People always say that you have to cycle about twice as long as you run to get the same results. I don't quite understand why. If I cycle for 30min at a heart rate of 160bpm, or I run for 30min at a heart rate of 160bpm, I should have the same cardio workout. No? I get that I'm training different muscles, but apart from that I really can't see the difference.
I'm asking since I recently picked up cycling and it seems I can cycle for much much longer than I can run, even when I'm doing both at the same heart rate. Additionally cycling seems to put far less strain on my knees, and it does seem to positively improve my overall fitness, including both speed and distance I can run.