STROKE IS A LEADING CAUSE of disability in older

Transcription

1 1308 Reliability of Treadmill Exercise Testing in Older Patients With Chronic Hemiparetic Stroke C. Lynne Dobrovolny, MA, Frederick M. Ivey, PhD, Marc A. Rogers, PhD, John D. Sorkin, MD, PhD, Richard F. Macko, MD ABSTRACT. Dobrovolny CL, Ivey FM, Rogers MA, Sorkin JD, Macko RF. Reliability of treadmill exercise testing in older patients with chronic hemiparetic stroke. Arch Phys Med Rehabil 2003;84: Objective: To assess the test-retest reliability of cardiopulmonary measurements during peak effort and submaximal treadmill walking tests in older patients with gait-impaired chronic hemiparetic stroke. Design: Nonrandomized test-retest. Setting: Hospital geriatric research stress testing laboratory. Participants: Fifty-three subjects (44 men, 9 women; mean age, 65 8y) with chronic hemiparetic gait after remote ( 6mo) ischemic stroke. Patients had mild to moderate chronic hemiparetic gait deficits, making handrail support necessary during treadmill walking. Interventions: Peak effort and submaximal effort treadmill walking tests were conducted and then repeated on a separate day at least a week later. Main Outcome Measures: Reliability coefficients (r) were calculated for heart rate, systolic blood pressure (SBP), oxygen consumption (VO 2 [L/min]), VO 2 (ml kg 1 min 1 ), respiratory exchange ratio (RER), rate-pressure product (RPP), and oxygen pulse during peak effort testing. The reliability coefficients for all but SBP and RPP data were calculated from the submaximal tests. Results: Heart rate (r.87), VO 2 peak (L/min) (r.92), VO 2 peak (ml kg 1 min 1 )(r.92), and oxygen pulse (r 93) were highly reliable parameters during maximal testing in this population. Submaximal testing produced highly reliable results for V O2 (L/min) (r.89) and oxygen pulse (r.85). All cardiopulmonary measures except RER had a reliability coefficient greater than.80 during submaximal testing in this population. Conclusion: Our study provides the first evidence that peak effort treadmill testing provides highly reliable oxygen consumption measures in chronic hemiparetic stroke patients using minimal handrail support. The submaximal tests were at or near the threshold level of reliability for the 2 most important From the Division of Gerontology, University of Maryland School of Medicine, Baltimore, MD (Dobrovolny, Ivey, Sorkin, Macko); Department of Neurology, Baltimore VA Medical Center, Baltimore, MD (Macko); and Department of Kinesiology, College of Health and Human Performance, University of Maryland, College Park, MD (Rogers). Supported by the Baltimore Veterans Administration Geriatrics Research, Education, and Clinical Center, a Veterans Affairs Medical Division Career Development Award, National Institute on Aging (grant nos. R29 AG , AG , NIA T32-AG00219), and The Claude D. Pepper Older Americans Independence Center from the National Institute on Aging (grant no. P60-AG12583). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or any organization with which the authors are associated. Reprint requests to Richard F. Macko, MD, Baltimore VA Medical Center, Geriatrics Service/GRECC BT (18) GR, 10 N Greene St, Baltimore, MD , rmacko@grecc.umaryland.edu /03/ $30.00/0 doi: /s (03) measures of V O2 (L/min) and V O2 (ml kg 1 min 1 )(r.89, r.84, respectively), with the remaining measures falling above.70. Key Words: Exercise test; Hemiparesis; Rehabilitation; Reliability and validity; Stroke by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation STROKE IS A LEADING CAUSE of disability in older Americans, with approximately 750,000 Americans suffering a stroke annually. 1,2 Two thirds are left with chronic neurologic deficits, which persistently impair function. 3-5 In particular, stroke-induced hemiparetic gait results in impaired mobility, poor balance, and increased risk of falls. 4 Spasticity, abnormal patterning of muscle activation during gait and decreased oxidative capacity of hemiparetic limb skeletal musculature are associated with a 1.5- to 2-fold increase in energy demand, as measured by oxygen consumption (V O2 ) for hemiparetic ambulation. 