Tried Tabata intervals on my wife's old rickety stationary bike.

total time = 34 minutes

15 min. WU
8 x 20 sec. all out w/10 sec. rest
15 min. CD

Studies have shown this workout to dramatically increase VO2 max.
Kind of liked it. Short and intense. Covered 1.4 miles during my cumulative 2:40 blasts. I think that converts to around 31 mph. I'll incorporate these into my injury-based training program.