If you want to make chins harder, just do them with one hand.
✓ Member
Analysis of the Chin-up
Howdy, Rip!
I've searched the books, forums, and videos for a detailed explanation of why chins over pull-ups, but I could only find the general (though correct) statement that chins work the biceps more, and more muscle is good. This lack of spoonfeeding has encouraged some internet people to claim that there is no reason behind the assertion that chins use more muscle, so pull-ups are better because they are more difficult.
To address this, and to ensure that I know what I'm talking about, I wrote up an analysis of chins and pull-ups based on principles of moment and anatomy. I'd appreciate it if you would take a look at it and critique it, and hopefully it will be useful to the denizens of the forum. Thanks!
Understanding Chin-Up and Pull-Up Mechanics: Why Chins are Better
By Dale Waters
Executive Summary
Chin-ups are not merely more “mechanically advantageous” than pull-ups; they actually enable the body to use more muscle. The supine grip encourages both pressing and pulling muscles to get involved, and even gets more out of the abs, hip flexors, and quads. Because of this, chins are the superior exercise and should have greater carryover to both presses and pulls.
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Chin-ups are an excellent exercise for strengthening the upper body. They have proven their worth time and time again across numerous disciplines, sports, and training philosophies. Chins are so good that they are the only non-barbell exercise officially prescribed in the Starting Strength Novice Linear Progression. However, chins are often compared unfavorably to pull-ups, with some internet philosophers claiming that chin-ups are just easy pullups, and therefore worse. This is foolish. We will now consider why this is so, looking at the effect of the different grips on moment and muscle usage. Ultimately, it will be obvious that chins use more muscle more effectively, and should be generally preferred to pull-ups.
Chin-up Moment: A Humerus Predicament
The moment arm in a chin is maximized when the humerus is parallel to the ground, as this maximizes the horizontal distance between the shoulder and elbow. Assume, for a moment, that a person were to chin with perfectly vertical forearms and a perfectly straight and vertical torso. The moment arm would be largest when the humerus and forearm make a right angle, and the moment arm would be the length of the humerus. This position requires a lot of effort to get to, and even more to maintain, if we wanted to stay there.
To remove this unnecessary moment, we must bring some of our weight forward to balance the system more easily. There are 2 ways to do this: bring the elbows forward and bring the trunk forward, both of which occur. Careful observation of people doing chins shows that the forearms angle forwards initially, and the trunk flexes while angling forward. The net effect of this is to reduce moment at all points relative to the first scenario. Once the humerus is parallel to the ground and moment is maximized, the focus of the system shifts from not letting the body get too far from the bar to bringing the body closer to the bar. As the body moves forward, the elbows move back and the trunk moves less forward due to Newton’s 3rd Law.
You may note, when observing a chin, that the forward elbow movement is far less pronounced than the trunk movement. This is due to three main factors: the elbows weigh less than the trunk thus are less useful counterweights, the trunk doesn’t have to deal with gripping the bar so it can rotate more easily, and the elbows will move back more intentionally so best not to get them too far ahead.
Pull Up Moment: Benches and Presses from the Hang
Unlike the chin, the pull-up doesn’t actually involve a lot of moment between the body and bar, as the arms go mostly sideways. However, there is some moment, and it is maximized in one of two positions, depending on proportions. Either moment is at its greatest when the nose/head must clear the bar, or when the chest is at the bar, as the entire body must be behind the bar. In either case, the moment is not great and it is near the top of the movement.
To make this easier for us, we can arch our back aggressively. Much like how arching the back in the bench press creates a more favorable angle and decreases ROM, arching in a pullup allows the shoulder to get a bit closer to the bar and makes the chest easier to touch. Additionally, it gets the head out of the way of the bar much like layback in the press.
One could try to get the shoulders even closer to the bar by bringing the legs or trunk forward like in the chin, but this is unwise. In the chin, moving some mass in front of the bar is necessary because the grip requires that some mass be behind the bar, thus moving weight forward simply evens things out. In the pull-up, this is not the case, and putting mass in front of the bar just makes things difficult.
