Diamond Sit-Up Twist-Back
Sit on floor with legs bent out to sides, soles of feet touching, and arms by sides. Lie back and extend arms overhead on floor to start. Sit up, reaching hands forward to touch floor in front of feet.
Then bend arms out to sides and lower upper body to floor, rotating torso toward left, then toward right. Return to start. That's 1 rep. Do 20 reps, then jog in place for 30 seconds.