PM R xx (2014) 1-6
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Original Research
Use of an Ankle-Foot Orthosis Improves Aerobic Capacity in Subacute Hemiparetic Stroke Patients Chul Woong Hyun, MD, Bo Ryun Kim, MD, PhD, Eun Young Han, MD, Sun Mi Kim, MD
Abstract Objective: To investigate aerobic capacity with and without an ankle-foot orthosis (AFO) in subacute hemiparetic stroke patients. Design: Prospective crossover intervention study. Setting: Rehabilitation clinic in secondary care. Patients: Patients diagnosed with first-ever cerebral stroke involving the cortical or subcortical area resulting in hemiparesis (n ¼ 15, 8 men and 7 women; average age, 62.1 years). Methods: All subjects participated in 2 continuous, symptom-limited, low-velocity graded treadmill exercise stress tests under 2 different conditions, namely, with and without an AFO. The rest interval between tests was at least 48 hours. The order of exercise stress tests was randomized. Main Outcome Measurements: To assess cardiorespiratory responses, oxygen consumption, heart rate, systolic blood pressure, diastolic blood pressure, rate-pressure product, and respiratory exchange ratio were measured continuously throughout the test, and peak values were obtained. The rating of perceived exertion was recorded immediately after each test. The percentage of the age-predicted maximal heart rate and total exercise duration were also measured. Gait function was assessed by the SixMinute Walk Test. Results: Using an AFO significantly increased peak oxygen consumption and Six-Minute Walk Test results. Peak values of each of heart rate, systolic blood pressure, diastolic blood pressure, rate-pressure product, and respiratory exchange ratio, rating of perceived exertion, percentage of age-predicted maximal heart rate, and total exercise duration were similar regardless of AFO use. Conclusions: Use of an AFO may improve aerobic capacity in subacute hemiparetic stroke patients, and may improve energy efficiency and gait endurance.
Introduction A major cause of disability is stroke, a common symptom of which is impaired gait function [1]. Although one study [2] reported that 85% of patients are able to walk independently with or without an aid at 6 months after their stroke, only 25% of these patients regain a normal gait pattern. After stroke, residual hemiparesis mostly leads to an asymmetrical gait pattern; that is, stroke patients show a typical gait characterized by muscle weakness, impaired balance, and poor intermuscular interjoint/intersegmental coordination [3,4]. Walking with a hemiparetic gait requires more energy than walking with a normal gait [5], and immobilityrelated deconditioning increases cardiovascular risk for stroke patients in a vicious cycle [6,7].
A recent study [8] reported that hemiparetic gait patterns may increase the energy cost of walking, thereby limiting activities of daily living (ADL) and impairing aerobic capacity in chronic stroke patients. The standard method for estimating aerobic capacity is to measure oxygen consumption (VO2) [9]. One study [10] of 25 adult hemiparetic patients with subacute stroke showed that VO2 peak was as low as 60% to 70% of the age- and gender-related normative values for sedentary individuals. Another study reported that gait deviation caused by muscle weakness could decrease one’s ability to reach maximal aerobic capacity as assessed using standard exercise stress tests [11]. Ankle-foot orthoses (AFOs) are usually prescribed for stroke patients with a hemiparetic gait. A recent study reported that AFOs prevent the paretic foot from
1934-1482/$ - see front matter ª 2014 by the American Academy of Physical Medicine and Rehabilitation http://dx.doi.org/10.1016/j.pmrj.2014.08.944
2
Ankle-Foot Orthoses in Subacute Stroke Patients
dragging when patients walk, and that AFO use may decrease the energy cost of walking and increase speed in people with chronic stroke [8]. However, this study recruited only chronic stroke patients and measured limited values, such as energy consumption, by a treadmill test on even level ground at a constant walking speed. For these reasons, the results are not readily generalizable to environments encountered in real life, such as variable gradients, or to other subgroups of stroke patients. A major rehabilitation goal for stroke patients is to increase their functional exercise capacity and walking endurance in the community. We hypothesized that using an AFO on the hemiparetic lower limb could