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A Note on Motion

I recently took some video of me doing pull ups to study to natural of the movement. Specifically, I’m interested in the velocity and acceleration (and forces) of a typical pull up. Results follow. *Warning: This may bore you, I’m not offended if you don’t read it*

Here’s the experiment set up. Basically just measuring distance traveled at each frame in the video.

Set-up: So I did some pull ups and recorded the displacement at each from.  From this I fond velocity (change in distance/time), and acceleration (change in velocity/ time).  It is noted that the calculations have some error, and this error is multiplied in each sucessive derivative (acceleration is not as accurate as velocity). This is expected, and can be accounted for if I wasn’t lazy.



Figure 1: Velocity of Pull Ups

As expected, velocity increases, reaches a maximum, and then declines or levels out. The polynominal fit of V1 is of particular interest. It shows a near zero velocity at the top of the pull up. This zero velocity time is exactly when the climber wants to contact the next hold. Practicing lock-offs and stopping at different points in the pull up may help the climber’s muscle memory to attain this “floating” point in different scenarios.


Figure 2: Acceleration of a Pull Up

This was my real objective of the experiment. I wanted to see how much additional force is exerted on the fingers when doing a pull up. It is shown that acceleration rates may typically be 3-4m/s^2, and possibly higher. For a 160 lbs. climber, this is equivalent to a dead hang with 56 additional pounds of resistance (albeit very briefly). Additionally, pull ups are working more muscles than dead hangs.

It is noted that the point where the acceleration crosses the x axis is the point of constant velocity of the climber.

Think of that time you pulled too hard and popped off, or of how you stalled out because you moved too slowly. Controlling your acceleration, and subsequent forces is vitally important, and yet isn’t typically a conscious concern.


Andrew - Whoa! Flash back to college physics class!April 23, 2009 – 7:55 am

Eli Powell - Yeah, I was a bit rusty in Excel, but I’ve wanted to check this out for at least a year. I think the results are an argument for weighted dead hangs. Additionally, the more bouldering I do the more I realize how important the movement (and muscle memory) is.April 23, 2009 – 9:50 am

Chris - Wow Eli. Not really helping dispel any engineer stereotypes, are we? In all honesty, it’s really good information though. Definatley makes me feel better about being lazy about doing pullups. And good advice on how to do pullups better in the future.April 23, 2009 – 10:21 am

kris - Nice work, buddy. You’re not the first I’ve heard come to the conclusion of the benefits that weighted hangs can provide. I know I’ve realized gains with them. However, you are the first I’ve heard try to justify them and your other conclusions on paper. Must’ve taken a little time… you mentioned your car broke down, huh?

Also, dug the “floating point” discussion. Control and a clear mind in those few seconds is critical.April 24, 2009 – 2:09 pm

Eli Powell - Thanks Kris. The main reason I don’t regularly do weighted hangs is because I’m lazy. Hopefully this argument is what I need to get back at it.

Yeah, by some miracle my car is running again. We’ll see how long it lasts.April 24, 2009 – 11:04 pm

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