Gait in Older Adults: A Review of the Literature with an Emphasis Toward Achieving Favorable Clinical Outcomes, Part I
Release Date: July 15, 2008
Expiration Date: July 15, 2009
Internists, family practitioners, geriatricians, cardiologists, and others who care for older patients.
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CONFLICT OF INTEREST RESOLUTION-CONTENT VALIDATION
In compliance with ACCME Standards for Commercial Support and NACCME’s policy and procedure for resolving conflicts of interest, this continuing medical education activity was reviewed by a member of the Advisory Board in June, 2008 for clinical content validity, to ensure that the activity’s materials are fair, balanced, and free of bias, and that the activity materials represent a standard of practice within the profession in the U.S. and that any studies cited in the materials upon which recommendations are made are scientifically objective and conform to research principles generally accepted by the scientific community.
Upon completion of this educational activity, participants should be able to:
1. Discuss both the “normal” and pathological gait changes that occur in older adults.
2. Explain temporal-distance measures of gait.
3. Describe functional outcome measures of gait.
4. Understand the relationship between distance walked in walk tests and aging or pathological gait.
This is Part I of a two-part article. Part I provides a gait and posture overview and discusses age-related changes and measures of gait. Part II (to be published in the next issue of Clinical Geriatrics) will focus on pathologies and interventions.
Changes in motor skills that occur with aging vary widely. It is generally accepted that many bodily functions decline with age, including the ability to walk. For older individuals, walking is one of the most important factors in maintaining an independent lifestyle and remaining in the community. As aging occurs, there can be distinct changes in gait patterns. There is some controversy in the field as to whether change occurs as a result of aging or as a result of pathology.1,2 There is tremendous heterogeneity in the process of aging and in the functional changes that occur in gait as one ages.3 Older adults can be divided into three sectors: the young-old (55-75 yr), the middle-old (76-84 yr), and the oldest-old (85+ yr).4 Various changes and challenges occur at each stage. All healthcare practitioners should be aware of the changes in gait as they may be indicative of subtle changes in multiple systems. Early identification and early intervention can be important in prevention of deterioration or secondary deficits.
It is important to examine the cardiovascular, neuromuscular, and musculoskeletal systems associated with age-related changes in gait. Are the changes affecting gait due to abnormalities in all bodily systems, or are certain systems more involved than others and in different timing sequences? Careful periodic assessment may help to identify changes as they occur and provide appropriate intervention to prevent dysfunction and loss of independence. Intervention to prevent dysfunction and/or remediate dysfunction should be individualized, and successful outcome may be dependent on the timing of the intervention.
For example, cardiovascular and pulmonary disorders (CVPD) are common in older persons.5 In fact, they are two of the most common causes of mortality, morbidity, and disability in older persons.5 The two most commonly occurring CVPD in older persons are heart failure and emphysema.5 Both of these chronic disorders have major detrimental effects on gait and other functional tasks due to impaired cardiovascular and pulmonary function which leads to skeletal muscle atrophy and myopathy.6,7 However, not all persons with CVPD experience impairments in gait or functional tasks.6-8
The purpose of this article is to provide a review of the literature on gait in older adults to assist the clinician in determining appropriate questions to ask regarding diagnostic and functional concerns about gait changes. Emphasis will be placed on age-related changes in gait and clinical measures of gait performance.
Gait and Posture Overview
Gait, when considered in the process of locomotion, involves several subtasks: (1) standing up from sitting, (2) generation of continuous movement to progress toward a destination, (3) maintenance of equilibrium during progression, (4) ability to meet the environmental constraints, and (5) initiation and termination of movement.9,10 The bipedal locomotor pattern is complex, consisting of maintaining the center of gravity (COG) over a continually changing base of support (BOS) that alternates in cycle between single-limb support and double-limb support. Postural stability and gait are intrinsically linked.11 According to the systems model, balance and mobility are maintained by cooperative interaction of the neuromuscular, musculoskeletal, somatosensory, visual, vestibular, and cognitive systems.11,12 Each of these components changes with age. Stability in gait is influenced by posture of the upper trunk, step length, step width, and speed. Changes in sensory processing that occur with aging make it difficult to predict individual variations.
