Effect of Arm Ergometry Training on Wheelchair Propulsion Endurance of Individuals with Quadriplegia

Transcription

1 Effect of Arm Ergometry Training on Wheelchair Propulsion Endurance of Individuals with Quadriplegia STEPHEN E. DiCARLO Arm cycle ergometry has een shown to e an effective mode of cardiopulmonary training for individuals with spinal cord injuries. Arm cycle ergometry training results in an increased maximal oxygen uptake, exercise-induced radycardia, and increased physical work capacity. Whether improvements in cardiopulmonary function parallel improvements in functional endurance, however, is unknown. In addition, no readily availale tool to evaluate improvements in functional endurance has een identified. The purpose of this investigation was to determine the effects of arm cycle ergometry training on the wheelchair propulsion endurance of individuals with spinal cord injuries. Eight adult men with quadriplegia were evaluated efore and after eight weeks of arm cycle ergometry training. A modified Cooper's -minute run-walk test, a sustained wheelchair propulsion task, was used to document improvements in functional endurance. Sumaximal exercise heart rate, physical work capacity, and maximal oxygen uptake were used to document improvements in cardiopulmonary function. The results demonstrate that improvements in cardiopulmonary function parallel increases in wheelchair propulsion endurance. A sustained -minute wheelchair propulsion task is shown to e a readily availale tool in the evaluation of functional endurance of individuals with spinal cord injuries. The improvements in wheelchair propulsion endurance should assist the individual in completing activities of school, work, recreation, and daily living. Key Words: Energy expenditure, Physical therapy, Spinal cord injuries. Individuals with quadriplegia secondary to spinal cord injury have a reduced physical work capacity (PWC). -4 Even limited activity results in fatigue in these individuals. Wheelchair propulsion for purposes of attending classes, work, and other activities of daily living causes significant fatigue.,6 Such fatigue prevents optimal participation in work and recreational activities. The role of endurance training in cardiopulmonary health has received considerale attention. Individuals who participate in high levels of endurance training tend to have a lower prevalence of, and mortality from, coronary artery disease. In addition, endurance training significantly decreases the risk of hypertension, 8 oesity, 9 and stroke. 0 Participation in endurance training results in improved cardiopulmonary function. Arm cycle ergometry training results in increased maximal oxygen consumption (Vo max ), exercise-induced S.E. DiCarlo, PhD, is a postdoctoral fellow, Department of Pharmacology, The University of Texas Health Science Center at San Antonio, 0 Floyd Curl Dr, San Antonio, TX (USA). This article was sumitted July 4, 986; was with the author for revision 0 weeks; and was accepted March, 98. Potential Conflict of Interest: 4. radycardia (decreased heart rates at rest and at sumaximal work loads), and increased PWC. -4 The role of endurance training in cardiopulmonary health " 0 and cardiopulmonary function -4 is well documented. These adaptations should result in significant improvements in functional endurance, therey, reducing fatigue during wheelchair propulsion and other ADL. No studies, however, have evaluated the effectiveness of arm ergometry training on functional endurance of individuals with spinal cord injuries. The purpose of this study was to evaluate the effects of arm cycle ergometry training on functional endurance of individuals with spinal cord injuries. Specifically, the effects of arm ergometry training on cardiopulmonary function and wheelchair propulsion endurance was determined. METHOD Sujects Eight male volunteers with quadriplegia secondary to cervical spinal cord injuries were selected from the student population and staff of two major universities (Ta. ). Each suject was instructed as to the nature of the project, and written informed consent was otained. The selection criteria included that the sujects ) e 8 to 0 years of age, ) e disaled for at least two years, ) have no current health prolems that would contraindicate exercise testing and training, and 4) had not participated in aeroic exercise training during the previous six months. The sample population was restricted to individuals disaled for a minimum of two years so that the effects of the spinal cord injury would have stailized. Testing Procedure The cardiopulmonary fitness of the eight sujects was determined efore and after participation in an eight-week aeroic conditioning program y assessing ) Vo max, ) heart rates at identical work loads, ) PWC, and 4) the distance propelled in a wheelchair in minutes. 6 The sujects' heart rates were monitored using a CM electrocardiograph transducer and a Narco Bio- Systems Desk Model Physiograph* strip chart recorder and oscilloscope. Oxygen and caron dioxide concentrations of * Narco Bio-Systems, Inc, PO Box, 6 Airport Blvd, Houston, TX PHYSICAL THERAPY