Muscular Contributions
Now that the mechanics have been sorted out, we can move on to the anatomy of chins. Supinating the hands and taking a relatively narrow grip allows for a fuller biceps contraction, and therefore a greater biceps contribution. The shoulder works in tandem with this and helps push the elbows forward at the start of the lift, though most of the effort is isometric. The pecs keep the elbows in, which preserves the biceps’ contribution. The triceps stabilize the trunk angle, then help to extend the shoulder. The abs, quads, and hip flexors keep the trunk flexed and angled forward. The grip often results in wrist flexion, though the degree varies substantially with trunk angle.
Pull-ups’ prone grip limits biceps involvement, as a full biceps contraction requires supination. The elbows-out position takes out much of the triceps and shoulders involvement as well. Arching the back contracts the entire posterior chain, potentially to the point of hyper extension and scapular retraction. Extending the back is easier if the anterior chain is relaxed, so the chest, abs, quads, and hip flexors are far less involved. The prone grip often results in wrist extension.
Obviously, there are other muscles involved, but they either play the same role in both movements or are too small to be noteworthy. The lats perform the same function in both lifts, so there is no reason to think that doing an equal number of chins or pull-ups would cause any difference in lat development. The idea that lats are worked more in pullups is likely because pull-ups have the arms wider, which displays the lats better. Ultimately, pull-ups show the “V” better, but don’t build the “V” better.
Conclusion: Chins for the Wins
Clearly, chins work more muscle mass to a greater degree than pull-ups. Since chins involve the abs, triceps, shoulders, and chest more, we can reasonably conclude that they help the pressing movements more than pullups do. Additionally, since we don’t hyperextend the back or retract the scapulae under a load, the carryover to the deadlift and other pulls should be about the same. While one could argue that the wrist flexion in chins might help with pulling grip or keeping wrists straight in pressing movements, it probably doesn’t matter, and if it did, we don’t need to pile on. Overall, it is clear that chins are not just easier than pull-ups, but are, in fact, an all-around better exercise.
TMPHBITEU
If you want to make chins harder, just do them with one hand.
Member
Wouldn't it save time to do them with two hands, though?Originally Posted by Mark Rippetoe
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I like these sorts of things, always a good learning experience to attempt to think these through. Consider my comments to be in the spirit of collaboration.
For ease of language and visualization, consider a side view of a chin-up, where the "camera" is facing north, and the athlete is facing west.
Just so I understand you completely, are you referring to the moment arm that the elbow flexors experience when trying to rotate the humerus upwards (counter-clockwise relative to camera)?
I can see how rotating the trunk/legs around the shoulder joint, such that the body tilts backwards (necessary if we want to clear a path for our head and torso, and also a natural byproduct of lat involvement), will bring the COM (of the load) closer to the elbow joint, but I'm not sure what you mean by "bring the elbows forward". Can you explain this more clearly?
My take on the elbows moving back is as follows:
If we analyze the movement within a statics framework, the COM of the body has to be centered underneath the bar. Now if the trunk and legs rotate around the shoulder joint (clockwise), the COM will be brought west of the bar. In order to balance this, gravity will cause the whole body (including the forearms) to rotate counterclockwise around the bar, thus causing the elbows to be situated east of the bar, with the forearms at an angle. An extreme example of this is the front lever position.
If we analyze the movement more dynamically, something else comes into play. Consider the angular momentum of the body, with respect to the bar. When you rotate the torso and legs clockwise around the shoulder joint (the lats do this), you are creating a clockwise torque on the body around the bar. If we ignore gravity (temporarily, I promise), then the angular momentum of the system, around the bar, must be conserved, and this will be reflected by the body rotating counterclockwise around the bar, again, bringing the elbows east of the bar. Because gravity does exist, it will cause the system to settle into equilibrium (where COM is situated directly under bar), but the body will still experience an initial counterclockwise torque around the bar, to balance the torque of the body rotating clockwise around the shoulder.
The above two accounts represent a different set of forces that cause the counterclockwise rotation of the body (including forearms) around the bar. In the first, gravity is the only force responsible (although the lats are causally linked by providing the initial clockwise rotation), and in the second, the lats are directly responsible for the counterclockwise rotation.
I've often tried to imagine how the shoulders are involved in chinups/pullups, but I always fail. Can you explain more clearly what you mean by "helps push the elbows forward". Do you mean that the shoulder musculature applies a torque to the humerus and rotates it clockwise around the shoulder joint (or at least isometrically prevents the humerus from rotating counter-clockwise)? If so, what is the load that the shoulder musculature is experiencing? Is it the weight of the arms?
