As I'm unable to run because of my shin injury, and have no working bicycle, my training plan has been reduced to strength training, walking and juggling.
I have found that if I spend a good hour juggling to music and doing tricks of various kinds, it can be quite a cardiovascular workout. Last night I was working on juggling three beanbags with one arm behind my back. After about 10 minutes of trying this on both side, I collapsed onto the couch, my heart racing like I had just run intervals at the track. Later on, working on 5-ball endurance and 5-ball half-showers, I found myself out of breath again.
So either I'm getting really out of shape, or juggling can be great cardio exercise.