6,7 Increasing evidence suggests that aerobic exercise training using a variety of modalities can improve cardiovascular fitness in chronic hemiparetic stroke patients In a controlled study, Potempa et al 10 demonstrated a 14% improvement in maximal V O2 among young stroke patients after a bicycle ergometer exercise training program. Additionally, our previous noncontrolled studies showed that 6 months of treadmill aerobic exercise training significantly increased VO 2 peak 8 and reduced the steady-state V O2 required to perform the same constant-rate submaximal treadmill walking task 9 in chronic older hemiparetic stroke patients. Furthermore, treadmill training in chronic stroke patients increases quadriceps strength, 12 decreases hamstring spasticity, 13 and improves ambulatory 14 and dynamic balance performance. 15 Thus, there is a strong rationale for using treadmill training in older hemiparetic stroke patients, given that it improves mobility and facilitates locomotor relearning. 14,16 Nevertheless, several confounding factors, including the need for handrail support and low fitness levels, may make the measurement of peak VO 2 and gait economy unreliable in this population. Abnormal gait patterns make handrail support essential for treadmill ambulation among stroke patients. 8 Unfortunately, handrail support by patients represents a potential confounder during testing for submaximal and peak oxygen consumption. 17 Only 1 study has determined the reliability of maximal V O2 responses to cycle ergometry in the stroke population, 10 finding cycle testing reliable, but no studies have been published regarding the reliability of these measures in this population on the treadmill. Because V O2 is a primary dependent variable in many exercise training studies, it is important to establish the test-retest reliability of peak and submaximal treadmill testing with handrail support. This will help determine the utility of cardiopulmonary variables as performance outcome measures in exercise intervention studies. The test-retest reliability of submaximal testing is relevant

2 TREADMILL TEST RELIABILITY IN STROKE, Dobrovolny 1309 to the ability to measure and interpret the energy cost of gait in the chronic hemiparetic stroke population. Therefore, the purpose of our study was to determine the test-retest reliability of cardiopulmonary measures of maximal and submaximal exercise treadmill testing in older, chronic hemiparetic stroke patients using minimal handrail support. We hypothesized that although stroke patients would display a broad range of exercise capacities, based on their heterogeneous neurologic deficit and fitness profiles, key cardiopulmonary measures for both maximal and submaximal exercise treadmill tests would demonstrate high test-retest reliability, defined by a reliability coefficient.85. METHODS Patients were recruited through physician referrals and direct contact at a rehabilitation hospital by a stroke neurologist and nurse study coordinator. To participate in our study, patients had to be capable of walking independently on the floor for 9m with the use of a walker or cane. The entry evaluation included a resting electrocardiogram, medical history, and physical examination. Stroke patients meeting the established entry requirements to this point then performed a graded exercise test (GXT) on a treadmill. The institutional review boards at the University of Maryland, Baltimore, and the University of Maryland, College Park, approved this study. All patients provided informed consent after the study was explained to them in detail. Exclusion criteria included congestive heart failure, peripheral arterial disease with claudication, cancer, pulmonary or renal failure, unstable angina, uncontrolled hypertension ( 190/110mmHg), moderate alcohol use ( 3oz liquor/d), dementia (Mini-Mental State Examination score, 22), severe aphasia (determined by clinical evaluation with a neurologist), orthopedic or pain conditions that limited participation in exercise testing, and major poststroke clinical depression (Center for Epidemiologic Studies Depression Scale score, 16). Patients with medically stable coronary artery disease, hypertension, and diabetes mellitus were included. Exercise Testing An initial bout of treadmill walking at 0 incline was first performed to assess gait safety and to select the target walking velocity for subsequent treadmill testing. 