Physiologic responses to recumbent versus upright cycle ergometry, and implications for exercise prescription in patients with coronary artery disease

Physiologic Responses to Recumbent Versus Upright Cycle Ergometry, and Implications for Exercise Prescription in Patients with Coronary Artery Disease Scott C. Bonzheim, MS, Barry A. Franklin, PhD, Christopher Dewitt, MS, Charles Marks, PhD, Brian Goslin, PhD, Robert Jarski, PhD, and Sherry Dann, BS

To clarify the influence of body position on exercise prescrtption, 14 men (mean age f standard deviation 60.0 f 6.1 years) with coronary artery disease who underwent randomized recumbent and upright cycle ergometer tests to volitional fatigue were studied. At 166 watts, heart rate (HR), systolic blood pressure, oxygen consumption (irOs), rate pressure product and rating of perceived exertion were greater (p
P

revious studies showedthat cardiorespiratory responsesto exercisemay vary from the upright to the supine position.‘** Becausethe recumbent position is intermediate to these it is important to clarify the effects that it may have on exercise performance. Moreover, appropriate guidelines are needed for prescribing exercisein the recumbent position, particularly when baseline studies are conducted using upright ergometry. The purposes of this investigation were to comparethe cardiorespiratory and perceptual responses of low-risk cardiac rehabilitation patients to upright and recumbent exercise, and to clarify the effect of body position on the exerciseprescription.

METHODS Subj&sr Our study group consistedof 14 men with documented coronary artery disease. Their physical characteristics,clinical status and medicationsare listed in Table I. Patients met the following criteria: negative symptom-limited exercisetest with oxygen consumption (VO2) within the preceding 12 months; normal exercise hemodynamics;aerobic capacity of >-5 METS (1 MET = 3.5 ml/kg/mm); absenceof serious ventricular arrhythmias; ejection fraction >4O?&;and participation in cardiac rehabilitation for >T4months, exercising at 60 to 80% of maximal VO2 (V02max). Exercise testing: After procurement of signed, informed consent, each patient performed randomly assigned recumbent and upright progressiveexercisetests within 1 week of each other at a similar time of day. Tests for upright work were conducted on a standard EC-3000 Cateye Ergociser and for recumbent work on a modified version of that device (Figure 1); thus, both ergometershad identical control consolesand eddy current resistancesystems. The protocol for the ergometer tests included a 2minute initial power output (warm-up) with the subject exercising at 25 watts (1 watt = 6.12 kgm/min), using a pedaling rate of 50 revolutions/minute. Thereafter, the power output was increased in stagesby 25 watts From the Denartment of Cardiac Rehabilitation, St. Joseph Mercy every 2 minutes until volitional fatigue (i.e., the work Hospital, Pon’tiac,and the Department of Exercise Science,Oakland rate at which the designatedpedal speedcould no longUniversity, Rochester,Michigan. Manuscript received June 7, 1991; er be maintained) or the power output at which signifirevisedmanuscript receivedAugust 18,1991, and acceptedAugust 19. cant clinical signs or symptoms (i.e., chest pain, sigAddressfor reprints: Scott C. Bonzheim,MS, Department of Cardiac Rehabilitation, St. JosephMercy Hospital, 900 Wocdward Ave- nificant ST-segment depression or serious ventricular arrhythmias) developed. For comparative purposes, a nue, Pontiac, Michigan 48341-2985.

40

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 69

JANUARY 1, 1992

standard submaximal power output (100 watts) was designated. Respiratory variables, heart rate (HR), blood pressure (standard cuff method) and perceived exertion were determined at each power output and at peak effort. Expired gas was collected and analyzed on-line every minute. The electrocardiogram was monitored continuously by oscilloscope,with 3-channel (VI, V=,,and aVF) recordings obtained throughout the exercise test, and 1Zlead electrocardiogramsrecorded at the end of each stage and during maximal exercise.Perception of the intensity of physical effort at submaximal and maximal exercise was obtained using the Borg (6 to 20) scale.3 Equipment enjoyment was assessedafter each test by the 1l-point Feeling scale (+5 = very good; +3 =good;+l = slightly good; 0 = neutral; -1 = slightly bad; -3 = bad; -5 = very bad).4 Metabolic data were obtained by the Medical Graphics CAD/Net System 2001. The systemincludes a computer assemblyfor on-line 60-secondcalculations min 1, minute ventilation, carbon dioxof VO2 (ml/kg/. id-eproduction (VCO2) and respiratory exchange ratio (VCOz /VOz). Before each test, the pneumotachometer was referencedwith a 3-liter syringe, and the gas analyzers were calibrated with room air and a certified oxygen/carbon dioxide concentration. Electrocardiogram and HR determinations were obtained using the Quinton 5000 Computer Assisted System for exercise.The electrocardiogram was calibrated to 1 mV/lO mm deflection before each test. StatWesr Data were compared using the paired t test. A p value <0.05 was consideredstatistically significant. Values are expressedas mean f standard error. Relations between relative VO2 (expressed as % VOzmax) and HR (expressedas % HRmax) were subjected to trend analysesusing the linear regressiontechniques outlined by Steel and Torrie.s Upright and recumbent regressions (slopes and intercepts) of % VOzmax on % HRmax were tested for equality by the large sample Z test and the multiple regressiondummy variable model.

