Is a Collapsed Bottom Arm a Big Deal?
It seems that no matter how high, or low, you vault all anyone comments on is whether or not your bottom arm is collapsed. Should you care? Probably not as much as the rest of the vault community, but you should probably care about your bottom arm only as much as you care about your pole carry, running mechanics, plant, jumping mechanics, swing etc. Although I don’t think a vaulter should have a collapsed bottom arm I do not think the emphasis that the vault community puts on it is not as important as they think.
The problem with placing too much emphasis on any one aspect or moment of the vault is that you may sacrifice phases before or after the aspect you are focusing on. Every phase of the vault has an important role in setting up the phase that follows and produces a full jump. Let’s use the plant as an example, if for example you want your athlete’s plant timing more consistent you may tell them to have a low pole carry so that they don’t have to worry about the timing of the pole drop. Now that might produce a more consistent plant but you are sacrificing runway speed due to the athlete dealing with the added carry weight. So the benefit of more consistent plant timing is negated by the fact that you cannot run with max speed.