The nice thing about biking is you could go for a 5 hour bike ride every day of the week. I know I am still building my running, but I don't think the joints could handle running long distances every day. I decide not to run yesterday in order to let my knees recover. I think it worked well. Yesterday my knees were sore, but they felt fine today even after the run. Also, I got a bit bored during the run today so I started picking up the pace for short intervals, so I could finish sooner.