THE RESTORATION OF walking plays an important role in

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1 953 Oxygen Consumption During Treadmill Walking With and Without Body Weight Support in Patients With Hemiparesis After Stroke and in Healthy Subjects Anna Danielsson, BSc, RPT, Katharina Stibrant Sunnerhagen, MD, PhD ABSTRACT. Danielsson A, Sunnerhagen KS. Oxygen consumption during treadmill walking with and without body weight support in patients with hemiparesis after stroke and in healthy subjects. Arch Phys Med Rehabil 2000;81: From the Department of Rehabilitation Medicine, Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden. Submitted June 28, Accepted in revised form December 13, Supported by a grant (project 03888) from the Swedish National Board of Health and Welfare, Swedish Medical Research Council, and by the Swedish National Association for the Neurologically Handicapped. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Katharina Stibrant Sunnerhagen, Göteborg University, Department of Rehabilitation Medicine, S Göteborg, Sweden /00/ $3.00/0 doi: /apmr Objective: To compare oxygen consumption during walking with body weight support (BWS) with oxygen consumption during unsupported treadmill walking. Design: Patient and reference group. Comparisons between two walking conditions within each group. Setting: Research laboratory of a university hospital. Participants: Nonrandom convenience sample of 9 hemiparetic and 9 healthy subjects, mean age of 56 and 57 years, respectively. Interventions: The subjects walked on a treadmill with 0% and 30% BWS at their self-selected and maximum walking speeds. The trials were performed twice. Main Outcome Measures: Ventilatory oxygen uptake (VO 2 ) and heart rate were measured by computerized breath-by-breath analysis and electrocardiography. Results: VO 2 was lower during walking with 30% BWS than during unsupported walking. At self-selected speed the Wilcoxon s signed rank p values were.01 for both patients and reference group; at maximum velocity, p values were p.02 for the patients and p.05 for the reference group. Patients heart rates were lower when they walked with 30% BWS than at 0% BWS, at both self-selected and maximum walking speeds ( p.05 and p.02, respectively). Conclusions: The 30% body weight supported condition requires less oxygen consumption than full weight bearing. Treadmill training with BWS can be tolerated by patients with cardiovascular problems. Key Words: Cerebrovascular accident; Gait; Energy expenditure; Exercise test; Rehabilitation by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation THE RESTORATION OF walking plays an important role in the rehabilitation of patients who have hemiparesis after stroke. Most treatment strategies include weight-bearing exercises combined with gait training. 1 A new method for reeducating gait in patients with neurologic disorders, body weight support (BWS) combined with treadmill locomotion, was introduced by Finch and Barbeau. 2 Gait training on the treadmill is task-specific, enabling the practice of complex gait cycles. BWS is supplied by a harness attached to a suspension device. 3 The concept is based on animal models of locomotion control described by Grillner. 4 BWS and treadmill stimulation facilitated the reeducation of a near normal gait pattern in spinalized cats, studied by Barbeau and Rossignol. 5 In humans, the method was originally introduced for patients with paraparesis after spinal cord injury. In patients with spastic paraparesis, 40% BWS showed immediate benefits for the walking pattern with straighter trunk and knee alignment during the stance phase. 6 In nonambulatory stroke patients, positive results in independence in gait function, muscle activation, and velocity were seen after treadmill training with 20% to 40% BWS, compared with physiotherapy according to the Bobath concept in a case study published by Hesse and coworkers. 7 A controlled study on the training effects achieved by 6 weeks of treadmill stimulation with BWS compared with treadmill with full weight-bearing in 100 stroke patients was recently reported by Visintin and colleagues. 