Medicine ball crunch

Lie supine with knees bent ~90\u00B0 and feet hip-width apart; hold the medicine ball against your chest with elbows tucked. Posteriorly tilt the pelvis to lightly flatten the low back; brace the abs and keep the neck neutral with a slight chin tuck. Exhale and curl the trunk, lifting head, shoulders, and upper back until the shoulder blades just clear the floor; keep the ball touching your chest. Pause briefly and squeeze the abs; do not pull with the arms or jut the chin forward. Inhale and lower slowly, placing the spine back down segment by segment until the shoulder blades touch. Maintain a small, controlled range and steady tension; stop if you feel low-back discomfort or hip flexor dominance.