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Apparently I can hold on to heavier dumbbells than others, but they can crush my hand much harder in a handshake. This tells me that support grip and crush grip can be very much apart. I believe there's not really a carryover from gripping strength to bar holding strength. I can only close the Trainer gripper, about 100 lbs. for a few reps, and my hands and forearms are dead.

I can, however, hold on to a 200 lb. dumbbell for a few seconds (one-handed).

I can also hang from a bar with almost my bodyweight added (200 lbs. + 200 lbs. = 400 lbs. of hanging support).

However, I know a guy who can't do either of the prior feats, but his grip in a handshake is quite impressive (overpowers mine). He also can't close much more than me in a gripper, but has a strong crushing grip.

My main question is, how does crushing grip differ from support in a muscular sense? Aren't they both the same recruitment of muscles used to close the hand?

How is it supposed to make sense that I can barely squeeze together a 100 lb. gripper spring, but can hold on to a 200 lb. dumbbell handle? Or support 200% of my weight hanging freely from a bar, but fail to crush an apple with my dominant hand?

I always hear people telling me I'm not too strong with my hands in handshakes for some reason (my grip strength is about average for an adult male in crush PSI), but average men can't hold a 200 lb. dumbbell in one hand. Anyone here could explain how the hand strength varies so much in different lifts (e.g. crush 200 lb. gripper, can't hold on to a 200 lb. bar, or hang with 200 lbs. added to bodyweight, but can't open a jar of pickles)?

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Hmm....this is a concept I haven't considered before. Curious to see what the answers are. –  Kneel-Before-ZOD May 1 at 21:44
    
Here's a guess: is it thumb strength? Both the comparisons you make are against a grip (bar or bodyweight) that are mostly held with your fingers vs. Those which require fingers and thumbs (gripper, pickle jar). –  brentlance May 2 at 0:39
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Here's a test: hang towels over the pull-up bar, like so: rosstraining.com/images/towelpullup.jpg. Try hanging from the towels instead of the bar. How much weight can you add using the towels? If the difference is a weak thumb, then you should have a great deal of difficulty hanging from the towels, and not be able to add much weight. –  brentlance May 2 at 14:17

1 Answer 1

For support grip and crush grip you use two different muscles (both are used, but in either movement, there is a different main muscle).

For the support grip, you flex the distant part of your phalanges (fingers) by the action of the flexor digitorum profundus.

For the crush grip, you flex the proximal part of your phalanges by the action of the flexor digitorum superficialis.

There are several explanations why the support grip is stronger. The simplest one would be that flex. dig. profundus is stronger. However, since they are of roughly equal size, the more likely explanation is a biomechanical one.

Because of the position of the muscles' tendons, with one (profundus) going under and through the other (superficialis), there is a better leverage for the profundus muscle. Also, the greater thickness allows for greater force production. This makes sense in evolutionary terms since we have done more "hanging" than "crushing" with our hands.

http://www.raddaily.com/data/articles/msk/fingertendons.jpg Here is a visual of the position of the tendons as they insert onto the phalanges.

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