8 The results showed more improved balance, motor function, and walking ability in the BWS group than in the non-bws group. The direct impact of BWS on the qualitative gait pattern in 11 hemiparetic subjects, studied by Hesse and colleagues, 9 showed more upright posture with 15% to 60% BWS compared with non-bws treadmill walking. 9 With 45% to 60% BWS, patients tended to walk tiptoe. In a study of 18 hemiparetic subjects, 10 single-stance duration of the affected leg increased, the relative double-support time decreased, and the swing symmetry improved with increasing BWS (15% and 30%). Simultaneously, vertical ground-reaction forces and functional activity of antigravity muscles decreased. Analysis of EMG showed less plantar flexor spasticity on the treadmill with 15% BWS, in 13 of the 18 subjects. On the treadmill, the therapist was able to provide initial contact with the affected heel, which could not be achieved during groundlevel walking. The authors concluded that, in the training of hemiparetic patients, BWS should be limited to 30%. The energy cost during locomotion in patients with hemiparesis after stroke is higher than in able-bodied persons walking at the same velocity. 11,12 Cardiovascular disorders can be causal, consequential or coexistent to stroke. In a review article, Roth 13 stated that heart disease is found in about 75% of patients who have suffered stroke. In an investigation of treadmill stress testing of stroke patients, 29% of the subjects without known heart disease had signs of myocardial ischemia. 14 Treadmill aerobic exercise in stroke subjects reduced energy expenditure and cardiovascular demands, as shown by Macko and associates. 15 Since cardiovascular comorbidities are quite frequent in the stroke patient population, knowledge of the energy cost of various exercise maneuvers is important in exercise planning.

2 954 OXYGEN UPTAKE IN WEIGHT-SUPPORTED WALKING, Danielsson The effects of BWS training on the treadmill for patients with hemiparesis after stroke are being investigated in a Swedish multicenter study. The present study raised the question of energy expenditure during walking under the BWS condition compared with full weight bearing. The harness we used partially restricted hip movement both in flexion and extension. Elevating the center of gravity causes hip excursion to decrease. 16 The suspension system in our apparatus caused a slight swinging movement toward the sides during walking, which can change the walking pattern. In our clinic, one therapist typically assists the patient with the leg movements. Many patients in our training study complained that their supporting hand became tired when they tried to avoid swinging. Thus, energy consumption might increase although body weight is supported. However, in patients with incomplete spinal cord injury, energy cost measured by heart beat frequency was lower in treadmill walking with 40% BWS than in unsupported treadmill walking. 6 Some patients 6 were also able to walk comfortably at a higher speed with BWS than with full weight bearing. No findings in other patient groups have been published on oxygen consumption during walking with BWS. The aim of the present study was to compare the metabolic cost (expressed as oxygen consumption) of walking with 30% BWS with unsupported walking on a treadmill. The hypothesis for the present study was that walking on a treadmill with 30% BWS consumes less oxygen than walking with full weight bearing. MATERIALS AND METHODS Subjects Inclusion criteria were: first occasion of stroke 6 to 32 months earlier, hemiparesis, walking disability with asymmetric walking pattern, fulfillment of an inpatient rehabilitation program after the acute phase with experience in BWS walking on the treadmill, walking ability with or without assistive device, and stable heart condition. Exclusion criteria included severe communication problems, severe heart failure, and orthopedic or pain problems affecting gait. Participating in the study were 9 patients, 6 men and 3 women. Before inclusion, the patient s general health and heart state were assessed by a physician. The mean age of the patients was 56 years (range, 42 to 66 yrs). Nine healthy volunteers with a mean age of 57 years (range, 42 to 65 yrs) were also examined as a reference group. Two of the patients, but none in the reference group, were smokers. For demographic and disease information, see