"When women are working out they tend to miss their shoulders," says celebrity trainer Viveca Jenson, who has worked with stars like Vanessa Hudgens and Hilary Duff. Read below for her favorite shoulder workout.WORKOUT Extend your arms out to your sides with straight elbows. Keep your shoulders down and away from your ears (this activates and tones the upper back). Flex and extend your wrists 30 times, moving the hands up and down. Do 30 small arm circles. Repeat.