CO 1991 S. Karger ACi, Basel 0028 2766/91 0574 0424S2.75/0
Nephron 1991:57:424-427
Exercise Tolerance of End-Stage Renal Disease Patients Michael Sagiv. Jacob Rudoy, Arie Rolstein. Nogali Fisher, Jacki Ben-Ari Department of Life Sciences and Sports Medicine, Zinman College of Physical Education, Wingate Institute, Nctanya, Israel
Key Words. Physical fitness • Exercise tolerance • Exhaustion • Lactate • Onset of blood lactic acid • Pulmonary function Abstract. The purpose of this study was to evaluate the exercise tolerance of end-stage renal disease patients, and to examine pulmonary function and blood lactate as its possible limiting factors. Ten end-stage renal disease patients (age 30± 11) were tested at rest and in a subsequent graded treadmill test to exhaustion. Velocity was 4.8 km /h and the grade was incremented by 2.5% every 4 min. One minute of rest, used for blood sampling, separated successive stages. Pulmonary functions (FVC, FEV|) at rest were both 76% of predicted. Resting heart rate, systolic and diastolic blood pressures, and ventilatory equivalent values were higher than normal. At peak exercise, heart rate, oxygen uptake, oxygen pulse and blood lactic acid were lower than normally predicted for maximal exercise, while ventilatory equivalent and diastolic blood pressure were higher. Only six patients reached blood lactate levels beyond 4 mM-l 1 (onset of blood lactic acid), at which point they utilized 88 ± 5% of their respective peak V„,. The results suggest that the low exercise tolerance demonstrated in end-stage renal disease patients is not limited by the somewhat compromised pulmonary capacity or by excessive blood lactate levels.
Most end-stage renal disease (ESRD) patients are physically handicapped in their daily life and many can not perform physical activity requiring much more than self-care [11]. Exercise tolerance, as measured by the attainable maximal oxygen uptake (V„,) in ESRD patients, is re ported to be much lower than expected for a healthy population [1, 9, 17, 18, 26]. Chronic renal failure is also often associated with the development of other risk fac tors for the accelerated development of coronary heart disease, such as hyperlipidemia and hypertension. Other conditions associated with ESRD include anemia, bone disease, myopathy and neuropathy [4, 10]. Previous studies have not clarified which factors are responsible for the diminished physical capacity. Since low aerobic capacity is usually associated with low-peak heart rate (HR) as well [9-11], it appears that the cardio
vascular system is not stressed and therefore does not constitute a limiting factor in ESRD patients’ exercise tolerance. Pulmonary function data of ESRD patients are hard to find as well as information concerning the functional capacity of their peripheral musculature. The purpose of the present study was to assess the possible roles of both the pulmonary system and the peripheral functional ca pacity - expressed by blood lactate (LA) - as limiting factors of ESRD patients' exercise tolerance.
Subjects and Methods Ten ESRD patients (3 females, 7 males; age 30±11) completed this study. All but 2 were on maintenance hemodialysis for 37 ± 50 months (range 3 138). One was on continuous ambulatory perito neal dialysis and one was in predialysis stage. All subjects had arteriovenous fistula. Subjects were excluded from this study if they suffered from anginal syndrome, cerebrovascular accident, clinical
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
Introduction
Exercise Tolerance of End-Stage Renal Disease Patients
425
Table 2. Cardiorespiratory values at rest
Variable
Mean ± SD
Variable
Urea, mg% Creatinine, mg% Hémoglobine, g dl 1 Glucose, mg% Phosphate, mg% Calcium, mg% Potassium, m E q l 1
159 ±20 10.2 ±1.9 9.36 ±1.7 105 ± 16 4.4 ±0.8 8.5 ±0.7 4.4 ±0.6
HR, beats min 1 82.2 DBP. mm Hg 88.3 SBP, mm Hg 148.5 V();, ml kg 1 min 1 4.0 O; P. ml beat 1 2.91 Ve. liters-min'1 8.8 VeEq 38.2 f, breaths - min 1 15.6 V„ liters 0.57 FVC, % predicted 76.3 FEV,, % predicted 76.4
