Mountain Climbers Start on all fours with your arms fully extended beneath your shoulders, supporting your weight on your hands and toes. Your back should be flat. 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 to a minute. Inchworm Stand with your feet hip-width apart and your core braced. Bending over at the waist, place your hands on the ground and walk your hands forward, keeping your legs straight. When your legs are parallel to the floor, walk your hands back toward your feet and return to a standing position. To make the exercise more challenging, you can add a pushup before walking your hands back. Perform 3 sets of 10 to 12 reps. Uppercuts In a wide stance, place your right foot one step ahead of your left foot, hips squared, facing forward. Using your right hand, punch up and across your body with a scooping motion. As you bring your right arm down again, punch up and across your body with your left hand. Continue alternating for 30 seconds, then switch your stance and continue alternating punches for another 30 seconds. Plank Jacks Begin on all fours, placing your hands directly under your shoulders, supporting your weight on your toes. Your legs and arms should both be fully extended. Jump your feet apart, wider than hip distance, then jump them back together. Perform 3 sets of 10 reps. Skaters Stand with your feet hip-width apart, knees slightly bent, arms at your sides. Bring your left arm up and across your chest as you jump to the right with your right foot, landing softly. As you land, swing your left leg behind you as if you are roller skating. Immediately jump to the left with your left foot, bring your right arm up and across your chest, and sweep your right leg behind you. Repeat in a continuous motion for 1 minute. Burpees Stand with your feet hip-width apart, arms at your sides. Bend your knees, swing your arms back and jump off the ground as high as you can. 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 for 30 seconds to a minute.