(Consult your chiropractor before doing this or any other exercise.)
Start: Standing behind a chair, or in front of a wall. Place hands on backrest or wall for balance.
Exercise: Place one foot behind other. Keeping heel on floor, bend knee and lean hips forward.
You should feel tension behind lower leg, close to ankle. Hold for 30-60 seconds, relaxing muscles of lower leg. Switch sides, and repeat 2X per side.