TOWARD A BETTER UNDERSTANDING OF GAIT CHANGES WITH AGE AND DISABLEMENT:  NEUROMUSCULAR ADAPTATION.  Exercise and Sport Science Reviews, Vol. 31, No. 2, April 2003.

            Chris A. McGibbon

ABSTRACT

As persons age, there is usually a reduction in walking speed, stride length, and cadence while an increase in double support time occurs.  Is this done to provide a more stable base of support, or rather a neuromuscular adaptation?  This author reviews multiple articles and research in the current literature to determine if there is a plausible theory for the problem, or if it is multifaceted.

Of all the studies covered, almost all indicate that there is a reduction in the force and magnitude of the plantarflexors during the final portion of stance.  This reduction may be an attempt to reduce the destabilizing forward acceleration of the body, but the result includes reduced stride length and increases in double support time.

When looking at the hip musculature, the studies have varied results, with some indicating greater forces for the hip flexors, while others indicate greater hip extensor moments.  The reduction in plantarflexion force may require an adaptation via greater hip flexor forces in some persons. Plantarflexion propels the body, but also assists in creating the swing through motion of the limb after toe off.   Other persons may develop hip flexor tightness, and rely on a passive stretch reflex of the hip flexors and increased hip extensor moments to help propel the leg forward.  In subjects that display this behavior, the ankle plantar flexion angles are reduced and there may be the possibility of hip flexor contractures.  This appears to be more common in patients with OA of the knees and subsequent limited ROM.

It appears that the current literature strongly supports the notion that neuromuscular adaptations are either direct or indirect responses to a primary impairment, and exist to fulfill a compensatory role in both healthy elderly persons, and elderly persons with known pathologies. 

COMMENTS

An informative article that outlines current research regarding gait deviations in the elderly, slightly critiques their shortcomings, and summarizes what is seen and how it may play into what is actually seen clinically.  For those more interested, read the article for the actual studies, or contact me.

One interesting note was that all the studies indicate that there is a reduction in the power output and strength of the ankle plantar flexors.  Seeing this just by watching older persons walk may be why I incorporated calf raises into all my elderly persons programs for either the knee or the ankle, and even the hip and back.  I also incorporate it into the programs for persons with balance dysfunction, ataxia, or CVA.  Why not?  This is a motion and action we all do on every step, so why not address it?  I may need to change the method of delivering the exercise, and get away from simple calf raises and perhaps work towards explosive calf raises.

The literature differs on whether patients have full hip extension or lack hip extension, and they also differ on whether there are certain strategies of strong or weak hip extensors/flexors.  The author suggests that both may occur, depending on the compensation strategy employed by the patient for certain physiological problems.  The best bet clinically is to assess the range of hip extension, along with the strength of the hip flexors and extensor to find out what strategy they may be using, correct the deficits, and adjust for the original problem.

I am not familiar with any studies that review alterations in gait patterns due to physical therapy intervention.  The best one would be to assess the isokinetic and/or closed chain strength of the plantarflexors compared to younger individuals, and then reassess both strength, subjective functional reporting, and gait after an aggressive PT calf strengthening intervention.  A subgroup could perform simple calf strengthening and have their results compared to one who performs more explosive maneuvers.  Exclusion criteria would certainly have to include claudication patients, who would be limited in their ability to perform these exercises.  No reference was made regarding this patient population, who may decrease their plantarflexion forces to reduce pain of claudication.