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I'm currently encountering a weird discrepancy between the force I can generate to lift my body with one arm and the amount of weight I can pull down with one arm at the lat machine, using a one-handed handle.

At this machine I can only pull 60kg (132lbs) twice, as compared to lifting my 86kg (190lbs) bodyweight two thirds of the way.

Many people report they only have to lift 65-75% of additional bodyweight on weighted pullups to manage an OAC. This makes sense because your body is in a more efficient pulling position for the OAC, thus utilizing more muscles and furthermore less muscles are pulling in contradicting directions, thus fewer forces are canceling themselves out.

However, this does not apply for the OAC vs. One arm lat pull (OLP). Can friction of the machine play such a big role? It has a 1-to-1 transmission, and only one big wheel to direct the rope. My knees press against some stabilizer, may this cause my body to tilt less, and therefore utilize less muscles?

My general question is, where does this discrepancy originate from?

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Perhaps I've misinterpreted what you're saying, but it sounds like you can do 2 reps of 60kg compared to two-thirds of a rep of 86kg. What do you think the discrepancy is? –  Anthony Grist Jun 21 '13 at 9:23
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2 Answers

Set the lat pull machine to 80kg, don't place your legs under the knee pads. Perform a TWO handed lat pull down. If your body lifts off the ground rather then pulling the lat pull handle down then there is clearly extra frictional resistance on the machine. Try again for 85kg. At 85kg your body should come off the seat but the pulldown machine handle should also move a little down.

If you've determined the pully weight is correct you must be cheating a little and using momentum to help you with the One-Armed Chinup. I'm currently 81kg and can do a 75kg single arm lat pull, but I can't do a one arm chin-up

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This is because the motion is completely different when doing a pull-up and when pulling down on the lat machine. I for example could chin-up my bodyweight + as much weight attached to my body. I couldn't pull down as much on the lat machine. Your body works in a different way on these two similar but yet different exercises.

I have released a tutorial online two years ago regarding the one arm chin-up/pull-up. It's one of the most popular on youtube now, I am encouraging to watch it for additional ideas. In case you have more time check out the narrated version of the tutorial, I am explaining A LOT about this exercise and how it works. Cheers and good luck.

If you have any additional questions about the exercise please fire away.

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