The Journal of The American Paraplegia Society
ISSN: 0195-2307 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yscm19
Physiologic Responses of Elite Paraplegic Road Racers to Prolonged Exercise Steven P. Hooker & Christine L. Wells To cite this article: Steven P. Hooker & Christine L. Wells (1990) Physiologic Responses of Elite Paraplegic Road Racers to Prolonged Exercise, The Journal of The American Paraplegia Society, 13:4, 72-77, DOI: 10.1080/01952307.1990.11735823 To link to this article: http://dx.doi.org/10.1080/01952307.1990.11735823
Published online: 02 Jun 2016.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yscm19 Download by: [Australian Catholic University]
Date: 19 August 2017, At: 00:49
PHYSIOLOGIC RESPONSES OF ELITE PARAPLEGIC ROAD RACERS TO PROLONGED EXERCISE* Steven P. Hooker, Ph.D., Christine L. Wells, Ph.D.*
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
ABSTRACT The purpose of this study was to determine cardiopulmonary and selected metabolic responses in spinal cord injured (SCI) paraplegics during prolonged arm crank exercise (ACE). Six male and one female elite SCI paraplegic (T4-12 lesions) road racers performed 40 continuous minutes of ACE at 60% of peak ACE oxygen uptake (V02). Blood samples (30 ml) were collected via antecubital venipuncture at rest and minutes 20 and 40 of ACE for determinations of hemoglobin, hematocrit, serum free fatty acid (FFA), and blood lactate (LA) concentrations. No significant differences were observed over time for V02 or pulmonary ventilation. Heart rate recorded at minutes 30 and 40 was significantly elevated' above HR at minutes 10 and 20 of ACE indicating the presence of an upward drift in HR in paraplegics performing prolonged ACE. Compared to rest, LA concentration was significantly higher at minute 20 and remained relatively stable thereafter. A significant increase in FFA concentration at minute 40 combined with a significant decline in the respiratory exchange ratio suggested a preference for lipid substrate utilization by exercising muscle as ACE continued. The data indicate that the autonomic sympathetic nervous system impairment associated with paraplegia had no apparent adverse effects on cardiopulmonary or metabolic adjustments to prolonged ACE in these well-trained subjects. KEY WORDS: spinal cord injury, arm crank ergometry, oxygen uptake, heart rate, respiratory exchange ratio, free fatty acid, lactate, plasma volume. INTRODUCTION
Whereas physiologic responses in able-bodied subjects performing prolonged exercise have been well-documented,1.2 only three studies have reported physiologic responses to prolonged exercise in spinal cord injured (SCI) subjects.3-5 This is unfortunate since traumatic SCI impairs autonomic sympathetic nervous system function which could result in inadequate cardiopulmonary and metabolic adjustments to exercise. 6 In addition, there are a growing number of SCI persons participating in prolonged upper-body exercise during recreational and competitive sporting events. In able-bodied persons, sympathetic nervous system outflow increases during physical activity to augment oxygen and energy substrate delivery to exercising muscle? The proper mobilization and delivery of oxygen and energy substrates to active muscle is crucial for optimal aerobic exercise performance. Indeed, inadequate substrate availability has been linked to onset of fatigue during prolonged exercise.8·9 In addition, inadequate oxygen delivery to exercising muscle will result in a greater reliance on anaerobic metabolism for energy production and has•Exercise and Sport Research Institute, Arizona State University Tempe,AZ Address reprint requests to: Steven P. Hooker, Ph.D. Research and Development (151), Veterans Affairs Medical Center, 4100 W. Third Street Dayton, OH 45428 (513) 268-6511, X2880 Some information in this paper appeared in abstract form in the 1989 ASIA Abstract Digest.
72
ten onset of fatigue. 1 Traumatic SCI limits sympathetic neural activation which may affect subsequent availability of oxygen and energy substrates, and therefore, adversely affect prolonged exercise performance. Thus, the purpose of the present study was to characterize the pattern of cardiopulmonary and selected metabolic responses in SCI persons during prolonged exercise. Although not necessarily representative of the average SCI population, competitive paraplegic road racers were selected as subjects since they are frequently exposed to bouts of prolonged upper-body exercise. In addition, arm crank exercise (ACE) was employed because this exercise mode is commonly prescribed for rehabilitation of SCI patients and highly reproducible during exercise testing. METHODS
Subjects Seven (6 male, 1 female) elite paraplegic road racers with T4-T12 lesions participated in the study. Subject characteristics were (mean± SO) 35.0 ± 6.1 years of age and 61.6 ± 5.7 kg of body weight. Each subject had incurred a traumatic SCI within the past 8-14 years, and five were diagnosed as neurologically complete with respect to loss of infralesional motor and sensory function. At the time of the study, each subject was actively training for and competing in the Open Division of the 1987 Invacare Cup Road Racing Series.
