Med balls are one of the best tools to help you develop a strong core. However, as with any type of equipment, you need to perform exercises that are appropriate for your fitness level. (Watch Abby Wambach work her core with a med ball.)

Med balls are commonly used to load traditional core movements. For example, let’s look at the Crunch. By holding the med ball over your chest, you challenge your core with more weight than you do with the standard bodyweight version. This is a great way to build core strength, especially if you’ve hit a strength plateau. (Learn how to break through a plateau.)

Below are four med ball core exercises, arranged in a progression from least to most advanced. Choose one of them based on your fitness level and add it to your core workout. Start with two sets of eight reps and gradually progress to three sets of 20 reps before trying the next variation.

Standard Crunch (Beginner)

• Lie on the floor with your knees bent holding a med ball directly over your chest with your arms straight.
• Perform a Crunch, pressing the med ball straight up.
• Slowly lower to start position.

Twist Crunch (Beginner)

• Lie on your back with your knees bent holding a med ball at your chest.
• Crunch up until your torso is at a 45-degree angle with the floor.
• Rotate left and touch the med ball to the floor outside your hip. Perform to the right.
• Return med ball to the center, and slowly lower to start position.

Partner Pass (Intermediate)

• Lie on your back with your knees bent holding a med ball at your chest.
• Have a partner stand facing you, two to three feet away from your feet.
• Sit up and toss the med ball to your partner.
• Catch a return pass and slowly lower to start position.

6-Pack Abs (Advanced)

• Lie on your back with your legs straight holding a lightweight med ball overhead.
• Keeping your legs and arms straight, fold up so your hands and feet meet above your belly button.
• Place the med ball between your feet.
• Lower to start position.
• On the next rep, pass the med ball to your hands and alternate.