Women generally have limited upper-body strength, so once you've started working out, it's important to strengthen the link between your arms and your trunk—the rotator cuff. Straight-Arm Plank to Side Plank 1. Start kneeling on all fours with both hands under your shoulders. 2. Extend both legs out behind you, feet hip-width apart and toes tucked under into a straight-arm plank. 3. Hold this plank position for 10 seconds. 4. Next, shift all your body weight to the right arm and rotate your entire left side up toward the ceiling, turning and stacking your feet on top of each other and extending your left arm up to the ceiling so your whole body faces the left. 5. Hold for 5 seconds, slowly lower back to straight-arm plank, and then rotate to the right side and repeat the hold.