JAm Paraplegia Soc Vol13 No 4
October 1990
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
The test protocols and procedures were approved by the University Human Subjects Research Review Committee. Each subject gave written consent after being informed of experimental procedures, purpose of the study, and any potential benefits and risks of the experiments. Procedures A Monark Rehab Trainer (Monark-Crescent AB, Varberg, Sweden) was used for all ACE tests. This device was mounted on an adjustable steel frame similar to that previously described. 10 The crank axis was adjusted to mid-sternum level and the arms were positioned 90 degrees from the body, with slight elbow flexion in the extended position. Subjects were instructed to maintain a cranking cadence of 70 RPM. A visual display of cadence was provided during each test with a digital meter attached to the ergometer. All subjects initially completed a continuous, graded ACE test to volitional fatigue for determinations of peak power output (PO) and peak oxygen uptake (V02). One or two days following the maximaleffort tests, all subjects performed 40 continuous minutes of ACE at a PO associated with 60% of peak V02. Simple regression equations derived from the PO versus vo2 data generated during the maximal-effort tests were used to determine the appropriate PO for the prolonged tests. Physiological variables During the 40-minute ACE tests, the subjects breathed through a two-way Daniels valve for 2 minutes each, beginning at minutes 8, 18, 28, and 38. Expired air was collected in a S-liter chamber from which a sample of air was continuously drawn. Expired 02 and carbon dioxide (C02) content were analyzed with applied Electrochemistry S-3A and Beckman LB-2 analyzers, respectively. Expired gas volumes were measured with a Parkinson-Cowan CD4 gas meter fitted with a rotary potentio~eter. From these measures, pulmonary ventilation (VE, 1min-1, BTPS), V02 (lmin-1, STPD), C02 production CVC02, 1min-1, STPD), and respiratory exchange ratio (RER) were calculated with a computerized metabolic measurement program. Heart rate (HR) was continuously monitored and recorded for 15 seconds at minutes 10, 20, 30, and 40 with a Hewlett-Packard ECG oscilliscope-cardio-tachometer unit. The subjects came to the laboratory in the morning following an overnight fast and reported not having used caffeine, nicotine, or medications at least 8 hours preceding any test as requested. Blood (30 ml) was collected via antecubital venipuncture following 20 minutes of rest in a seated position (minute 0) and during ACE at minutes 20 and 40. To allow for blood collection during ACE, the subject momentarily
October 1990
stopped cranking with one arm, but continued to crank with the contralateral arm. During this time, a technician assisted with arm cranking to maintain a steady work rate. An aliquote portion of each blood sample was placed in two test tubes and one microtube. Blood lactate (LA) concentration was immediately determined from the blood aliquote in the microtube with an automated LA analyzer (YSI Model 23L, Yellow Springs, OH). One test tube was centrifuged for 30 minutes after which serum was removed. This serum sample was kept on ice until frozen at -40°C and subsequently analyzed for free fatty acid (FFA) concentration with a test kit (WAKO Pure Chemical Industries, Dallas, TX) utilizing an in vitro enzymatic colormetric technique. The remaining test tube was centrifuged for 15 minutes, refrigerated, and transported to a local facility (National Health Laboratories, Tempe, AZ) for determinations of hemoglobin (Hb) and hematocrit (Hct). Each variable was analyzed in duplicate, and serum samples for each subject were analyzed in one assay. Inter-assay and intra-assay variability ranged from 3-7% for FFA and 1-2% for LA, HB, and Hct. Changes in plasma volume (~PV) were determined from Hb and Hct concentrations using the method of Dill and Costill. 11 The effects of the change in ~PV upon changes in the absolute concentrations of LA and FFA were determined with equations developed by HillP Statistical Treatment Cardiopulmonary, metabolic, and plasma volume data were statistically analyzed with one-way, repeated-measures analysis of variance (ANOVA) and Tukey post hoc tests. The alpha level of significance was established as .05. RESULTS Mean values for peak PO, absolute V02 (l·min- 1), relative V02 (ml kg-1min- 1), HR, and RER elicited by Table 1. Peak values for power output and physiologic responses during the graded arm crank exercise test in paraplegic road racers (n=7). Mean± SD.
