Situp shakage

[ComeToJesus]

I've noticed that I shake like a madman when I hold the situp position halfway up. This is especially true when my legs are secured by something/someone. I was just wondering why this is. I'm fairly strong at the abs, and can easily pump out many situps, yet even on the first one I'd be shaking like crazy. It's not fatigue, so I was just wondering what could be the reason?

[IronFist]

Are your legs shaking or your abs shaking?

It's probably the same reason your arm shakes if you make a really tight fist. I don't know what the reason is, but I know that it does :D

[ComeToJesus]

whole upper body goes nuts. I mean I don't see other people having this problem. Well it's not that much of a problem, just looks werid :D

[inic]

Had that all the time back in the army for some reason. Only seemed to happen when doing situps/crunches. I dont get it when doing swiss ball situps or even V-situps