Does anybody know why it is that when you do arm curls on a bench (barbell) you can lift heavier than when standing up? When sitting down and doing them on a bench i can arm curl 120-130 pounds and standing i have trouble with 100. If anything it should be the other way round because when standing it is a lot easier to cheat. Even so i have found that doing them standing to be a little more effective than sitting down.
i’ve seen a similiar trend in myself with shoulder presses, seated and standing. I think the cause is you have to use some of your muscular-nervous system energy to maintain standing up, which inhibits how much energy you can use for the actual lift.
If your using a barbell on a seated curl, then you probably can’t go down as far on the negative cuz the barbell would hit your legs. So you have a shorter range of motion than if you were standing, hence more weight.