table 1. All subjects gave their informed consent to participate in the study, which was approved by the Ethics Committee at the Faculty of Medicine at Göteborg University. Functional Assessment The subjects were assessed by a physical therapist before the recording procedure. A walking test 17,18 was performed indoors, and the subjects wore their preferred shoes. Assistive devices were used if necessary. The time required to walk over 30m, once at a self-selected pace and once at the patient s maximum speed, was measured. Walking ability was classified according to the Functional Ambulation Categories, 19 a 6-point ordinal scale in which: 0 indicates nonfunctional, dependent walking; 1, continuous weight and balance support from one person; 2, balance or coordination support from one person; 3, verbal supervision; 4, help on stairs and uneven surfaces; and 5 indicates independent walking on all surfaces. Leg motor and sensory functions were assessed according to the Fugl-Meyer scale, 20 an ordinal scale in which the maximum score of 34 indicates normal movement control in the affected side and 12 indicates normal sensory function in the affected leg, compared with the nonaffected side. For examination results, see table 2. The subject s activity level was scored by the Physical Activity Scale for the Elderly (PASE), 21 an instrument comprised of self-reported occupational, household, and leisure activity items. The patients (n 9) scored a mean of 30% of the Subject Sex Age (yrs) Table 1: Background Data for Patient and Reference Group Weight (kg) Height (cm) Stroke Diagnosis Site of Lesion Cardiovascular Disorder Time Since Stroke Onset (mo) Patient group 1 M Infarction L hemi Hypertension 18 2 M Infarction L hemi 8 3 M Hemorrhage L hemi 24 4 M Infarction L hemi 28 5 M Infarction R pons Hypertension/AP 15 6 M Infarction L hemi Arrhythmia* 24 7 F Hemorrhage L hemi Hypertension 11 8 F Infarction R hemi 7 9 F Hemorrhage R hemi 15 Reference group 10 M M M M M M F F F Abbreviations: M, male; F, female; L, left; R, right; hemi, hemisphere; AP, angina pectoris. * Patient 6 had an on-demand pacemaker.

3 OXYGEN UPTAKE IN WEIGHT-SUPPORTED WALKING, Danielsson 955 Table 2: Patients Assistive Devices, Walking Ability, and Motor and Sensory Function Subject Assistive Device FAC* F-M Leg Motor Score F-M Leg Sensory Score 1 None None Cane, AFO None Cane Cane Cane Cane Cane, AFO Abbreviation: AFO, ankle foot orthosis. * Functional Ambulation Categories, maximum score 5. Fugl-Meyer scale, maximum score 34. Fugl-Meyer scale, maximum score 12. score of an age- and sex-matched normal reference group (a population-based sample from our lab). Mean PASE values in the healthy subjects were above the values of an age- and sex-matched reference group. Equipment The equipment for walking with BWS consisted of a standard treadmill attached to a weight-supporting apparatus. a The treadmill size was 0.5m 1.6m; it had speeds of 0 to 2m/sec in 0.1m/sec or 0.1km/h intervals. The apparatus could provide any level of BWS between 100% and 0%. The selected level of weight relief was held constant throughout the gait cycle by its following the vertical displacement of the body. To obtain BWS, the subject wore a modified mountain climber s harness with an adjustable belt around the pelvis. The belt was attached at 3 points (one ventral, one lateral, one dorsal) to an adjustable strap around each thigh. The shoulder straps of the harness were attached to a bar whose lifting strap was fastened at a central point above the subject s head. An adjustable crossbar for hand support was mounted in front of the subject. An emergency stop button was mounted on the bar. Oxygen consumption (VO 2 ) was estimated by a system for continuous breath-by-breath analysis of expired air. b A face mask was placed over the subject s nose and mouth and fastened with elastic straps around the head and neck. The subject was told to breathe through his/her mouth. For electrocardiographic registration, 3 self-adhesive electrodes were placed on the subject s thorax. Levels of oxygen and carbon dioxide, respiratory ratio, and heartbeat frequency were continuously monitored; mean values were recorded every 30 seconds. The values were printed after each test. Measurement Procedure Treadmill