bone damage, severe anemia or uncontrolled hypertension. Sub jects averaged 59.4±8.7 kg in weight. 166 ± 11 cm in height and 13 ± 5% in body fat. The subjects' hematological profiles are given in table I. The trials were approved by the clinical committee on human subjects. Upon arrival at the laboratory, informed consent was obtained from each subject. Then, the subjects were weighed by an electronic scale ( ± 0.05 kg), and measured for height, using a stadiomctcr (±0.5 cm). Adipose fat (% fat) was assessed from three skinfolds (abdomen, subscapula and triceps) using a skinfold caliper ( ± I mm). Next, pulmonary functions - FVC‘ and FEV| - were measured, using a computerized spirometer (Spiro-Analyser ST200, Fukuda-Sangyo, Japan). To normalize the data for comparison purposes, values were computed as percentages of predicted values (15). All subjects had left ventricular hypertrophy defined from twelve-leads ECG using the criteria of SV: + RV,., ml kg 1 min 1 22.6 8.87 O; P. ml beat 1 Ve, liters min 1 50.9 VeEq 37.3 f, breaths min 35.5 V„ liters 1.43 LA, m M -f1 5.0
10 9 9 10 10 9 10 10 10 10 10
The test was typically performed until the point of subjective exhaustion an d /o r voluntary withdrawal. Otherwise, the test was terminated in accordance with the guidelines of the American College of Sports Medicine [2], A plot of LA concentration versus treadmill grade was drawn for each subject to determine the 4 niM-i 1 onset of blood lactic acid (OBLA). The treadmill grade corresponding to OBLA was deter mined via interpolation between the last grade preceding OBLA and the one immediately following it. The V„; at OBLA was determined similarly using the V„, values corresponding to the afore-mentioned grades. Statistical treatment consisted of descriptive analysis (means ± 1 SD).
Results All subjects completed the testing without any medi cal complications or electrocardiographic irregularities. At rest (table 2), V,,,, CLP, V e , a n d V, values were within normal limits while the HR, SBP. DBP. and VeEq values were above those reported for normal individuals
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
Table I. Biochemical values for the ESRD patients (n = 10)
426
Sagiv/Rudoy/Rotstein/Fisher/Ben-Ari
low Vo;n,as was associated with a relative low maximal oxygen pulse (8.8 m l/beat).The low average hemoglobin value (9.36±1.7) in our subjects and the fact that all of them had arteriovenous fistula [14,25] may reflect a lower oxygen-carring capacity than in normals [21]. Maximal values for HR found in the present study are in line with findings of previous studies [5, 16, 23], the low maximal values of V0;, 0 2P and LA may be due to another mecha nism for the lowered work capacity of our subjects. Al though we did not utilize echocardiographic measure ments, our patients had left ventricular hypertrophy based on electrocardiographic criteria [24]. Thus, we can not state that our subjects had a concentric left ventricu lar hypertrophy. However, concentric hypertrophy of the heart is often found in patients undergoing chronic hemodialysis treatment. This is caused by chronic pres Discussion sure overload which in turn may lead to heart failure and ESRD patients, whether or not on chronic hemodialy exertion even at rest. At thesame time, this condition may sis, are characterized by a sedentary life-style, limited cause deconditioning of the peripheral muscles. It should work capacity, and reduced aerobic power [4, 5, 11, 13]. be noted that both our subjects, as well as those in most of Many uremia-related factors such as abnormal endo the other reports, were not coaxed beyond the point of crine, neural, neuromuscular, biochemical, hematologi subjective exhaustion and voluntary withdrawal. Minute cal, and cardiovascular functions may affect physical ventilation at test termination was only some 50% of that work capacity either centrally or peripherally. These fac normally expected at maximal exercise [3], This finding tors may compromise various segments of the oxygen can be only partly accounted for by the somewhat com transport chain and the working muscles' metabolic pro promised FVC and FEV, (76% of normal). However, cesses or, possibly, even affect the perception of fatigue since FEV( is not only an indicator of airway status but of and the threshold of pain. Many of these plausible factors respiratory-muscle strength as well, and s in c e /a n d V, were extensively reviewed recently by Painter and Han were quite normal for the observed