improve aerobic capacity and walking endurance in subacute stroke patients. Therefore, this study aimed to measure cardiorespiratory responses of subacute stroke patients elicited during an incremental exercise stress test during which the gradient is increased gradually. Patients carried out the stress test twice, once with and once without an AFO. The results were compared to demonstrate whether AFOs confer any benefit in terms of cardiovascular fitness and gait endurance during walking in the sorts of reallife environments encountered by these patients. Methods Participants In total, 15 patients (8 men and 7 women; average age, 62.1 years; range, 45-76 years) with subacute (ie, within 3 months) stroke participated in this study. The patients were recruited after attendance at the Department of Physical Medicine and Rehabilitation in our hospital between September 2012 and June 2013 for first-ever cerebral stroke involving the cortical or subcortical area. Their diagnosis was confirmed clinically by computed tomography or magnetic resonance imaging. Patient evaluation included a medical history, physical and neurological examinations, a resting 12lead electrocardiogram (ECG; CH 2000 Cardiac Diagnostic System, Cambridge Heart Inc, Tewksbury, MA), and calculation of body mass index (BMI). Our inclusion criteria included the ability to walk at least 3 minutes with or without an aid, but without standby assistance, and an ankle dorsiflexor muscle weakness grade of “less than fair” on the hemiparetic side as assessed manually by muscle test. Exclusion criteria were as follows: advanced congestive heart failure, peripheral arterial disease with claudication, unstable angina, uncontrolled hypertension (>190/110 mm Hg), severe cognitive impairment with a Korean version of the MiniMental Status Examination (K-MMSE) score of 200 mm Hg; or (4) HR peak within 15 beats per minute of the predicted maximal HR [16]. Gait function was assessed using the Six-Minute Walk Test (6MWT) performed along a 50-m corridor. This is a commonly used, standardized measure of exercise tolerance and functional walking capacity in people with compromised mobility [17]. Patients were instructed to walk along without disturbance, and could use their customary assistive devices during the test, but were requested to walk without support when possible. Statistical Analyses All statistical analyses were performed using the SPSS statistical package (version 14.0, SPSS Inc, Chicago, IL). All measures were quantified using descriptive statistics. The Wilcoxon signed-rank test was used to compare peak cardiorespiratory responses and 6MWT test results obtained with and without AFO. A P value .05). Discussion In the present study, we found that wearing an AFO had a beneficial effect on cardiovascular fitness and gait endurance of subacute stroke patients during walking. We confirmed that using an AFO increased VO2 peak during incremental exercise stress testing at variable inclines, as well as the distance walked during the 6MWT. The HR peak and RPP peak achieved by the subjects were similar to each other with and without the use of an AFO, indicating that use of an AFO when walking may increase the energy efficiency of muscles. A possible explanation of this finding is that, when using an AFO, patients have a more normalized gait, in which the actions of their pelvis, hips, knees, and ankles are well coordinated, enhancing efficiency and energy expenditure. Especially, with the AFOs, reduction of a steppage gait pattern may have enhanced the efficiency of energy expenditure. In addition, the added stability of the AFOs may have improved pelvic motion, thus reducing the vertical displacement. Finally, the added stability in controlling dorsiflexion may have assisted in normalizing the closely linked actions of ankle and knee motion. Such changes may have contributed a combined
