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Research Reports |
MB King, MD, is a geriatrician in the Hartford Hospital Geriatric Program, Hartford, Conn, and Assistant Professor of Medicine, University of Connecticut School of Medicine, Farmington, Conn.
JO Judge, MD, is Vice President of Medical Services, Masonicare, Wallingford, Conn, and Associate Professor of Medicine, University of Connecticut Health Center, Farmington, Conn
R Whipple, PT, is Assistant Professor of Neurology, University of Connecticut Health Center
L Wolfson, MD, is Chairman and Professor, Department of Neurology, University of Connecticut Health Center and Hartford Hospital
Mark Thomas, MD, Odin Kuiper, MD, Asif Ali, MD, Doug Mangan, and Mawuena Quist assisted with the physical performance testing
Address all correspondence to Dr King at Hartford Hospital Geriatric Program, Burlingame Bldg, 2nd Floor, 400 Washington St, Hartford, CT 06106 (USA) (mking{at}nso.uchc.edu)
Submitted December 12, 1998;
Accepted September 9, 1999
 | Abstract |
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Key Words: Older people • Physical performance • Reliability • Responsiveness
| Introduction |
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 TopAbstract Introduction MethodResultsDiscussion and ConclusionsReferences |
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In this pilot study, we used 2 performance tests—the 8-item Physical Performance Test (PPT-8)2 and the 6-minute walk test3—as outcome measures in a 12-week exercise intervention for community-dwelling older people with mild mobility impairments. These tests were chosen from a long list of available performance measures because they measure the ability to do several common daily tasks (PPT-8) and endurance (6-minute walk test). Physical Performance Test (PPT) scores have been shown to predict adverse outcomes of nursing home placement or death.4 The 7- and 9-item PPTs have been validated in older outpatients, demonstrating internal consistency for the individual items tested as well as construct and concurrent validity.2 In the study describing the development of the PPT as a physical performance measure,2 concurrent validity was established by finding that the PPT-7 and PPT-9 scores were highly correlated with the modified Rosow-Breslau scale scores, instrumental and basic activities of daily living scale scores, and the Tinetti gait score. Use of the PPT-8 as an outcome measure in an intervention study has not been reported. The 6-minute walk test was originally developed as a measure of exercise capacity in patients with chronic heart failure or pulmonary diseases.3,5 Test-retest reliability has been determined in patients with peripheral arterial occlusive disease.6 The 6-minute walk test has also been used as an outcome measure in studies to improve fitness in people with single chronic diseases (osteoarthritis of the knee,7 chronic lung disease8,9), but it has not been used in studies of older people with varied or multiple causes of functional impairment.
In this article, we describe the reliability and responsiveness of these 2 performance measures. The aim of this pilot study was to test the sensitivity of these measures to detect change in performance after an intervention designed to improve the capacity to carry out common daily activities in older community residents. We did not examine the validity of these measures. Data from this study can be used to improve the accuracy of study size estimates for definitive intervention trials in older subjects with early mobility impairment.
| Method |
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TopAbstractIntroductionMethodResultsDiscussion and ConclusionsReferences |
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Of 150 interested volunteers who attended the group meetings, 98 volunteers met the entry criteria. The first 55 eligible volunteers then gave consent to participate and were scheduled for a focused history and physical examination, which included cardiac, neuromuscular, and joint examinations. The Mini-Mental State Exam (MMSE) and a questionnaire about performance of basic activities of daily living were also given. The 43 remaining eligible volunteers were placed on a contact list for future studies. Exclusion criteria included: assistance with activities of daily living; cognitive impairment (MMSE score of <24); stroke, Parkinson disease, or other major neurologic deficit; coronary artery disease or congestive heart failure with symptoms during moderate activity; poorly controlled hypertension; inability to walk 8 m independently; use of neuroleptics or benzodiazepines; or current physical therapy. Ten volunteers did not complete entrance testing or were excluded by study criteria after the physical examination.
The first 26 volunteers who met the study criteria were assigned to the exercise program, and the 19 subsequent enrollees were assigned to a control group. The subjects' average age was 77.9 years (SD=5.9, range=70–92). Seventy-one percent of the subjects were women, and 79% had 12 or more years of education. Twenty-eight percent of the subjects reported having fallen in the past year, and 55% reported moderate difficulty with one or more of the mobility-related activities. Transportation was provided by senior center van to volunteers who were otherwise unable to get to the senior center where the exercise program and testing took place. Thirty-seven subjects (18 subjects in the intervention group, 19 subjects in the control group) completed the study.