level of Ve, it appears reasonable to suggest that while respiratory mechanics son [19] and Painter [20], Our subjects demonstrated moderately elevated SBP may have been a contributing factor to the reduced exer and DBP at rest and during the various stages of the test. cise tolerance, it could not alone explain the peak V,,_. of The mechanism underlying this exaggerated blood pres our subjects reaching only 56% of the normally expected sure response may be due to volume overload, elevated value. The kinetics of LA accumulation was normal. How peripheral resistance or autonomic regulatory dysfunc tion [6,12,20]. However, while this quite certainly reflects ever, LA values prior to reaching OBLA were consider systemic ill-effects of the disease, it does not, by itself, ably higher than normal (typically 2-4 m M \ 1 rather constitute a limiting factor of exercise tolerance. than the normal 1-2 range). This may be indicative of an The low working capacity of our subjects is mani early and disproportionate reliance on anaerobic metab fested by the very low peak V02 of 23.2 ±3.9 olism in the working muscles or of difficulties in LA ml -kg 1-min 1which is well in agreement with reports on removal. However, this cannot explain the low peak LA similar patients [1, 5, 9,11,17-19, 26] and constitutes only values compared to those typically achieved by normals 56% of corresponding value of 41 m l k g ' m i n 1 [8], and it strongly suggests that LA as such was not the reported by Pollock et al. [21] for normal age-comparable limiting factor of our subjects' exercise tolerance. This is subjects. Coincidently this value of the average normal well in agreement with some reports [24] but in disagree Vojmax reported by Pollock et al. [21] is very close to that ment with others [4, 13] reporting normal LA values at found in our laboratory (41.6 ml kg 1- min ') when testing submaximal and near-maximal exercise. Our finding a group of normal subjects (4 males and 6 females, aver stand in partial agreement with those of Barnea et al. [5] age age 32.2±8). Thus, by all standards, the subjects in who found comparable peak LA levels in their patients. the present study have a very low aerobic capacity. This However, these levels did not differ from control values.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
[14, 15]. FVC and FEV, were both 76% of that predicted for normals [22]. OBLA determination was possible in only 6 subjects (4 subjects did not reach the 4 mM l 1 LA level even at peak exercise). In those subjects OBLA occurred at a mean treadmill grade of 6.9 ±2.6% and V„; of 1.261 •min ', corresponding to 88 ± 5% of their respective peak Vo2. Values at peak exercise revealed that our ESRD pati ents did not achieve values of V03, 0 2P, HR, and LA nor mally predicted at maximal exercise, while DBP and VeEq were higher [5,15,16,18]. For comparable absolute work loads, HR, SBP, DBP, and VeEq reached higher values than those observed in normal subjects (table 3) [3,21].
Exercise Tolerance of End-Stage Renal Disease Patients
References 1 Allen PI, Adams GE, Pokroy N, Rusby AW, Marlon AM, Bern stein MJ: The effect of exercise-centered multidisciplinary inter vention program on chronic renal failure patients (abstract). Med Sci Sports Exerc 1981:13:138. 2 American College of Sports Medicine: Guidelines for Graded Exercise Testing and Exercise Prescription ed 2. Philadelphia, Lea & Febiger, 1980, pp 23-27. 3 Astrand PO, Rodahl K: Textbook of Work Physiology, ed 3. New York. McGraw-Hill. 1986. pp 229-232. 4 Ayus J, Frommer P, Young JB: Cardiac and circulatory abnor malities in chronic renal failure. Semin Nephrol 1981:1:112-123. 5 Barnea N, Drory Y, laina A, Lapidot C, Reisin E, Eliahou H, Kellermann JJ: Exercise tolerance in patients on chronic hemo dialysis. IsrJ Med Sci 1980:16:17-21. 6 Borst JGG, Borst-de-Geus A: Hypertension explained by Starl ing’s theory of circulatory homeostasis. Lancet 1963; i: 677 -682. 7 Davis JA, Frank MH, Whipp BJ, Wasserman K: Anaerobic threshold alterations caused by endurance training in middleaged men. J Appl Physiol 1979;46:1039—1046. 8 Farrel PA. Wilmore JH, Coyle EF. Billings JE, Costill DL: Plasma lactate accumulation and distance running perform ance. Med Sci Sports Exerc 1979:11:338-344.
