David M. Wert

Validation of a Measure of Smoothness of Walking

BACKGROUND Altered biomechanics and/or neural control disrupt the timing of postures and muscle patterns necessary for smooth and regular stepping. Harmonic ratio of trunk accelerations has been proposed as a measure of smoothness of walking. We sought to validate this measure of smoothness by examining the measure in groups expected to differ in smoothness (ie, young and old) and across walking conditions expected to affect smoothness (ie, straight path, curved path, and dual task). METHODS Thirty young (mean age = 24.4 ± 4.3 years) and 30 older adults (mean age = 77.5 ± 5.1 years) who could ambulate independently participated. We measured linear acceleration of the body along vertical, anterior-posterior, and medial-lateral axes using a triaxial accelerometer firmly attached to the skin over the L3 segment of the lumbar spine during straight path, curved path, and dual task (reciting every other letter of the alphabet) walking. RESULTS Older adults had lower harmonic ratio anterior-posterior (HR(AP)), that is, were less smooth in the direction of motion and walked more slowly than young adults for all walking conditions. Once the analyses were adjusted for walking speed, only HR(AP) differed between young and old participants for all walking conditions. For the most part, both young and old participants were less smooth for slow pace walking, curved path walking, and dual task walking compared with usual pace straight path walking. CONCLUSIONS The harmonic ratio, calculated from trunk acceleration, is a valid measure of smoothness of walking, which may be thought of as a measure of the motor control of walking.

Impact of Exercise to Improve Gait Efficiency on Activity and Participation in Older Adults With Mobility Limitations: A Randomized Controlled Trial

Background Definitive evidence that exercise interventions that improve gait also reduce disability is lacking. A task-oriented, motor sequence learning exercise intervention has been shown to reduce the energy cost of walking and improve gait speed, but whether the intervention also improves activity and participation has not been demonstrated. Objective The objective of this study was to compare the impact of a task-oriented, motor sequence learning exercise (TO) intervention and the impact of an impairment-oriented, multicomponent exercise (IO) intervention on activity and participation outcomes in older adults with mobility limitations. The mediating effects of a change in the energy cost of walking on changes in activity and participation also were determined. Design This study was a single-blind, randomized controlled trial. Setting The study was conducted in an ambulatory clinical research training center. Participants The study participants were 47 older adults (mean age=77.2 years, SD=5.5) with slow and variable gait. Intervention The intervention was a 12-week, physical therapist–guided program of TO or IO. Measurements Measures of activity (gait speed over an instrumented walkway; daily physical activity measured with an accelerometer; confidence in walking determined with the Gait Efficacy Scale; and physical function determined with the total, basic lower-extremity, and advanced lower-extremity components of the Late-Life Function and Disability Instrument [Late-Life FDI]) and participation (disability limitation dimension and instrumental role [home and community task performance] domain components of the Late-Life FDI) were recorded before and after the intervention. The energy cost of walking was determined from the rate of oxygen consumption during self-paced treadmill walking at the physiological steady state standardized by walking speed. An adjusted comparison of activity and participation outcomes in the treatment arms was made by use of an analysis of covariance model, with baseline and change in energy cost of walking added to the model to test for mediation. Tests were used to determine the significance of the mediating effects. Results Activity improved in TO but not in IO for confidence in walking (Gait Efficacy Scale; mean adjusted difference=9.8 [SD=3.5]) and physical function (Late-Life FDI basic lower-extremity component; mean adjusted difference=3.5 [SD=1.7]). Improvements in TO were marginally greater than those in IO for gait speed, physical activity, and total physical function. Participation improved marginally more in TO than in IO for disability limitations and instrumental role. Limitations The older adults were randomized to the intervention group, but differences in baseline measures had to be accounted for in the analyses. Conclusions A TO intervention that improved gait also led to improvements in some activity and participation outcomes in older adults with mobility limitations.

