work to rest ratio. . . .
so balls-to-the-wall for 20 secs . . . rest, or super easy effort/coast for 140 sec. (1:7)
In my experience, certain methods / devices need a little tweek here.
The C2Rower sprints? I find 25-30 sec of work is better, less rest times.
Prowler: 20 sec seems right (full sprint with heavy load)
Air Dyne: same, real hard to pull off 20 sec .
When you do these work periods, you should feel like dying. MAybe the first round won;t seem so bad . . .from the 2nd round on, should all seem like death.
have fun :0