On biking...if biking 9 miles
I here some people talk about biking 2-4 miles then tanking, others talk about 20-30 mile rides.. depends on what, when, where, and all that like any other excercise....
In early biking season, I like to do short loops, and change up intensities as much as I can. I live on top of a mountain, so I don't have much choice on intensity on the way up, so I'll go for a 6 mile ride, 3 down, to warm up, stretch, then do HIIT esque things on the way up.. sprint, rest, sprint, rest, moderate, sprint, moderate, rest, ect... That would be a day 1, on day 2 I'd try to make it as far as I could without resting. Now when I'm out on a trail, I usually do anywhere from 5-7 miles mountain biking (sometimes I'll like to do like 15-17 miles but those are epics), when I do this, I try to just keep a good pace, that keeps me sweating, and my heartrate up around what I feel is about 75-80% so I can keep going (don't want to tap out at 5 miles on a 7 mile ride) and you want to have fun!