reduction in both the physiologic demand and total volume of active skeletal muscle [18]. Several studies [19-21] assessing the mechanical functioning of AFOs in stroke patients reported that they reduced the amount of work required at the ankle, but the positive hip work showed a tendency to increase by using the AFO in those patients. We did not confirm these findings by measuring kinematic and kinetic parameters of joint movement, and neither did we obtain electromyograms from lower limb muscles through gait analysis; arguably, however, AFOs may help to address problems arising from fatigue of the lower limb muscles caused by lack of motor control or motor asymmetry between paretic limb and nonparetic limb. The exact mechanism for improved peak aerobic capacity using instrumental gait analysis would be warranted through further investigation. Previous studies of the benefits of AFOs in hemiparetic stroke patients during walking focused primarily on the analysis of energy consumption, rather than peak cardiorespiratory responses [22-24]. These studies reported that AFOs decreased energy cost calculated per unit distance traveled, improved physiological performance, and resulted in a relative reduction in physiological demand. An important point to note about our study is that we evaluated peak aerobic capacity and walking endurance at a comfortable walking speed on uneven ground with and without an AFO. By contrast, most studies mainly measure peak cardiorespiratory responses in stroke patients during incrementally graded exercise stress tests, adjusting both speed and incline. After discharge from hospital, hemiparetic stroke patients are often reluctant to wear the AFO on their hemiparetic side during ambulation or ADLs, mainly because of discomfort during donning the AFO. Therefore, our study has clinically
C.W. Hyun et al. / PM R xx (2014) 1-6
important implications for subacute hemiparetic stroke patients, as it indicates the value of emphasizing the benefits of AFOs in terms of enhancing independent living through improved cardiovascular fitness and endurance. In addition, the VO2 peak of stroke patients was found to be less than that in a group of age- and gendermatched, nondisabled, sedentary but otherwise healthy individuals in whom VO2 peak levels ranged between 25 and 30 mL$kg1$min1 [25]. The reduced cardiovascular fitness is possibly due to central factors, such as lower than normal cardiac output, as well as peripheral factors, such the loss of strength and coordination reducing the number of recruitable motor units [26] and diminished capacity for oxidative metabolism in paretic muscle tissue [27]. The low aerobic capacity in stroke survivors may increase the energy costs of any movements that involve residual functional deficits, leading to low levels of social participation and a poor quality of life [28]. Our results suggest that using AFOs may improve energy efficiency during walking and may have a positive impact on social participation and quality of life for subacute hemiparetic stroke patients. Gait endurance is an important factor enabling stroke patients to carry out meaningful ADLs [29]. In our study, wearing an AFO significantly improved 6MWT (which is closely correlated with gait endurance); therefore, our results suggest that gait endurance of stroke patients may be improved by using AFOs in the absence of extra walking training. A possible explanation for these findings is that the increased VO2 peak associated with using an AFO leads to increased energy efficiency and improved gait, enabling patients to walk farther. The added stability may also improve gait endurance, most likely through facilitating a biomechanical effect of the orthosis. Study Limitations This study has several limitations. First, the sample size was relatively small; thus, we did not perform subgroup analysis according to stroke type or area. Second, although our subjects had ankle dorsiflexor muscle weakness graded less than fair on their hemiparetic side, all patients could walk for at least 3 minutes with or without an aid but without standby assistance. Therefore, these findings have limited generalizability, and are not applicable to all subacute stroke patients needing an AFO because of ankle dorsiflexor muscle weakness. Third, we could not evaluate aerobic capacity using different types of AFOs. Use of different types of AFOs would possibly change the results. Finally, we did not consider the effect of gait speed when comparing peak cardiorespiratory responses when using and not using an AFO, because we focused on the change of peak cardiorespiratory response at a comfortable walking speed.
5
