You just have to find what's best for you and make it work. It may seem like going for a workout before a 12 hour shift is crazy, but you feel much more awake, sharper mentally and your body will feel loose and relaxed and not all tensed and tight from a long night of sleep. If you wait til after the shift it is usually much more difficult to get yourself motivated to go.
For myself, although I have a gym membership I can never make it. Drive time, no gas money, no babysitter, homework...you name it, it seems to pop up whenever I try to get to the gym. And in truth, I am not much of a fan of running on a treadmill like a bored hamster with no where to go..actually I am not a fan of running period
So I finally got sick of life getting in between myself and my health and so I figured out something that works for me.
My and my children spend a lot of time outside and as I was sitting there on my butt watching them play I started looking around for what I could do for workouts. We have a very long drive way and I can do sprints. Other easier days I walk up and down the driveway (one part is a little steep so it really gets the legs good) and around our house over and over. I can hit all the major muslces by doing push-ups, sit-ups, burpees, squats, planks, jumps, lunges. My husband has some old tires lying around so I pick one up and use it like something I had seen on a work out show where you take a weighted ball that is a little bouncy and you squat to pick it up, bring it up over your head and then using your whole body you force it down to slam it into the ground. Works your whole body and feels good, like your taking out a little frustration
Sometimes I will even pick two up, one on each shoulder, and walk them up and down the drive way, like a farmers walk. As with all these excercises, be sure you are using proper body mechanics so you do not injury yourself.
All this while still keeping watch on the kids while they enjoy being outside. I can do it whenever I can because my gym is just right in my backyard. For me I enjoy the freedom of not having other people staring at me while I work out or dealing with a busy gym. I love being outside and I like making my workout resemble something that prepares my body for real life...for example, I will do a short run by picking up one of my kids and doing a slow jog across the hay field, great practice for if one of them were bit by a snake while we were out hiking and I had to get them home quick, that sort of thing....practice to be super-mom lol.