Association of Body Mass Index With Self-Report and Performance-Based Measures of Balance and Mobility

Background The incidence of obesity is increasing in older adults, with associated worsening in the burden of disability. Little is known about the impact of body mass index (BMI) on self-report and performance-based balance and mobility measures in older adults. Objective The purposes of this study were (1) to examine the association of BMI with measures of balance and mobility and (2) to explore potential explanatory factors. Design This was a cross-sectional, observational study. Methods Older adults (mean age=77.6 years) who participated in an ongoing observational study (N=120) were classified as normal weight (BMI=18.5–24.9 kg/m2), overweight (BMI=25.0–29.9 kg/m2), moderately obese (BMI=30.0–34.9 kg/m2), or severely obese (BMI≥35 kg/m2). Body mass index data were missing for one individual; thus, data for 119 participants were included in the analysis. Mobility and balance were assessed using self-report and performance-based measures and were compared among weight groups using analysis of variance and chi-square analysis for categorical data. Multiple linear regression analysis was used to examine the association among BMI, mobility, and balance after controlling for potential confounding variables. Results Compared with participants who were of normal weight or overweight, those with moderate or severe obesity were less likely to report their mobility as very good or excellent (52%, 55%, 39%, and 6%, respectively); however, there was no difference in self-report of balance among weight groups. Participants with severe obesity (n=17) had the lowest levels of mobility on the performance-based measures, followed by those who were moderately obese (n=31), overweight (n=42), and of normal weight (n=29). There were no differences on performance-based balance measures among weight groups. After controlling for age, sex, minority status, physical activity level, education level, and comorbid conditions, BMI still significantly contributed to mobility (β=−.02, adjusted R2=.41). Conclusions Although older adults with severe obesity were most impaired, those with less severe obesity also demonstrated significant decrements in mobility.

Motor Learning Versus Standard Walking Exercise in Older Adults with Subclinical Gait Dysfunction: A Randomized Clinical Trial

To compare the effect of motor learning with that of standard exercise on measures of mobility and perceived function and disability.

Perceived Effort of Walking: Relationship With Gait, Physical Function and Activity, Fear of Falling, and Confidence in Walking in Older Adults With Mobility Limitations

Background Although clinicians have a number of measures to use to describe walking performance, few, if any, of the measures capture a persons perceived effort in walking. Perceived effort of walking may be a factor in what a person does versus what he or she is able to do. Objective The objective of this study was to examine the relationship of perceived effort of walking with gait, function, activity, fear of falling, and confidence in walking in older adults with mobility limitations. Design This investigation was a cross-sectional, descriptive, relational study. Methods The study took place at a clinical research training center. The participants were 50 older adults (mean age=76.8 years, SD=5.5) with mobility limitations. The measurements used were the Rating of Perceived Exertion (RPE) for walking; gait speed; the Modified Gait Abnormality Rating Scale; energy cost of walking; Late Life Function and Disability Instrument (LLFDI) for total, basic, and advanced lower-extremity function and for disability limitations; activity and restriction subscales of the Survey of Activities and Fear of Falling in the Elderly (SAFFE); activity counts; SAFFE fear subscale; and Gait Efficacy Scale (GES). The relationship of the RPE of walking with gait, function, activity, fear, and confidence was determined by using Spearman rank order coefficients and an analysis of variance (adjusted for age and sex) for mean differences between groups defined by no exertion during walking and some exertion during walking. Results The RPE was related to confidence in walking (GES, R=−.326, P=.021) and activity (activity counts, R=.295, P=.044). The RPE groups (no exertion versus some exertion) differed in LLFDI scores for total (57.9 versus 53.2), basic (68.6 versus 61.4), and advanced (49.1 versus 42.6) lower-extremity function; LLFDI scores for disability limitations (74.9 versus 67.5); SAFFE fear subscale scores (0.346 versus 0.643); and GES scores (80.1 versus 67.8) (all P<.05). Limitations The range of RPE scores for the participants studied was narrow. Thus, the real correlations between RPE and gait, physical function, and psychological aspects of walking may be greater than the relationships reported. Conclusions The perceived effort of walking was associated with physical activity and confidence in walking. Reducing the perceived effort of walking may be an important target of interventions to slow the decline in function of older adults with mobility limitations.

