Chin-up lad...

September 8, 2009 6:58 AM

Stupid physics question from a implied bet about fitness...

Talking about fitness with my boss, it came up that he comfortably does two arm chin-ups and is working on doing one arm chin-ups. I, however, can't do them at all.

I happen to weigh almost exactly twice what he does.

It was concluded that me doing a two arm chin-up is as impressive as him doing a one armed one.

Q1) Is this reasoning even vaguely logical and/or accurate?

This then got me thinking... He has the knowledge that he can lift his 12st frame by 2ft (or however far it is) but I have no idea how much weight I can lift using my arms. Obviously it's less than my 23st, but I have no idea how much. Short of tying a lot of helium balloons to my feet, I'm not sure how I could work it out either.

Q2) How can I gauge how much of my weight I can lift at the moment, and how can I track this should I rise (sorry) to the challenge?

Bonus marks for answers that don't involve expensive gym equipment.

[If anyone has any great ideas on how to target the relevant muscles, that would be appreciated too...]

posted by twine42 to Health & Fitness (22 answers total)

You need a doorway chin up bar and a bathroom scale.

Stand on the scale and attempt to do a pull up with out just dropping your feet. Have a partner read the scale and subtract from your actual weight.
posted by ian1977 at 7:11 AM on September 8, 2009

by 'dropping your feet' I meant without just instantly starting from a hanging position, instead...do it entirely from a standing position until you achieve air from your armstrength alone. or...well, you know what I mean.
posted by ian1977 at 7:13 AM on September 8, 2009

Q1) The asymetry of a one armed chin-up makes it harder and more impressive
Q2) Stand on a bathroom scale

To target the relevant muscles:
go climbing
practice chin-ups with your feet lying on a chair
posted by Akeem at 7:19 AM on September 8, 2009 [1 favorite]

I'm not sure ian1977's solution is very effective. I considered the bathroom scale, but you'd really have to lift 11st of the 23st weight while someone applied a force equivalent to 12st upwards on your feet through the scale. Just pulling enough to have the scale read 12st without actually moving isn't really equivalent to the muscle action involved in doing a chin-up.

A more realistic exercise would involve a climber's harness, an 11st weight (builder's rubble bag filled with concrete blocks maybe?) and a pulley (or failing that, a chin-up bar capable of supporting 35st)...

Basically, you have a weight equal to the amount you want to 'lose', and have a rope running over a pulley (or super-strong bar), with you attached at the other end. This would allow you to simulate what it would be like to weigh 12st, and also allow you to do a full chin-up motion. And of course by varying the counterweight you can find out exactly how much you can lift.

So yes, a certain amount of equipment may be required.
posted by le morte de bea arthur at 7:20 AM on September 8, 2009

This doesn't address the physics/musculature part of your question, but has he always been able to do a chin-up? And have you never been able to do one?

In my mind, at least, it's incredibly impressive to accomplish any fitness goal that you've never been remotely able to do before. It's less impressive if you've been able to do it since the age of seven.
posted by Metroid Baby at 7:22 AM on September 8, 2009 [1 favorite]

1. Eh, sorta. Physical strength is at least partly genetic and all tied up in things like the type of muscle fibers you possess and how your tendons are attached, etc etc. So in that sense it's never going to be a "fair" because you're starting from two different places. That said, percentage of body weight is a pretty frequent basis for bets like this.

2. Lat pull machine is probably going to be your best bet. Pretty much every gym has one.

You may want to try a combination of weight loss/strength training if you want to win the bet, assuming that's allowed.
posted by electroboy at 7:27 AM on September 8, 2009

in terms of mechanical Work done to lift an object of Mass m a distance of d. then I think the work is proportional to the mass? so its twice as much work isnt it?
posted by mary8nne at 7:27 AM on September 8, 2009

I mean its twice as much work for you to lift yourself.
posted by mary8nne at 7:29 AM on September 8, 2009

Is this reasoning even vaguely logical and/or accurate?

Well, the amount of force you can impart on things (including pulling yourself up on a bar) is proportional to your weight, which is why there are things like weight classes in boxing. Chin ups are really hard for everyone though, but on the same token spending a lot of time working on them will eventually have good results for everyone too.

If anyone has any great ideas on how to target the relevant muscles, that would be appreciated too...

