According to this study done on couch potatoes over 12 weeks. The HIT portion was done on a stationary bike:
2 minute warm-up
20 seconds all out
2 minutes easy
20 seconds all out
2 minutes easy
20 seconds all out
3 minute cool down
That's it. 10 minutes total, with 60 seconds of real exercise.
What are the limits to this? Could someone become elite with some kind of HIT program?