Hello guys,
so Joe I heard you talked on your IG Live that you are not big fan of leg extensions because of shear forces they produce, if I understood correctly.
Could you please tell more about shear forces ?
Thanks
Every singe exercise involves a component of “sheering” force. Sheering force is actually produced by your own body/muscles in response to force from an exercise. If you imagine doing a DB lateral raise, it’s the sheering force that keeps your arm from ripping off at the GH joint and falling straight down to the ground.
It gets a bit complicated from there (I’ll likely do a video on it), but if you can produce similar torque at a joint, with shorter moment arms, and more load, compared to longer moment arms and less load… less sheering force will come with it. So that’s a better option (especially if you have pre existing joint issues). So for this, that would be like a squat/leg press compared to a leg extension.
I did actually miss-speak on the live though. My knee issues are actually at the patellofemoral – in which case it’s more about compressive force. And for me, leg extensions aggravate it more than squat/press type motions
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