TABLE I Subject Characteristics

(n = 14) No.

Physical characteristics* Age (yrs) Height (cm) Weight (kg) Clinical status Myocardial infarction Bypass surgery Myocardial infarction/angioplasty Myocardial infarction/bypass surgery Myocardial infarction/angioplasty/bypass gery Medications p-adrenergic blockers Digitalis glycosides Antiarrhythmics Nitrates Calcium antagonists Antihyperlipidemic agents Antiplatelets *Values are expressed as mean r standard

60 k 6 177 k 5 a5+ ii

sur-

1 2 3 6 2

4 1 2 4 a 4 12 dewation.

RESULTS All 14 subjects completed the recumbent and up right ergometer protocols without demonstrating signiticant ST-segment depression (11.0 mm horizontal or downsloping), serious ventricular arrhythmias, or abnormal blood pressureresponsesor symptoms. Maximal exercise responsesto recumbent and up right cycle ergometry are listed in Table II. The validity of thesedata is reflected by a respiratory exchangeratio aboveunity, the attainment of 88 to 91% of agapredicted maximal HR, and a high rating of perceivedexertion (very hard to very, very hard). Peak power output (watts) and exercise time (minutes) were significantly FIGURE l.LlFCPlus2OOOcydeeqgometexasusadforregreater (p
RECUMBENT VERSUS UPRIGHT CYCLE ERGOMETRY

41

TABLE Ill Comparison of Submaximal Exercise Responses to Recumbent and Upright Cycle Ergometry*

TABLE II Comparison of Maximal Exercise Responses to Recumbent and Upright Cycle Ergometry*

Oxygen consumption (ml/kg/min) Heart rate (beats/min) Oxygen pulse (ml/beat) Ratings of perceived exertion Ratings on Feeling scale Systolic blood pressure (mm Hg) Diastolic blood pressure (mm Hg) Rate pressure product (mm Hg x beats/ min x lo-*) Power output (W)t Exercise time (min) Respiratory exchange ratio Minute ventilation (liters/ min)

Recumbent

Upright

p Value

22.7 + 1.5

22.6 + 1.6

NS

Oxygen consumption (ml/

141 ? 3 14.0 5 0.9 17.9 + 0.3

145 2 5 13.5 + 0.9 17.7 + 0.3

NS NS

+3.7 f 0.3 202 + 6

+2.9 k 0.4 204 + 4

NS NS

91.6 ‘- 3

NS

90 f 4 285 2 12

297 2 12

177 13.8 1.2 89

154 11.8 1.3 96

+ 7 & 0.5 f 0.03 ZL 6

zk 5 f 0.4 2 0.03 + 7

Heart rate (beats/min) Oxygen pulse (ml/beat) Ratings of perceived exertion Systolic blood pressure

NS

p Value

13.6 + 0.6

16.0 ? 0.9

0.001

104 -t 4 11.5 2 0.7 10.7 + 0.7

115 2 4 12.0 2 0.6 11.7 r 0.7

0.001 NS 0.001

170 + 5

183 + 5

0.01

79 2 4

87 2 3

0.01

177 2 8

212 2 11

0.001

(mm Hg) Diastolic blood pressure (mm Hg) Rate pressure product (mm Hg x beats/ min x lo-*)

NS

*Standard submaxlmal work rate = 100 W; values expressedas mean ? standard error. NS = not slgnlficant.

0.001 0.001 NS

NS

submaximal power output (100 watts) are listed in Table III. Relative VOz, HR, rating of perceivedexertion, systolic and diastolic blood pressures,and rate pressure product were significantly greater (p
% PO,max

Upright

kg/min)

*Values are expressedas mean f standard error; fl W = 6.12 kgmimin-1. NS = not significant.

loo80-

Recumbent

.... .