18 Patients were instructed to minimize handrail support to that necessary for stabilizing balance, and a gait support belt was worn as a safety measure but no assistance was provided unless gait difficulties were observed. Patients successfully completing at least 3 consecutive minutes of treadmill walking at greater than.09m/s (0.2mph) then proceeded to graded treadmill stress testing. After 15 minutes of seated rest, a constant-velocity, progressive GXT to volitional fatigue was performed using a Sensor- Medics Max 1001 treadmill a with continuous electrocardiogram b and vital signs monitoring. The GXT was terminated on patient request if gait instability was observed or according to the guidelines of the American College of Sports Medicine. 19 Eligible patients included those achieving adequate exercise intensities of 70% or more of age-predicted heart rate maximum (HRmax) without significant signs of myocardial ischemia or other contraindications to participating in low-to-moderate intensity aerobic exercise training. 19 On 2 separate days, a submaximal treadmill exercise test (submax test), with the measurement of V O2, was performed to determine the economy of gait. This test consisted of a constant-rate submaximal treadmill task, representative of slow hemiparetic ambulation, using the same velocity calibrated treadmill, with patients wearing the same shoes and/or orthoses on each testing occasion. Because untrained hemiparetic stroke patients cannot typically sustain their self-selected floor walking velocity (SSWV) on a treadmill, 6,20,21 testing was performed at 70% of their average SSWV, which also elicited approximately 70% of each individual s HRmax. Pulmonary ventilation, V O2, carbon dioxide production, and the respiratory exchange ratio (RER) were continuously measured with a metabolic system. a The initial 6 minutes of the walking test allowed for steady-state V O2 to be achieved, and the mean rate of V O2 was determined from the subsequent 3 minutes of walking. If patients could not tolerate walking for 10 minutes, they were encouraged to complete a minimum of 5 minutes, and the mean rate of V O2 was determined from the final 3 minutes of walking. After a 15-minute rest period, peak exercise capacity (VO 2 peak) was measured by open-circuit spirometry during constant-velocity, progressive, graded treadmill testing to volitional fatigue. Both peak and submaximal treadmill tests were repeated on separate days, 1 week apart, at the same time of day, approximately 1 to 2 hours after a light meal, using the same protocol. This allowed for quantification of reliability. The same testers were used for the repeated tests. Safety Issues All patients wore a gait belt during their initial GXT. No assistance was provided unless the supervising physician observed gait instability. Participants were always instructed to grasp the handrail on the treadmill with at least 1 hand for support. Each patient was continuously observed for gait instability during all treadmill tests. The reliability coefficient 22 was calculated to determine reliability for the parameters of heart rate, oxygen consumption, RER, systolic blood pressure (SBP), diastolic blood pressure, and oxygen pulse during both the submaximal and peak treadmill tests. High reliability was defined as r greater than Fig 1. Screening summary outlining the number of volunteers qualifying for each phase of the study.

3 1310 TREADMILL TEST RELIABILITY IN STROKE, Dobrovolny Table 1: Physical Characteristics Mean Range Age (y) Weight (kg) Height (cm) Body mass index (kg/m 2 ) Latency (mo) Self-selected walking speed (mph) NOTE. Values are mean SD (N 53). All analyses were performed using Statistical Analysis Package. c Data are reported as means standard deviations (SDs). RESULTS A total of 88 patients with a history of ischemic stroke ( 6mo earlier) and mild to moderate chronic hemiparetic gait deficits, were recruited from the Baltimore VA and University of Maryland Medical Systems and underwent screening evaluations (fig 1). We enrolled 53 of these patients, including 44 men and 9 women, with a mean age of 65 8 years (range, 46 85y). Thirty-six patients were African American and 17 were white. Fifteen of the patients wore an ankle-foot orthoses. Twenty-five patients needed a single-point cane for ambulation, 10 used a quad cane, and 5 needed a walker. Location of stroke was almost evenly distributed, with 23 patients having a right-hemisphere stroke with left hemiparesis, 24 having a left-hemisphere