Toon says "strenghten up", Roy! (Not upper.)
Hey Toon, I cycle, as this gives a good all over workout with the focus on the legs, where the real power is needed. (You still have to support your upper body on the handlebars.) As I'm 43, this means I need to do a bit of stretching to stop my hamstrings cramping up. Nothing major, but keep an eye on everything from the legs through the glutes, into your back and even down into your arms if you cycle and bowl, as you'll be working similar groups often and they can get stiff. I've even had wrist pain that my miraculous massage guy in Canberra traced back to my calf, gluteous and hamstring groups. Hurt like hell. Funnily, bowling would relieve the pain.
Take it really easily if you haven't been on a bike in a while, though. It's harder than it looks and a lot harder than bowling. That said, it's good clean fun and I love getting out on the bike. Very mentally refreshing, as often all you think about is pushing the pedals and listening to music. In case you're wondering, it's safer to listen to music than you think on a bike. There are very few cars that make less noise than my headphones can. Quite surprising just how loud cars are when you really listen... Music definitely helps with intensity and duration for something rhythmic like cycling. Create an up-beat playlist that's fun and it's amazing just how much more you can do. I've done rides that would have almost killed me once and with the right music, I'm out of the saddle up the big hills home in Canberra from Lake Burley Griffin.
Pilates is brilliant too, but I get bored doing it!
Worth doing a beginners course to understand core strength and decide if it's for you. Tai Chi is awesome for balance and coordination, but again, I get bored. (I'm so easily distracted..! Oh look, something shiny...)
Hope this helps.
Cheers,
Jason