Standing Russian Twist 

Starting Position 
Hold a medicine ball between both hands and stand tall with your back straight, shoulders relaxed, abs engaged, legs straight, and feet placed slightly wider than your hips. Extend your arms straight in front of you, holding the ball at chest or shoulder level. 

Action 
EXHALE: Without dropping your arms, pivot on your left foot and rotate the ball and your torso as far as you can to the right. INHALE: Return to the starting position. EXHALE: Reverse direction; pivot on your right foot and rotate all the way to the left (not pictured). INHALE: Return to the starting position to complete one rep. 

Special Instructions 
Keep your abs engaged, back straight, and shoulders relaxed away from your ears. 

Muscles Worked: Abs, Obliques, Shoulders