Conclusions We evaluated the effects of using AFOs on peak cardiorespiratory responses to a graded exercise test in subacute hemiparetic stroke patients. Our study demonstrated that use of an AFO may improve aerobic capacity in these patients. These findings suggest that using an AFO could have a beneficial effect on cardiovascular fitness and gait endurance in subacute hemiparetic stroke patients. References 1. Foulkes MA, Wolf PA, Price TR, et al. The Stroke Data Bank: Design, methods, and baseline characteristics. Stroke 1988;19:547-554. 2. Wade D, Hewer RL. Functional abilities after stroke: Measurement, natural history and prognosis. J Neurol Neurosurg Psychiatry 1987; 50:177-182. 3. Waters RL, Mulroy S. The energy expenditure of normal and pathologic gait. Gait Posture 1999;9:207-231. 4. Hsu A, Tang P, Jan M. Analysis of impairments influencing gait velocity and asymmetry of hemiplegic patients after mild to moderate stroke. Arch Phys Med Rehabil 2003;84:1185-1193. 5. Gersten JW, Orr W. External work of walking in hemiparetic patients. Scand J Rehabil Med 1971;3:85-88. 6. Lakka TA, Laukkanen JA, Rauramaa R, et al. Cardiorespiratory fitness and the progression of carotid atherosclerosis in middleaged men. Ann Intern Med 2001;134:12-20. 7. Sui X, LaMonte MJ, Blair SN. Cardiorespiratory fitness as a predictor of nonfatal cardiovascular events in asymptomatic women and men. Am J Epidemiol 2007;165:1413-1423. 8. Thijssen DH, Paulus R, van Uden CJ, et al. Decreased energy cost and improved gait pattern using a new orthosis in persons with long-term stroke. Arch Phys Med Rehabil 2007;88:181-186. 9. Danielsson A, Wille ´n C, Sunnerhagen KS. Measurement of energy cost by the physiological cost index in walking after stroke. Arch Phys Med Rehabil 2007;88:1298-1303. 10. Pang MY, Eng JJ, Dawson AS, et al. The use of aerobic exercise training in improving aerobic capacity in individuals with stroke: A meta-analysis. Clin Rehabil 2006;20:97-111. 11. Eng JJ, Dawson AS, Chu KS. Submaximal exercise in persons with stroke: Test-retest reliability and concurrent validity with maximal oxygen consumption. Arch Phys Med Rehabil 2004;85:113-118. 12. Kelly JO, Kilbreath SL, Davis GM, et al. Cardiorespiratory fitness and walking ability in subacute stroke patients. Arch Phys Med Rehabil 2003;84:1780-1785. 13. Macko R, Katzel L, Yataco A, et al. Low-velocity graded treadmill stress testing in hemiparetic stroke patients. Stroke 1997;28:988-992. 14. Kim BR, Han EY, Joo SJ, et al. Cardiovascular fitness as a predictor of functional recovery in subacute stroke patients. Disabil Rehabil 2014;36:227-231. 15. Thompson WR, Gordon NF, Pescatello LS. ACSM’s guidelines for exercise testing and prescription. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009. 16. Howley ET, Bassett DR, Welch HG. Criteria for maximal oxygen uptake: Review and commentary. Med Sci Sports Exerc 1995;27: 1292-1301. 17. Tang A, Sibley KM, Bayley MT, et al. Do functional walk tests reflect cardiorespiratory fitness in sub-acute stroke? J Neuroeng Rehabil 2006;3:23. 18. Bean J, Walsh A, Frontera W. Brace modification improves aerobic performance in Charcot-Marie-Tooth disease: A single-subject design. Am J Phys Med Rehabil 2001;80:578-582. 19. Desloovere K, Molenaers G, Van Gestel L, et al. How can push-off be preserved during use of an ankle foot orthosis in children with
Ankle-Foot Orthoses in Subacute Stroke Patients
6
20.
21.
22.
23.
hemiplegia? A prospective controlled study. Gait Posture 2006;24: 142-151. Wolf SI, Alimusaj M, Rettig O, et al. Dynamic assist by carbon fiber spring AFOs for patients with myelomeningocele. Gait Posture 2008;28:175-177. ˚ , Eriksson M, Gutierrez-Farewik EM. Effects of carbon Bartonek A fibre spring orthoses on gait in ambulatory children with motor disorders and plantarflexor weakness. Dev Med Child Neurol 2007; 49:615-620. Maeda N, Kato J, Azuma Y, et al. Energy expenditure and walking ability in stroke patients: Their improvement by ankle-foot orthoses. Isokinetics Exerc Sci 2009;17:57-62. Franceschini M, Massucci M, Ferrari L, et al. Effects of an anklefoot orthosis on spatiotemporal parameters and energy cost of hemiparetic gait. Clin Rehabil 2003;17:368-372.
24. Fatone S, Gard SA, Malas BS. Effect of ankle-foot orthosis alignment and foot-plate length on the gait of adults with poststroke hemiplegia. Arch Phys Med Rehabil 2009;90:810818. 25. Ivey F, Macko R, Ryan A, et al. Cardiovascular health and fitness after stroke. Top Stroke Rehabil 2005;12:1-16. 26. Burke D. Spasticity as an adaptation to pyramidal tract injury. Adv Neurol 1988;47:401-423. 27. Potempa K, Braun LT, Tinknell T, et al. Benefits of aerobic exercise after stroke. Sports Med 1996;21:337-346. 28. Nancy EM, Sharon WD, Sara A, et al. Disablement following stroke. Disabil Rehabil 1999;21:258-268. 29. Liu J, Drutz C, Kumar R, et al. Use of the Six-Minute Walk Test poststroke: Is there a practice effect? Arch Phys Med Rehabil 2008; 89:1686-1692.