stroke with right hemiparesis, 1 patient having bilateral strokes, 2 patients having brainstem strokes, and 4 patients having cerebellar strokes. Further details related to the subject characteristics, and level of disability can be seen in table 1. Table 3: Reliability of Submaximal Exercise Testing Measurements in Stroke Patients Parameter Test 1 Test 2 Reliability Coefficient 95% CI Heart rate (bpm) O 2 (L/min) * O 2 (ml kg 1 min 1 ) RER Oxygen pulse (ml/beat) * NOTE. Values are mean SD (n 51). *P.05. Peak Exercise Test Comparison of the 2 peak treadmill tests (VO 2 peak) performed 1 week apart allowed for the determination of the reliability coefficient for a number of cardiopulmonary parameters. Patients completed the peak tests at mph, at a 9% 4% grade in minutes. During these tests, only 9% of our stroke patients achieved a true V O2 max based on RER greater than 1.1 and achievement of age-predicted HRmax. Reliability data for the peak exercise test was determined in 53 subjects, as shown in table 2. VO 2 peak (expressed both as ml kg 1 min 1 and L/min) was highly reliable in the stroke patients tested (r.92) (table 2). In addition, HRpeak (r.87) and oxygen pulse (r.93) were highly reliable in these patients. Postexercise SBP, peak RER, and peak rate-pressure product (RPP) had reliability coefficients that fell below the previously defined highly reliable range (.85) (table 2). Submaximal Exercise Test Data from the 2 submaximal treadmill tests (walking economy) are shown in table 3. Testing was completed at mph, 0% grade, and the duration was minutes. Thirty-two of 51 patients completed 9 to 10 minutes of walking, 9 completed 7 to 8 minutes, and 10 completed 5 to 6 minutes of submaximal walking. (Data for 2 of the subjects submaximal tests were irretrievable because of computer equipment error.) Fatigue was the primary reason cited for stopping the test in all patients during the submaximal testing. Reliability was determined in 51 subjects for heart rate, V O2 (L/min), V O2 (ml kg 1 min 1 ), RER, and oxygen pulse. Data from the 2 submaximal exercise tests revealed high reliability for V O2 (L/min) and oxygen pulse (r.89, r.85, respectively). Heart rate and V O2 (ml kg 1 min 1 ) fell just below the.85 cutoff, while RER proved the least reliable of the 4 parameters measured during submaximal exercise testing (table 3). DISCUSSION This is the first study to demonstrate that peak treadmill testing is highly reproducible in older chronic hemiparetic stroke patients. A high reliability coefficient associated with heart rate, VO 2 (L/min), VO 2 (ml kg 1 min 1 ), and oxygen pulse provides evidence that peak exercise testing is reliable in this population. Studies 24,25 have shown that the test-retest reliability of maximal exercise testing is high (r range,.95.99) in young, healthy individuals. Four studies have evaluated the reliability of maximal V O2 testing in older individuals. Sidney and Shephard 28 performed V O2 max testing in 15 sedentary men and Table 2: Reliability of Peak Exercise Testing Measurements in Stroke Patients Parameter Test 1 Test 2 Reliability Coefficient 95% CI HRpeak (bpm) * SBP (mmhg) (postexercise) Vo 2 peak (L/min) * VO 2 peak (ml kg 1 min 1 ) * RER peak (CO 2 output/o 2 uptake) RPP peak 21, , Oxygen pulse peak (ml/beat) * NOTE. Values are mean SD (N 53). Abbreviation: CI, confidence interval. *P.05.

4 TREADMILL TEST RELIABILITY IN STROKE, Dobrovolny 1311 women aged 60 to 83 years, and showed that repeat testing yielded a correlation coefficient of.96 in men and.86 in women. The reproducibility of V O2 max data and submaximal measures of fitness was measured by Foster et al 27 in 8 healthy, sedentary, 80-year-old women. The subjects performed 3 incremental maximal treadmill tests 5 to 10 days apart. No significant differences were found in V O2 max between trials, measured either in L/min (.77.79) or ml kg 1 min 1 ( ). In addition, there were no differences in HRmax between the 3 tests. The use of ventilatory or lactate thresholds as submaximal measures of fitness was determined not to be applicable for women in the eighth decade of life, because thresholds were not definable. Tonino and Driscoll 29 estimated the reliability of cardiopulmonary parameters associated with maximal and submaximal treadmill testing in 9 healthy older subjects, aged 62 to 79 years. The