9 Goldberg AP, Geltman EM, Hagberg JM, Gavin JR, Delmez ME, Carmey AM, Naumowicz A, Oldfield M, Hortex H: The therapeutic benefits of exercise training for hemodialysis pa tients. Kidney Ini 1983:16 (suppl):S303-S309. 10 Goldberg AP: Lipid abnormalities in hemodialysis patients: Implications and treatment. Perspect Lipid Dis 1984;2:17-24. 11 Gutman RA. Stead WW, Robinson RR: physical activity and employment status of patients on maintenance dialysis. N Engl .1 Med 1981:304:309-313. 12 Guyton AC, Granger HJ, Coleman TG: Autoregulation of the total systemic circulation and its relation to control of cardiac output and aterial pressure. Circ Res I97L28&29 (suppl l):93— 97. 13 Kettner A, Goldberg A, Hagberg J, Delamez J, Harter H: Cardiovascular and metabolic responses to submaximal exer cise in hemodialysis patients. Kidney Int 1984:26:66 71. 14 Johnson GJR, Blythe WB: Hemodynamic effect of ateriovenous shunt used for hemodialysis. Ann Surg 171;715—723,1970. 15 Knudson RJ, Slatin RC, Lebowitz MD, Burrows B: The maxi mal expiratory flow-volume curve. Normal standards, variabil ity. and effect of age. Am Rev Resp Dis 1976:113:587-600.
16 Lundin AP, Stein RA, Frank F, LaBelle P. Berlyne GM, Krasnow N, Friedman EA: Cardiovascular status in long-term hemo dialysis patients: An exercise and échocardiographie study. Nephron 1981:28:234-238. 17 Painter P, Messer-Rehak D, Hanson P, Zimmerman SW, Glass NR: Exercise capacity in hemodialysis, CAPD, and renal trans plant patients. Nephron 1986:42:47-51. 18 Painter PL, Nelson-Worel NJ, Hill MM, Thoemberg RD, Shelp RW, Harrington RA. Weinstein BA: Effects of exercise training during hemodialysis. Nephron 1987;43:87-93. 19 Painter P, Hanson P: A model for clinical exercise prescription: Application for hemodialysis patients. J Cardiopulm Rehabil 1987;7:177-189. 20 Painter PL: Exercise in end-stage renal disease: in Pandolf KB (ed): Exercise and Sport Science Reviews. New York, Macmil lan, 1988, pp. 305-340. 21 Pollock ML, Wilmore JH, Fox SM: Health and Fitness through Physical Activity. New York, John Wiley, 1978. 22 Ruppel G: Manual of Pulmonary Function Testing, ed 2. St Louis, Mosby, 1979. 23 Shalom R. Blumenthal JA, Williams RS, McMurray RG, Dennis VW: Feasibility and benefits of exercise training in patients on maintenance dialysis. Kidney Int 1984;25:958-963. 24 TE-Chun, Chou: Electrocardiography: Usfulness and limita tions. Cardiovasc Rev Rep 1981:2:192-201. 25 Von-Bibra, Castro HL, Autenrieth G. McLeod A, Surland HJ: The effect of ateriovenous shunts on cardiac function in renal dialysis patients - An échocardiographie evaluation. Clin Neph rol 1978:9:205:209. 26 Zabetakis PM, Gleim GW, Pasternak FL, Saraniti A, Nocholas JA, Michelis MF: Long duration submaximal exercise condi tioning in hemodialysis patients. Clin Nephrol 1982:18:17 -22. Accepted: May 25,1990 Dr. Michael Sagiv Department of Life Sciences and Sports Medicine Zinman College of Physical Education Wingate Institute, Netanya 42902 (Israel)
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A common complaint of our subjects upon quitting the test was of muscle fatigue and pain rather than dizzi ness or shortness of breath - well in line with other reports [5]. This observation coupled with our findings of low peak LA and higher than normal VeEq values, point to a common factor, such as disease-related acidosis or reduced buffering capacity, as a likely additional factor in limiting our patients’ exercise tolerance. Since blood pH and buffering capacity were not tested, this proposi tion remains to be validated. In 6 of our subjects OB LA occurred at 88% of peak Vo; instead of the 45-70% typically found in the anaerobic threshold, OBLA, or ventilatory threshold parameters of untrained normals [7], Four of our subjects had to termi nate their tests even before reaching the 4 mM-1 1 LA level (OBLA). This finding provides further support to our claim that LA did not limit peak VQ2 and exercise tolerance in our subjects. Unless a complete dissociation between LA and ventilatory behavior can be shown in ESRD patients, our findings stand in contrast to previous ones by Zabetakis et al. [26] who found their patients' ventilatory threshold to occur at only 40% of Vo2max« While exercice tolerance of ESRD patients is undoub tedly limited by physiological factors, it remains unclear, however, to what extent the observed low tolerance is due to specific disease-related changes and how much of it is a reflection of the low quantity and intensity of their habitual physical activity.
