I started cycling back in August. I purchased a low-cost hybrid. Due to a busy family life, I only cycle during lunch hours, and not every day.
600 miles later, I can cycle much farther and faster than back in August. Still riding the same bike.
When I started, 7 miles at 12.8Mph pretty much did me in. Today 13.2 miles at 14.8Mph is only an OK ride. I know, 2Mph isn't exactly startling, but given my limited timeframe, I'm very happy with it. I wish I had time to go on long rides, but I just don't.
However, I don't feel any fitter than I did then.
So here is the question: How much is my improvement my body adapting to cycling (putting on muscle, for example), and how much is an improvement in my cardio? And more importantly, how do you measure them separately?