As a fellow runner, though my distances are getting shorter, there is definitely a difference between cycling fitness and running fitness. BTW - I am 52, so not the youngest of this group. Keep pedaling, just like running you are building strength and endurance, just using muscles differently than running. If you want speed, I would recommend finding a road bike. The old ones still work great and there are some great bikes on Craigslist if you are patient, or if you buy new get at least Tiagra level groupset.