3. Back extension Stand in armpit-deep water facing the pool wall and hold onto the edge with your hands shoulder-width apart and elbows relaxed. Bend both knees and place feet flat against the wall at about waist height, slightly farther apart than your arms. Holding onto the edge, inhale as you let your legs extend behind you. Use your abdominal muscles to tilt your pelvis and control your legs until you’re in a prone float position and your feet are at the water’s surface, separated slightly. Bend elbows as needed. Exhale and curl your back like a cat as you bend your knees in toward your chest; then bring your feet to the wall to the starting position. Do 4–6 repetitions. Stretches the spine and relaxes the lower back; strengthens abs, back and upper-thigh muscles; helps develop body control.