Try your left hand

Here’s a new suggestion to add to the list, “ways to open a tight jar”:
Try your left hand.


I’m studying human anatomy this semester, and today’s section was about the muscles in the arm and the movements ascribed to each muscle. According to the book I’m using, the movements involved in unscrewing a jar allow the left arm to apply more force to the jar than the right arm can.
Here’s a way to visualize the reason: Hold out your right arm and pretend you’re opening a jar – rotate your hand counterclockwise. If you think about it, that motion is the same as holding your hand palm-up and then flipping it so that your palm faces down – called “pronation” in the anatomical terminology.
Now hold out your left arm, and pretend to open a jar. Again, turn your hand counterclockwise – remember “righty-tighty, lefty-loosey”. That motion is like flipping your hand from palm-down to palm-up (called “supination”).
It turns out that pronation (palm-up to palm-down) uses one set of muscles, and supination (palm-down to palm-up) uses other muscles. While pronation requires two muscles in the forearm, supination involves the biceps. That means opening a jar with your left hand adds the force of a much stronger muscle than your right hand would use.
So if your right hand just can’t budge that mean jar lid, switch hands. Your left hand can give more strength. Cool, huh? After I read this in my anatomy book, I realized that I tend to use my left hand to open jars, even though I’m right-handed.

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2 Responses to Try your left hand

  1. Jen says:

    You totally lost me on the explanation, but good to know!

  2. Mom says:

    Hmmm…so, if your left hand is stronger at opening jars, your right hand must be better at tightening jars. Is that why my mayonnaise and pickle jars are so hard to open after you tighten them?!

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