90/90 Hip Switch

Sit on the floor with one leg in front, hip externally rotated and knee bent ~90° (shin roughly perpendicular to the body), and the other leg out to the side, hip internally rotated and knee bent ~90°. This is the 90/90 position. To perform the switch, lift both knees and rotate the hips to bring the legs to the mirror-image position on the other side, lowering both knees down. Continue switching side to side.

The drill trains active hip internal and external rotation (hip-complex, hip-lateral-rotators) — ranges often restricted by prolonged sitting. The hip is a mobility joint in the joint-by-joint scheme (stability-vs-mobility), and limited hip rotation pushes compensatory motion onto the lumbar spine and knees. It develops active mobility (mobility-vs-flexibility) and appears in warm-ups and mobility flows (see dynamic-warmup-overview).

Coaching:

• Sit tall with a long spine; hinge forward over the front shin to deepen if desired.
• Work within a pain-free range and let it improve over reps/sessions; do not force the knees down.
• Typical dose: ~6–10 switches (each side), or hold each position briefly.
• For a single-joint maximal-control version of hip rotation, see hip CARs (exercise-hip-cars).

• 90/90 seated position (front leg externally rotated, side leg internally rotated, both knees ~90°); rotate side to side.
• Trains active hip internal and external rotation.
• Hip = mobility joint; poor rotation loads the lumbar spine/knees.
• Sit tall, pain-free range, don't force; ~6–10 switches.

• dynamic-warmup-overview — mobility/warm-up drill.
• stability-vs-mobility — hip-as-mobility-joint rationale.
• hip-complex, hip-lateral-rotators — joint/muscles.
• exercise-hip-cars — maximal-control hip-rotation version.