Gait performance is an indicator of general health status1 and a strong predictor of risk for developing dementia,2,3 falls,4 and institutionalization5 among older adults. Improvement in gait speed has been associated with longer survival in older adults.6 Treadmill-walking training (TWT) is a widely used rehabilitation method to improve gait in individuals with various neurological conditions.7–9 However, the use of TWT as an intervention to improve gait performance among frail older adults and its feasibility in this high-risk population have not been well studied. Gait performance is mostly reported in terms of velocity; on the contrary, other gait parameters such as stride-to-stride gait variability (fluctuation of stride length from 1 gait cycle to the next) are also recently recognized as a strong predictor of negative outcomes, including injurious falls among older adults.4,10 Information of TWT effects on gait parameters other than velocity is limited. In this case series, we described feasibility and tolerance of low- to moderate-intensity TWT of 8-week duration and its effect on different gait parameters in 4 frail older individuals. The knowledge gained from this preliminary study will help to design future TWT interventions to improve gait performance in frail older adults.
Recruitment of Participants
We recruited potential participants from a waiting list of research volunteers at our research center,11 who were initially identified through the Bronx County Board of Elections voter registration lists. From this list, 12 individuals were contacted by a telephone call by a research assistant. Of the 12, 2 refused to participate and 10 were invited to undergo in-person screening to determine eligibility to participate in this pilot study. Inclusion criteria on in-person interview was age 70 years and older as well as presence of frailty modified from the Fried criteria12 by meeting at least 3 of the following 5 attributes: slow gait (<1 m/s); unintentional weight loss (>10 lb during prior year); muscle weakness (self-report of poor grip strength); self-reported exhaustion; and low levels of physical activity (exercise once a week or less). Exclusion criteria were Mini-Mental State Examination score of 25 or less, self-reported activity limitations requiring personal assistance in 7 activities of daily living (bathing, dressing, grooming, feeding, walking indoors, toileting, and transfer from a chair) by using the disability questionnaire developed by Gill and Kurland,13 or contraindications14 for participation in exercise program such as uncontrolled hypertension or unstable angina. Among the 10 individuals who completed the in-person evaluation, 1 refused to participate in this study, 4 did not meet frailty criteria (ie, not frail), 1 was excluded because of uncontrolled hypertension, and the remaining 4 individuals (2 men and 2 women) participated in the study. Written informed consent was obtained from all participants, and all study protocols were approved by the committee on clinical investigations at Albert Einstein College of Medicine.
Information on medical illness and medications was collected by using structured questionnaires designed for the Einstein Aging Study.2,15–17 Height and weight at baseline were measured by a research assistant trained to collect anthropometric data. Knee extensor strength was also assessed since knee extensor strength is a known correlate of gait velocity in frail older adults.18 A board-certified physiatrist with research experience of studying frail older adults measured isometric knee extensor strength in kilograms of force by using a hand-held dynamometer (Lafayette Manual Muscle Test System, Lafayette Instrument Company, Lafayette, Illinois) with 90[HALFWIDTH WHITE CIRCLE] of knee flexion. Maximum value of 3 trials was obtained for each side, and the mean of the values from both sides was recorded for each participant at baseline and posttraining. The results were then converted into Newtons by multiplying kilograms by 9.81 m/s2.
Quantitative Assessment of Gait
Research assistants conducted quantitative gait assessments by using a computerized walkway (457 × 90.2 × 0.64 cm) with embedded pressure sensors (GAITRite system, CIR systems, Inc, Havertown, Pennsylvania). The GAITRite system is widely used in clinical and research settings and has excellent validity and reliability for measuring temporal and spatial gait parameters.19 The interrater reliability for gait velocity was reported to be excellent in our cohort20 (intraclass correlation [ICC], 0.96). All research assistants completed training for the administration of instructions to participants, operation of software program, and data processing and were certified on test procedures. Participants were asked to walk on the walkway at their “usual pace” in a quiet well-lit hallway without windows or other distractions, wearing comfortable footwear. All participants had previous exposure to the walkway and were allowed practice trials before the baseline assessment to minimize practice effects. On the basis of footfalls recorded on the walkway, the software automatically computes gait parameters as the mean of 2 trials. We a priori selected 5 gait parameters for analysis: velocity (cm/s), stride length (cm), swing time (ms), double support phase (%), and stride-to-stride gait variability on the basis of associations with adverse outcomes, including falls and disability reported in our and other studies.4,21,22 Stride-to-stride gait variability was operationally defined as change in stride length from 1 gait cycle to the next and calculated as (coefficient of variation [COV]23,24 of stride length). The COV of stride length was included for analysis, since it was shown to be a better predictor for falls, including injurious falls compared with other gait parameters in our previous study.4 Gait parameters were measured at baseline, weekly during TWT, and immediately posttraining. The baseline and posttraining values were reported descriptively.