During walking, all coordinating control systems are challenged in order to negotiate the environment that entails initiating and terminating gait, turning, avoiding obstacles, changing direction, stepping over objects, or avoiding objects. A better understanding of gait changes in the older adult and methods to improve gait are important since approximately 50% of falls have been observed to occur during some form of locomotion.13
Balance becomes less sharp in the decade of the 60s, and difficulty maintaining balance is greatly exacerbated as one ages, as seen by the number of falls that occur in elderly persons in their 80s. Postural control loss occurs more frequently in the presence of pathology and when the lack of compensatory mechanisms occurs. Adequate or appropriate postural control includes vertical postural alignment of the head, trunk, and limbs, and the ability to make compensatory movement strategies in the presence of internal and external perturbation. The main goal is to achieve maintenance of the center of mass (COM) or COG over the BOS12 within the limits of stability (LOS). The LOS is projected by sway angles that create a projected ellipse of a cone of stability. Factors influencing LOS are similar when standing in place, walking, and sitting without trunk support. In walking, a new LOS is established with each step.14 Somatosensory, visual, vestibular, neuromuscular, and musculoskeletal systems must work in concert to maintain postural stability.
As we examine gait, it is often difficult to determine which changes are normal age-related changes and which can be attributed to a primary or secondary pathology. Some consensus can be found in the literature regarding the following general kinematic changes with aging, including: (1) slower velocity, and (2) decreased stride and step length with increased stride frequency.4,15-19 Observed are average speed declines of 12% to 16% per decade for free gait speed and up to 20% decline for maximum gait speed.15
Several researchers have identified a variety of gait characteristics observed to change in community-dwelling adults as a result of aging and the manifestations of acute and chronic disease. These changes include increased double-limb support from 18% in the young to 26% in the elderly. In addition, there is a mild decrease in push-off with flat-foot heel strike. Forward trunk flexion increases as a result of osteoporotic processes, postural control, core weakness, or a combination of these factors. There is increased elbow and knee flexion and smaller toe clearances. Smaller toe clearances may be a contributory factor in falling, especially during turning.16,20 Gait variability, defined as the stride-to-stride fluctuations in walking, are unchanged in healthy older adults.
Impairment in the ability to avoid obstacles was attributed to both delayed onsets and reduced response amplitudes of motor units detected through electromyography (EMG) results in a recent study of community-dwelling adults (mean age, 71 yr) who participated in some type of sports.21 In a group of less-fit older persons, one might expect to find an even greater difficulty with obstacle avoidance due to even poorer EMG activity.
Physiologic factors that affect gait dynamics include neural control, muscle function, and posture control, which are impaired by aging and/or neurodegenerative diseases. Changes in the cardiovascular system and mental health can also affect the variability of gait. One can look at changes in the physiologic and neuromuscular systems as contributory to the gait changes with aging, specifically the loss of cross-sectional muscle mass (10-40%), decrease in type I and type II muscle fibers, prolonged contraction time and one-half relaxation time, and a decrease in conduction velocity in sensory and motor nerves in both the central and peripheral nervous systems.16,22 Furthermore, within the articular cartilage, there is formation of crosslinks and loss of elastic fibers, resulting in stiffer joint capsules and ligaments that affect the quality of movement and gait.22,23 The resultant movement pattern will be slower, more uncertain and uncoordinated, and lacking full range of motion.
Postural Control and Balance
Under most circumstances, the balance of older persons functions efficiently; however, when there is impairment in the sensory modalities, muscle strength, or muscle range of motion, postural instability may occur. Visual input is important for automatic reactions in response to uneven floors or avoiding hazards.24 Visual changes such as macular degeneration can cause decreased visual acuity or decreased response to special circumstances, such as adaptation to dark or glare. Somatosensory input may be impaired, with peripheral neuropathy or other pathology interfering with touch and pressure sensory information through the feet. Somatosensory processing is important for maneuvering on uneven surfaces. Decrements or disordered sensorimotor processing have been identified25-27 and may contribute to trip or slip types of falls during walking. Data suggest that under conditions that restrict sensory input from two modalities, the balancing ability of older persons is limited.28-30 Research by Duncan et al31 suggests that older adults have greater postural sway when standing and walking than do younger people. Woollacott and Tang9 reported a significant association between increased postural sway and lower walking speed.
