An earlier Gray Institute® blog discussed the need to go “beyond the anatomical model” in order to appreciate how muscles work in function. The conventional approach to muscles looks at the joints that the muscle(s) crosses and describe what happens if the muscle shortens. Often this perspective is limited to a single plane of motion. Gray Institute’s approach (as discussed in that blog) is to focus on muscle activity that is 3D, econcentric, synergistic, and task-specific. The adductors (Magnus, Longus and Brevis) have amazing functional capabilities when considered both conventionally and with the “one joint beyond” perspective.
The conventional approach to muscles would emphasize that these muscles adduct the hip. And indeed they can. However, in weight-bearing activities, the majority of hip adduction is created by gravity, acting on the center of mass, driving the pelvis down on the unsupported side. If both feet are on the ground, hip adduction will be created if the pelvis slides towards that leg. So if during upright activities, the hip adduction is not created by the hip adductor muscles, then what is the functional purpose of this large mass of muscle?
Many years ago, Gary Gray used the analogy of the angled supports (struts) of a table to represent the stabilizing function of controlling motion between the pelvis (table top) and the femurs (table legs). In the frontal plane, the adductor muscle has a major role in controlling abduction of the stance hip as the pelvis slides toward the opposite leg. With both feet on the ground the right adductors control adduction of the left hip.
One of the unique anatomical features of the adductor muscles as a group is that their function in the sagittal and transverse planes is dependent on the starting joint position. If the hip is flexed, then some portion of the adductor group will create extension. If the hip is extended, then another portion will create flexion. This occurs in every walking cycle. As the front leg goes through flexion, the adductors will decelerate the flexion and then create extension (along with many other muscles). But at this same time, the back leg is going through hip extension. The adductors on that side will help slow down this motion (along with the hip flexors) and then actually help create the hip flexion occurring during the forward swing of the leg. This same type of position-dependent function occurs in the transverse plane, as the adductors can function as internal or external rotators.
All this and the “one joint beyond” perspective has not yet been addressed. Since the adductors control the femur, what is the effect at the knee? With the foot on the ground, if the adductors flex the hip, they will flex the knee. Extension of the femur will extend the knee. In the frontal plane, active adduction of the femur will abduct the knee. The decelerating abduction of the femur can decelerate knee adduction on the same side(again depending on the position of the hip). With the foot stable on the ground, whatever the adductors do to the femur in the transverse plane will have the opposite effect at the knee.
Above the hip, the adductors’ influence on the pelvis will transfer to motions at the Sacro-iliac joint, pubic symphysis, and the lumbar spine. The three-dimensional role of the adductors at the hip is clear. So we have to accept that the adductors can, and will, have an effect in each plane at the lumbar spine. Understanding these effects is a challenge for all, especially when the actual function is dependent on the position of the hip joint.
What can be much more helpful to all movement practitioners is to translate this “limited” insight into a recognition of all the problems that the adductors can create at the hip, spine, and knee. Gary Gray would want us to “see” that the adductors are dynamic struts. They lengthen (load) and shorten (explode) in all three planes. If the adductors muscles become static struts during function, many tissues will be at risk of injury. The loss of dynamic function of the adductor muscles can be due to weakness, actual shortening, or neuro-perceptual “tightness”. Either way, if the adductor muscles fail to lengthen and shorten, function decreases and injury risk increases dramatically.
The difficulty in assessing the adductors during weight-bearing function has been greatly reduced by the creation of the Analysis Movements of 3DMAPS® from the Gray Institute®. By utilizing lunges and arm swings, the willingness of the hip adductors to contribute to a whole body movement can be determined in terms of both mobility (motion) and stability (control of motion). Even with an incomplete understanding of the contribution of the adductors muscles to the hip, spine, and knee, the success (or lack thereof) of the body to integrate and coordinate the different joints into a single movement is revealed by the Analysis Chains of 3DMAPS®.