427
Nephron 1991:57:424-427
Exercise Tolerance of End-Stage Renal Disease Patients Michael Sagiv. Jacob Rudoy, Arie Rolstein. Nogali Fisher, Jacki Ben-Ari Department of Life Sciences and Sports Medicine, Zinman College of Physical Education, Wingate Institute, Nctanya, Israel
Key Words. Physical fitness • Exercise tolerance • Exhaustion • Lactate • Onset of blood lactic acid • Pulmonary function Abstract. The purpose of this study was to evaluate the exercise tolerance of end-stage renal disease patients, and to examine pulmonary function and blood lactate as its possible limiting factors. Ten end-stage renal disease patients (age 30± 11) were tested at rest and in a subsequent graded treadmill test to exhaustion. Velocity was 4.8 km /h and the grade was incremented by 2.5% every 4 min. One minute of rest, used for blood sampling, separated successive stages. Pulmonary functions (FVC, FEV|) at rest were both 76% of predicted. Resting heart rate, systolic and diastolic blood pressures, and ventilatory equivalent values were higher than normal. At peak exercise, heart rate, oxygen uptake, oxygen pulse and blood lactic acid were lower than normally predicted for maximal exercise, while ventilatory equivalent and diastolic blood pressure were higher. Only six patients reached blood lactate levels beyond 4 mM-l 1 (onset of blood lactic acid), at which point they utilized 88 ± 5% of their respective peak V„,. The results suggest that the low exercise tolerance demonstrated in end-stage renal disease patients is not limited by the somewhat compromised pulmonary capacity or by excessive blood lactate levels.
Most end-stage renal disease (ESRD) patients are physically handicapped in their daily life and many can not perform physical activity requiring much more than self-care [11]. Exercise tolerance, as measured by the attainable maximal oxygen uptake (V„,) in ESRD patients, is re ported to be much lower than expected for a healthy population [1, 9, 17, 18, 26]. Chronic renal failure is also often associated with the development of other risk fac tors for the accelerated development of coronary heart disease, such as hyperlipidemia and hypertension. Other conditions associated with ESRD include anemia, bone disease, myopathy and neuropathy [4, 10]. Previous studies have not clarified which factors are responsible for the diminished physical capacity. Since low aerobic capacity is usually associated with low-peak heart rate (HR) as well [9-11], it appears that the cardio
vascular system is not stressed and therefore does not constitute a limiting factor in ESRD patients’ exercise tolerance. Pulmonary function data of ESRD patients are hard to find as well as information concerning the functional capacity of their peripheral musculature. The purpose of the present study was to assess the possible roles of both the pulmonary system and the peripheral functional ca pacity - expressed by blood lactate (LA) - as limiting factors of ESRD patients' exercise tolerance.
Subjects and Methods Ten ESRD patients (3 females, 7 males; age 30±11) completed this study. All but 2 were on maintenance hemodialysis for 37 ± 50 months (range 3 138). One was on continuous ambulatory perito neal dialysis and one was in predialysis stage. All subjects had arteriovenous fistula. Subjects were excluded from this study if they suffered from anginal syndrome, cerebrovascular accident, clinical
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
Introduction
Exercise Tolerance of End-Stage Renal Disease Patients
425
Table 2. Cardiorespiratory values at rest
Variable
Mean ± SD
Variable
Urea, mg% Creatinine, mg% Hémoglobine, g dl 1 Glucose, mg% Phosphate, mg% Calcium, mg% Potassium, m E q l 1
159 ±20 10.2 ±1.9 9.36 ±1.7 105 ± 16 4.4 ±0.8 8.5 ±0.7 4.4 ±0.6
HR, beats min 1 82.2 DBP. mm Hg 88.3 SBP, mm Hg 148.5 V();, ml kg 1 min 1 4.0 O; P. ml beat 1 2.91 Ve. liters-min'1 8.8 VeEq 38.2 f, breaths - min 1 15.6 V„ liters 0.57 FVC, % predicted 76.3 FEV,, % predicted 76.4