The loss of motor and cognitive function that affect gait, balance, and fine motor coordination may be related to degenerative changes in the cerebellum. Degenerative processes causing dysynergic and dysmetric movements seen in some pathologies such as multiple sclerosis are also perhaps attributed to cerebellar degeneration. The cerebellum plays a role in motor control and in cognitive processes related to learning complex motor sequences. Changes that occur in the cerebellum with aging are not well understood and whether the changes have a role in age-related motor control and cognitive decline needs further investigation.32,33
Changes in thoracic-lumbar alignment that may occur with osteoporosis and anterior vertebral body collapse create a change in the COG over the BOS, causing forward head, forward trunk lean, or backward trunk lean in compensation to the changes in trunk alignment. Somatosensory processing reaction time,34 lower-extremity muscle strength, lower-extremity joint pain, and changes in trunk alignment can contribute to decreased balance and mobility skills that are identified as strong predictors of the likelihood for falls.35
Measures of Gait
Diagnostic and Treatment Selection–Oriented Measures
Gait performance is a key factor in maintaining functional independence of community-dwelling healthy elderly, as well as those with chronic diseases such as stroke, Parkinson’s disease (PD), diabetes mellitus, and multiple sclerosis (MS). When clinicians encounter patients who display gait abnormalities, they are faced with two basic types of questions: “What is causing this problem, and how might it be alleviated?” and “How serious is this problem in terms of affecting the patient’s overall function, safety, and quality of life?” The nature of the question the clinician is asking will influence the type of assessment tool she/he will select to evaluate the patient in question.
The first type of question, “What is causing this problem, and how might it be alleviated?”, is diagnostic in nature and useful in driving treatment method selection. For example, consider a patient with a positive Trendelenburg sign during gait (ie, dropping of the pelvis on the side opposite the weight-bearing limb during stance). This gait abnormality is usually caused by weakness in the hip abductor muscle (gluteus medius) of the weight-bearing limb, which in turn can be produced by a variety of disorders such as arthritis, stroke, diabetes, or MS. It might also be seen secondary to pain in the hip or lower extremity with or without muscle weakness. The point is that this type of finding (positive Trendelenburg sign) could best be used to drive a treatment selection aimed at the specific cause of the gait abnormality—in this example, strengthening the hip abductor muscle and/or reducing pain in the lower limb.
Constellations of specific qualitative symptoms can also assist the physician in making or confirming a clinical diagnosis of disease. Examples include the classic shuffling, festinating gait seen in patients with PD; the stiff-legged gait with drop foot and hip circumduction seen in patients with stroke; the ataxic gait of patients with MS; or simply the shortened step length, wider BOS, forward stooped posture, and decreased arm swing seen in elderly gait.36 Additional information on types of gait and possible etiologies will be provided in Part II.
Observational Gait Analysis
Detailed qualitative gait evaluations, also termed observational gait analysis (OGA), describe the motions of all body segments and joints during each phase of gait.37 Training and experience with the technique is critical, as OGAs have been shown to have only moderate reliability in several studies.37 Well-trained physical therapists can be very useful in analyzing the nature of the gait disturbance, simply by observing a patient walk, and its probable cause (eg, weakness, poor range of motion, disordered muscle tone, or abnormal sensorimotor control). They can also recommend exercises, stretching, and modalities that would best alleviate the source of the problem.
Comprehensive Laboratory Assessment of Gait
Laboratory-based analyses offer more sophisticated methods for gait analysis. Such evaluations typically include quantitative assessments of the kinematics and kinetics of gait, as well as a record of the EMG activity of muscles during gait, time-synced to the kinematic and kinetic data.38 They offer superior reliability versus OGA, especially for fast-paced movements. Laboratory analyses of gait are now more widely available but are expensive. These gait evaluations provide a wealth of quantitative information about gait performance, which can be very useful for major decisions about treatment, such as recommendations about surgery, type of prosthesis, or type of orthosis that may be appropriate for a particular patient.
Outcome and Functionally-Oriented Measures
The second type of question facing clinicians who encounter patients with gait abnormalities, “How serious is this problem in terms of affecting the patient’s overall function, safety, and quality of life?”, requires a different sort of measure. An appropriate outcome measure will give an assessment of function that can be used across multiple diagnoses, be quick and easy to use, and will correlate well with function. The outcome tool may or may not necessarily give information about what sorts of treatments would work best for that particular patient. A variety of measurement tools that require little to no special equipment, and that have been evaluated for reliability and validity, are now available for use by clinicians. Some examples are discussed below.
