when someone is performing a standing arm lock is it advantageous to resist bending down and stay in an upright position?

Yes, keeping you're back straight is always a good idea. However, as you lower yourself to one knee turn to get your arm back to your center and strike to the groin or hip with the other hand. The other option is to try and roll out of it for a counter. Most of the time when this is applied correctly it's too late for anything.

im a little confused about your question. are you asking: if you are having a standing lock done to you, should you bend down or stand up and resist.

 

to which my answer would be, bend down. if you resist, it will break your arm. if you bend over you can do any number of things in the way of rolls and counters.

 

howveer, if you're asking if it's good to keep your back straight when preforming an arm lock, then i would say yes, absolutley. in most techniques i can think of it is extremely important that you keep your back straight and your knees bent. this helps you maintain your balance and keep from getting pulled over by the opponent.