Got back on the bike about a year and a half ago after a 20+ year lay off, and I have a question.
I have ridden a couple centuries over the past year, which I ride at about 15 mph. I would like to start doing some longer rides, and some more challenging rides, but want to know how high I should set my sights. Let's face it, I am not 30 any more and I am well past the point where I can build muscles. Will I gain anything by doing interval work?