Disclosure C.W.H. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose
E.Y.H. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose
B.R.K. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Aran 13 gil 15, Jeju-si, Jeju, 690-767, Republic of Korea. Address correspondence to: B.R.K.; e-mail: [email protected] Disclosure: nothing to disclose
S.M.K. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose This work was supported by the research grant from the Hyocheon Academic Research Fund of Jeju National University in 2012. Submitted for publication June 2, 2014; accepted August 10, 2014.
www.pmrjournal.org
Original Research
Use of an Ankle-Foot Orthosis Improves Aerobic Capacity in Subacute Hemiparetic Stroke Patients Chul Woong Hyun, MD, Bo Ryun Kim, MD, PhD, Eun Young Han, MD, Sun Mi Kim, MD
Abstract Objective: To investigate aerobic capacity with and without an ankle-foot orthosis (AFO) in subacute hemiparetic stroke patients. Design: Prospective crossover intervention study. Setting: Rehabilitation clinic in secondary care. Patients: Patients diagnosed with first-ever cerebral stroke involving the cortical or subcortical area resulting in hemiparesis (n ¼ 15, 8 men and 7 women; average age, 62.1 years). Methods: All subjects participated in 2 continuous, symptom-limited, low-velocity graded treadmill exercise stress tests under 2 different conditions, namely, with and without an AFO. The rest interval between tests was at least 48 hours. The order of exercise stress tests was randomized. Main Outcome Measurements: To assess cardiorespiratory responses, oxygen consumption, heart rate, systolic blood pressure, diastolic blood pressure, rate-pressure product, and respiratory exchange ratio were measured continuously throughout the test, and peak values were obtained. The rating of perceived exertion was recorded immediately after each test. The percentage of the age-predicted maximal heart rate and total exercise duration were also measured. Gait function was assessed by the SixMinute Walk Test. Results: Using an AFO significantly increased peak oxygen consumption and Six-Minute Walk Test results. Peak values of each of heart rate, systolic blood pressure, diastolic blood pressure, rate-pressure product, and respiratory exchange ratio, rating of perceived exertion, percentage of age-predicted maximal heart rate, and total exercise duration were similar regardless of AFO use. Conclusions: Use of an AFO may improve aerobic capacity in subacute hemiparetic stroke patients, and may improve energy efficiency and gait endurance.
Introduction A major cause of disability is stroke, a common symptom of which is impaired gait function [1]. Although one study [2] reported that 85% of patients are able to walk independently with or without an aid at 6 months after their stroke, only 25% of these patients regain a normal gait pattern. After stroke, residual hemiparesis mostly leads to an asymmetrical gait pattern; that is, stroke patients show a typical gait characterized by muscle weakness, impaired balance, and poor intermuscular interjoint/intersegmental coordination [3,4]. Walking with a hemiparetic gait requires more energy than walking with a normal gait [5], and immobilityrelated deconditioning increases cardiovascular risk for stroke patients in a vicious cycle [6,7].
A recent study [8] reported that hemiparetic gait patterns may increase the energy cost of walking, thereby limiting activities of daily living (ADL) and impairing aerobic capacity in chronic stroke patients. The standard method for estimating aerobic capacity is to measure oxygen consumption (VO2) [9]. One study [10] of 25 adult hemiparetic patients with subacute stroke showed that VO2 peak was as low as 60% to 70% of the age- and gender-related normative values for sedentary individuals. Another study reported that gait deviation caused by muscle weakness could decrease one’s ability to reach maximal aerobic capacity as assessed using standard exercise stress tests [11]. Ankle-foot orthoses (AFOs) are usually prescribed for stroke patients with a hemiparetic gait. A recent study reported that AFOs prevent the paretic foot from
1934-1482/$ - see front matter ª 2014 by the American Academy of Physical Medicine and Rehabilitation http://dx.doi.org/10.1016/j.pmrj.2014.08.944
2
Ankle-Foot Orthoses in Subacute Stroke Patients