Physical Performance Testing
All subjects were tested with the PPT-8 and the 6-minute walk test. The PPT is designed to measure the ability to use the upper and lower extremities in everyday activities, and it was developed as a 7- or 9-item test. The performance of the following tasks is timed and scored in the 7-item PPT: writing a sentence, simulated eating, lifting a book and putting it on a shelf, putting on and removing a jacket, picking up a small object from the floor, turning 360 degrees, and walking 15.2 m (50 ft). The 9-item PPT includes 2 additional items: climbing one flight of stairs and counting the number of flights of stairs the subject is able to ascend.2 The ninth item (the number of flights of stairs) was dropped in this pilot study because we believed there was the potential for subjects to become fatigued with climbing multiple flights of stairs. Climbing a single flight of stairs was included along with the other 7 items because we believe it measures performance of an important (albeit more difficult) daily physical activity. An 8-item PPT has not been described in the literature, but because the 7- and 9-item PPTs have both been validated,2 we decided, after discussion with the developer of the test (David B Reuben, MD; personal communication), to use the 8-item test and to examine the results for internal consistency. Each PPT-8 item was scored from 0 points (lowest) to 4 points (highest) according to published test protocol.2 The maximum total PPT-8 score was 32 points.
The 6-minute walk test was administered on an indoor 32-m course with low-pile carpeting. Subjects were instructed to walk as far as they could in 6 minutes. At 2 and 4 minutes, they were informed of the time elapsed and were given the standard encouragement, "You're doing a good job."5 The distance (in meters) walked in 6 minutes was recorded. Electronic pulse monitors* were worn around the chest and on the wrist and were used to record heart rate throughout the test. Heart rate at 6 minutes was compared from first baseline measurement to follow-up tests.
There were 4 testers for the PPT-8: 3 medical students who were masked to group assignment and an unmasked investigator who did not participate in the exercise training. A geriatrics fellow who was masked to group assignment was the single tester for the 6-minute walk test. Testing occasions are shown in Figure 1. Interrater reliability of the PPT-8 was checked by having 2 raters simultaneously time each of 18 subjects during the first baseline test. In order to establish test-retest reliability for the PPT-8 and the 6-minute walk test, 22 subjects in the intervention group were tested on 2 additional occasions, each 1 to 2 weeks apart, after the first baseline test and before beginning the intervention. Because we believed interrater reliability was excellent for the PPT-8, repeat testing was done either by the same rater or by a different rater. The 37 subjects who completed the 12-week study were tested with the same measures at the end of the intervention. Results were compared with the first baseline test results, as about half of the subjects had only one baseline test.
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In phase 1, each session began with brisk walking. Subjects were instructed to walk at a moderate intensity, using the Borg Rating of Perceived Exertion Scale13 (intensity of 12–14 on the 6–20 Borg Rating of Perceived Exertion Scale). Walking duration was increased from 6 minutes in the first week to a maximum of 15 minutes in the third week, which was then maintained through week 6. Subjects who became tired were permitted to rest and then resume walking. Resistance exercises were performed using sandbags or dumbbells, and props such as chairs, doorways, mats, and walls. Exercises with the following movements were used: ankle plantar flexion and dorsiflexion, performed in a standing position; knee and hip extension by step-ups, using increasing step height (15.2–20.3 cm [6–8 in]) and adding weighted vests; elbow flexion/biceps curls with progressively increasing dumbbell weights; wall push-ups; seated "dips;" and hip flexion and abduction using increasing sandbag resistance at the ankles. Hip flexion was performed supine, with the inactive leg in hooklying. Hip abduction was performed in side-lying, with the knee and hip flexed on the down side.
The first week of training was a breaking-in period in which submaximal loading was used (ie, 
15 repetitions at moderate effort). In free-weight exercises (elbow flexion, dorsiflexion, hip abduction, hip flexion), loads were estimated on the basis of 1 or 2 trial-and-error attempts, using sex, medical and exercise history, and the therapist's impressions of the subject's robustness and walking vigor as factors. During week 2, in conjunction with performance impressions from week 1, an 8- to 10-repetition maximum load level was estimated. Two sets were carried out with each muscle group, with a goal of 15 repetitions each before increasing the load by 0.45 to 1.13 kg (1.0–2.5 lb). Similar repetition criteria were used for exercises using principally body weight (heel-ups, push-ups, dips, step-ups); however, the load was increased by altering body position or by use of props. For example, plantar-flexion (heel-rises) progression was as follows: bilateral 
bilateral on 3.8-cm (1.5-in) block unilateral unilateral on block unilateral on block with weighted vest. Dips were done straight-sitting on a mat (or in a chair if the subject was unable to get to the floor) by pushing down against blocks of progressively increasing height. For step-ups, all subjects started with 15.2-cm blocks. Beginning with the third week, block height was increased to 20.3 cm, unless the subject developed knee pain. All subjects were candidates for vest loading. Vests could not accommodate more than 4.5 kg (10 lb). The starting load was always 0.9 kg (2 lb). The week in which initial loading began (not earlier than week 2), and the subsequent increase in loading, was determined by the exercise leader, taking into consideration factors such as subject height and weight, sex, exercise history, disease burden, history of knee pain and pathology, and perceived degree of exertion or discomfort during step-ups with no weight during week 1.
