Contract glutes and shift forward, then rotate hips to the left until you feel a stretch in the front of pelvis (B). (health.com)
You can stretch all of your intrinsic back muscles, at least to some extent, by curling your head, neck, trunk, and pelvis forward toward the fetal position. (yogajournal.com)
Keeping pelvis and knees in place and back straight, slowly rotate to one side against the tension. (healthcommunities.com)