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Stand with your feet shoulder-width apart. Your feet should be planted immediately before your jump. Keep the rest of your body relaxed. Be careful that your knees don't point inwards in a "knock knee" or Valgus position. They should be positioned over the second toe. Let your arms hang loosely at your sides while you crouch into the half-squat. They'll provide a lot of momentum when you jump, so don't keep them in front of you or above you before you jump. You don't need to spend lots of time meditating on your jumps before doing them, but it helps to visualize the steps you'll take. Visualize the push-off and see yourself leaping in the air toward (or over) your target. You'll be focused on the series of steps and tasks you're about to complete, ensuring a successful jump. As soon as you've crouched into a half-squat, immediately spring up into a high jump. Push off from the balls of your feet. Extend your hips, knees, and ankles as far and as quickly as you can. Gradually bring your arms behind your back while keeping them at your sides. When you start to jump up, powerfully swing your arms forward and up into the air. This should help propel you up and provide momentum. Exhale when you're doing the motion, like when you lift weights. Land on the balls of your feet rather than on your toes. Make sure to land with your knees bent and slightly aligned forward. Both of your legs should equally accept the weight of your landing. This will absorb the shock of hitting the ground and prevent knee injury.
Position your foot. Pay attention to your arms. Visualize your jumps. Spring upward into a jump. Swing your arms while you jump. Control your landing.