2 RESEARCH TABLE Demographic Data for Sujects Suject Age (yr) Occupation Level of Lesion Type of Lesion Duration of Disaility (yr) Pretraining Body Weight (kg) Posttraining college counselor C-C6 congenital expired air were measured using the Beckman OM- oxygen analyzer and the Beckman LB- caron dioxide analyzer as descried y Wilmore and Costill. The gas analyzers were calirated efore each test, with a standard caliration gas. Inspired gas was measured y a Parkinson-Cowan gas meter that had a potentiometer connected with oth the physiograph recorder and a computer for the measurement of ventilation volumes. Standard metaolic calculations were made with a computer system programmed in a asic computer language. A Monarch cycle ergometer was used for arm pedaling. The cycle was mounted on a taletop and secured with clamps so that the pedal axis was at shoulder height for each suject. The sujects' wheelchairs were positioned at the tale so that slightly less than full elow extension would occur at the furthermost point in the pedal's revolution range., Because the sujects had no intrinsic hand function, their hands were secured to the foam-padded pedals with elastic andages., Each Vo max test was administered at noon with the suject in the fasting state. Environmental conditions were standardized for all test sessions. Room temperature was maintained etween to C. Each test included a warm-up period followed y continuous, multistage cycling performance until the suject's maximal voluntary effort was reached. The criteria used to determine maximal effort included no further increase in Vo max despite an increase in work load or a respiratory quotient of one or higher. The multistage test egan with a resistance of kg and an arm Beckman Instruments, Inc, 0 Haror Blvd, Fullerton, CA 964. Dynasciences Medical Products, Township Line Rd, Blue Bell, PA 94. Quintron Instruments, 0 44th Ave, W Seattle, WA TABLE Multistage Testing Stage (-min) 4 6 Resistance (kg) a pedaling rate of rpm ( kg.m) for two minutes. At the end of the twominute stage, pedaling rate was increased to rpm at kg ( kg-m) for two minutes. This pattern of increasing the pedaling rate y 0 rpm at the eginning of each susequent two-minute period was continued until a pedaling rate of rpm was reached. At this stage, the sujects were unale to pedal faster without decreases in efficiency and rhythm. Consequently, the resistance was increased to 0.6 kg (Ta. ). The pedaling rate was kept constant y the sujects pedaling to the rhythm of a metronome and with encouragement y the investigator (S.E.D.). Functional endurance was determined with a -minute sustained wheelchair propulsion task. Sujects were instructed to egin on a signal and to continue wheeling around a 00-m indoor track until a stop signal was given. Sujects were instructed to start out at a moderate rate to "pace" themselves. The sujects determined their individual strategy for optimal performance. Time was measured with a Swiss stopwatch." At the end of the protocol, Pedaling Rate (rpm) 0 (kg-m) a One kilogram is the amount of force acting on a mass of kg at the normal acceleration of gravity. One kilogram-meter is the unit of work derived from the equation: W = F.D = force times distance. Compass Instrument and Optical Co, Inc, 04 E th St, New York, NY 000. an investigator (S.E.D.) determined the distance in kilometers that had een covered during minutes. Each test was repeated three times on alternate days. For each suject, the farthest distance covered during the trials was used for the data analysis. Training Procedure The training mode was arm pedaling on a Monarch cycle ergometer on a schedule of three times each week for an eight-week period. Training was supervised closely, and daily logs were maintained for oth work load and training heart rate. The monitoring procedure made it possile to adjust the work load periodically to maintain the desired heart rate. The training heart rate was determined y the maximal heart rate reserve method of Karvonen and associates. 8 This method consists of calculating the maximal heart rate reserve. The maximal heart rate reserve is the difference etween the resting heart rate and the maximal heart rate. The training heart rate was determined as a percentage of the maximal heart rate reserve. Fifty to sixty percent of the maximal heart rate reserve was used as the training heart rate. The resting and Volume 68 / Numer, January 988 4

