It is a widespread proposition on multiple fitness websites that joints are better able to withstand compressive forces than shear forces.

For example: Precision Nutrition and Boot Camp Military Fitness.

But I can't find any evidence that this is true.

From first-hand experience I do believe it to be true. Take the leg extension, a commonly used isolation (single-joint) exercise that involves extension of a weight. All I've gotten from the leg extensions were joint pains.

For those who have exercised using these machines vs a squat/push-up, I think we can agree the latter is less harmful on the joints.

So where is the scientific evidence for this claim?

  • (This is an unusual question, because it seems you already accept the claim.) It would be good to link to a sample of the "multiple fitness websites", so we can see the claims. At the moment, it isn't clear whether the claim is the joints are stronger or less likely to be injured or you are more likely to "see results" (?).
    – Oddthinking
    Mar 1 '15 at 22:26
  • @Oddthinking A simple google search for the claim "joints...forces" turns it up google.com/….
    – Jossie
    Mar 1 '15 at 22:31
  • 2
    Here is an example site, that makes the argument that shear forces are more likely to injure the knee than compression.
    – Oddthinking
    Mar 1 '15 at 22:33
  • 2
    (Ah, we overlapped with comments.) Yes, a Google search turns up a lot of claims, but select some explicitly which make the claim you want investigated. You talk about "results" which is muddying the waters if the question is about injury.
    – Oddthinking
    Mar 1 '15 at 22:34

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