subjects performed repeat tests 1 week apart and were allowed to lightly grip the handrail during testing. No significant differences were noted between the trials for HRmax and V O2 max (ml kg 1 min 1 ). However, submaximal heart rate decreased 4% and submaximal V O2 decreased 5% between trials. There was no reported difference in maximal RER between tests. The authors concluded that V O2 max was a reliable measure in healthy older adults, but submaximal heart rate and V O2 data were not. The reliability of the VO 2 peak measurements in the older stroke patients in our study was comparable with the reproducibility of V O2 max assessments in cardiac patients (r.95) and in healthy older men and women (r range,.86.96). 24,28 It should be emphasized, however, that only 9% of our stroke patients undergoing maximal-effort treadmill testing achieved a true V O2 max based on RER greater than 1.1 and achievement of age-predicted HRmax. Most of our stroke patients failed to achieve a true V O2 max and, on average, only reached 81% of the age-predicted maximum heart rate during maximal testing in our laboratory, due to a variety of causes including medications (21% were on -blockers), biomechanical limitations, physical deconditioning, or some combination of these factors. Nevertheless, it was important to establish that peak VO 2 measurements obtained from disabled stroke patients are reliable to assess their utility in detecting potential changes elicited by an exercise training intervention. Use of the same testers on the 2 occasions of peak testing may have introduced a potential bias. However, testers sought to minimize this bias by not reviewing the specific oxygen consumption values of the first test before conducting the second a week later. In addition, patients were unaware of their performance, eliminating that potential source of bias. All patients exercised to volitional fatigue during the maximal test on both occasions. The reproducibility of peak VO 2 testing is further substantiated by a study in younger stroke patients, aged 43 to 72 years. Potempa et al 10 reported on the reliability of peak cycle ergometry after 2 tests were conducted within 48 hours of each other on 25 randomly selected stroke patients. The reliability of the peak test responses was high, with intraclass correlation coefficients of.94 for VO 2 peak,.97 for heart rate,.99 for work rate, and.83 for SBP. Thus, maximal-effort exercise testing in younger stroke patients was found to be reliable using a cycle ergometer. These figures are comparable with our present findings for VO 2 peak (r.92) and heart rate (r.87). It was important to establish that cardiopulmonary parameters were reliable during treadmill walking because, unlike cycle ergometry, there exists the large potential confounder of significant handrail support necessary for hemiparetic ambulation. In the current investigation, we found that submaximal data from treadmill testing was reliable for V O2 (L/min) in our population of chronic hemiparetic stroke patients. V O2 (ml kg 1 min 1 ), the second most important reliability measure, fell slightly below the pre-established criterion for high reliability during submaximal testing (r.84). We interpret this minor discrepancy between the test-retest reliability for V O2 adjusted according to body mass and absolute rate of V O2 (L/min) on the submaximal testing as attributable to minor fluctuations in the weight of the stroke patients, which were observed between tests. CONCLUSION The results show that the measurement of peak functional capacity by graded treadmill exercise testing in stroke patients was very reliable for the measures of heart rate and V O2. Our results do not support previous efforts in healthy elderly populations, which suggest that submaximal effort testing is not reliable. In the older chronic hemiparetic stroke population, our method of submaximal testing proved to be reliable for V O2 (L/min). References 1. Williams GR, Jiang JG, Matchar DB, Samsa GP. Incidence and occurrence of total (first ever and recurrent) stroke. Stroke 1999; 30: Wade DT, Hewer RL. Functional abilities after stroke: measurement, natural history and prognosis. J Neurol Neurosurg Psychiatry 1987;50: Gresham GE, Fitzpatrick TE, Wolf PA, McNamara PM, Kannel WB, Dawber TR. Residual disability in survivors of stroke the Framingham study. N