If you watch the kids, most of them do some form of Off-Ice exercises. Jumping, spirals, Pilates, Yoga or a combination of these things. Their coaches will either encourage, or in most cases, facilitate these things.
It is rare to see the same thing with Adult Skaters. This blows my mind, because IMO, Adult Skaters need more Off Ice than the kids, not less. We sit more and older bodies get stiff, so we need more stretching, and we need to work up the cardio to help us move faster. It's unfair to state that Adults are not as flexible or as fast as the kids, when there is no guidance to help adults improve their flexibility or get up the oomph to go that fast. (It only looks effortless. It's not!)
Off Ice for adults is even more critical when it comes to jumps, spirals, and lunges. I waltz jumped all over dry land before trying it on ice, and I still do. Lunges on dry land are way less frightening, same thing with spiral stretches. Even spirals on the boards are incredibly helpful. But adults seem to be tossed to the proverbial wolves, and told to do all these things without the benefit of Dry Land training. When they look awkward and stiff, it's just a self-fulfilling prophecy. Were Adult Skate Coaching up to me, I would give adult students a stretch/jump/lunge/spiral routine to work on from Day One of Alpha Class. Even though these things wouldn't be touched On-Ice for a long time, the foundations would be built.
So, given that I had very little to go on by way of making my own Off-Ice routine to build cardio, core strength and flexibility, I made my own. I bought this book, and it's a huge help.
On the mornings I do not skate, I run two miles to start. Nota Bene: I did not start out with Two Miles, and I will not do the full two if my knee is testy. I started walking a mile, and gradually added run time until I was up to 2 miles. This took me about 3 months. So, do not feel bad if you cannot run a full mile right away. Do what you can.
After I run, I stretch my legs thoroughly. Spiral stretch holding onto a pole or something, and lunge stretches the same way. After that, try it standing on your own.
If you can, take a Pilates class and learn some good Core exercises. Planking, leg lifts, and crunches (Pilates style crunches, not the back hurting crunches that I hated) all work well. Core strength is indispensable in skating. Enlisting a personal trainer for a session or two to step your through exercises tailored to you is a wonderful idea. I did, and it really got me over the "I hate exercise" thing, because she knew routines that didn't hurt me.
Dry Land Jumps, yes, look ridiculous, but Isolated rotations are good for you. If you can't get all the way around, do halfway. Then try for 3/4. Just pick a landmark and go from there. After a few of these, go through your jump repretoire. Waltz jump is getting more complicated as it evolves, so doing it off-ice helps my uncoordinated self build muscle memory. I'm still looking for a way to do Dry Land Salchow and Lutz, so anyone who knows me and can show me, please do!
I do my Off-Ice three times per week. It makes a difference, trust me. So, do Off-Ice. Do it regularly. As everyone loves to say, "You're not a kid." Whatever you do, the key words here are: Do what you can. If you cannot do 10 reps, do five. Do two. Do whatever, just try to do more the following week. So, get yourself back into fighting shape, and work out! Because, speaking from experience, it feels really good to lap a little kid.