dragging when patients walk, and that AFO use may decrease the energy cost of walking and increase speed in people with chronic stroke [8]. However, this study recruited only chronic stroke patients and measured limited values, such as energy consumption, by a treadmill test on even level ground at a constant walking speed. For these reasons, the results are not readily generalizable to environments encountered in real life, such as variable gradients, or to other subgroups of stroke patients. A major rehabilitation goal for stroke patients is to increase their functional exercise capacity and walking endurance in the community. We hypothesized that using an AFO on the hemiparetic lower limb could improve aerobic capacity and walking endurance in subacute stroke patients. Therefore, this study aimed to measure cardiorespiratory responses of subacute stroke patients elicited during an incremental exercise stress test during which the gradient is increased gradually. Patients carried out the stress test twice, once with and once without an AFO. The results were compared to demonstrate whether AFOs confer any benefit in terms of cardiovascular fitness and gait endurance during walking in the sorts of reallife environments encountered by these patients. Methods Participants In total, 15 patients (8 men and 7 women; average age, 62.1 years; range, 45-76 years) with subacute (ie, within 3 months) stroke participated in this study. The patients were recruited after attendance at the Department of Physical Medicine and Rehabilitation in our hospital between September 2012 and June 2013 for first-ever cerebral stroke involving the cortical or subcortical area. Their diagnosis was confirmed clinically by computed tomography or magnetic resonance imaging. Patient evaluation included a medical history, physical and neurological examinations, a resting 12lead electrocardiogram (ECG; CH 2000 Cardiac Diagnostic System, Cambridge Heart Inc, Tewksbury, MA), and calculation of body mass index (BMI). Our inclusion criteria included the ability to walk at least 3 minutes with or without an aid, but without standby assistance, and an ankle dorsiflexor muscle weakness grade of “less than fair” on the hemiparetic side as assessed manually by muscle test. Exclusion criteria were as follows: advanced congestive heart failure, peripheral arterial disease with claudication, unstable angina, uncontrolled hypertension (>190/110 mm Hg), severe cognitive impairment with a Korean version of the MiniMental Status Examination (K-MMSE) score of 200 mm Hg; or (4) HR peak within 15 beats per minute of the predicted maximal HR [16]. Gait function was assessed using the Six-Minute Walk Test (6MWT) performed along a 50-m corridor. This is a commonly used, standardized measure of exercise tolerance and functional walking capacity in people with compromised mobility [17]. Patients were instructed to walk along without disturbance, and could use their customary assistive devices during the test, but were requested to walk without support when possible. Statistical Analyses All statistical analyses were performed using the SPSS statistical package (version 14.0, SPSS Inc, Chicago, IL). All measures were quantified using descriptive statistics. The Wilcoxon signed-rank test was used to compare peak cardiorespiratory responses and 6MWT test results obtained with and without AFO. A P value .05). Discussion In the present study, we found that wearing an AFO had a beneficial effect on cardiovascular fitness and gait endurance of subacute stroke patients during walking. We confirmed that using an AFO increased VO2 peak during incremental exercise stress testing at variable inclines, as well as the distance walked during the 6MWT. The HR peak and RPP peak achieved by the subjects were similar to each other with and without the use of an AFO, indicating that use of an AFO when walking may increase the energy efficiency of muscles. A possible explanation of this finding is that, when using an AFO, patients have a more normalized gait, in which the actions of their pelvis, hips, knees, and ankles are well coordinated, enhancing efficiency and energy expenditure. Especially, with the AFOs, reduction of a steppage gait pattern may have enhanced the efficiency of energy expenditure. In addition, the added stability of the AFOs may have improved pelvic motion, thus reducing the vertical displacement. Finally, the added stability in controlling dorsiflexion may have assisted in normalizing the closely linked actions of ankle and knee motion. Such changes may have contributed a combined