bone damage, severe anemia or uncontrolled hypertension. Sub jects averaged 59.4±8.7 kg in weight. 166 ± 11 cm in height and 13 ± 5% in body fat. The subjects' hematological profiles are given in table I. The trials were approved by the clinical committee on human subjects. Upon arrival at the laboratory, informed consent was obtained from each subject. Then, the subjects were weighed by an electronic scale ( ± 0.05 kg), and measured for height, using a stadiomctcr (±0.5 cm). Adipose fat (% fat) was assessed from three skinfolds (abdomen, subscapula and triceps) using a skinfold caliper ( ± I mm). Next, pulmonary functions - FVC‘ and FEV| - were measured, using a computerized spirometer (Spiro-Analyser ST200, Fukuda-Sangyo, Japan). To normalize the data for comparison purposes, values were computed as percentages of predicted values (15). All subjects had left ventricular hypertrophy defined from twelve-leads ECG using the criteria of SV: + RV,., ml kg 1 min 1 22.6 8.87 O; P. ml beat 1 Ve, liters min 1 50.9 VeEq 37.3 f, breaths min 35.5 V„ liters 1.43 LA, m M -f1 5.0
10 9 9 10 10 9 10 10 10 10 10
The test was typically performed until the point of subjective exhaustion an d /o r voluntary withdrawal. Otherwise, the test was terminated in accordance with the guidelines of the American College of Sports Medicine [2], A plot of LA concentration versus treadmill grade was drawn for each subject to determine the 4 niM-i 1 onset of blood lactic acid (OBLA). The treadmill grade corresponding to OBLA was deter mined via interpolation between the last grade preceding OBLA and the one immediately following it. The V„; at OBLA was determined similarly using the V„, values corresponding to the afore-mentioned grades. Statistical treatment consisted of descriptive analysis (means ± 1 SD).
Results All subjects completed the testing without any medi cal complications or electrocardiographic irregularities. At rest (table 2), V,,,, CLP, V e , a n d V, values were within normal limits while the HR, SBP. DBP. and VeEq values were above those reported for normal individuals
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
Table I. Biochemical values for the ESRD patients (n = 10)
426
Sagiv/Rudoy/Rotstein/Fisher/Ben-Ari
low Vo;n,as was associated with a relative low maximal oxygen pulse (8.8 m l/beat).The low average hemoglobin value (9.36±1.7) in our subjects and the fact that all of them had arteriovenous fistula [14,25] may reflect a lower oxygen-carring capacity than in normals [21]. Maximal values for HR found in the present study are in line with findings of previous studies [5, 16, 23], the low maximal values of V0;, 0 2P and LA may be due to another mecha nism for the lowered work capacity of our subjects. Al though we did not utilize echocardiographic measure ments, our patients had left ventricular hypertrophy based on electrocardiographic criteria [24]. Thus, we can not state that our subjects had a concentric left ventricu lar hypertrophy. However, concentric hypertrophy of the heart is often found in patients undergoing chronic hemodialysis treatment. This is caused by chronic pres Discussion sure overload which in turn may lead to heart failure and ESRD patients, whether or not on chronic hemodialy exertion even at rest. At thesame time, this condition may sis, are characterized by a sedentary life-style, limited cause deconditioning of the peripheral muscles. It should work capacity, and reduced aerobic power [4, 5, 11, 13]. be noted that both our subjects, as well as those in most of Many uremia-related factors such as abnormal endo the other reports, were not coaxed beyond the point of crine, neural, neuromuscular, biochemical, hematologi subjective exhaustion and voluntary withdrawal. Minute cal, and cardiovascular functions may affect physical ventilation at test termination was only some 50% of that work capacity either centrally or peripherally. These fac normally expected at maximal exercise [3], This finding tors may compromise various segments of the oxygen can be only partly accounted for by the somewhat com transport chain and the working muscles' metabolic pro promised FVC and FEV, (76% of normal). However, cesses or, possibly, even affect the perception of fatigue since FEV( is not only an indicator of airway status but of and the threshold of pain. Many of these plausible factors respiratory-muscle strength as well, and s in c e /a n d V, were extensively reviewed recently by Painter and Han were quite normal for the observed level of Ve, it appears