Engl J Med 1975;293: Gresham GE, Phillips TF, Wolf PA, McNamara PM, Kannel WB, Dawber TR. Epidemiologic profile of long-term stroke disability: the Framingham study. Arch Phys Med Rehabil 1979;60: Jorgensen HS, Nakayama H, Raaschou HO, Olsen TS. Recovery of walking function in stroke patients: the Copenhagen stroke study. Arch Phys Med Rehabil 1995;76: Corcoran PJ, Jebsen RH, Brengelmann GL, Simons BC. Effects of plastic and metal leg braces on speed and energy cost of hemiparetic ambulation. Arch Phys Med Rehabil 1970;51: Gersten JW, Orr W. External work of walking in hemiparetic patients. Scand J Rehabil Med 1971;3: Macko RF. Functional mobility in chronic hemiparetic stroke patients [abstract]. J Investig Med 1998;46:192A. 9. Macko RF, Desouza CA, Tretter LD, et al. Treadmill aerobic exercise training reduces the energy expenditure and cardiovascular demands of hemiparetic gait in chronic stroke patients. A preliminary report. Stroke 1997;28: Potempa K, Lopez M, Braun LT, Szidon JP, Fogg L, Tincknell T. Physiological outcomes of aerobic exercise training in hemiparetic stroke patients. Stroke 1995;26: Rimmer JH, Riley B, Creviston T, Nicola T. Exercise training in a predominantly African-American group of stroke survivors. Med Sci Sports Exerc 2000;32: Smith GV, Macko RF, Silver KH, Goldberg AP. Aerobic exercise training improves quadriceps strength in chronic hemiparetic stroke survivors: preliminary report. J Neurorehabil Neural Repair 1998;12: Smith GV, Anderson PA, Silver KH, Macko RF. Task-oriented treadmill exercise training reduces spasticity and improves hamstring strength in chronic hemiparetic stroke patients: preliminary report. Stroke 1999;30: Silver KH, Macko RF, Goldberg AP, Smith GV. Effects of aerobic treadmill training on gait velocity, cadence, and gait symmetry in chronic hemiparetic stroke. J Neurorehabil Neural Repair 2000;14: Smith GV, Forrester L, Urban S, Silver KH, Macko RF. Effects of treadmill training on translational balance perturbation response in chronic hemiparetic stroke patients. J Stroke Cerebrovasc Disord 2000;9:

5 1312 TREADMILL TEST RELIABILITY IN STROKE, Dobrovolny 16. Forrester LW, Macko RF, Smith GV. Short-term treadmill exercise in chronic stroke: evidence of differential fatigue effects in quadriceps muscles. In: Proceedings of the 3rd World Congress in Neurological Rehabilitation; 2002 Apr 2-6; Venice, Italy. p Christman SK, Fish AF, Bernhard L, Frid DJ, Smith BA, Mitchell L. Continuous handrail support, oxygen uptake, and heart rate in women during submaximal step treadmill exercise. Res Nurs Health 2000;23: Macko RF, Katzel LI, Yataco A, et al. Low-velocity graded treadmill stress testing in hemiparetic stroke patients. Stroke 1997;28: American College of Sports Medicine. ACSM s guidelines for exercise testing and prescription. Philadelphia: Lea & Febiger; Bard B. Energy expenditure of hemiplegic subjects during walking. Arch Phys Med Rehabil 1963;44: Mol VJ, Baker CA. Activity intolerance in the geriatric stroke patient. Rehabil Nurs 1991;16: Winer BJ. Statistical principles in experimental design. New York: McGraw-Hill; Safrit MJ. Measurement in physical education and exercise science. St. Louis: Times Mirror/Mosby College Publishing; Bruce RA, Kusumi F, Hosmer D. Maximal oxygen uptake and nomographic assessment of functional aerobic impairment in cardiovascular disease. Am Heart J 1973;85: Taylor HL. Maximal oxygen uptake as a measure of cardiovascular performance. J Appl Physiol 1955;8: Fielding RA, Frontera WR, Hughes VA, Fisher EC, Evans WJ. The reproducibility of the Bruce protocol exercise test for the determination of aerobic capacity in older women. Med Sci Sports Exerc 1997;29: Foster VL, Hume GJ, Dickinson AL, Chatfield SJ, Byrnes WC. The reproducibility of VO 2 max, ventilatory, and lactate thresholds in elderly women. Med Sci Sports Exerc 1986;18: Sidney KH, Shephard RJ. Maximum and submaximum exercise tests in men and women in the seventh, eighth, and ninth decades of life. J Appl Physiol 1977;43: Tonino RP, Driscoll PA. Reliability of maximal and submaximal parameters of treadmill testing for the measurement of physical training in older persons. J Gerontol A Biol Sci Med Sci 1988; 43:M Suppliers a. SensorMedics, Savi Ranch Pkwy, Yorba Linda, CA b. MAX-1ECG; GE Medical Systems, Milwaukee, WI c. SAS Institute Inc, 100 SAS Campus Dr, Cary, NC