Lie on your back with your legs straight and pointing vertically upwards (90° hip angle); your arms should also be straight, pointing towards the ceiling or your feet, whilst keeping your lower back as flat as possible against the floor. Lift your upper body slightly by engaging your abdominal muscles, guiding your hands towards your feet in a controlled manner. Only your shoulder blades should lift off the floor. Hold the position briefly at the top, then slowly lower the upper body again (without resting it completely on the floor). If the tension is maintained correctly (lower back on the floor), the focus remains clearly on the abdomen and does not shift too much towards the hip flexors.
Attention:
Do not swing your body (instead, use a controlled movement), do not pull on your neck (hands should not be on your head), do not arch your back (lower back should not lift off the floor), do not let your legs tilt backwards (this causes you to lose tension), do not make the movement too large (do a crunch, not a sit-up).
Lighten:
Bend your knees slightly instead of keeping them fully straight, rest your hands on your thighs and slide them towards your knees, rest your feet against a wall, reduce the range of motion (lift only slightly).
Harden:
Add extra weight to your hands (e.g. a small dumbbell), keep your legs even more vertical and stable, perform a slow eccentric phase, hold the top position for a little longer (isometric), combine with leg raises (lowering legs + crunch).