speeds for the patient group were based on the individual self-selected and maximum overground walking velocities and varied from 0.2 to 1.0m/sec to 0.2 to 1.4m/sec. For the reference group, self-selected walking velocity for sex and age category (control values from a population-based sample in our lab) was chosen as a base and varied from 1.0 to 1.1m/sec; the maximum speed was estimated from the individual overground walking test and varied from 1.3 to 1.6m/sec. The treadmill handlebar was adjusted so that the subject s elbow was flexed at about 90. All subjects were instructed to hold one hand on the bar without putting weight on it. BWS level was adjusted by lifting the subject to the 100% BWS level for a few seconds, then lowering the subject to 30% BWS. Before the recording started, subjects were habituated to walking on the treadmill with the harness on, with 0% BWS and 30% BWS, for about 5 minutes at the self-chosen and maximum speeds selected. For habituation to the mask and recovery, each recording was preceded by seated rest for 7 minutes with the face mask fastened, without the mouthpiece. The mouthpiece was then applied, and the recording was started with 3 minutes of seated habituation and registration of baseline values. Data were gathered during a period of 6 minutes of walking. During the walking session, subjects gave values of their perceived exertion on the Borg CR-10 scale. 22 If a patient was unable to maintain 6 minutes of walking, the test was interrupted after 4 minutes. Recordings were made with 0% and 30% BWS in randomized order, first at the self-selected and then at the maximum velocity. Within 1 week, the procedure was repeated with the BWS conditions in reverse order. The methods errors of oxygen consumption, ml/(kg min), were 7.05% at self-selected speed with 0% BWS (n 18, fig 1), 10.14% at self-selected speed with 30% BWS (n 18), 5.99% at maximum speed with 0% BWS (n 13), and 4.45% at maximum speed with 30% BWS (n 13). Anticipating that a patient might be unable to walk at a higher velocity, we used only 1 speed. Statistics Descriptive statistics were used for demographic and background data. Recorded values of VO 2 /kg, ie, ml O 2 /(kg min) and heartbeat frequency (beats/min) from the last 2 minutes of the walking tests were the basis of mean values used for further calculations. For calculation of methods error, values of VO 2 /kg were analyzed by the Dahlberg formula. Mean values with standard errors of the mean from the first and second trials were used for group comparison between the 0% BWS and 30% BWS conditions. Mean values of VO 2 /kg and heartbeat frequency during walking with 0% BWS were compared with the values recorded when walking with 30% BWS at the selfselected speed and at the maximum speed. The Wilcoxon s signed rank test was used for comparisons of differences between paired observations within each study group. A significance level of p.05 was used. Fig 1. Mean oxygen uptake (VO 2 ) with 0% body weight support at self-selected walking speed, on first and second trials:, stroke;, reference.

4 956 OXYGEN UPTAKE IN WEIGHT-SUPPORTED WALKING, Danielsson RESULTS Overall, the oxygen consumption values from the second trial were lower than at the first measurement (fig 1). The differences were not significant, however. The subjects in the reference group reached significantly higher levels of VO 2 /kg than the subjects in the patient group. All subjects reached steady state after 2 minutes of walking. Mean values based on the last 2 minutes of the measurement did not differ from mean values based on the last 4 minutes in those subjects who managed to walk for 6 minutes. Only 4 of the patients could sustain walking for 6 minutes at the self-selected speed; in 5 patients with low walking endurance, measurement was stopped after 4 minutes. At the self-selected speed (fig 2), the mean oxygen uptake, VO 2 ml/(kg min), with 0% BWS was (.49) for the patients (n 9) and (.45) for the reference group. With 30% BWS, the values were significantly lower, 9.42 (.51), p.01 for the patients (n 9), and (0.28), p.01 for the reference group. At maximal velocity the mean oxygen uptake in the patients (n 8) was (.65) with 0% BWS and significantly lower, 9.88 (0.69), p.02, with 30% BWS. For the