The bridges series strengthens the hip, pelvis and spine. You will need a yoga block. Try to do the entire series, three times for each movement, build up to 5 repetitions. Standing on the block places one hip in flexion and the other extension, smiliar to what your hips do while walking. The differences in the height of the foot requires that your pelvis remain level. The pelvis will tilt toward one side if your gluteals are not engaging equally. Place your hands on top of you pelvis to feel that it is level if you cannot feel it tilt.