Warmup: Jumping jacks, 2 minutes, then:
Step 1 Stand with your legs shoulder-width apart, knees slightly bent.
Step 2 Bring right arm out to 90° angle, with hand behind head, fingers lightly at ears.
Step 3 Crunch to side, bringing elbow to knee at waist level.
Step 4 Moving fast, do 10/20 reps, then switch sides.