reference group, walking at maximum speed the mean oxygen uptake values with 0% BWS were (.38) ml/ (kg min) and significantly lower (p.05) with 30% BWS, (.47), (fig 3). Heart rate in the patient group was significantly lower ( p.05) during walking with 30% BWS than with 0% BWS at the self-selected velocity. The mean beats per minute (n 9) were 96.7 (3.95) and (3.97), respectively. At maximum velocity (n 8), the mean value for beats per minute was (4.3) with 0% BWS; and with 30% BWS it was significantly lower ( p.02), at (4.14). The respiratory ratio was unchanged throughout the 4 measurements. The highest mean value for the patients was 0.79, and for the reference group it was.78. The ratings of perceived exertion did not unambiguously follow the changes in oxygen consumption. The patients seemed to find walking with 30% BWS somewhat easier than walking with 0% BWS than did the reference group. Some subjects in the reference group found the harness uncomfortable and felt that the suspension gave an unnatural walking pattern. DISCUSSION The method of measuring oxygen consumption used in the present study showed high reproducibility in stroke patients and Fig 2. Mean oxygen uptake (VO 2 ) with 0% and 30% body weight support (BWS) at self-selected walking speed:, stroke;, reference. Fig 3. Mean oxygen uptake (VO 2 ) with 0% and 30% body weight support (BWS) at maximum walking speed:, stroke;, reference. healthy subjects. The difference in VO 2 between the first and second trial was not significant. All subjects tolerated the face mask well. The limitations of the present study are: small investigation group, incomplete matching of patient and reference group, and large variations in functional limitations and time since stroke onset in the patient group. However, the protocol, requiring repeated measurements, gave strength to the study. The results of the present investigation showed that oxygen uptake was reduced when subjects walked with 30% of their body weight supported, compared with unsupported walking. The reduced oxygen consumption can be attributed to energy expenditure during walking being related to body weight. 23 A reduction of the mechanical work to lift the center of mass vertically as described by Duff-Raffaele and coworkers 24 might further explain the lower energy cost. No assessments of displacement in center of mass and no calculation of mechanical work were made in the present study. The lower heart rate noted during walking with 30% BWS is similar to findings reported in spastic paraparetic patients walking with 40% BWS, compared with walking with full weight bearing. 6 We chose 30% BWS to investigate the impact of BWS on oxygen consumption because it is the level we most frequently use in the initial phase of BWS gait training of stroke patients. Our experience, supported by Hesse s findings, 9 is that higher levels can affect the gait pattern in an undesired manner. Other studies 6-8 on BWS gait training have started at levels of 40% or below. Finch et al 16 showed in a study of healthy subjects that BWS levels exceeding 70% gave an unnatural walking pattern. Healthy subjects 16 were unable to walk at their normal comfortable speed at any level of BWS between 30% and 70%. Although no electromyography (EMG) recordings were made in the present study, a general decrease in the EMG mean burst amplitude in muscles active during the stance phase was seen in spastic paretic patients, 6 in hemiparetic subjects, 9 and in a study of healthy subjects 16 while body weight was supported compared with full weight bearing. These findings could implicate that BWS might reduce energy expenditure during walking. Finch 16 found that with 70% BWS, the EMG amplitudes in the trunk muscles of healthy subjects increased. More recent EMG results from Hesse et al 10 showed a more physiologic activation pattern of the erector spinae in stroke patients with 15% or 30% of BWS as compared with floor walking. To obtain the most favorable muscle activation pattern in hemiparetic patients, a limit of 30% BWS has been suggested by Hesse. 9