A major challenge in assessing gait is the identification of those individuals with gait abnormalities that place them at risk for loss of function, mobility, and independence. The International Classification of Functioning, Disability and Health provides a common framework for all practitioners to identify impairments, functional limitations, and participation restrictions and related disability.39 Functional assessments, an essential component in this process, can be useful as a quick screen to identify the need for more extensive evaluation by a physical therapist or other practitioner. In the community-dwelling older person, the simple assessment of response to fast and/or slow perturbation, single-limb, tandem and semi-tandem stance, and the Romberg test can be helpful in identifying those elderly persons who may benefit from a referral for further in-depth postural examination.
Instrumentation to measure postural control usually entails fairly sophisticated equipment, such as force platforms. Posturography identifies complex dynamic and static postural measures such as LOS, directional control of a target by weight shift, and projection of the COG in relation to BOS. In addition, some posturography instrumentation can distort or disturb somatosensory input by moving a weight-bearing platform, distorting vision or vestibular input.11,40-42 The goal of postural assessment testing is to identify the impairments in postural control or combinations of impairments in order to develop intervention activities or exercises. Gait and postural assessment are usually integrated into multi-task activities. A detailed list of functional assessments of gait and postural control can be found in Table I.19,43-54
Functional Ambulation Classification Scale
The Functional Ambulation Classification (FAC) scale is a clinically useful rating tool that distinguishes among six levels of gait, ranging from fully dependent to fully independent.55,56 No equipment is required for administration of the test. The instrument categorizes patients according to basic motor skills necessary for functional ambulation, without assessing the factor of endurance. “Ambulation” in this test is defined as the ability to walk 10 feet or more outside parallel bars, with supervision or physical assistance from no more than one person. Ambulation aids, such as walkers, crutches, orthoses, etc., are allowed as needed to achieve the highest independent rating. The six categories and their operational definitions are shown in Table II.55,56 The test has been used to extensively evaluate the relationship of temporal-distance (TD) measures of gait to functional walking status in patients with neurological impairments. In a longitudinal study of 101 patients with acute stroke, Kollen et al57 used this FAC measure as an outcome variable to examine how improvement in several impairments contributed to overall improvement of gait function. They found that improvement in standing balance control was more important than improvement in leg strength or than reduction of synergy influence in increasing overall gait function. Further, they found that reduction in visuospatial inattention was independently related to improvement in gait. More recently, the tool has been further validated for use in evaluating change in walking ability over time in patients with stroke.58
Temporal-Distance Measures of Gait
The TD measurement of gait is a clinically feasible, quantitative approach to gait assessment that has been in use for many years.59-63 Temporal-distance measures include all the measures that can be derived from the interaction of the footfall pattern with the contact surface versus time. Such measures include step and stride length, stance and swing time, double-support time, unilateral stance time, velocity, cadence, and step width, as well as the variability associated with each of these measures. (Table III provides an overview of commonly used terms to describe gait.)
Measurements can be derived using equipment as simple as paper and inkpad affixed to the shoe sole,55,56,59 but such methods are time-consuming and labor-intensive. Relatively inexpensive methods such as instrumented gait mats (Gait Mat II, E.Q., Inc, Chalfont, PA 18914) or portable methods such as electronic shoe inserts with accompanying computer software (The Stride Analyzer, B&L Engineering, Tustin, CA 92780) now offer a fast, convenient way to obtain such measures.
A consistent finding from multiple studies conducted using TD measures of gait is that velocity is a very robust measure of gait, particularly relative to function.55,64-70 Thus, if one has no special equipment available, a simple measure of walking velocity can offer a very useful and valid outcome measure for monitoring patients over time. Velocity can easily be obtained by using a stopwatch and a measured distance (30 ft, with the middle 20 ft used to time the patient) with the patient ambulating at a self-selected velocity. The main question of interest to clinicians is, “What values of walking velocity correlate with what levels of gait function?” The answer to this question is summarized in Tables II and IV. A detailed investigation of TD measures in patients with stroke and MS showed them to be reliable and valid measures. As functional scores improved, the TD values became closer to scores obtained from healthy subjects.55,56 Table II shows gait velocity data for 61 subjects disabled with MS or stroke, at different FAC levels. One can see that velocity values increase approximately linearly as functional category improves. Values shown in Table IV represent a composite of data and information compiled from multiple published studies. Healthy subject value is weighted means of values from nine studies,59,63,71-77 and values for impaired subjects are weighted means from eight studies.55,64-70 Note that since the FAC categories do not consider endurance, there is a ceiling effect of the FAC at 6. Table IV is designed to show how differences in velocity driven by strength and endurance affect the function of higher-level community ambulators. Thus, the FAC scale may prove more useful for subjects with moderate-to-severe disabilities, while measures such as velocity or the 6-minute walk test (described below) may prove more useful in a less disabled, community-active population.
