If you're looking to build up shooting strength, I have a workout that I use to build up and maintain what I need for shooting my 66# longbow - basically a light weightlifting routine that attempts to focus on the back and other muscles I need to shoot, but without having to go to a gym. Maybe you can pick and choose some things here that might help.
It doesn't require much for equipment....
1) Bowfit or similar resistance band
2) A few dumbbells or freeweights
3) A GripMaster (gotta have strong fingers too!)
I run through this general cycle 3-4 times:
Stretching bowfit band: 10-15 reps (explained below)
One arm rowing: 10-15 reps each side (pretty easy, just google it)
Push-ups: 10 - 20 (try to do each one slowly)
Bowfit: 10-15 reps (each side)
Gripmaster: ~40 reps each hand (google it)
(You would start with just one or two cycles through at low repetitions, and work you way up with both repetitions and weight. Don't hurt yourself!)
When I say "stretching the bowfit band" what I mean is to hold your arms out in front of you gripping each end of the straight band. Keep your arms straight and pull the band. You will end up with your arms sticking straight out to your sides with the band stretched across your chest. Focus on pinching your shoulder blades together and use those muscles to do the pulling.
The one arm rowing works your back and shoulder muscles. A google search can explain it better than I can.
One of my larger struggles is keeping my bow arm strong for the 'pushing' part of the draw. To help with this, I've tried doing push-ups a few different ways, but I think I have gotten my best results by just slowing them down. I suppose it would be like drawing a bow slowly and holding at anchor, then repeating. It's much more difficult than running through an equal number of push-ups at regular speed.
Using the bowfit to simulate drawing a bow helps exercise your shooting muscles, and you can vary the resistance by buying a heavier band, doubling the band back around, etc. So you can use that to work up in weight over time. I use my standard 3-finger draw here to help get those muscles involved as well. Just pretend it's a string. (I have started using the BowTrainer for this portion of the workout instead. Less finger pinch, doesn't wear through bands as quickly.)
The Gripmaster is a spring-loaded hand exerciser, but it has individual springs for each finger. This helps ensure that each finger gets a workout, instead of just tagging along with the stronger ones. I like to focus on using just fingertips, since my fingertips hold my bowstring during the draw. Note that the strength-building here is done by repetitions, not by straining against a heavier model. (This seemed to help my release when I started doing it a few years ago. I don't know that I can exactly describe why, but I think the difference is that I can get a cleaner release when my fingers easily hold the string versus fingers that are straining to hold on for dear life.)
I have also noted that if I start to get tired at the end of a long 3D shoot (like today in Nebraska... 7 hours of shooting?), it's usually my fingers that start to give out first. I can draw, get to anchor, and my fingers decide to release before my brain is really done settling in on my spot. When this starts to happen, it takes a LOT of focus to keep it in check. I wouldn't say this is necessarily the classic target panic that people refer to, but it certainly is a case of uncontrolled release and it is caused by fingers that are just a bit too weak or tired. If my fingers hold up well, I can avoid this problem much easier.
So I apologize if that got a bit long-winded, but you can take or leave the parts as necessary. Your mileage may vary, but it keeps me shooting despite having a day job that involves nothing but computer work!
Mark