So, I have a schwinn electric bike. The weather here is often too bad for me too run, so I have been using it a lot. I have been experimenting with cardio, and figured out a pretty brutal routine.
To start, the warm up is start on level 8, about 75% of your sprinting speed, like a fast jog, and every 30 seconds, up the level, keeping the pace, until you hit the maximum resistance level. Take a minute break, keeping your heart rate up. The resistance on here is what kills you. Once you get there, it goes like this:
-One minute full sprint (RPM has to be above 105), then:
-30 seconds clap pushups (as fast as you can),
-30 seconds pullups/chin ups (fast as you can, good form), or
-60 seconds core work (you can do whatever here, as long as you are hitting it hard.)
Make sure you hit all three, the only reason for options is that you will burn out with clap pushups and pull ups before the work out is done.
for 20-30 minutes of bike time.
I did this yesterday and burned 1200 calories on the full resistance part of the bike alone.