Four-time World Cup champion skier and Olympic gold medalist Lindsey Vonn has a rigorous training schedule, particularly during the off-season. With her sights set on the 2018 Olympics in Pyeongchang, South Korea, Vonn works out six to eight hours a day, six days a week during the summer, incorporating everything from cycling to sand training to tight rope walking.

RELATED: What Lindsey Vonn’s Recovery From Knee Injury Looks Like

Core training is especially critical for Vonn’s balance and control on the slopes. Check out the following moves Vonn is performing this summer to maintain a strong center.

1. Physioball Plank with Knee-to-Elbow

• Assume a push-up position, keeping your elbows in line with your shoulders and your back straight.
• Raise your feet to balance on a physioball, hip-width apart.
• Rotate your hips to one side and tuck your knees toward your elbow on the same side.

2. Weighted Plank Hold

• Assume a plank position with your elbows in line with your shoulders and your body in a straight line.
• Have a partner place a weight in the center of your back. Start light.

3. Side Plank with Physioball Squeeze

• Lie on your side with a physioball between your lower legs and ankles.
• Raise up onto your elbow, keeping it in line with your shoulder.
• Maintaining a straight torso, hold and squeeze the ball with your inner thighs.

4. Back Extension

• On a Back Extension machine (or balancing face down with your hips on a physioball), squeeze your glutes and raise your upper body until it is parallel to the floor.
• Lower with control and repeat.

5. Kneeling Med Ball Slams

• Kneel on a mat, engage your legs and reach overhead holding a med ball (or sand bag), taking care not to arch your back.
• Tightening your core and using your upper torso for momentum, slam the ball down to the ground.
• Repeat.

6. Physioball Windshield Wipers

• Lie flat on your back with a physioball between your feet.
• Raise and straighten your legs until they are vertical.
• Sway your feet slowly from side to side, maintaining a secure hip position on the mat.

7. Med Ball V-Extensions

• Sitting on the ground with your knees bent, lean slightly back keeping your spine straight and your chest up.
• Holding a medicine ball, extend your arms over your head and your legs out slowly.
• With control, bring your arms and legs back in.

8. Bench Scissor Kick with Med Ball Toss

• Sitting on a bench, lean slightly back keeping your spine straight and your chest up.
• Keeping your legs straight, perform small Scissor Kicks.
• Have a partner toss you a med ball. Catch it and move it to one side of your waist, then the other.
• Toss the ball back.