This was a good one we did today.
All on assault bike.
The goal is to get 600 + calories in 60 minutes. BUT!
Every 4th minute you do 10 air squats, 10 pushups, 10 situps. Remaining time in the minute you can rest.
So its 15 x 4 minute sets - 3 minutes bike 1 minute 10 - 10 - 10
Quick and nasty.