reduction in both the physiologic demand and total volume of active skeletal muscle [18]. Several studies [19-21] assessing the mechanical functioning of AFOs in stroke patients reported that they reduced the amount of work required at the ankle, but the positive hip work showed a tendency to increase by using the AFO in those patients. We did not confirm these findings by measuring kinematic and kinetic parameters of joint movement, and neither did we obtain electromyograms from lower limb muscles through gait analysis; arguably, however, AFOs may help to address problems arising from fatigue of the lower limb muscles caused by lack of motor control or motor asymmetry between paretic limb and nonparetic limb. The exact mechanism for improved peak aerobic capacity using instrumental gait analysis would be warranted through further investigation. Previous studies of the benefits of AFOs in hemiparetic stroke patients during walking focused primarily on the analysis of energy consumption, rather than peak cardiorespiratory responses [22-24]. These studies reported that AFOs decreased energy cost calculated per unit distance traveled, improved physiological performance, and resulted in a relative reduction in physiological demand. An important point to note about our study is that we evaluated peak aerobic capacity and walking endurance at a comfortable walking speed on uneven ground with and without an AFO. By contrast, most studies mainly measure peak cardiorespiratory responses in stroke patients during incrementally graded exercise stress tests, adjusting both speed and incline. After discharge from hospital, hemiparetic stroke patients are often reluctant to wear the AFO on their hemiparetic side during ambulation or ADLs, mainly because of discomfort during donning the AFO. Therefore, our study has clinically
C.W. Hyun et al. / PM R xx (2014) 1-6
important implications for subacute hemiparetic stroke patients, as it indicates the value of emphasizing the benefits of AFOs in terms of enhancing independent living through improved cardiovascular fitness and endurance. In addition, the VO2 peak of stroke patients was found to be less than that in a group of age- and gendermatched, nondisabled, sedentary but otherwise healthy individuals in whom VO2 peak levels ranged between 25 and 30 mL$kg1$min1 [25]. The reduced cardiovascular fitness is possibly due to central factors, such as lower than normal cardiac output, as well as peripheral factors, such the loss of strength and coordination reducing the number of recruitable motor units [26] and diminished capacity for oxidative metabolism in paretic muscle tissue [27]. The low aerobic capacity in stroke survivors may increase the energy costs of any movements that involve residual functional deficits, leading to low levels of social participation and a poor quality of life [28]. Our results suggest that using AFOs may improve energy efficiency during walking and may have a positive impact on social participation and quality of life for subacute hemiparetic stroke patients. Gait endurance is an important factor enabling stroke patients to carry out meaningful ADLs [29]. In our study, wearing an AFO significantly improved 6MWT (which is closely correlated with gait endurance); therefore, our results suggest that gait endurance of stroke patients may be improved by using AFOs in the absence of extra walking training. A possible explanation for these findings is that the increased VO2 peak associated with using an AFO leads to increased energy efficiency and improved gait, enabling patients to walk farther. The added stability may also improve gait endurance, most likely through facilitating a biomechanical effect of the orthosis. Study Limitations This study has several limitations. First, the sample size was relatively small; thus, we did not perform subgroup analysis according to stroke type or area. Second, although our subjects had ankle dorsiflexor muscle weakness graded less than fair on their hemiparetic side, all patients could walk for at least 3 minutes with or without an aid but without standby assistance. Therefore, these findings have limited generalizability, and are not applicable to all subacute stroke patients needing an AFO because of ankle dorsiflexor muscle weakness. Third, we could not evaluate aerobic capacity using different types of AFOs. Use of different types of AFOs would possibly change the results. Finally, we did not consider the effect of gait speed when comparing peak cardiorespiratory responses when using and not using an AFO, because we focused on the change of peak cardiorespiratory response at a comfortable walking speed.