3 maximal heart rates were determined during the exercise test. Maximal heart rates for individuals with cervical lesions range from aout to pm.,4 The limited maximal heart rate is due to the small muscle mass availale to perform the exercise and the reduced sympathetic nerve innervation to the heart resulting from interruption of sympathetic efferent fiers. The sympathetic cholinergic efferent nerve fiers that control sweating also are interrupted y cervical lesions. I found it necessary to apply cool water over the forehead, arms, and shoulders of the sujects to prevent their ody temperature from rising during the testing and training procedures. The training intensity (ased on heart rate) was relatively low when compared with intensities prescried for ale-odied individuals. During the early stages of conditioning, the sujects exercised at rpm against a resistance of kg for minutes to produce a target heart rate of aout % to % of maximal heart rate reserve. This work load was continued throughout the first week of training. During the second week, the sujects exercised for minutes at the same work load and for an additional minutes at kg.m and rpm. The sujects susequently exercised at the greater work load for increasingly longer periods of time until the eighth week, when they worked at rpm for a 0- minute period. Each suject's work load was modified to reach the target heart rate of aout % to % of maximal heart rate reserve. Thus, each suject initially trained with long outs of lowintensity work loads, progressed to equal outs of low- and high-intensity work loads, and finally exercised for long outs at high-intensity work loads (Ta. ). Data Analysis Differences in pretraining and posttraining PWC, Vo max, and wheelchair propulsion endurance were analyzed y the Student's paired t test. Heart rate responses to the exercise test performed efore and after the eight-week conditioning program were analyzed y a two-way analysis of variance (ANOVA) for repeated measures. Significant effects determined y the ANOVA were evaluated using Duncan's multiple range test. Pearson product-moment correlation coefficients were used to determine the degree of variation of two trials of the wheelchair propulsion task. TABLE Changes in Training over Time Week a a 4a a 6a a 8a Resistance (kg) Pedaling Rate (rpm) (kg.m) Time (min) Pretraining Heart Rate Posttraining Heart Rate Fig.. Comparison of pretraining and posttraining heart rates at identical sumaximal work loads. Note the significant (p <.0) decrease in heart rate at every sumaximal work load during the posttraining test. All sujects were ale to continue 66% longer (4 minutes) during the posttraining test than during the pretraining test. (kg m) Fig.. Comparison of pretraining (light) and posttraining (shaded) physical work capacities (PWCs). Note the 4% increase in PWC during the posttraining test. The increase in PWC was significant at the.0 level. 4 PHYSICAL THERAPY

4 RESEARCH Fig.. Comparison of pretraining (light) and posttraining (shaded) maximal oxygen consumption (Vo max). Note the 99% increase in Vo max during the posttraining test. The increase in Vo max was significant at the.0 level. paired t test also revealed significant (p <.0) increases in mean PWC. The mean PWC increased from 06 ±6.8 kg-m/min to ± 9.6 kg-m/min. Body weights at the time of the posttraining test (4. ± 6.9 kg) were not significantly different from the pretraining test weights (6. ± 8. kg). The paired t test demonstrated significant (p <.0) increases in mean wheelchair propulsion distance. Mean wheelchair propulsion endurance increased from pretraining values of.8 ± 0. km to posttraining values of. ±0.4 km. The Pearson product-moment correlation coefficient of.9 demonstrated a high positive correlation etween trials on the wheelchair propulsion task for all sujects. These results demonstrate a high degree of consistency and reliaility for this readily availale tool for the assessment of functional endurance. Distance (km) Fig. 4. Comparison of pretraining (light) and posttraining (shaded) wheelchair propulsion endurance in kilometers. Note the 8% increase in wheelchair propulsion endurance during the posttraining test. The increase in wheelchair propulsion endurance was significant at the.0 level. The farthest distance covered during two of the three trials for all sujects was used for the data analysis. RESULTS The results of the t tests performed on the data from the efore and after eightweek conditioning program indicate that the arm ergometry training program resulted in decreased heart rates for each sumaximal work load (Fig. ); increased PWC (Fig. ); increased Vo max (Fig. ); and increased wheelchair propulsion endurance (Fig. 4). The results of the two-way ANOVA for repeated measures indicated that the increases in heart rate during testing were significant (p <.0). The data analysis also revealed a significant (p <.0) treatment-y-group interaction, indicating that the pretraining heart rates were significantly higher than the posttraining heart rates at identical work loads. Pretraining heart rates were etween 98 and 06 pm during the first two minutes of testing, whereas posttraining heart rates varied from 84 to 9 pm during the first two minutes of testing at identical work loads. During the second two-minute stage, heart rates ranged from 4 pm to the maximum of 4 pm during the pretraining test. Posttraining heart rates were 96 to 98 pm. The