I've only very recently started hobby jogging in my mid-forties after training for many years in MMA and general bodybuilding. I started jogging for the first time a few weeks ago since I was a schoolboy (apart from very occasional ten minute treadmill warmups or warmdowns). After less than 50 miles under my belt I managed to complete my first 5K of continuous running in 29 minutes. I still have maybe 14 lbs of fat I can lose and given I'm still at the stage where every time I run I'm going either further or faster, it seems to me that if I became a little more serious and maintained it for several years, I could get close to 22 minutes at around the age of 50, by which point I would probably start getting slower as aging outpaced any further possible improvements through training.
But the question is, could I still maintain much of my muscle mass? I never want to look like a scrawny hobby jogger, and in fact want to put on some muscle to get closer to where my physique was a few years ago when I was hitting the gym more regularly. I have time to train twice a day, an hour for running and an hour for weights, but I don't want to exceed 30 miles a week. As I approach 50, I would like to set myself a challenge of being buff and fit. So is 17 inch biceps and 22 min 5K unrealistic? Perhaps setting a Mile target would be better? The thing is 5K is the benchmark for every hobbyjogger, and also I want to compete in local races, of which there are obviously more 5Ks. Maybe I should even just go for an 800m time goal (it was my first love as a schoolboy, and managed 2:50 when I was 12 with little training. It would be nice to run faster than that at 50).