Get down on all fours, with your hands directly under your shoulders and your knees directly under your hips. Keep your spine in a neutral position (no arching or rounding of the back), look down and actively engage your core. Extend one arm forwards and one leg backwards (crossed), hold the position briefly (without wobbling). Hips and shoulders remain parallel to the floor, gaze towards the floor (neck neutral), maintain tension throughout the body. Then bring the arm and leg back in a controlled manner and lower them. Switch sides for the next repetition.
Attention:
Do not arch your back (when extending your leg); do not tilt or rotate your pelvis to the side; do not perform the movement too quickly (loss of stability); do not lift your arm/leg too high (instead, stay in line in a controlled manner); do not overextend your neck (look straight ahead rather than down).
Lighten:
Move only your arm or only your leg; keep the movement smaller; work without holding the position; keep your hands slightly raised (e.g. on a bench).
Harden:
Hold the stretched position for longer; perform repetitions more slowly (greater tension); use an unstable surface (e.g. a balance pad); add extra weight (e.g. a light weight on the leg); add extra resistance (e.g. a band around the foot or arm).