The effects of a decrease in gait velocity and stride length can be appreciated by the simple measure of distance walked during a timed walking test. Distance ambulated is likely the simplest and most widely used method to clinically examine the gait of an older person with CVPD and other disorders, and involves measuring the total distance ambulated within a specific time period (often 6 or 12 min).6-8 Subsequent investigations of gait in persons with CVPD identified that 6 minutes is an optimal test duration due to a variety of clinical and statistical issues (eg, shorter duration that is more likely to discriminate due to less variance than the 12-minute walk test).78,79
The 6-minute walk test has been described as a functional performance measure that has been associated with a variety of psychological, physical, and functional measurements.6-8 A clinically useful characteristic of the 6-minute walk test in persons with CVPD is the prediction of oxygen consumption and survival using the 6-minute walk test distance ambulated.80,81 In fact, based upon a 6-minute walk test distance of 288 meters, a patient with heart failure has an estimated peak oxygen consumption of 12.6 mL/kg/min and a poorer survival than a person walking more than 300 meters.81 Furthermore, many prediction equations exist with which to estimate an individual’s distance walked in 6 minutes based on several clinical characteristics such as gender, age, height, and weight.19,82-85 A sampling of these prediction equations are shown in Table V.
From the equations in Table V, it is apparent that age plays a major role in determining the distance an individual is able to ambulate. In fact, the regression coefficients of all of the equations shown in Table V reveal a decrease in 6-minute walk distance with advancing age (a decrease from 2.99 to 5.78 meters for each additional yr).19,82-85 This can be better appreciated by examining the results of the Steffen et al19 study (Table V). Examination of these data also reveal that women tend to ambulate less than men during the 6-minute walk test. Finally, Bohannon86 performed a meta-analysis of 42 studies utilizing pedometers to look at the steps taken per day by adults, with one of the most notable findings being the low mean number of steps taken by adults age 65 years or older compared to adults less than 65 years of age (6565 steps vs 9797 steps). The fewer number of steps taken by older adults places them in a “low active” category which is likely to influence their health and level of fitness. Gait, therefore, can be a powerful indicator of fitness, survival, and the need for therapeutic interventions in persons with and without CVPD. Furthermore, use of a pedometer to quantify daily steps may be a particularly useful vehicle to promote increased walking in older adults, which is likely to facilitate improved health and gait. Methods such as this and other therapeutic interventions aimed to improve gait will be addressed in Part II.
Changes in motor skills that occur with aging vary widely. For older individuals, walking is one of the most important factors in maintaining an independent lifestyle and remaining in the community. As aging occurs, there can be distinct changes in gait patterns. Balance and gait are integrally related and must be considered together in examination of gait changes as a person ages. The balance of older persons functions efficiently in most cases; however, when there is impairment in the sensory modalities, muscle strength, or muscle range of motion, postural instability may occur and falls may result. All healthcare practitioners should be aware of the changes in gait as they may be indicative of subtle changes in multiple systems. Early identification and early intervention can be important in prevention of deterioration or secondary deficits. Researchers have identified a variety of gait characteristics observed to change in community-dwelling adults as a result of aging and the manifestations of acute and chronic disease.
The authors owe a special debt of gratitude to Julia Stoner, SPT, for her assistance with the manuscript preparation. She demonstrated amazing competence, patience, and skill far beyond all expectations.
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Dr. Harris is Associate Professor and Chair in Physical Therapy; Dr. Holden is Associate Professor in Physical Therapy and a Visiting Scientist at the McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA; Mr. Cahalin is Clinical Professor of Physical Therapy; Dr. Fitzpatrick is Associate Clinical Professor in Physical Therapy; Dr. Lowe is Associate Clinical Professor in Physical Therapy; and Dr. Canavan is Assistant Professor in Physical Therapy and in the Program in Athletic Training, Department of Physical Therapy, Northeastern University, Boston, MA.