Phase 2 sessions (Tab. 1) began with 15 minutes of a self-paced 6-component endurance circuit that emphasized functional tasks requiring force and balance. The next 60 minutes was devoted primarily to balance and flexibility exercises. Some exercises were carried over or modified from phase 1 for purposes of maintaining force and endurance gains attained in phase 1.
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Dropouts and Adherence
Eight of the 26 subjects assigned to the intervention group dropped out of the study. Seven of those subjects dropped out within the first 4 weeks. No control group subjects dropped out of the study. Three subjects dropped out of the study because of surgery or intercurrent illness, 3 subjects did not tolerate the exercise program (increased joint or muscle pain), and 2 subjects quit because of other commitments. For those subjects who completed the exercise intervention, average attendance was 86.3% (SD=8.7%, range=55%–100%); subjects performed 97% of assigned exercises during the sessions. Two subjects with arthritis of the knee noted increased symptoms during training but continued to exercise with minor adjustments in their programs.
Data Analysis
SYSTAT 4.2
2 and SPSS Release 6.0
3 software were used for the statistical analyses. Cronbach's alpha was used to determine internal consistency of the PPT-8 as a scale and was compared with that of the PPT-7 in this study. Interrater reliability of baseline measurements was determined using the intraclass correlation coefficient (ICC). The ICC described by Fleiss14 was used to determine test-retest reliability of the baseline measurements, as the study conformed to a one-way random-effects model.
The data for all subjects who had follow-up testing were included in the analysis for responsiveness to change. A repeated-measures analysis of variance (ANOVA) was used to test for a time (repeated-measures) effect and an exercise (group x time) effect. The RI was determined by dividing the mean change in score (PPT-8) or distance walked (6-minute walk test) for the intervention group by the square root of twice the mean square error for the change in score or distance walked in the control group.1 The relationship between PPT-8 score on the first baseline test and change in score at follow-up was measured using linear regression. A similar analysis was done on the 6-minute walk test results.
| Results |
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TopAbstractIntroductionMethodResultsDiscussion and ConclusionsReferences |
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=22.1 points, SD=4.5) to the third baseline test (=23.2 points, SD=4.8). The differences in 6-minute walk test distance did not reach statistical significance when tested by repeated-measures ANOVA. The ICC for the PPT-8 was .88, and the ICC for the 6-minute walk test was .93.
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A regression analysis was used to determine whether baseline performance predicted response to training. Subjects in the intervention group with poor performance on the PPT-8 at the baseline test had the greatest improvement in performance (r=.38, P<.05 for PPT-8; Fig. 2). There was no relationship between baseline distance (in meters) walked and improvement on the 6-minute walk test. The RI was calculated as .8 (2.4/3.1) for the PPT-8 and .6 (30/52) for the 6-minute walk test.
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| Discussion and Conclusions |
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TopAbstractIntroductionMethodResultsDiscussion and ConclusionsReferences |
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The 12-week exercise intervention was designed to improve muscle force, endurance, flexibility, and balance, the key factors affecting physical function.12 In our previous FICSIT (Frailty and Injuries: Cooperative Studies on Intervention Techniques) study in which we used an intensive, high-tech program of balance and muscle force exercises, we found that older individuals made gains in both balance and force production only if they had a program that incorporated both balance and resistance exercise.15
Our goal in this study was to pilot test an exercise program for older people beginning to have mobility impairment that could be carried out at a senior center without high-tech equipment. The objective was to improve flexibility and endurance as well as force and balance in functional activities. Although we believe that clinically meaningful gains were made by the intervention group after 12 weeks, we would expect even better performance after a longer intervention. The 2 tests used as outcome measures were chosen because they measured changes in performance that were expected with this exercise intervention. The PPT-8 measures performance of usual activities requiring force, balance, and flexibility, and the 6-minute walk test is a measure of endurance. When compared with the control group's scores, the improvement in the PPT-8 scores in the intervention group was clinically meaningful. Subjects in the intervention group with poor performance at baseline testing had the greatest improvement in PPT-8 scores. This finding may have been the result of a ceiling effect, with better performers at baseline testing already being close to the maximum achievable score. There was a greater improvement in the 6-minute walk test distance in the intervention group when compared with that of the control group at follow-up, but this difference did not achieve statistical significance.