Recumbent

-

Upright

DISCUSSION This study evaluated the cardiorespiratory and perceptual responsesof patients with coronary artery diseaseto graded recumbent and upright cycle ergometry. At a standard submaximal power output (100 watts), upright exercisewas performed at a greater physiologic cost than was recumbent cycle ergometry. Although responsesto maximal exercisewere not significantly different, the recumbent position yielded a longer exercise time and a higher power output (177 vs 154 watts). Previous studies reported no difference* or even a decrease’ in maximal exercise duration or work load achieved with supine versus upright exercise.Our results are in contrast to the data of Proctor et al6 and Walsh-Riddle and Blumenthal,’ but in agreementwith the findings of Smith et al8 Relative VO2 and HR at 100 watts were 15 and 10% lower, respectively, in the recumbent than in the upright position. Attenuated cardiorespiratory responses to submaximal recumbent ergometry may be attributed to reduced external work (i.e., weight of the legs did not have to be raised against gravity), increased internal muscular efficiency, or both.g-ll These factors likely contributed to the increasedpeak power output and exercise time when subjectspedaled in the recumbent po-

60-

FIGURE 2. Reamhnt

andqnightreP

gRdOllhOSShOWslllllhrObBOllbO-

40-

twoonruknubrul oxygentiptAo (% tf~)ondhoortmto(%HRmax).hl BwflImnda,y=%v0zmax,omlX=% HRmox.

200 *

I 20

I 40

1 60

I 80

I 100

% HRmax

42

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 69

JANUARY 1, 1992

sition. In contrast, total body energy output and caloric expenditure were unaffected by body position, because peak somatic VO2 was comparable during upright and recumbent exercise (22.6 vs 22.7 ml/kg/r@). Oxygen pulse, calculated by dividing VO2 by HR, has been shown to be a good relative measure of the stroke volume times the arterial-mixed venous oxygen difference of the blood.i2J3 The greater VO2 at the standard submaximal work rate (100 watts) during upright exercisewas primarily attributed to a greater HR, becauseoxygen pulse was not significantly different between upright and recumbent ergometry (Table III). Alterations in venous return on left ventricular contractility and stroke volume may have also contributed to the differences in cardiorespiratory responses. Perceptual responsesto recumbent and upright exercise were assessedby the Feeling (enjoyment)4 and conventional Borg3 scales.Although enjoyment ratings were not significantly different, 8 of 14 patients preferred the recumbent to the upright ergometer, 3 preferred the upright ergometer and the remaining 3 had no preference. Perceived exertion ratings seemed to parallel somatic and myocardial aerobic requirements. At 100 watts, patients perceived recumbent cycling to be significantly easier than upright exercise.(10.7 vs 11.7; p
TABLE IV Estimated Percentage of Maximal Oxygen Consumption (% VO2max) at Selected Percentages of Relative Heart Rate (% HRmax) from the Regression Equations for % \iOzmax on % HRmax for Studies Involving Men % HRmax 70 Investigators Londeree & Ames16 Hellerstein et all7 Hellerstein et aI”* Saltin et aIla Taylor et alI9 Fardy et alzO Skinner & Jankowski*l Ojat Katch et al** Present study*

Exercise Mode TM CE CE TM TM, CE CE AE TM TM CE CE RE

Slope

intercept

1.37 1.41 1.32 1.20

-41 -42 -35 -34 -43 -36 -29 -52 -29 -45 -32 -33

1.44 1.30 1.20 1.50 1.28

1.39 1.26 1.24

*Cardiac patients. Wnpublished doctoral dissertation, Pennsylvania State Unwrslty, AE = arm ergometer; CE = cycle ergometer; RE = recumbent treadmill.

a5

% \jO*max 55 57 57 50 58 55 55 53 61 53 57 54 1973. ergometer;

76 78 77 68 79 74 73 76 80 73 76 73

TM =

Furthermore, these studies show remarkably similar regressionsof % VOzmax on % HRmax, despite differences in subject age, presenceor absenceof coronary artery disease,fitness classification (VOzmax vs age), training status, muscle groups exercisedor testing modality. In establishing the work rate for exercisetraining it is important to emphasizethat although maximal physiologic responsesto recumbent and upright ergometry are similar, cardiorespiratory and perceptual responses to recumbent exerciseare decreasedfor any given power output. Consequently,a power output consideredappropriate for upright exercisetraining will likely need to be increased for recumbent training. An advantageof the recumbent cycle ergometer appearsto be its use in patients with limited cardiorespiratory reserves.At a standard submaximal power output, aerobic requirements are significantly lower during recumbent than during upright exercise The recumbent cycle also allows patients to achieve the same maximal HR and energy expenditure as upright ergometry, but over a wider power output range. Therefore, it is applicable to subjects with higher functional capacities as well. Study iimitaths: Thesefindings cannot be extrapolated to all cardiac patients. The low-risk patients in this study had undergone 24 months of physical training that may well have influenced their cardiorespiratory responsesto exercise.Moreover, our data are probably not applicable to patients with myocardial ischemia or congestive cardiac failure. Previous reports indicate that the supine posture is an important potentiator of exercise-inducedmyccardial ischemia.’ In such studies, the degree of ST-segment depressionwas significantly greater during exercisein the supine posture for a given HR. This concern, however,would likely be attenuated, because the recumbent (leaning) position RECUMBENT VERSUS UPRIGHT CYCLE ERGOMETRY 43

usedin this study is betweensupineand upright exercise.