If you have a pull up bar, you can do the easy part of the pull up or chin up and work your way up to a real one. Get a chair or just jump up so that you can start at the "top" of a pull up, and just hang there as long as you can. Once you get good at that, start at the top and slowly lower yourself down to a hang (i.e. the second half of a pull up). Then once you can do those easily, work on pulling yourself up from bent arms and then eventually a dead hang. Then work on doing a bunch of those in a row or move onto one arm pull ups.
posted by burnmp3s at 7:30 AM on September 8, 2009

You probably don't want to BUY an assisted chin-up machine, but many gyms have them. It's a very cool feeling the first time you use one, and it trains the right muscles. You adjust the weight down until you can do it yourself -- or that's the theory. Using one will also tell you how much weight you need in the counterbalance which, I guess, tells you how much you can actually lift.
posted by The Bellman at 7:33 AM on September 8, 2009

I know you said "no expensive gym equipment", but I will point out that many gyms have what's called a "chin-up assist machine". It's a weight machine that pretty much works like la morte de bea arthur describes: you rest your knees on a pad that's connected to a pulley system; as the pad ascends, the pulleys allow some counterweights to descend, and vice versa. If you're really curious about question 2, you might call around to the local gyms and see if they have one.
posted by Johnny Assay at 7:33 AM on September 8, 2009

It really depends on the definition of the word "impressive".

Given that you weigh twice as much as him, if you can just barely do a two arm chinup and he can just barely do a one arm chinup then you can deduce that you have roughly equivalent arm strength (in fact, you would have slightly more, since he is likely doing his one arm chinup with his dominant arm, and thus using more than half his total arm strength).

However, I would hardly say that your feat is equally impressive, given how much easier it is to maintain a higher muscle mass when you weigh more.
posted by 256 at 7:47 AM on September 8, 2009

I can only speak to the first question. I think one good factor to work in, from a biophysics angle, is the square-cube law. Basically, if I "double" a given organism in all three dimensions, it is now twice as tall, twice as wide, and twice as deep.

This means that its mass (assuming density and proportion remained constant) is now eight times as much, but the cross-section of one of its limbs, which is a direct relation upon strength, only goes up by a factor of four. This is why insects insects can move around things which weigh more than they do manyfold — were they blown up to our size, they'd be nearly unable to move. Strength goes up by size squared, mass goes up by size cubed; square-cube law.

This leads to structural difficulties, which is why very large organisms have thick, stumpy feet.

If you use m for mass and s for strength, you might see something like m² is proportional to s³.

Now, assuming that your proportions are identical (which is a big assumption), at twice his mass you should be at 2^2/3 of his strength, or about 1.587 of his strength. And you're using it to lift twice the mass he is.

Of course, this calculation is really just a description of how large the cross-section of your upper arms should be as compared to his. It is unlikely that you're almost exactly 26% larger (2^1/3) larger than he is in every direction. I'd go with the experimental method and do a tape measure, remembering that here you are measuring circumference, so that does not go up as a cube or a square, just linearly. Use the old standbys to get from circumference to cross-sectional area. Even that is an approximation, at best, since we do not know how much bone you have in either case, slurping up the area which we naively ascribe to muscle.

Fun, eh?
posted by adipocere at 7:49 AM on September 8, 2009 [2 favorites]

According to google, 12 st = 168 lbs, and 23 st = 322 lbs.

Q1:He is wrong. One 2-handed chinup by you is equivalent to 18 2-handed chinups by him.

Take the number of reps you can do and the weight and the number he can do and the weight. Plug this weight in to the w and the reps into r in the second formula on this page (Brzycki Formula, for future reference). That equation gives your and his one rep maximum.

Using this formula, if you could do one full chinup, it would be the rough equivalent of him doing 18 chinups at his weight.

The reason for this is that the muscle does not behave linearly, nor can it grow linearly.

Furthermore, a chin-up doesn't work your arms, it primarily works your back. The muscles in the arm, shoulders, and chest that are used merely assist the back muscle and stabilize the joints. A one-handed chinup engages the back muscles in a way that is considerably morecomplex than just half of it.

Now you can compare your one rep max to his. But this comparison is pointless, as he may be taller, shorter, different bodytype, etc. Secondly, who the hell cares how many chinups you can do. You could put him to shame by doing squats, because your legs are conditioned to move twice his weight all the time. His legs probably cannot move your weight even once.


Q2: How to track you improvement.

It will be hard to diligently improve doing chin-ups if you can't complete one, because you'll never get to work the muscle in its full range of motion. But in general, for any exercise, you work to failure (I.e. keep doing reps until you can't anymore) and you plug the reps and the weight into that formula to get your 1 rm. The next outing to the gym should select a new weight such that you achieve that same 1RM in 8 reps. But you try to do more than 8, so that the time after that, the 1RM number is higher.