The RI is a good indicator of the ability of a test to detect meaningful change due to an intervention. The responsiveness of a measure is determined both by the improvement in scores due to the intervention and by the variability of scores from baseline to follow-up in the control group. Thus, the RI increases as the difference in intervention group scores from baseline to follow-up increases and the variability in change in control group scores decreases.1,16
In our study, the RI of the 2 measures was calculated by using the change in scores (PPT-8) or meters walked (6-minute walk test) observed in the intervention group as the clinically meaningful difference. One danger of using this method to determine the RI is that the intervention may have produced an effect that was greater or less than the minimally clinically important difference or one that was statistically significant but clinically unimportant. We feel that the improvements obtained by the intervention group on both measures were clinically meaningful, based on data from our study and the results of previous studies. Although we used a new, untested intervention, the intervention was designed to improve the performance of the tasks tested by the performance measure. Five items tested by the PPT-8 (stair climbing, walking, stooping, lifting, and turning) were directly or indirectly practiced. When our analysis was limited to these 5 items, the results were similar to those obtained with the 8-item scale, suggesting that the PPT-8 was measuring meaningful improvements resulting from the intervention. The moderate intensity of the walking component of the intervention did not lead to improvement in 6-minute walk test distance in the intervention group when compared with the control group. Judging by the RI of .6, we would have needed almost 3 times as many subjects per group to show a statistically significant difference between groups. As this was a pilot intervention, we used this information in planning sample size for a larger and longer intervention project.
The results of previous studies indicate the changes seen after our exercise intervention were clinically meaningful. In one prospective study,4 there was a baseline difference of 3.7 points on the PPT-7 between older people who, at 18 to 24 months follow-up after an initial health and function screening, were living at home and those who were living in a nursing home or had died. The 6-minute walk test has been used in intervention studies, although not previously in this population. An 8-week program of fitness walking in 102 patients aged 40 years or more with osteoarthritis resulted in a 70-m increase in 6-minute walk test distance; control subjects had a 17-m decrease.7 Twenty-one subjects, aged 49 to 71 years, with chronic heart failure improved their 6-minute walk test distance by 18% after 16 weeks of aerobic training.8 The 6-minute walk test distance improved by 57 m in a study of older patients, aged 70 to 89 years, with chronic obstructive airways disease who had a 12-week program of home exercise and respiratory rehabilitation.9 Although the differences in PPT scores and improvements in 6-minute walk test distance were greater in the studies cited than in our study, we believe the 2.4-point improvement in PPT-8 scores that we found was a minimally clinically meaningful change. A 2-point improvement in PPT-8 scores would indicate that the person did 2 of the 8 tasks faster, or had decreased time for one task enough to improve by 2 points.
The relatively high dropout rate and number of musculoskeletal complaints in the intervention group highlight the challenges of intervening in older people with self-reported mobility impairments or impaired physical performance. Five of the 8 dropouts were for reasons unrelated to the intervention; 3 of these dropouts were for intercurrent illness or surgery—reasons that may be expected in frail older people. Five subjects in the intervention group complained of joint or muscle pain due to the intervention, and 3 of the 5 subjects dropped out because they could not tolerate the exercise program. Efforts were made to adjust the program for these individuals, and we were able to retain 2 of the 5 subjects. It is possible that the pace or intensity of the present intervention was too high for some subjects or that, in attempting to provide a uniform training stimulus, we were not sufficiently sensitive to preexisting musculoskeletal problems. A trade-off between providing a uniform stimulus (or intervention "dose") and possibly increasing side effects of training must be made in the design of intervention trials for frail older people. Efforts must also be made to assess the exercise goals of older people and their commitment to an exercise intervention prior to enrollment in a study. Given the small size of the study and the short duration of the training, the results reported here are very encouraging for intervention trials designed to improve performance.
| Footnotes |
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This study was approved by the University of Connecticut Health Center Institutional Review Board.
This work was supported by National Institute on Aging grants AG-09675 and AG-13631, and by funds provided by the University of Connecticut Center on Aging.
* Polar Electro Inc, 370 Crossways Park Dr, Woodbury, NY 11797. 
SYSTAT Inc, 1800 Sherman Ave, Evanston, IL 60201.
SPSS Inc, 444 N Michigan Ave, Chicago, IL 60611.
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TopAbstractIntroductionMethodResultsDiscussion and ConclusionsReferences |
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