You can intensify this cardio workout by repeating the circuit up to 6 times. Beginners should perform the circuit once or twice only. High Knees Find a square on the floor that’s large enough to step inside or create one with tape. Stand to the left of it. Then, bring your right knee up to your chest and step down inside the square. Do the same with your left knee. Bringing your right knee to your chest again, step out of the square. Repeat on your left. You should now be on the opposite side from when you started. Repeat the motions in the opposite direction and continue for 30 seconds. Crossovers Stand to the left of the square you found or created. Step your left foot to the inside of the square, crossing it over your right leg, then bring your right foot to the outside of the square. Bring your left foot outside the ring so that it aligns with your right foot. Then repeat the movement in the opposite direction. Continue alternating as quickly as you can for 30 seconds. 180-Degree Twists Stand with your left foot inside of the square, your right foot outside of it so that your feet are hip-distance apart. Jump and rotate your body 180 degrees, keeping your left foot inside the square. Jump again, rotating back to starting position. Repeat the movement as quickly as your can for 30 seconds. Then, switch sides, keeping your right foot inside the square. Repeat for 30 seconds. Mountain Climbers Begin on all fours with your arms fully extended beneath your shoulders. Straighten your legs all the way back and prop yourself up on your toes. Bring your left knee to your chest, then quickly switch legs, driving your left leg back as you bring your right knee up to your chest. Repeat in a continuous motion for 30 seconds. Burpees Stand tall with your feet hip-distance apart, arms at your sides. Bend your knees, swing your arms back and jump off the ground as high as possible. When you land, bend your knees, place your hands on the floor in front of you, directly beneath your shoulders, and jump your feet back so that you land in a push-up position. Bend your elbows and lower your chest to perform a push-up. Jump both feet forward and stand. Repeat the moves for 30 seconds. Ski Jumps Stand with your knees slightly bent, feet hip-distance apart. Jump from side to side, landing on both feet. Continue as quickly as possible for 30 seconds.