off the center and placing it on the outer edges.
Sadly this all falls apart once you lift. You become the support so all that weight is on you/arms/chest. The weight may be distibuted to a more outer placde on the bar since it bends, but none the less, the weight is on the bar youre connected to and are pressing.
04-06-2009, 10:36 AM
I guess a way of checking this would be load a bar with a 1-2 rep max weight with two different types of loaded bars. One with smaller weights pushing the weight further out and one with bigger weight allowing it to stay inside.
04-06-2009, 11:57 AM
:dl:Weight is weight...there is no differnce.
I will say that it FEELS like its lighter when I stack on 45's instead of slapping the big 100's ont he bar...but I know its all in my head.
If anything, the more the bar bends, the HARDER it is to bench, as you actually have to lower the weight just a little bit further and deeper when you have a bend in the bar. It may help just a tiny fraction in deads, as when the bar bends, you actually are picking it up a fraction of an inch higher than if it were a super stiff bar. I don't think it is anything that you could really notice though.
I just like seeing the thing bow like a stick in the mirror :dl:
04-06-2009, 12:56 PM
The further a bar is loaded towards its edges, the more it will bend in the middle...thats simple leverages.
If the bar bends a lot in the middle its easier to deadlift because you are 'moving' it (bending the middle) a few inches before the plates even break the ground. So effectively its like pulling with the weights on ~2" high blocks.
So 363 with tons of 2.5 kg plates will be easier to deadlift than 363 will mostly 45's because the bar will bend more and you have to pull it less far.
04-06-2009, 01:27 PM
The more the bar bends, the more inertia you use to move the weight.
Why do you think you can move more on an Oly set than a standard? Same principle.
04-10-2009, 08:33 AM
04-10-2009, 05:26 PM
Weight is weight. It won't matter once it's in your hands. There are only 2 viable reasons why it seems harder:
1) You are a head case like 99% of the people in the gym and get psyched out by the "look" of big weight.
2) The greater number of smaller plates has a greater variability in their actual weight, and this stacked up in your favor (i.e. they're a little light).
Don't over think this. Lots of guys have trouble with #1. I had a friend miss 405 a billion times before he smoked it when it was a bunch of change on the bar and he didn't know it was 405.
04-10-2009, 06:00 PM
It can make a difference if it is due to leverage.
For example, if you are curling 100lb made up of two 50lb plates on a bar, when your arms are parallel to the ground the distance to the end of the weights from your elbow( which is the fulcrum) will be greater than if it made up of lots of smaller weights with smaller diameters.This means the force on your arms will be greater as the weight has more leverage.
04-10-2009, 09:16 PM
Pop is right, especially about the headcase comment, lol. And what you guys are saying about a deadlift would really only correlate to an Okie bar, and it would probably have to be extra long with hundreds on the farthest outside portion of the bar, not 2.5's, and the problem would end up being that the rebound or whip would shake the bar out of your hand. Everyone is thinking a little too much.
04-10-2009, 10:55 PM
The fulcrum length is from your elbow to the bar, not to the weights. The center of mass of the weight is the caenter of the bar regardless of the diameter of the weights used. The force is dependent only on the weight of the bar, not how far apart the weights are, or their diameter. You can grip the bar anywhere you want and the force on your arms will be the same. It might feel a little different to you because you're stronger/weaker at different grip widths, but it's all the same.
Now if you want to get real technical, the deflection in the bar will make a difference when deadlifting, because the further you deflect the bar before the weights break from the ground the "easier" the lift will be... but that's still not what the OP was asking. FWIW I'm a mechanical engineer. I own this stuff.
04-11-2009, 06:56 AM
This is what I dont get. If I hold a 7ft bar by one end and do a curling motion with it , it feels heavier than if I hold it by its centre and do the same motion.
Surely this applies to the weights as the mass of the weights extends further out from the bar with bigger discs giving more leverage??
04-11-2009, 11:25 AM
If you were to take a 10lb weight that was 1ft in diameter and put it on your arm, the center of mass of the plate would be 6" in, and since that would be 6" towards your elbow you would have a small lever, and it would "feel" lighter than if you held a 10lb plate in the palm of your hand.
When you turn the weights sideways to put them on a bar, relize that the center of the mass is still the center of the plate, but all the force is transferred to the bar. Thus, regardless of the diameter of the plates, the bar is the mechanism through which you exert force. Since that is a constant, the diameter of the plates doesn't matter. See what I mean?
With your 7ft bar example, if you pick up one end of it, it IS a lever -a very long one at that. Any weight on the end will have a tremendous moment arm from which you would have quite a lot of force to resist. When you grab it in the center it is balanced, no moment arm. The "distance" would only make a difference if the opposite side wasn't balanced.
04-11-2009, 01:25 PM
04-13-2009, 07:58 PM
It is, but the forces are balanced as you have an equal force on the opposite side of the plate. Think of a balanced teeter-totter. It doesn't matter how much weight is on it, as long as both kids weigh the same, all force goes through the center. If one is much heavier then they hit the ground and the analagy goes to hell.
04-13-2009, 08:33 PM
04-13-2009, 09:14 PM
Wow to some of the theories in this thread.
OP, if you are deadlifting, then using at least one large disk will make it easier, because it gives the bar more floor clearance (hence you don't have to bend down as far)...which is why all rubber Olympic weights are the same size.
04-13-2009, 11:23 PM
04-14-2009, 01:31 AM
04-14-2009, 09:57 AM
I have lifted things that weighed well over my limits because I didnt know how heavy it was. Alot of this weightlifting thing is psychological. Why is it a 86 year old grandmother can lift up and hold a semi-tailor thats on its side because it is laying on her grandchild?
I would go with half mind over matter and half God.
If a loved one is in trouble...500 pounds aint nothin but a peanut.
04-14-2009, 11:43 AM
04-16-2009, 06:00 PM
Simple thing... treat the weight as equally dense circle with a varying radius, and integrate it over the diameter. No matter the plate size, the center of mass and gyration will be right in the middle. So long as the diameter does not directly affect the lift in the way deadlifting does, you could curl with a 6ft wide plate on the bar and it wouldn't make a difference in the weight lifted compared to smaller plate of equal weight, at least in the same plane as your arms are rotating.
Too many times have I though about moment arms, center of gravity and rotation, as well as deform (getting bar whip) while lifting. I thought I was the only one lol.
Once this gets cleared up... here is another mind ****. While driving, imagine one of your wheels. Now take a snapshot in the smallest amount of time imaginable of the wheels movement and tell me.... around what point is the wheel rotating?
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