But be aware that at 322 lbs, you place considerable strain on your joints by doing chinups. So I would not receommend you try to do chinups, instead go to a gym and do specific back and arm exercises that train the muscles individually and safely. Then you'll notice you start to get stronger and you start to lose weight, which will make the eventual chinups easier because your muscles are stronger and you weigh less.
posted by Pastabagel at 7:52 AM on September 8, 2009

It was concluded that me doing a two arm chin-up is as impressive as him doing a one armed one.


To answer this questions specifically, no. The lighter you are, the easier 1 handed versions of common bodyweight exercises, like chinups and pullups are. This is because the one-handed version relies much more on the stabilizer muscles. Otherwise, you would expect people to be able to do half as many one-armed chinups as they can do two armed. But often, they can do a dozen two armed, and no -one armed. This is because the stabilizer muscles are not capable of stabilizing 200% as much weight, but rather only at most 160%.

Your boss is light at 168lbs, so one armed chin-ups are sort-of-impressive.

But again comparing two people is really stupid, particularly with some arbitrary exercise like chinups. How measuring strength by seeing who can knock the other one over?
posted by Pastabagel at 8:02 AM on September 8, 2009

A one-armed pullup is a different game than a two-armed pullup, as others have mentioned. Firstly, moving x weight with one arm is harder than moving 2x weight with two arms, in general. Don't know why this is so, but it is. You can press more weight on a barbell than you can on two dumbells. Secondly, with a one-arm pullup you'll be hanging asymmetrically and thus pulling at a different angle. Not sure if this makes it harder or easier (I think probably a lot harder), but a one-armed pullup is some hard fucking business no matter how you cut it. No matter who was doing it, I would be impressed.

I don't think there's any objective measure of what's impressive, but I think a better comparison is this: if he can do one pullup with 11st hanging from a belt, that's as impressive as you doing one pullup.
posted by creasy boy at 8:44 AM on September 8, 2009

Here's proof that it can be done.
posted by creasy boy at 8:51 AM on September 8, 2009

Comparing one arm chins vs two arm chins is silly, the former requires far greater motor unit activation and relative strength than the latter. Very few rock climbers can perform a one arm chin while almost all bodybuilders regardless of weight can do at least a pullup.

With proper training, at most it will take you a few weeks to learn to perform one chinup, the same can't be said for a one arm chin regardless of the weight of the individual.
posted by zentrification at 10:45 AM on September 8, 2009 [1 favorite]

If you want to do pull-ups but don't want to use any equipment, I'd recommend trying jumping pull-ups until you can do a proper one. It's basically just like a pull-up in the sense that you get your chin over the bar, but you jump to get the added power necessary to get over the bar. This way, it's still all your exertion getting you over the bar and you're not requiring any assistance from an outside source. Do these often and you'll be pulling up in no time.
posted by scrutiny at 10:59 AM on September 8, 2009

Nthing the assisted chin-up machine. One brand is "Gravitron". Again, you don't want to buy one, but to use one at a gym.

So one use, obviously, is to train up so that you can do an unassisted chin-up. (It works, trust me.)

But the other option is just to use it to figure out how much weight you can pull down. The machine basically lets you subtract from your body weight (you stand on a little platform that is counter-weighted). If you can do one with 50 pounds of assistance, you can pull down your body weight minus 50 pounds.

The reason to distinguish these goals is simple -- the former requires JOINING a gym, and the latter only requires visiting one once... in the free trial period. Cheaper.

Also, don't forget that chin-ups and pull-ups are different. Chin-ups are palm towards you, and pull-ups are palms out. *I've* always found chin-ups much easier than pull-ups -- I'm female and have never been able to do a single pull-up -- but apparently this is a little controversial.
posted by kestrel251 at 11:13 AM on September 8, 2009

I know people who can do a one armed chin up. Usually they're smaller (max around 5'9"), lighter (150-160) and have shorter arms.

The longer your arms, the longer the moment arm is - What you're doing is "work".
Since you're moving a greater distance, and the force required is greater (since you have longer moment arms), and you weight more, you're working far harder. And this doesn't even take into account how your physical muscularture attaches to your bones.
posted by filmgeek at 5:45 PM on September 8, 2009

When I used to do serious chin ups I ended up adding weight to make it harder. I got so that I was adding past my own body weight but I still couldn't do a one armed chin up. When I tried the pain in my rotator cuff was intense enough that I was pretty sure if I pulled any harder I'd cause damage.

It was disappointing because my grandfather could do one armed chin ups with either arm - at 72 years old.
posted by substrate at 1:24 PM on September 11, 2009