I have touched my bike only a few times this winter. I decided to run a half marathon in early february, so I am just now getting back on my bike. I think I have a solid aerobic base from all the running. Do I need to go through a full base cycle on the bike? Even though my cardio system would be fine, I don't think my legs could handle a three hour ride at 19mph. How do you suggest I proceed from here? Would it be beneficial for me to go on say a 2-3 hour ride with my heart rate around 130bpm and casually ride my legs into cycling shape? I am 19 years old, so my max is ~200bpm.