I run. At least four times a week. Its something I love to do and as much as physical for me its a psychological need. I also enjoy walking/hiking on the weekends.
On the days I don't run I do Pilates. Its great for core strength and I greatly prefer it to Yoga. Aerobics and similar classes I just plain hate, lol.
I know I should and keep planing to add some strength/weight training to nicely round it up. Unlike a lot of people I actually love the gym and used to go regularly. The reason I stopped going is because my work/life schedule got changed thus turning my nice mid-morning ritual into an afternoon nightmare. The only time I can go 4-6pm is their rush hour i.e. everything is packed with middle aged old farts that strut around like a bunch of cocks (as in bird) and try to ogle girls they can never have. Creeps.

As far as holding positions goes, personally I never had any problem except some of them are murder on the knees, lol. But I don't know if you can do much about that.