Plank and Straight-Arm Kickback Work your arms and abs together with this plank variation. Start in a plank position, holding a dumbbell in each hand. Open your feet wider than hip width for a stronger base of support. Lift your left arm behind you as high as you can. Bring your left arm back into plank to complete one rep. Do 10 to 15 reps with each arm. Use five- to 10-pound weights. Image Source: POPSUGAR Photography / Kathryna Hancock