Extra practice, strength training etc. will improve your scores if:
1. You're following a sensible programme.
2. Your technique is solid.
3. You shoot at least twice a week, if not more.
Personally, when I managed to combine these three, I did see a significant jump in my scores. Injury put a stop to that (I tore a shoulder muscle in the gym while trying a new piece of equipment unsupervised - my own stupid fault).
Ki Sik Lee in Total Archery says that his archers usually only have one day a week off. Any more than that, and muscle memory starts to fade.
As for me, at the moment I'm doing the following:
1. Shooting twice a week. I try to shoot a few arrows at short range in the back garden if for some reason I can't make it to the range.
2. Reversal training. I can currently do 20 repetitions of 30 seconds with some 40lb limbs, and I do this every other day. I'm hoping to build up to every day (except the days I shoot on) and then to start using the heavy Marksman limbs I have at the back of the cupboard instead.
3. I have a light fibreglass bow in the living room. I practice my drawing technique with this several times a day.
I've also made an appointment to get back to the gym to get fit again, which I'm sure will help.
(For info on reversals, see
http://www.texasarchery.org/Document..._exercises.htm)