Exercising with a stability ball helps improve balance and targets specific muscle groups.

You may think a stability ball— also known as a physioball or Swiss ball—looks like a giant beach ball. Still, it’s no toy. This trendy exercise gear with origins in physical therapy can add a challenge to your workout.

A stability ball can help you tone your core or trunk muscles and boost overall strength, endurance, and flexibility, says the American College of Sports Medicine. Every exercise is harder on a stability ball because the ball is unstable. Gripping the ball and maintaining your balance as you work out on it forces you to engage your abdominal, back, and hip muscles.

The key is using a ball that’s the right size for your height. If you’re 5 feet tall or less, use an 18-inch ball. A 22-inch ball is best if you’re 5 feet 1 inch to 5 feet 7 inches tall. Go with a 26-inch ball if you’re 5 feet 8 inches to 6 feet 2 inches tall, and a 30-inch ball if you’re more than 6 feet 2 inches tall. While you’re sitting on the ball, your knees and trunk should be at a 90-degree angle.

The firmer the ball, the tougher the workout. A less-inflated ball lets you sink in more, which makes it easier to keep your balance. Consider using a softer ball if you’re new to this prop or to exercise in general.

Many classes can teach you how to use the ball, but you can learn on your own. Here are three exercises to get the ball rolling.

The Plank, Stability Ball Style
This exercise targets your back and abdominal muscles.

Here’s how: Lie on your stomach atop a stability ball. Walk yourself forward until the front of your thighs or knees rests on the ball. The closer to your feet the ball is, the harder this exercise will be.

With a flat back, pull your shoulders back and down and fully extend your arms. Hold this plank position briefly while tightening your abdominal and glute muscles. Slowly walk yourself back to your starting position.

Triceps Extension
This exercise combines a stability ball with dumbbells to strengthen your abdominals and triceps (the back of your arms).

Here’s how: Sit on the ball with your feet hip-width apart. Tighten your abs and pull your shoulders and back down. Hold a dumbbell with both hands behind your head with your elbows bent.

As you exhale, slowly straighten your arms, extending the dumbbell directly overhead until your elbows are almost locked. Inhale and slowly bend your elbows to return the dumbbell behind your head to the start position. Take care not to hit the back of your head.

During each repetition, try to keep your head, torso, upper arms, wrists, and feet planted. Avoid hyperextending your lower back as you extend your elbows overhead.

On the Ball Push-Ups
The ball adds complexity to traditional push-ups because you’ll be balancing and engaging your abdominal muscles as you push off the ball with your arms.

Here’s how: Place your hands shoulder-width apart on the ball and move your feet back until your chest is over the ball. You should be in a push-up position on the ball instead of the floor.

Slowly bend your elbows, lowering your chest to the ball. Concentrate on keeping your back flat; don’t let your hips sag. Hold this position for two seconds before extending your arms to the start position. Continue with additional reps.

By Sandra Gordon, a feature writer for Vitality. For more information, visit the American Council on Exercise at www.acefitness.org.

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