Challenging Gait Conditions Predict 1-Year Decline in Gait Speed in Older Adults With Apparently Normal Gait

Background Mobility often is tested under a low challenge condition (ie, over a straight, uncluttered path), which often fails to identify early mobility difficulty. Tests of walking during challenging conditions may uncover mobility difficulty that is not identified with usual gait testing. Objective The purpose of this study was to determine whether gait during challenging conditions predicts decline in gait speed over 1 year in older people with apparently normal gait (ie, gait speed of ≥1.0 m/s). Design This was a prospective cohort study. Methods Seventy-one older adults (mean age=75.9 years) with a usual gait speed of ≥1.0 m/s participated. Gait was tested at baseline under 4 challenging conditions: (1) narrow walk (15 cm wide), (2) stepping over obstacles (15.24 cm [6 in] and 30.48 cm [12 in]), (3) simple walking while talking (WWT), and (4) complex WWT. Usual gait speed was recorded over a 4-m course at baseline and 1 year later. A 1-year change in gait speed was calculated, and participants were classified as declined (decreased ≥0.10 m/s, n=18), stable (changed <0.10 m/s, n=43), or improved (increased ≥0.10 m/s, n=10). Analysis of variance was used to compare challenging condition cost (usual − challenging condition gait speed difference) among the 3 groups. Results Participants who declined in the ensuing year had a greater narrow walk and obstacle walk cost than those who were stable or who improved in gait speed (narrow walk cost=0.43 versus 0.33 versus 0.22 m/s and obstacle walk cost=0.35 versus 0.26 versus 0.13 m/s). Simple and complex WWT cost did not differ among the groups. Limitations The participants who declined in gait speed over time walked the fastest, and those who improved walked the slowest at baseline; thus, the potential contribution of regression to the mean to the findings should not be overlooked. Conclusions In older adults with apparently normal gait, the assessment of gait during challenging conditions appears to uncover mobility difficulty that is not identified by usual gait testing.

Improving Motor Control in Walking: A Randomized Clinical Trial in Older Adults with Subclinical Walking Difficulty

OBJECTIVE To test the proposed mechanism of action of a task-specific motor learning intervention by examining its effect on measures of the motor control of gait. DESIGN Single-blinded randomized clinical trial. SETTING University research laboratory. PARTICIPANTS Adults (N=40) aged ≥65 years with gait speed >1.0m/s and impaired motor skill (figure-of-8 walk time >8s). INTERVENTIONS The 2 interventions included a task-oriented motor learning and a standard exercise program; both interventions included strength training. Both lasted 12 weeks, with twice-weekly, 1-hour, physical therapist-supervised sessions. MAIN OUTCOME MEASURES Two measures of the motor control of gait, gait variability and smoothness of walking, were assessed pre- and postintervention by assessors masked to the treatment arm. RESULTS Of 40 randomized subjects, 38 completed the trial (mean age ± SD, 77.1±6.0y). The motor learning group improved more than the standard group in double-support time variability (.13m/s vs .05m/s; adjusted difference [AD]=.006, P=.03). Smoothness of walking in the anteroposterior direction improved more in the motor learning than standard group for all conditions (usual: AD=.53, P=.05; narrow: AD=.56, P=.01; dual task: AD=.57, P=.04). Smoothness of walking in the vertical direction also improved more in the motor learning than standard group for the narrow-path (AD=.71, P=.01) and dual-task (AD=.89, P=.01) conditions. CONCLUSIONS Among older adults with subclinical walking difficulty, there is initial evidence that task-oriented motor learning exercise results in gains in the motor control of walking, while standard exercise does not. Task-oriented motor learning exercise is a promising intervention for improving timing and coordination deficits related to mobility difficulties in older adults, and needs to be evaluated in a definitive larger trial.

What Is the Relation Between Fear of Falling and Physical Activity in Older Adults

OBJECTIVE To describe the association between fear of falling (FOF) and total daily activity in older adults. DESIGN Cross-sectional observational study. SETTING Ambulatory clinical research training center. PARTICIPANTS Community-dwelling older adults aged ≥64 years (N=78), who were independent in ambulation with or without an assistive device. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES FOF was defined by self-reported fear ratings using the Survey of Activities and Fear of Falling in the Elderly and self-reported fear status determined by response to the following question: Are you afraid of falling? Physical function was assessed using the Late Life Function and Disability Instrument. Physical activity was recorded using an accelerometer worn on the waist for 7 consecutive days, and mean daily counts of activity per minute were averaged over the 7-day period. RESULTS Fear ratings were related to total daily activity (r=-.26, P=.02). The relation was not as strong as the relation of function and physical activity (r=.45, P<.001). When stratified by exercise status or functional status, fear was no longer related to total daily activity. Physical function explained 19% of the variance in physical activity, whereas the addition of fear status did not add to the explained variance in physical activity. CONCLUSIONS FOF is related to total daily physical activity; however, FOF was not independently associated with physical activity when accounting for physical function. Some FOF may be reported as a limitation in function.