reasonable to suggest that while respiratory mechanics son [19] and Painter [20], Our subjects demonstrated moderately elevated SBP may have been a contributing factor to the reduced exer and DBP at rest and during the various stages of the test. cise tolerance, it could not alone explain the peak V,,_. of The mechanism underlying this exaggerated blood pres our subjects reaching only 56% of the normally expected sure response may be due to volume overload, elevated value. The kinetics of LA accumulation was normal. How peripheral resistance or autonomic regulatory dysfunc tion [6,12,20]. However, while this quite certainly reflects ever, LA values prior to reaching OBLA were consider systemic ill-effects of the disease, it does not, by itself, ably higher than normal (typically 2-4 m M \ 1 rather constitute a limiting factor of exercise tolerance. than the normal 1-2 range). This may be indicative of an The low working capacity of our subjects is mani early and disproportionate reliance on anaerobic metab fested by the very low peak V02 of 23.2 ±3.9 olism in the working muscles or of difficulties in LA ml -kg 1-min 1which is well in agreement with reports on removal. However, this cannot explain the low peak LA similar patients [1, 5, 9,11,17-19, 26] and constitutes only values compared to those typically achieved by normals 56% of corresponding value of 41 m l k g ' m i n 1 [8], and it strongly suggests that LA as such was not the reported by Pollock et al. [21] for normal age-comparable limiting factor of our subjects' exercise tolerance. This is subjects. Coincidently this value of the average normal well in agreement with some reports [24] but in disagree Vojmax reported by Pollock et al. [21] is very close to that ment with others [4, 13] reporting normal LA values at found in our laboratory (41.6 ml kg 1- min ') when testing submaximal and near-maximal exercise. Our finding a group of normal subjects (4 males and 6 females, aver stand in partial agreement with those of Barnea et al. [5] age age 32.2±8). Thus, by all standards, the subjects in who found comparable peak LA levels in their patients. the present study have a very low aerobic capacity. This However, these levels did not differ from control values.
Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/6/2018 4:55:26 PM
[14, 15]. FVC and FEV, were both 76% of that predicted for normals [22]. OBLA determination was possible in only 6 subjects (4 subjects did not reach the 4 mM l 1 LA level even at peak exercise). In those subjects OBLA occurred at a mean treadmill grade of 6.9 ±2.6% and V„; of 1.261 •min ', corresponding to 88 ± 5% of their respective peak Vo2. Values at peak exercise revealed that our ESRD pati ents did not achieve values of V03, 0 2P, HR, and LA nor mally predicted at maximal exercise, while DBP and VeEq were higher [5,15,16,18]. For comparable absolute work loads, HR, SBP, DBP, and VeEq reached higher values than those observed in normal subjects (table 3) [3,21].
Exercise Tolerance of End-Stage Renal Disease Patients
References 1 Allen PI, Adams GE, Pokroy N, Rusby AW, Marlon AM, Bern stein MJ: The effect of exercise-centered multidisciplinary inter vention program on chronic renal failure patients (abstract). Med Sci Sports Exerc 1981:13:138. 2 American College of Sports Medicine: Guidelines for Graded Exercise Testing and Exercise Prescription ed 2. Philadelphia, Lea & Febiger, 1980, pp 23-27. 3 Astrand PO, Rodahl K: Textbook of Work Physiology, ed 3. New York. McGraw-Hill. 1986. pp 229-232. 4 Ayus J, Frommer P, Young JB: Cardiac and circulatory abnor malities in chronic renal failure. Semin Nephrol 1981:1:112-123. 5 Barnea N, Drory Y, laina A, Lapidot C, Reisin E, Eliahou H, Kellermann JJ: Exercise tolerance in patients on chronic hemo dialysis. IsrJ Med Sci 1980:16:17-21. 6 Borst JGG, Borst-de-Geus A: Hypertension explained by Starl ing’s theory of circulatory homeostasis. Lancet 1963; i: 677 -682. 7 Davis JA, Frank MH, Whipp BJ, Wasserman K: Anaerobic threshold alterations caused by endurance training in middleaged men. J Appl Physiol 1979;46:1039—1046. 8 Farrel PA. Wilmore JH, Coyle EF. Billings JE, Costill DL: Plasma lactate accumulation and distance running perform ance. Med Sci Sports Exerc 1979:11:338-344.