Intervention (Treadmill-Walking Training)
The treadmill (T630m, SportsArt Fitness, Woodinville, Washington) walking training protocol was based on the recommendations of the American College of Sports Medicine14 and American Heart Association25 for older adults. The training sessions were held 3 times per week over an 8-week period (total 24 sessions). Each training session started with 5 minutes of warm-up walking at comfortable speed. Then, the speed was gradually increased to the level of workload, at which participants felt “somewhat hard” (12–14 on Borg scale26) for two 15-minute sessions with 1- to 2-minute break in between (total 30 minutes) followed by a 5-minute cooldown period. However, training interval was gradually increased from six 5-minute intervals per session to two 15-minute training periods per session over the first 2 weeks. As recommended,25 a gradual approach was applied to increase the exercise intensity in participants with low baseline level of physical activity and who were unfamiliar with treadmill walking. No suspension harness was used; however, the treadmills included extended side handles for safety and participants were allowed to hold onto the side railing during the training. Pulse and blood pressure were assessed before and after each session to ensure that the values were not deviated by 10 or more (per minute, mm Hg) from the values of initial assessment for pulse and systolic blood pressure. During TWT, participants were monitored for both with a subjective rating scale (Borg scale score27) as well as the heart rate tracked by a physiatrist (study clinician) with extensive clinical experience in the rehabilitation of frail older adults. Subjective rating scale (Borg scale score) was assessed every 5 minutes during the entire session. Study clinician encouraged the participants to increase the training velocity if the subjective rating of exercise intensity was low (fairly light, Borg scale score <12). The treadmill speed was reduced or the exercise was aborted if there were any untoward symptoms such as cardiovascular symptoms, fatigue, or excess workload (hard, Borg scale score >14). Heart rate was measured during the break between the two 15-minute training periods, and the second period was only initiated after the value was less than the 70% of estimated maximum heart rate (220 minus age14).
Two men (aged 72 and 74 years) and 2 women (aged 74 and 81 years) participated in the study (Table 1). One participant was morbidly obese (body mass index of 44.0). Three participants reported hypertension that was well controlled. One participant had history of coronary artery disease and was being managed medically. Two participants had history of gout; however, there was no evidence of active arthritis in their joints. Two participants missed 1 session each, and 1 participant missed 2 sessions of the 24 sessions due to the reasons not related to health, resulting in an overall high participation rate (95.8%). None of the 4 participants engaged in any exercise activities other than the TWT protocol during the 8-week training period.
None of the 4 participants had used a treadmill before this study. All participants held onto the side rails during most training sessions but particularly at training velocities that were higher than their usual overground gait velocity. No participants experienced falls or near falls during the intervention. There were no medical complaints, including chest pain, shortness of breath, excessive fatigue, or pain in the joints, reported during TWT or after the session. Mild soreness of calf muscles was reported by 1 participant with morbid obesity in the third week, which resolved spontaneously before the next session. Three participants reported that the overall TWT experience was enjoyable and expressed desire to continue the training after the study was over. One participant (woman, aged 81 years) reported that she felt less tired in doing daily activities with TWT, however, could not continue TWT without supervision. All participants felt that the supervised TWT was safe. They also expressed the opinion that TWT helped them walk better compared with the baseline.
Gait Performance of Overground Walking
All participants started TWT at a velocity lower than their baseline gait velocity during overground walking. All 4 participants were able to walk on the treadmill continuously for two 15-minute periods at or higher than the baseline gait velocity by the third week (sessions 7–9). The values of pre- and posttraining for gait parameters and knee extensor strength are summarized in Table 1. Following TWT, gait velocity showed improvement in all participants by 6.4 to 26.8 cm/s (mean percentage increased from baseline, 18.8%), which was larger than the meaningful change in gait velocity (4 cm/s) among older adults reported in our cohort28 and in another cohort.29 Interestingly, the largest improvement in gait velocity (27.2% increase from baseline) was noted in the oldest participant (age, 81 years) who had the highest gait velocity at baseline. Even 1 morbidly obese participant showed modest improvement in gait velocity by 8.4 cm/s (8.8% from baseline).
