Gait Disorders

Walking is often referred to as a series of controlled falls because walking requires the ability to shift weight and balance on one limb, take a step, and catch the body mass with the stepping limb. The ability to walk is a fundamental requirement for independence in mobility; however, the changes that occur with aging can limit mobility and potentially affect independence. An estimated 13% to 15% of older adults experience gait disorders even with “normal aging.” The gait changes associated with aging are slowed speed, decreased step and stride lengths, and a compensatory increase in the number of steps per second or cadence.

Other biomechanical changes occur in the stance and swing phase of gait. During stance, older adults display a wider base of support, greater hip abduction, more “toe out,” and greater amount of time in double support than do younger individuals. During the swing phase of gait, less dorsiflexion is compensated for by greater hip and knee flexion and results in great toe clearance. There is reduced trunk and pelvic rotation and less vertical movement compared with that in younger people. All of these create a more stable but less fluid gait. These changes are gradual and progressive, and they tend to be more noticeable in individuals who are age 70 years and older. Both internal and behavioral issues are implicated. Internal alterations in musculoskeletal, neuromuscular, and physiological systems contribute to the changes observed in gait, whereas behavioral factors such as reduced physical activity, perceptions of reduced health status, and fear of falling are also cited. Finally, increasing comorbidities of aging—arthritis, joint replacements, and strokes—interfere with lower extremity function and gait.

Musculoskeletal changes are both subtle and profound. Reduced range of motion in the trunk, hips, knees, and ankles can have a direct impact on walking. Kyphotic postures with increased thoracic flexion and forward head move the center of mass anteriorly and limit step initiation during early swing. Reduced strength in the hip and knee extensors and ankle plantar flexors decrease the vertical force production needed to take a step. Decreased gait speed may result from a reduction in muscle mass, increased fatty content in the muscle, and a shift in fiber composition, especially a decrease in the number of Type II muscle fibers.

Nervous system changes parallel those in the musculoskeletal system. Reduced visual, vestibular, and proprioceptive sensations affect gait. The peripheral nervous system has reduced nerve conduction velocities, longer latencies, and higher thresholds that influence the ability to respond quickly to sudden changes. In addition to loss of muscle fibers, there is a loss of motor units and reduced myoneural excitability. All of these together result in poorer ability to stand on one leg, a critical component of walking. There are also increasing problems integrating sensory and motor information.

Physiological changes encompass reduced cardiovascular and pulmonary capacity. Although the [Page 234]energy expenditures during walking are similar for younger and older adults, reduced walking speeds will compensate for any increase in energy expenditure with aging. Older adults often complain that they have limited endurance when walking and may require more frequent rests. Reduced cardiopulmonary capacity may result in a decreased exercise tolerance for any activity, often manifest during stair climbing when energy demands can stress an individual's capacity. Poor autonomic vascular responses may put an older person at risk for postural hypotension when moving from lying or sitting to standing. When pathology is added, cardiopulmonary capacity could limit the functional goals for a particular patient. For example, an older person with an amputation is often not a candidate for ambulation training with a prosthesis because the energy demands exceed the individual's capacity.

...