5
Conclusions We evaluated the effects of using AFOs on peak cardiorespiratory responses to a graded exercise test in subacute hemiparetic stroke patients. Our study demonstrated that use of an AFO may improve aerobic capacity in these patients. These findings suggest that using an AFO could have a beneficial effect on cardiovascular fitness and gait endurance in subacute hemiparetic stroke patients. References 1. Foulkes MA, Wolf PA, Price TR, et al. The Stroke Data Bank: Design, methods, and baseline characteristics. Stroke 1988;19:547-554. 2. Wade D, Hewer RL. Functional abilities after stroke: Measurement, natural history and prognosis. J Neurol Neurosurg Psychiatry 1987; 50:177-182. 3. Waters RL, Mulroy S. The energy expenditure of normal and pathologic gait. Gait Posture 1999;9:207-231. 4. Hsu A, Tang P, Jan M. Analysis of impairments influencing gait velocity and asymmetry of hemiplegic patients after mild to moderate stroke. Arch Phys Med Rehabil 2003;84:1185-1193. 5. Gersten JW, Orr W. External work of walking in hemiparetic patients. Scand J Rehabil Med 1971;3:85-88. 6. Lakka TA, Laukkanen JA, Rauramaa R, et al. Cardiorespiratory fitness and the progression of carotid atherosclerosis in middleaged men. Ann Intern Med 2001;134:12-20. 7. Sui X, LaMonte MJ, Blair SN. Cardiorespiratory fitness as a predictor of nonfatal cardiovascular events in asymptomatic women and men. Am J Epidemiol 2007;165:1413-1423. 8. Thijssen DH, Paulus R, van Uden CJ, et al. Decreased energy cost and improved gait pattern using a new orthosis in persons with long-term stroke. Arch Phys Med Rehabil 2007;88:181-186. 9. Danielsson A, Wille ´n C, Sunnerhagen KS. Measurement of energy cost by the physiological cost index in walking after stroke. Arch Phys Med Rehabil 2007;88:1298-1303. 10. Pang MY, Eng JJ, Dawson AS, et al. The use of aerobic exercise training in improving aerobic capacity in individuals with stroke: A meta-analysis. Clin Rehabil 2006;20:97-111. 11. Eng JJ, Dawson AS, Chu KS. Submaximal exercise in persons with stroke: Test-retest reliability and concurrent validity with maximal oxygen consumption. Arch Phys Med Rehabil 2004;85:113-118. 12. Kelly JO, Kilbreath SL, Davis GM, et al. Cardiorespiratory fitness and walking ability in subacute stroke patients. Arch Phys Med Rehabil 2003;84:1780-1785. 13. Macko R, Katzel L, Yataco A, et al. Low-velocity graded treadmill stress testing in hemiparetic stroke patients. Stroke 1997;28:988-992. 14. Kim BR, Han EY, Joo SJ, et al. Cardiovascular fitness as a predictor of functional recovery in subacute stroke patients. Disabil Rehabil 2014;36:227-231. 15. Thompson WR, Gordon NF, Pescatello LS. ACSM’s guidelines for exercise testing and prescription. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009. 16. Howley ET, Bassett DR, Welch HG. Criteria for maximal oxygen uptake: Review and commentary. Med Sci Sports Exerc 1995;27: 1292-1301. 17. Tang A, Sibley KM, Bayley MT, et al. Do functional walk tests reflect cardiorespiratory fitness in sub-acute stroke? J Neuroeng Rehabil 2006;3:23. 18. Bean J, Walsh A, Frontera W. Brace modification improves aerobic performance in Charcot-Marie-Tooth disease: A single-subject design. Am J Phys Med Rehabil 2001;80:578-582. 19. Desloovere K, Molenaers G, Van Gestel L, et al. How can push-off be preserved during use of an ankle foot orthosis in children with
Ankle-Foot Orthoses in Subacute Stroke Patients
6
20.
21.
22.
23.
hemiplegia? A prospective controlled study. Gait Posture 2006;24: 142-151. Wolf SI, Alimusaj M, Rettig O, et al. Dynamic assist by carbon fiber spring AFOs for patients with myelomeningocele. Gait Posture 2008;28:175-177. ˚ , Eriksson M, Gutierrez-Farewik EM. Effects of carbon Bartonek A fibre spring orthoses on gait in ambulatory children with motor disorders and plantarflexor weakness. Dev Med Child Neurol 2007; 49:615-620. Maeda N, Kato J, Azuma Y, et al. Energy expenditure and walking ability in stroke patients: Their improvement by ankle-foot orthoses. Isokinetics Exerc Sci 2009;17:57-62. Franceschini M, Massucci M, Ferrari L, et al. Effects of an anklefoot orthosis on spatiotemporal parameters and energy cost of hemiparetic gait. Clin Rehabil 2003;17:368-372.
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Disclosure C.W.H. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose
E.Y.H. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose
B.R.K. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Aran 13 gil 15, Jeju-si, Jeju, 690-767, Republic of Korea. Address correspondence to: B.R.K.; e-mail: [email protected] Disclosure: nothing to disclose
S.M.K. Department of Physical Medicine and Rehabilitation, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Republic of Korea Disclosure: nothing to disclose This work was supported by the research grant from the Hyocheon Academic Research Fund of Jeju National University in 2012. Submitted for publication June 2, 2014; accepted August 10, 2014.
