Although some of the theories for training related to muscle fiber types are now being contested, I think it is a good way to think about bringing up a lagging body part.
Slow twitch-high volume, lower intensity, longer training sets
Fast twitch-lower reps, heavier, shorter time for sets
Some people, myself included, have fast twitch biceps and slow twitch triceps for example.
I move some scary weights with my tris, but nearly not as much with bis.
MOST people are pretty evenly divided fast and slow.
If you are mostly fast twitch, or should I say fast twitch predominate you can probably push some really heavy weights with that muscle group.
All that being said, if you have been going heavy or lower reps and not getting the results you want, then try high volume (or vice versa).
I am not a big fan of having a separate arm training day, they do get hit enough with the other compounds IMO, and it may be overtraining that is slowing their growth.
What has worked best for me is tagging on one or two exercises for tris after doing back, or one or two for bis after chest.
That way, my arms are really being trained twice a week, no need for a separate day.