Here's an interesting approach to circuit training involving created by Ross Enamiait. You may have seen our feature on Ross' awesome skipping training here.
"Are you interested in a conditioning protocol that is guaranteed to provide variety and intensity?
Look no further than a standard deck of cards. One sample could include pushups and burpees. Perform one set of burpees for every red card (Hearts and Diamonds) and one set of pushups for every black card (Spades and Clubs).
To perform the workout, you will start with a fully shuffled deck of cards (52 cards). All face cards (Jack, Queen, and King) have a value of 10. Aces will have a value of 11. Number cards will be face value (ex. 7 of spades = 7 pushups). Jokers are optional, and can be set to any value. For example, a joker could involve 20 reps (of burpees or pushups) or perhaps 50 reps of a different exercise (ex. 50 squats).
Work through the entire deck. Each card requires a set of pushups or burpees, depending on the color. Your goal is to work through the entire deck as fast as possible. If burpees are too difficult, switch over to a squat thrust without the jump.
Each shuffle of the deck will provide a new workout. You can perform several exercises with this protocol (ex. pushups, squats, burpees, pull-ups, etc.).
Mix it up and have fun with it."
This will really get your Heart pumping. Perform this circuit twice a week maximum.