The easy challenge – basic stretches, followed by 5 burpees and 5 squats.
The advanced challenge – basic stretches followed by 3 sets of 10 situps, 10 pushups and 10 squats.
For burpees: http://exercise.about.com/…/cardio…/ss/cardioexercises_2.htm
Burpees are a challenging exercise that burns calories, increases intensity and works the entire body. Get pictures and descriptions of the squat thrust cardio exercise.