During gait when the front (lead) foot hits the ground, a Chain Reaction® occurs. Gravity and forward momentum meet the ground reaction force (GRF) to produce specific joint motions from the foot to the lumbar spine. The joint motions lengthen and load the muscles. After decelerating the motions that occur upon heel strike, the same muscles reverse the motion, transforming the load into the “explode” to move the body forward. When the right foot strikes the ground, the three relative joint motions that occur in the lead hip are flexion, adduction, and internal rotation. In addition to knowing the joint motions that are created, movement practitioners must know the specific REAL bone motions that produce those RELATIVE joint motions.
The adduction of the lead hip in the frontal plane is created by the REAL bone rotations of adduction of the femur and lateral flexion in the direction towards the trail leg. So, if the right heel strikes the ground, the right femur adducts and the pelvis goes through lateral flexion to the left (left side of the pelvis drops). There is also a translation (sliding of the pelvis to the right) that adds to the Chain Reaction® biomechanics that produce the RELATIVE joint adduction. This adduction lengthens and loads the posterior-lateral hip muscles which decelerate this movement, and then transform the decelerating load into an acceleration that drives the pelvis towards the opposite leg.
There could be a physical joint limitation of adduction, but often the cause is elsewhere in the Chain Reaction®. If we designate the right leg as the lead leg, let’s consider some of the biomechanical causes that would limit the REAL bone motions. Adduction of the right femur could be consciously restricted if there was medial knee pain. Restricted eversion / pronation at the right subtalar joint (that should be created by the ground reaction force) would limit the knee movement into a valgus/abducted position. The resulting Chain reaction would inhibit adduction of the femur. In either case, the Left Same Side Lateral Analysis Movement in 3DMAPS® would indicate less than optimal movement. The Right Opposite Side Lateral Mobility Analysis would require even more subtalar joint eversion / pronation in the lunging (right) foot.
Restrictions of pelvis motion will also limit RELATIVE hip adduction. Both the lateral flexion to the left and the translation to the right provide contributions to the joint motion. A tight illio-tibial band can restrict both REAL bone motions of the pelvis. Limited lumbar spine motion could also reduce movement of the pelvis. When the pelvis laterally flexes to the left, this produces lateral flexion to the right of the lumbar spine above. Loss of lumbar right lateral flexion will influence the right hip adduction occurring in the lead leg. In 3DMAPS® the Left Opposite Side Lateral Analysis Movement creates right hip adduction by driving the pelvis into left lateral flexion and translating it to the right, allowing the practitioner to check the REAL motion of the pelvis. To determine if the lumbar spine could be causing restricting pelvis motion, there are two Movement Analysis Chains that use the arms to drive the spine into right lateral flexion. One is the Left Same Side Lateral Chain (discussed above), and the other is the Right Opposite Side Lateral Chain.
The power of 3DMAPS® is that once the movement impairments are identified, a logical sequence of movements can be designed by using the Performance System.