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-   -   Weighted box jumps and ACL strain (http://board.crossfit.com/showthread.php?t=48356)

Kevin Shaughnessy 07-03-2009 01:14 PM

Weighted box jumps and ACL strain
 
It seems to me that weighted box jumps must place alot of stress on the ACL when you land. Anyone here know of anyone or are themselves experiencing ACL problems because of weighted box jumps?

Steven Low 07-03-2009 02:04 PM

Re: Weighted box jumps and ACL strain
 
Squats, like jumping, theoretically you don't need an ACL for... Although improper muscle balance, poor mechanics, or odd landings may through that out of the window.


not sure why you would want to do weighted box jumps though... just make the box higher or something.

John Seiler 07-03-2009 02:37 PM

Re: Weighted box jumps and ACL strain
 
+1.

And I hope you mean landing on the box, not on the ground after jumping off the box. That's a really bad idea.

Steven Southrey 07-06-2009 03:19 PM

Re: Weighted box jumps and ACL strain
 
Jumping can put a strain on the ACL especially if you have suffered a previous knee injury and/or your mechanics are wrong. The risk areas are taking off and landing. The risk from taking off is small and can essentially be eliminated by strengthening the leg muscles and practicing sound jumping mechanics. 99% of jumping-related knee injuries are the landing. The landing impact causes a lot of force on all the leg joints; somewhere between x3 to x5 times your body weight.

Now here's why box jumps are so good for the knees. You still gain the benefits of jumping exercises but minimize the risk of injury. If you jump 24 inches up then you land with the force of a 24 inch landing. With a 20 inch box jump (for example), you're only landing with a 4 inch landing and greatly reducing the impact portion of the jump.

Hope that helps.

David Nittler 07-07-2009 11:44 AM

Re: Weighted box jumps and ACL strain
 
Jump up - step down.

So long as you don't go all wonky and fall off you should be golden. Start low, and work your way up.

Landing on top of a box jump is generally a very gentle affair. Jump up, and just put your feet on the box when you're high enough. Far less stress on the knees than jogging for example.

Graeme Howland 07-08-2009 11:50 PM

Re: Weighted box jumps and ACL strain
 
Quote:

Originally Posted by Steven Southrey (Post 619584)
Now here's why box jumps are so good for the knees. You still gain the benefits of jumping exercises but minimize the risk of injury. If you jump 24 inches up then you land with the force of a 24 inch landing. With a 20 inch box jump (for example), you're only landing with a 4 inch landing and greatly reducing the impact portion of the jump.

Hope that helps.

This. Do you mean weighted box jumps like with a weight vest? There are some DeFranco vids on youtube of that. I don't see how it would place any more strain on knees than a normal box jump. If you mean doing it holding DBs or some other method of extra weight, I think that would screw up the jumping mechanics.

Blair Robert Lowe 07-09-2009 01:03 AM

Re: Weighted box jumps and ACL strain
 
Doing it with DB, isn't much different. I simply hold one in each hand by my side. I don't get to swing my arms, but I probably could and that actually may be easier to some degree.

I was using about 30% of my BW. 50lbs@165

John Devine 07-09-2009 07:15 AM

Re: Weighted box jumps and ACL strain
 
Quote:

Originally Posted by John Seiler (Post 618320)
+1.

And I hope you mean landing on the box, not on the ground after jumping off the box. That's a really bad idea.

Quote:

Originally Posted by David Nittler (Post 620113)
Jump up - step down.

:confused: I would always drop off the box with both feet and then jump back up. Effectively starting each rep from on top of the box. The point being to get a better stretch response and improve vertical jumping performance. It sounds like that may be incorrect or at least a bad practice. Can someone explain?

Fred Wenger 07-09-2009 11:00 AM

Re: Weighted box jumps and ACL strain
 
As far as I know, you should never do weighted plyometrics, as the forces exerted on your joints are extreme plus it may cause dysfunctional movement patterns.

Caz Berkowitz 07-09-2009 01:29 PM

Re: Weighted box jumps and ACL strain
 
Quote:

Originally Posted by Steven Southrey (Post 619584)
....Now here's why box jumps are so good for the knees....you're only landing with a 4 inch landing and greatly reducing the impact portion of the jump.

Wow, thanks, it's so common-sensish when you explain it yet I never really got it before.
I need to do more box jumps!


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