9 Goldberg AP, Geltman EM, Hagberg JM, Gavin JR, Delmez ME, Carmey AM, Naumowicz A, Oldfield M, Hortex H: The therapeutic benefits of exercise training for hemodialysis pa tients. Kidney Ini 1983:16 (suppl):S303-S309. 10 Goldberg AP: Lipid abnormalities in hemodialysis patients: Implications and treatment. Perspect Lipid Dis 1984;2:17-24. 11 Gutman RA. Stead WW, Robinson RR: physical activity and employment status of patients on maintenance dialysis. N Engl .1 Med 1981:304:309-313. 12 Guyton AC, Granger HJ, Coleman TG: Autoregulation of the total systemic circulation and its relation to control of cardiac output and aterial pressure. Circ Res I97L28&29 (suppl l):93— 97. 13 Kettner A, Goldberg A, Hagberg J, Delamez J, Harter H: Cardiovascular and metabolic responses to submaximal exer cise in hemodialysis patients. Kidney Int 1984:26:66 71. 14 Johnson GJR, Blythe WB: Hemodynamic effect of ateriovenous shunt used for hemodialysis. Ann Surg 171;715—723,1970. 15 Knudson RJ, Slatin RC, Lebowitz MD, Burrows B: The maxi mal expiratory flow-volume curve. Normal standards, variabil ity. and effect of age. Am Rev Resp Dis 1976:113:587-600.
16 Lundin AP, Stein RA, Frank F, LaBelle P. Berlyne GM, Krasnow N, Friedman EA: Cardiovascular status in long-term hemo dialysis patients: An exercise and échocardiographie study. Nephron 1981:28:234-238. 17 Painter P, Messer-Rehak D, Hanson P, Zimmerman SW, Glass NR: Exercise capacity in hemodialysis, CAPD, and renal trans plant patients. Nephron 1986:42:47-51. 18 Painter PL, Nelson-Worel NJ, Hill MM, Thoemberg RD, Shelp RW, Harrington RA. Weinstein BA: Effects of exercise training during hemodialysis. Nephron 1987;43:87-93. 19 Painter P, Hanson P: A model for clinical exercise prescription: Application for hemodialysis patients. J Cardiopulm Rehabil 1987;7:177-189. 20 Painter PL: Exercise in end-stage renal disease: in Pandolf KB (ed): Exercise and Sport Science Reviews. New York, Macmil lan, 1988, pp. 305-340. 21 Pollock ML, Wilmore JH, Fox SM: Health and Fitness through Physical Activity. New York, John Wiley, 1978. 22 Ruppel G: Manual of Pulmonary Function Testing, ed 2. St Louis, Mosby, 1979. 23 Shalom R. Blumenthal JA, Williams RS, McMurray RG, Dennis VW: Feasibility and benefits of exercise training in patients on maintenance dialysis. Kidney Int 1984;25:958-963. 24 TE-Chun, Chou: Electrocardiography: Usfulness and limita tions. Cardiovasc Rev Rep 1981:2:192-201. 25 Von-Bibra, Castro HL, Autenrieth G. McLeod A, Surland HJ: The effect of ateriovenous shunts on cardiac function in renal dialysis patients - An échocardiographie evaluation. Clin Neph rol 1978:9:205:209. 26 Zabetakis PM, Gleim GW, Pasternak FL, Saraniti A, Nocholas JA, Michelis MF: Long duration submaximal exercise condi tioning in hemodialysis patients. Clin Nephrol 1982:18:17 -22. Accepted: May 25,1990 Dr. Michael Sagiv Department of Life Sciences and Sports Medicine Zinman College of Physical Education Wingate Institute, Netanya 42902 (Israel)
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A common complaint of our subjects upon quitting the test was of muscle fatigue and pain rather than dizzi ness or shortness of breath - well in line with other reports [5]. This observation coupled with our findings of low peak LA and higher than normal VeEq values, point to a common factor, such as disease-related acidosis or reduced buffering capacity, as a likely additional factor in limiting our patients’ exercise tolerance. Since blood pH and buffering capacity were not tested, this proposi tion remains to be validated. In 6 of our subjects OB LA occurred at 88% of peak Vo; instead of the 45-70% typically found in the anaerobic threshold, OBLA, or ventilatory threshold parameters of untrained normals [7], Four of our subjects had to termi nate their tests even before reaching the 4 mM-1 1 LA level (OBLA). This finding provides further support to our claim that LA did not limit peak VQ2 and exercise tolerance in our subjects. Unless a complete dissociation between LA and ventilatory behavior can be shown in ESRD patients, our findings stand in contrast to previous ones by Zabetakis et al. [26] who found their patients' ventilatory threshold to occur at only 40% of Vo2max« While exercice tolerance of ESRD patients is undoub tedly limited by physiological factors, it remains unclear, however, to what extent the observed low tolerance is due to specific disease-related changes and how much of it is a reflection of the low quantity and intensity of their habitual physical activity.
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