Interpreting the Need for Initial Support to Perform Tandem Stance Tests of Balance

Background Geriatric rehabilitation reimbursement increasingly requires documented deficits on standardized measures. Tandem stance performance can characterize balance, but protocols are not standardized. Objective The purpose of this study was to explore the impact of: (1) initial support to stabilize in position and (2) maximum hold time on tandem stance tests of balance in older adults. Design A cross-sectional secondary analysis of observational cohort data was conducted. Methods One hundred seventeen community-dwelling older adults (71% female, 12% black) were assigned to 1 of 3 groups based on the need for initial support to perform tandem stance: (1) unable even with support, (2) able only with support, and (3) able without support. The able without support group was further stratified on hold time in seconds: (1) <10 (low), (2) 10 to 29, (medium), and (3) 30 (high). Groups were compared on primary outcomes (gait speed, Timed “Up & Go” Test performance, and balance confidence) using analysis of variance. Results Twelve participants were unable to perform tandem stance, 14 performed tandem stance only with support, and 91 performed tandem stance without support. Compared with the able without support group, the able with support group had statistically or clinically worse performance and balance confidence. No significant differences were found between the able with support group and the unable even with support group on these same measures. Extending the hold time to 30 seconds in a protocol without initial support eliminated ceiling effects for 16% of the study sample. Limitations Small comparison groups, use of a secondary analysis, and lack of generalizability of results were limitations of the study. Conclusions Requiring initial support to stabilize in tandem stance appears to reflect meaningful deficits in balance-related mobility measures, so failing to consider support may inflate balance estimates and confound hold time comparisons. Additionally, 10-second maximum hold times limit discrimination of balance in adults with a higher level of function. For community-dwelling older adults, we recommend timing for at least 30 seconds and documenting initial support for consideration when interpreting performance.

Use of Stance Time Variability for Predicting Mobility Disability in Community-Dwelling Older Persons: A Prospective Study

Background and Purpose:Mobility disability is a serious and frequent adverse health outcome associated with aging. Early identification of individuals at risk for mobility disability is important if interventions to prevent disability are to be instituted. The objectives of this prospective study were to (1) determine the magnitude of stance time variability (STV) that discriminates individuals who currently have mobility disability (prevalent mobility disability) and (2) determine the magnitude of STV that predicts a new onset of mobility disability at 1 year (incident mobility disability). Methods:A total of 552 community-dwelling older adults were evaluated as part of the Cardiovascular Health Study, a longitudinal cohort study. Stance time, in milliseconds, was determined from 2 passes on a 4-m computerized walkway at self-selected walking speed, and STV was defined as the standard deviation from approximately 12 individual steps. Mobility disability was defined as self-reported difficulty walking a one-half mile. Receiver operating characteristic (ROC) curves were plotted to determine an optimal cutoff value for STV for prevalent and incident mobility disability, and the area under the receiver operating characteristic curve (AUC) was computed. Results:The optimal cutoff score for STV (maximizing sensitivity and specificity) for prevalent mobility disability was 0.037 seconds (sensitivity = 65%, specificity = 65%, AUC = 0.70) and for incident 1-year mobility disability was 0.034 seconds (sensitivity = 61%, specificity = 60%, AUC = 0.65). The use of likelihood ratios demonstrated a gradient of risk across values of STV, with mobility risk increasing as values of STV increased. Discussion and Conclusion:Values of STV may be useful in identifying older adults with mobility disability and at risk for future disability. We recommend the more conservative estimate for identifying risk, STV = 0.034 seconds, which maximizes the sensitivity and minimizes false negatives. The relatively modest values on the validity indices could possibly be improved by increasing the reliability of the measurement of STV. Clinicians should interpret the cutoff values liberally and use STV in conjunction with other measures until further work is completed to validate STV as an indicator of mobility disability.