Seated Leg Extension on Ball
This will improve balance, core, quadriceps, and hamstring strength; and hamstring flexibility. Sit on a ball, tall and upright, with your feet no more than shoulder-width apart and you hands resting on the sides of the ball. Tighten your abdominal muscles. Keeping your right foot flat on the floor, extend your left leg fully, tightening your thigh muscles. Hold for 10 seconds. Repeat 5 times with each leg.
Remove your hands from the ball and keep them out to the sides so your body forms a T. For even more of a challenge add ankle weights. Start with 1 or 2 pounds. Also, try doing this while on the ball of your foot, rather than keeping your foot flat on the floor.