By the time your 53 if you are anything like me, you'll be in need of new joints all over the place.
My advice as an ex professional frogman (who had to be superfit back in the day) try this.
First bin the running.
But to get your cardio vascular work out from sports with less impact on your joints try, cycling which is great, as is swimming.
Try this exercise for swimming:
We used to call them unders and overs, and they will make you fitter than ever, your lung capacity will increase no end.
So you swim a length of your local baths with front crawl as fast as you can (overs), then you relax whilst you swim the return length back underwater (unders). Repeat by however many you want, however as an ex diver, I got to the situation were I could swim a mile on top of the water and a mile underneath of the water.
That will take you to different level of fitness trust me.
However if you really want to punish your body by running, then to get really fit try "Fartlek" running. Which basically is jog a lampost and sprint a lampost.
Good luck!!