For fun and fitness, it’s hard to beat the value of a stability ball. You can do exercises to strengthen muscles, improve balance and increase flexibility.
Stability balls come in many sizes. To choose one appropriate for your height, when you sit up straight, your hips and knees should form a right angle.
First, work on being able to balance as you sit on the ball. Then you can try exercises. Start with 5 to 8 reps and build up to 10 to 15.
For crunches, sit on the ball, feet flat about hip-width apart, arms crossed over your chest. Tighten your abs and lean back until you feel the tension. Hold, return to start and repeat.
For squats, stand holding the ball in front of you. Bend your knees, back straight and arms parallel to the floor. Tighten your abs and rotate your torso to the left. Hold, return to start and repeat to the right.
For planks to strengthen your core, lie over the ball on your stomach, feet touching the floor behind you. Lean forward to touch the floor in front of you with your hands (your feet will lift up). Walk your hands forward until the ball is under your thighs. With shoulders directly above your hands, balance on your hands and on the ball as you tighten your abs. Hold for as long as you can maintain good form, return to start and repeat.
Even though the ball is an inexpensive piece of equipment, take care of it by regularly checking the inflation and cleaning it with a mild soap.
Spine-Health has more about stability balls and how to use them.