11. Enoka RM. NemomechanicalBasisof Kinesiology.Champaign,IL: Human Kinetics Publishers,1988:163. 12. WassermanK, Hansen JE, Sue DY, Whipp BJ. Principles of Exercise Testipg and Interpretation. Philadelphia: Lea & Febiier, 1987:37. 13. Astrand PO, Rcdahl K. Textbook of Work Physiology:PhysiologicalBasisof Exercise. New York: McGraw Hill, 1977:333-365. REFERENCES 1. Currie PJ, Kelley MJ, Pitt A. Comparisonof supineand erect bicycle exercise 14. Franklin BA, Hellerstein HK, Gordon S, Timmis GC. Cardiac patients. In: electrocardiography in coronary heart disease:accentuationof exerciseinduced Franklin BA, Gordon S, Timmis GC, eds.Exercise in Modern Medicine. BaltiischemicST depressionby supine posture.Am J Cardiof 1983;52:1167-1173. more: Williams and Wilkins, 198944-80. 2. Steingart RM, Wexler J, Slagle S, ScheuerJ. Radionuclideventriculographic 15. Strauss HW, Pitt B. Gated cardiac blood-pool scan: use in patients with responsesto gradedsupineand upright exercise:critical role of the Frank-Starling coronary heart disease.Prog Cardiomuc Dis 1971;20:207-216. 16. Londeree BR, Ames SA. Trend analysis of the % VOzmax-HR regression. mechanismat submaximal exercise.Am J Cardiol 1984;53:1671-1677. Med Sci Sports Exert 1976;8:122-125. 3. Borg G. Perceivedexertion as an indicator of somaticstress.Scmd J Rehabil 17. Hellerstein HK, Hirsch EZ, Ader R, Greenblott N, Siegel M. Principles of Med 1970;2:92-98. 4. Rejeaki WJ, Kenney EA. FitnessMotivation. Champaign,IL: Life Enhance- exerciseprescription for normals and cardiac subjects.In: Naughton JP, HellersteinHK, eds.ExerciseTestingand ExerciseTraining in Coronary Heart Disease. ment Publications, 1988:55-59. New York Academic Press, 1973:129-168. S. Steel RG, Torrie JH. Principles and Proceduresof Statistics. New York: 18. Saltin B, BlomqvistG, Mitchell JH, JohnsonRL Jr, Wildenthal K, Chapman McGraw Hill, 1960:67-86. 6. Proctor D, Sinning W, Quinn T, Roemmich J, Ehrlich V, Goodpaster B. CB. Responseto exerciseafter bed rest and after training. Circulorion 1968;37 Submaximalresponsesto upright, recumbentand supinebicycle ergometerexer- and 38 (suppl 7):1-78. 19. Taylor HL, Haskell W, Fox SM. Blackbum H. Exercisetests:a summaryof cise.(abstr). Med Sci Sports Exert 1990;22:S12. 7. Walsh-Riddle M, Blumenthal JA. Cardiovascular responsesduring upright proceduresand conceptsof stresstestingfor cardiovasculardiagnosisand function and semirecumbentcycle ergometry testing. Med Sci Sports Exert 1989;21: evaluation. In: Blackbum H, cd. Measurementin ExerciseElectrocardiography. Springfield, IL: Charles C Thomas, 1969259. 581-585. 8. Smith JC, Hill DW, Zolfochary MC, Davis GM. Effect of seat back angleon 20. Fardy PS, Webb D, Hellerstein HK. Benefits of arm exercise in cardiac rehabilitation. Physician Sporrsmed 1977:5:30-41. responsesto cycle ergometry (a&r). Med Sci Sports Exert 1990;22:S12. 21. Skinner JS, Jankowski LW. Individual variability in the relationshipbetween 9. Abbot BC, Bigland B, Ritchie JM. The physiologicalcost of negativework. J heart rate and oxygen intake. Med Sci Spm Exert 1974;6:68. Physiol (Land) 1952;117:380-390. 22. Katch V, Weltman A, Sady S, FreedsonP. Validity of the relative percent 10. Winter DA, Quanbury AO, Reiner GD. Analysis of instantaneousenergyof concept for equating training intensity. Eur J Appl Physiol 1978;39:219-227. normal gait. J Eiomech 1976;9:253-257.

44

THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 69

JANUARY 1, 1992