I was trying to find out the details of this movement throught the seach here and www.exrx.net, but didnt find anything about it. My question is this: Do you push it straight up from the forhead or in an arch towards the belly?
You arch the bar towards your mid-section but trying to ensure that you keep your elbows tucked in, if you find that cannot do that then the wirght is probably a little too heavy.
You might also be better off using an EZ bar, i find that using a barbell puts quite a bit of pressure on your wrists.
A great variation is to push straight up as you said. The end of the movement looks like your arms are slightly "over" your head, or roughly 45 degrees from the floor. This variation puts the triceps under a constant tension and takes the lats out of the concentric portion of the movement-less chance of momentum this way. This works well on declines also.
On any skull crusher exercise you should start with the bar straight above your forhead and let the bar go back. The bar will end up behind your head. The goal is to keep the bar behind your eyes for the proper develoment. You will notice a big difference in the amount of weight you can do when you get the form down pat.
I like what cwick has said. When I perform any lying extension I now prefer to keep the bar behind the eyeline. That is, I push the bar from my forhead/hairline straight up or actually back, behind my head a bit.
I'm in week 3 of EDT and I've been substituting the skull crushers with the sitting overhead tricep extension machine. I know it's not nearly as effective, but when fatigue is such a factor with EDT, it keeps my form regulated even when I'm beat.
Other than the obvious drawbacks, have any of you done the same thing? Or should I sacrifice a little form just to execute skull crushers?
abn: I'd stick to the exercise you most desire to do. In this case, it seems to be the lying extension. Make sure you follow the load parameters and don't select a weight that will be too heavy when the going gets tough.
Also, with EDT, it's important to choose exercises that can be done back to back quickly -- that is, with little to no down time from the first exercise in the superset to the second.