Adapted/adopted the Humane Burpee - may not be much of a circuit since I survived it but let me know what you think
1 arm KB swings 20# x 20 (each arm maybe that's obvious but some need specifics :) )
2 arm KB swings 30# x15
Goblet Squats 30# KB x10
Pushups x10
I managed 5 rounds of this in 25 minutes. Before this, I rode the stationary bike for 30 (moderate (for me) intervals). Afterwards, I used the manual treadmill for 30.
Madness? This is CARDIO! :) - YMMV
Old enough to know better, young enough not to care.
I'm an eternal rookie - As soon as I stop learning I start dying.