Something...Eastern Bloc tough.
Allow us to suggest Kettlebell Conditioning, an hour-long fitness class that puts your weight room routine to shame.
Less a traditional workout than an experience that would prepare you for breaking out of a Siberian labor camp, the kettlebell regimen was developed by Russian special forces and used to train Soviet soldiers. At first things start out easy, a couple warm-up exercises, a few jumping jacks, the old touch-your-toes.
Then the instructor introduces your prop for the day: a cannonball with a cast-iron handle. It comes in weight denominations ranging from ten to eighty pounds (go for the ten-spot on your first try, no one's judging). You then begin an intensive heave-ho of the metal orb ranging from squats to one-arm side swings to push-ups pivoting on the ball. The only occasional breaks are for more jumping jacks.
The net result is that your heart feels like it's about to break free of your chest and, if done regularly, your core and overall body begin to take on the tautness of a Russian gymnast.
Or maybe Dolph Lundgren.