Tall People Lifting Weights
January 1, 2005 6:23 PM   Subscribe

I heard once that taller people have a harder time lifting weights. It seems logical enough an idea. Because taller people have longer limbs the same amount of weight will have great leverage. So it would take a larger muscle on the person with the longer limbs.
If someone 5 foot 4 inches can dumbell press X amount of weight how much more impressive is someone 6 foot 4 doing the same amount? Is there a nifty equation even?
posted by Napierzaza to Sports, Hobbies, & Recreation (13 answers total)
posted by Doohickie at 7:51 PM on January 1, 2005

I guess one could use the 'work' needed to lift the weight, as in Work = Weight x Height.
posted by sexymofo at 8:10 PM on January 1, 2005

There is definitely more "work" (in the physics sense) being done by the taller person. But I think what the poster is getting at is that more torque needs to be supplied to move a weight that is further out (because of long arms, for example). I doubt there is a trivial equation, unless you focus on one particular movement (i.e. bicep curl).
posted by knave at 8:39 PM on January 1, 2005

I'm not completely sure what a "dumbbell press" is. Perhaps you can work out the difference using these equations.

That is, if you can simply model the displacement vector you can get an estimate of the work ratios. If that doesnt answer your question, take a look at The Physics of Weightlifting.

On preview: yeah, you need to define a simple movement first.
posted by vacapinta at 8:41 PM on January 1, 2005

Weight training machines (nautilus and all the derivatives) are "geared" usually around foot pounds.

How many feet the weight is being moved.

A simple variation can work for you here.

Take a friend and do a bench press.

Measure the vertical distance of the weights. Instant comparison.

But there isnt' a formula; not that you couldn't derive them. It's a problem due to the moment arm distance varying in rotary motions for people with different shoulder to elbow and elbow to hand differences
posted by filmgeek at 9:08 PM on January 1, 2005

If you're just looking for the difference in torque at one point, say the beginning of a curl, then the equation you're looking for is:

torque = FRsin(theta)
F is the weight of the dumbbell
R is the length of the forearm
sin(theta) is 1 at that point.

So it's actually just: torque = FR

If, instead, you want the difference in total work done lifting the weight to different heights, you'd have to integrate over theta and i'll let someone else take care of that.
posted by SAC at 10:35 PM on January 1, 2005

Vacapinta - a dumbbell press is a bench press done with dumbbells instead of the bar. Often, people who can't lift the bar (45 lbs) do dumbbell presses until they can work up to the bar. However, dumbbell presses are actually harder than traditional bench presses because you don't have the stabilization of the bar and you can't compensate for a weaker side. You also have to concentrate harder on form.

I've never thought that longer limbed people would have to work harder to lift the same amount of weight as a shorter person. That's an interesting thought.
posted by Juicylicious at 10:38 PM on January 1, 2005

I recall this being mentioned during one of the powerlifting events at the Olympics this year. One of the favorites, and I believe a world champion for his weight class, was well over 6 feet tall. That meant he had to lift the bar to a height of almost 9 feet while the rest lifted the bar just over 7.

I would think the biggest factor here would be the ratio of the distance between the joints and the tendons to the overall length of the bones. If two people had the same tendon offset from the joint, the person with the shorter bones would have a definate power advantage for the same muscle force.
posted by Yorrick at 11:22 PM on January 1, 2005

I have to admit that it's because I'm tall that I thought about it in the first place (rationalization and all that). Thanks for the equations I always wanted to know just how significant the difference was, so I know just how much I'm kidding myself.

How do they gear the Nautilus that way? It sounds interesting. Are the makers of Nautilus machines real techies?
In terms of sample movement something like a bicep curl is probably easiest as it's fairly isolated.
Thanks for the links vacapinta I'll check them out, as well as the equation SAC.
posted by Napierzaza at 11:29 PM on January 1, 2005

Oh, the powerlifting thing got me thinking. I neglected to mention that. Most power lifters are shorter not to mention gymnasts right? I suppose there must be 6 foot+ people who can do taxing stuff like the rings etc but it must be uncommon.