Those are my questions for now.
✓ Member
You are correct. The shoulder extensors are doing something, but I believe it has more to do with the angle of the body than horizontal distance to the bar.
At the beginning of a chin, the elbows move/roate forward slightly relative to the lifter, or west in your verbal illustration. Theoretically, a frictionless hand would allow for more forward elbow travel than there actually is, but in reality the forward elbow movement is small. It may be that the forward rotation is primarily a result of re-committing to the grip at the bottom, but it was the moment section so I talked about moment.
I'm not sure that in all statics positions the COM is under the bar in a useful sense. Obviously, since the bar/earth don't tip over, the body/bar/ground system is in balance, but the body itself prefers some of these positions to others. Hanging from the bar and being in a stiff-armed dip position are far easier than having right angles at the elbow and body because of the relative energy expenditure to keep the body in those positons.
In the 90/90 position, bringing the trunk forward/west actually puts the body's COM under the bar, as before the COM was actually behind/east of the bar. The trick is that the proper trunk angle is dependent on the elbow angle, so it changes. Ideally, the COM moves only up and down, with any horizontal movement being cancelled out. This is difficult for all the physics reasons you mentioned, but also because of coordination issues and that the muscles don't fatigue or react at the same rate.
I was a bit sloppy with the use of the word "shoulder." I suspect that the anterior delt band helps the pecs keep the elbows in and forward (as in not flared out), and also provides stability isometrically for the biceps to pull against. The posterior delt actually helps to extend the shoulder joint at the top half, while also stabalizing with the lateral delt throughout.
And your collaboration is most welcome!
Member
The COM will always settle so that it is underneath the bar, no matter what position the joints are at. If you have the isometric strength to maintain awkward configurations (like the front lever), then the system will achieve balance exclusively by rotation of the forearm (which itself is connected to the rest of the body) around the bar.
Here's a good thought experiment that helped this click for me:
Imagine you have a solid T-shaped piece of metal. The "T" is upside down, and connected to the bar via a frictionless hinge joint - basically you have a balance scale hanging from the bar. Now if the T is evenly weighted, the T will hang perfectly vertically. With the camera facing north, suppose that the T is oriented such that the arms are directed east and west of the bar.
Now ask yourself what happens if you place a weight on the west arm of the letter (imagine you glue the weight on or something, so it doesn't fall off the arm). If you think the forces through, you'll understand that the whole T will rotate counterclockwise. If you add the weight suddenly, it will rotate quite a bit, and then oscillate until it reaches its new equilibrium point. If you add the weight very slowly, it will end up in that equilibrium position. In this new position, the stem will not hang vertically anymore.
And so it is with a chin-up. If you hang vertically from the bar, and very slowly raise your legs until they are at right angles to your torso, you will notice that your forearms no longer hang vertically from the bar.
Thanks, that makes sense I think. Need to think it through carefully, but I think you've helped it start to click for me.
✓ Member
I think I'm in agreement here, but I have one (potentially semantic) issue. Imagine an absurdly strong person that can hold his body completely parallel to the ground in a superman position. The lifter's COM is clearly not under the bar, however, the overall system is in balance, provided nothing tips over and the lifer remains rigid. My initial point was that it takes less effort to maintain a balanced system if the lifter's COM is under the bar. A parallel would be how in a squat, the heavier the bar gets the closer it's position approximates the lifter/bar system's COM, but the actual human's COM doesn't change.
The difference between a lifter and your T is that a lifter's hands provide a very non-negligible amount of friction, which my OP aluded to as a potential reason for most of the movement being in the trunk. Because of this, the forearms can't easily rotate to achieve balance, so the rest of the joints are responsible. I'm not sure we actually disagree on anything here,
Member
Your issue is more substantial than semantic - it's completely valid - I had meant to include the friction caveat in my post, but forgot to until after replying.
The superman in your condition, in addition to having unbelievable amounts of strength in his wrist extensors, would have to be squeezing the bar with a lot of force to produce the necessary friction to counter the gravitational torque.
It's an interesting question about how much friction plays an actual role in the dynamics of bar exercises. It might actually be easier to perform a muscle up if you were to wear silk gloves while gripping the bar
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