paired t test revealed significant (p <.0) increases in mean Vo max. The mean Vo max increased 99% from pretraining values of. ± 4 ml O kg - min - to posttraining values of. ±. ml O. kg -.mint -. The DISCUSSION The oserved effects of exerciseinduced radycardia, increased PWC, and increased Vo max demonstrate that arm pedaling on a slightly modified cycle ergometer is an acceptale mode of cardiopulmonary training for individuals who cannot train using conventional methods such as running, walking, or icycling. In addition, arm cycle ergometry significantly increased the wheelchair propulsion endurance of each suject. This study demonstrates that improvements in cardiopulmonary function parallel improvements in response to a clinically availale functional assessment tool. Replacement of Cooper's -minute run-walk test with a sustained -minute wheelchair propulsion task appears to e an appropriate tool in the assessment of functional endurance for individuals with spinal cord injuries. In addition, the wheelchair propulsion task is a reliale tool in the assessment of wheel chair propulsion endurance for individuals with quadriplegia. Individuals with spinal cord lesions have reduced PWC. -4 Because of their reduced PWC, their ADL tend to fatigue these individuals efore positive training effects can occur from their daily wheelchair propulsion activities.,6 The reduced PWC also limits activities of rehailitation, work, school, and recreation. Training-induced improvements in endurance will assist the individual with rehailitation and ADL and delay the fatigue that results from the laori- Volume 68 / Numer, January 988 4

5 ous routines involved with school, work, and recreation. The low training intensities used in this study demonstrate that significant improvements in cardiopulmonary and functional endurance occur at relatively low intensities of exercise in this patient population. Exercise performed at a lower level than the recommended guidelines also may e effective in eliciting training adaptations in other patient populations. CONCLUSION This study demonstrates that significant increases in cardiopulmonary function and functional endurance occur at very low training intensities in this patient population. A -minute sustained wheelchair propulsion task is a readily availale and reliale tool for the assessment of wheelchair propulsion endurance of individuals with spinal cord injuries. Improvements in cardiopulmonary function after training parallel improvements in functional endurance. The improved functional endurance should assist the individual in performing ADL.. Pollock ML, Miller HS, Linnerud AC, et al: Arm pedaling as an endurance training regimen for the disaled. Arch Phys Med Rehail :48-44,94. Eklom B, Lunderg A: Effects of physical training on adolescents with severe motor handicaps. Acta Paediatr Scand 6:8-88, 96. DiCarlo SE: Improved cardiopulmonary status after a two-month program of graded arm exercise in a patient with C6 quadriplegia: A case report. Phys Ther 6:46-49,98 4. Gass GC, Camp EM: Physiological characteristics of trained Australian paraplegic and tetraplegic sujects. Med Sci Sports :6-9, 99. Glaser RM, Sawka MN, Wilde SW, et al: Energy cost and cardiopulmonary responses for wheelchair locomotion and walking on tile and on carpet. Paraplegia 9:9-0,98 6. Voight E, Bahn D: Metaolism and pulse rate in physically handicapped when propelling a wheelchair up an incline. Scand J Rehail Med :0-06,969. Paffenarger RS, Hale WE: Work activity and coronary heart mortality. N Engl J Med 9:4-,9 8. Ressl J, Chrastek J, Jandova R: Haemodynamic effects of physical training in essential hypertension. Acta Cardiol (Brux) :-, 9 9. Oscai LB: The role of exercise in weight control. Exerc Sport Sci Rev :0-,9 REFERENCES 0. Paffenarger RS, Laughlin ME, Gima AS, et al: Work activity in longshoremen as related to death from coronary heart disease and stroke. New Engl J Med 8:09-4,90. Astrand PO, Rodahl K: Textook of Work Physiology: Physiological Basis of Exercise. New York, NY, McGraw-Hill Inc, 90, pp DiCarlo SE, Supp MD, Taylor HC: Effect of arm ergometry training on physical work capacity of individuals with spinal cord injuries. Phys Ther 6:04-0,98. Clausen JP, Trap-Jensen T, Lassen NA: Effects of training on heart rate during arm and leg exercises. Scand J Clin La Invest 6:9-0,90 4. Clausen JP, Klausen K, Rasmussen B, et al: Central and peripheral circulatory changes after training of the arms or legs. Am J Physiol :6-68,9. American College of Sports Medicine (ed): Guidelines for Graded Exercise Testing and Exercise Prescription, ed. Philadelphia, PA, Lea & Feiger, 9, pp - 6. Cooper KH: Aeroics. Philadelphia, PA, M Evans & Co Inc, 968. Wilmore JH, Costill DL: Semiautomated systems approach to the assessment of oxygen uptake during exercise. J Appl Physiol 6:68-60,94 8. Karvonen MJ, Kentala E, Mustala O: Effects of training on heart rate: Longitudinal study. Annates Medicinae Experimentalis et Biologiae Fenniae :0-,9 44 PHYSICAL THERAPY