Stand upright on the balls of your feet with your feet shoulder-width apart, holding a skipping rope in your hands. Jump steadily in place and simultaneously swing the rope (under your feet and overhead).
Attention:
Without putting your heels down (jumping on the balls of your feet/tips of your toes). Keep your upper body upright (tense your core).
Lighten:
Lower intensity (slower swinging).
Harden:
Higher intensity (very fast jumping); additional weight (on the feet).
Variant I:
Pull the tips of your feet towards your knees with each jump (bend your feet).
Variant II:
Integrate jump shapes: Double jumps, crossing arms, alternating left/right heel taps on the floor, straddle jumps, jumping in step position, alternating jumps, etc.
Note:
Two single jumps replace one double jump in training (1 double under = 2 x single rope jumps). Instead of jumping rope, the knee lift (skipping) is often chosen as a substitute (no material required).