5 OXYGEN UPTAKE IN WEIGHT-SUPPORTED WALKING, Danielsson 957 CONCLUSION The breath-by-breath analysis system for measuring oxygen consumption during exercise may well be used in the testing of stroke patients. The clinical implication is that BWS decreases the oxygen demand during treadmill walking and thus circulatory aspects do not limit the use of BWS training compared with non-bws treadmill training. BWS might be used for reconditioning extremely deconditioned patients after long bedrest, when their aerobic capacity is very low. Whether BWS can make it possible for stroke patients to walk at a higher velocity or for a longer distance than walking with full weight bearing, must be further investigated. Acknowledgment: The authors acknowledge the assistance of biomedical analyst Gull-Britt Henning for the collection and processing of data. References 1. Carr J, Shepherd R. A motor relearning programme for stroke. London: Heinemann Medical Books; Finch L, Barbeau H. Hemiplegic gait: new treatment strategies. Phys Ther Can 1986;38: Norman KE, Pepin A, Ladouceur M, Barbeau H. A treadmill apparatus and harness support for evaluation and rehabilitation of gait. Arch Phys Med Rehabil 1995;76: Grillner S. Locomotion in vertebrates: central mechanisms and reflex interaction. Physiol Rev 1975;55: Barbeau H, Rossignol S. Recovery of locomotion after chronic spinalization in the adult cat. Brain Res 1987;412: Visintin M, Barbeau H. The effects of body weight support on the locomotor pattern of spastic paretic patients. Can J Neurol Sci 1989;16: Hesse S, Bertelt C, Jahnke MT, Schaffrin A, Baake P, Malezic M, et al. Treadmill training with partial body weight support compared with physiotherapy in nonambulatory hemiparetic patients. Stroke 1995;26: Visintin M, Barbeau H, Korner-Bitensky N, Mayo N. A new approach to retrain gait in stroke patients through body weight support and treadmill stimulation. Stroke 1998;29: Hesse S, Helm B, Krajnik J, Gregoric M, Mauritz K. Treadmill training with partial body weight support: Influence of body weight release on the gait of hemiparetic patients. J Neurol Rehabil 1997;11: Hesse S, Konrad M, Uhlenbrock D. Treadmill walking with partial body weight support versus floor walking in hemiparetic subjects. Arch Phys Med Rehabil 1999;80: 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: Zamparo P, Francescato MP, De Luca G, Lovati L, di Prampero PE. The energy cost of level walking in patients with hemiplegia. Scand J Med Sci Sports 1995;5: Roth EJ. Heart disease in patients with stroke: incidence, impact, and implications for rehabilitation. Part 1: classification and prevalence. Arch Phys Med Rehabil 1993;74: Macko RF, Katzel LI, Yataco A, Tretter LD, De Souza CA, Dengel DR, et al. Low-velocity graded treadmill stress testing in hemiparetic stroke patients. Stroke 1997;28: Macko RF, DeSouza CA, Tretter LD, Silver KH, Smith GV, Anderson PA, 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: Finch L, Barbeau H, Arsenault B. Influence of body weight support on normal human gait: development of a gait retraining strategy. Phys Ther 1991;71: Lundgren-Lindquist B, Aniansson A, Rundgren A. Functional studies in 79-year-olds. III. Walking performance and climbing capacity. Scand J Rehabil Med 1983;15: Witte US, Carlsson JY. Self-selected walking speed in patients with hemiparesis after stroke. Scand J Rehabil Med 1997;29: Holden MK, Gill KM, Magliozzi MR, Nathan J, Piehl-Baker L. Clinical gait assessment in the neurologically impaired. Reliability and meaningfulness. Phys Ther 1984;64: Fugl-Meyer AR, Jaasko L, Leyman I, Olsson S, Steglind S. The post-stroke hemiplegic patient. 1. A method for evaluation of physical performance. Scand J Rehabil Med 1975;7: Washburn RA, Smith KW, Jette AM, Janney CA. The Physical Activity Scale for the Elderly (PASE): development and evaluation. J Clin Epidemiol 1993;46: Noble BJ, Borg GA, Jacobs I, Ceci R, Kaiser P. A category-ratio perceived exertion scale: relationship to blood and muscle lactates and heart rate. Med Sci Sports Exerc 1983;15: Åstrand P, Rodahl K, editors. Textbook of work physiology. New York: McGraw-Hill; Duff-Raffaele M, Kerrigan DC, Corcoran PJ, Saini M. The proportional work of lifting the center of mass during walking. Am J Phys Med Rehabil 1996;75: Suppliers a. TR Spacetrainer; TR Equipment AB, Box 116, S-57322, Tranås, Sweden. b. Medical Graphics Cardiopulmonary Exercise Testing System; Medical Graphics Corp, 350 Oak Grove Parkway, St. Paul, MN