I know that most bodybuilders are pretty short. Partly due to the same amount of muscle looking better on a smaller frame as well as it being easier to lift more. Not to mention *cough*Short-man complex*cough*.

I downloaded a video from the prelinger archive about gymnastics and was totally blown away, it's so amazing.
posted by Napierzaza at 11:34 PM on January 1, 2005

A few thoughts. First, people vary a lot in the distance between the actual joint and the tendon attachment point. That's gotta make a difference that would confound any simple formula based on height. But, all other things being equal, the tall person will have a harder time when doing a movement where long levers are against them. It's not just height, either. I have long arms (me ape!) and short legs and I find pressing relatively difficult for someone my height and weight - pressing body weight at 180 lb will be a real achievement for me, whereas when I'm training I can squat 300 lb without too much hardship and I reckon I could build up to 360. (Don't ask me to do it now...)

Second, Nautilus is 9/10 bullshit as far as cam shape goes, for precisely that reason. You would need a custom built machine for you. Luckily, plain weights work just as well and Arthur was full of shit. Let us not be detained here by a detailed discussion of why.

Not all human joints are levered like that though. Eg, ankles are second class levers, elbows are third class. Famously, in body building, people of west African descent have crappy calf muscles. No one ever seems to put 2 and 2 together and note that they also have tend to have longer lower legs, so leverage means they don't need bigger calf muscles for the same force. Which is why those same guys with weenie calves are outsprinting me. (Well, it's one reason).

Napierzaza - I don't know from gymnasts, but I do know a lot of capoeira players, and invariably the most acrobatic players (though not necessarily the best capoeiristas) are short, and I think it's a simply matter of power-to-weight ratios. Just like you should always bet on the tall fat guy in a fight, bet on the small springy guy for acrobatics.

Small guys can often lift more than bigger guys with more apparent muscles. Partly technique, partly leverage, partly power-to-weight (think calf raise - if I weigh 180, and you weigh 220, but we have identical legs, I can lift a heavier stack than you, because I'm lifting 40 pounds less weight).

*ahem* at 5' 8", this effect works for me a lot in the gym compared to some taller guys, and it cheers me up. But you can't go around looking for arbitrary measures where you come off best, just so you can feel better. The best measure is what you could do before, not what anyone else does, precisely because as a unique combination of bio-mechanics, no one else is like you.
posted by i_am_joe's_spleen at 12:09 AM on January 2, 2005

I'm sorry Joe. We have to disagree on Nautilus (and arthur's sucessor Medx.)

Let's say he got the cam shape 85% accurrate. Well, that's going to work for most of the population under the bell curve. The resistance varies based on the muscular torque produced (the rotary joints are actually measured cams, especially from Medx.) Many cams went through a beta testing period.

It's still tons better than no cam at all. The advantage of these cams is that they're producing an varying force to the direction of motion. An example is a bicep curl with a dumbbell. At the beggiing of the motion (arm vertical) gravity is pulling downwards- but your arm is about to pull 90 degrees out of phase as it starts the rotary motion. Midpoint (parallel to the ground) both are correct - you're pulling opposite to gravity. At the top of the motion (hand nearly at your shoulder) again, you're pulling 90 degrees out of phase. Actually, for the record, that's a machine superiorirty (direct and opposite force).

The cam provides varying resistance.

The current Nautilus guys (and now the medx guys) certainly aren't the techies we'd like to see.

Probably the smartest machine design currently occurring comes down to Hammer. Oh, and Hammer? Designed by the son of the inventor of Nautlius - Gary Jones.
posted by filmgeek at 6:05 AM on January 2, 2005

You could do a study of the kinematics and dynamics in great detail and never really answer the question. Certainly the people who suggest you can calculate the difference in potential energy of the weight at the end of the lift have a point, but that is only a very small part of the effort required.

Longer members can mean a mechanical advantage for either you or the weight depending on the details. Which is to say, i_am_joe's_spleen has a pretty good grasp on the physics of it, I think.
posted by Chuckles at 8:45 AM on January 2, 2005

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