Similar to gait velocity, stride length increased in all participants by 4% to 22.2% and double support phase was reduced by 7.4% to 29.8% from baseline values. Swing time was reduced (improvement) in 3 participants, and there was no change in 1 participant (mean percentage reduction from baseline, 4.5%). The COV of stride length was reduced (improvement) in only 1 participant and increased (worse) in the other 3 participants. Knee extensor strength showed increase in only 1 participant and slight reduction in the other 3 after TWT.
Figure 1 shows the change in gait velocity during overground walking over the training period for each participant and the mean value of the peak treadmill training velocity. Mean peak training velocity (±SE) on the treadmill reached 4.4 (±0.8) km/h (123.0 ± 22.2 cm/s) during the last session of the training. The largest increment in the mean peak treadmill training velocity (±SE) after 2 weeks of familiarization was seen between the second and the third week, from 2.9 (±0.4) to 3.9 (±0.2) km/h (from 80.6 ± 11.1 to 108.3 ± 5.6 cm/s). Increasing trend in gait velocity during overground walking was shown for all participants, although there was some fluctuation in the values over the training period.
This case series shows that frail older adults were able to participate in 8 weeks of TWT without major complications. For frail older adults with sedentary lifestyle, TWT can be perceived as an overwhelming physical activity; however, our clinical observations in this small sample supported the feasibility of this approach in frail seniors. Introduction of TWT to our participants was gradual, starting at a treadmill velocity lower than the usual overground walking velocity and was done over multiple blocks of brief walking periods. Within a 2- to 3-week period (6–9 sessions), all participants were able to walk 15 minutes at the baseline gait velocity or higher. This training regimen seems to be well tolerated among frail older adults. All participants in our study after the intervention felt that supervised TWT was safe and enjoyable.
Treadmill-walking training induced improvements in most overground gait parameters except stride-to-stride gait variability in all participants in our pilot study. The magnitude of improvement in gait velocity was higher than meaningful change in gait velocity reported in previous studies.28,29 The mean percentage change from baseline was 10.8% increase for stride length, 17.1% reduction for double support phase, and 4.5% reduction for swing time. Meaningful change units have not been reported for these other gait parameters. Future studies examining whether the initial gain in overground walking is maintained with or without additional treadmill-training sessions will help to define optimal duration for treadmill exercises in frail older adults.
The effect of TWT on gait parameters in frail older adults has not been well described. Patterson and colleagues7 reported improvement in gait velocity and stride length in 39 stroke patients after 6 months of TWT (22% for gait velocity and 13% for stride length),7 which were comparable with our results in frail older adults. Stride-to-stride gait variability was not measured in that study. Six weeks of TWT improved gait velocity in 9 patients with Parkinson disease, but not stride-to-stride variability, as in our study.8 Alternate approaches such as extending TWT beyond 8 weeks may be explored to improve stride-to-stride gait variability.
The knee extensor strength increased in 1 participant and was reduced in the other 3 after TWT. However, these changes are smaller than the minimal detectable change (ranging from 21 to 55 N or 28% change from initial value) for knee extensor strength reported in the literature.30–32 The lack of detectable change in knee extensor strength in this study concurs with the results of a previous study that reported no significant improvement in knee extensor strength after 8 weeks of low-intensity aerobic exercise among sedentary older adults.33
The mechanisms underlying TWT effects on overground walking is not well understood. Treadmill-walking training may stimulate reorganization in the central nervous system34,35 or activate cortical areas involved in walking, such as the prefrontal cortex.36 The gait changes occurring within a short period (8 weeks) with relatively low exercise intensity in our study and no significant improvement in muscle strength favor neural mechanisms rather than solely a musculoskeletal or cardiovascular training effect.
Strengths of this case series include the weekly quantitative gait assessment with standardized protocol and minimal missing sessions. The main limitation of this study is small sample size, and our findings should be considered exploratory and used as guide to design studies of larger scale. Inclusion of morbidly obese individual could have affected the result. Although morbidly obese individual was able to complete all 24 training sessions, the size of improvement was relatively less than another participant with similar baseline gait velocity. It is possible that the overall effect of TWT on gait performance of frail older adults in this study might be underestimated by including the result of this morbidly obese participant. Other limitations include subjective assessment of grip strength and level of physical activity; however, similar subjective assessments were used to define frailty criteria in a previous study.37
Treadmill-walking training is well tolerated and may improve gait performance among frail older adults. These findings can help to design future studies to determine the optimal training period to improve gait as well as to design focused interventions for specific gait parameters in frail seniors.
The authors thank all individuals who participated in this study.
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