Random thoughts on the Symmetry of the Gait Cycle
Human gait is cyclical. For the most part, when one limb is engaged on the ground (stance phase), the other is in swing phase (in walking gait there is a brief period of double limb support), then the limbs switch tasks. For us to move cleanly and efficiently one would assume that the best way to do that would be to ensure that both limbs are capable of doing the exact same things, with the same timing, same skill, same endurance and same strength. For this clean seamless motor function, one must assume that there is complete limb symmetry (length, long bone torsion, the same rate and degree of pronation, supination, ankle dorsiflexion, hip internal/external rotation, same strength, power output etc) and one would hope there would be no injuries that had left a remnant mark on one limb thus encouraging a necessary compensation pattern in that limb (and one that would then have to be negotiated with the opposite limb). For example, when right ankle rocker (dorsiflexion) is impaired, early heel departure will occur and hip extension will be limited. An alteration in right glute function will follow. One could theorize that the left step length (the length of measure from right heel strike through to left heel strike) would be shortened. This would cause a premature load onto the left limb, and could very well force the left frontal plane to be more engaged than is desirable. This could lead to left core and hip frontal plane weakness and compensation patterns to be generated. To complicate the cyclical scenario, the time usually used to move sagittally will be partially used to move into, and back out of, the left frontal plane. This will necessitate some abbreviations in the left stance phase’s timely mechanical events. Some biomechanical events will have to be abbreviated or sped through and then the right limb will have to adapt to those changes. These are simple gait problems we have talked about over and over again here on the gait guys blog. These compensation patterns will include weaknesses as part of the pattern, and fixing those weaknesses does not address the right ankle rocker problem. Fixing said weaknesses merely encourages the brain to possibly continue to perpetuate necessary tightnesses in other muscles and motor linkages and engrain the compensations further or more complexly. It is easy to find something weak, it takes a sharp brain to find the sometimes silent sparking event underneath it all. One’s focused task should be, are you able to find the problem in this never ending loop of compensations and find a way to unwrinkle the system one logical piece at a time, or will you just chose to strengthen the wrinkled system and hope that the new strength on top of the compensations is adequate for you our your client ? One should not have to do daily or weekly rehabilitative sessions and homework to negate and alleviate symptoms, this is a far more durable machine than one that needs daily support. Rather, one that “seems” to need daily supportive homework/rehab is one that likely needs the underlying limitation to be uncovered. However, there are always exceptions. If one has a fixed issue, for example Foot Baller’s Ankle, then regular doses of lower limb anterior compartment work may be necessary to ensure that further ankle dorsiflexion range is not eroded.
Now, lets add another wrinkle to the system. What if there were problems before any injuries ? Meaning, what if there were problems during the timely maturation and suppression of the primitive reflexes ? Or problems in the timely appearance or maturation of postural reflexes? A problem in these areas may very well result in a central or peripheral nervous system malfunction and a representation of such in one’s movement and gait. But, that is a discussion for another time.
Shawn and Ivo, the gait guys
photo: courtesy of Thomas Michaud, from the excellent textbook, Human Locomotion