Power Output (W) Oxygen Uptake (1·min. 1) Oxygen Uptake Heart Rate (bt.
(1"kg-1min. 1)
min. 1)
Respiratory Exchange Ratio
136.00
±
17.00
2.60
±
.54
42.30
±
7.00
178.00
±
10.00
1.14
±
.09
the SCI paraplegics during the graded ACE test are presented in Table 1. The mean valuesforV02, VE,HR,RER,andrelative exercise intensity(% peak V02) at each data collection
JAm Paraplegia Soc Vol13 No 4
73
Table 2. Values for physiologic responses and relative exercise intensity during prolonged arm crank exercise. Mean (±SO).
DATA COLLECTION INTERVAL Min 18-20 Min 28-30
Min 8-10 Oxygen up-take 1.50 ± (1· min -1 ) Pulmonary 34.10 ± Ventilation (1-min- 1 ) Heart rate 124.00 ± (b-min- 1) RER 0.90 ± %Peak V02 58.20 ±
Min 38-40
0.25
1.56 ± 0.30
1.60 ± 0.27
1.62 ± 0.35
5.90
34.80 ± 8.00
36.60 ± 8.00
34.90 ± 8.50
16.00
130.00 ± 16.00
134.00 ± 19.00a
139.00 ± 15.ooa,b
0.05 4.50
0.89 ± 0.05 59.80± 3.60
0.86 ± 0.06a,b
0.85 ± 0.06a,b
61.70± 4.70
62.00 ± 5.60
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
REA = respiratory exchange ratio % peak V02 = percent peak oxygen uptake a significantly different from minute 8-10 (P s .05) b significantly different from minute 18-20 (P s .05)
interval are given in Table 2. The mean relative exercise intensity attained was 60.5 ± 1.7 per cent. No significant changes were observed for V02, VE, or relative exercise intensity during prolonged ACE tests after minute 10. These data indicate the subjects were in a relative physiologic steady-state throughout the prolonged ACE bout. A significant increase in HR occurred during the 40 minutes of ACE. The mean HR at minute 30 was significantly higher than at minute 10, and the mean HR at minute 40 was significantly higher than at minutes 10 and 20. A significant decrease in RER was observed over time during the40-minute ACE test. The mean RER for minutes 30 and 40 were each significantly less than at minutes 10 and 20. Compared to rest, mean LA concentration was significantly elevated by ACE at both minutes 20 and 40. However, there was no significant difference in LA con-
centration between minutes 20 and 40 of ACE (Fig. 1). The mean FFA concentration at minute 20 was not significantly different than at rest. By minute 40 of ACE, however, the mean FFAconcentration was significantly higher than at rest and at minute 20 (Fig. 2). Prolonged ACE resulted in a 6.7-6.9% mean decrease in .1PV. The relative .1PV, however, was not significantly different between minutes 20 and 40 of ACE (Fig 3). The relative .1PV was of insufficient magnitude to account for the changes observed in the absolute LA and FFA concentrations during prolonged ACEP Therefore, the changes in LA and FFA concentrations were primarily due to physiologic effects of prolonged ACE other than changes in PV.
1.5
SERUM FREE FATTY ACID
BLOOD LACTATE
(mmor·r1)
1
0.5
0
10
20
30
40
0
Fig 1. Blood lactate concentration (mean± SO) in spinal cord injured paraplegics during prolonged arm crank exercise. • Denotes significantly higher concentration than at rest (Ps .05).
74
10
20
30
40
TIME (minutes)
TIME (minutes)
Fig 2. Serum-free fatty acid concentration (mean± SO) in spinal cord injured paraplegics during prolonged arm crank exercise. ·oenotes significantly higher concentration than at rest and minute 20 (P
ISSN: 0195-2307 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yscm19
Physiologic Responses of Elite Paraplegic Road Racers to Prolonged Exercise Steven P. Hooker & Christine L. Wells To cite this article: Steven P. Hooker & Christine L. Wells (1990) Physiologic Responses of Elite Paraplegic Road Racers to Prolonged Exercise, The Journal of The American Paraplegia Society, 13:4, 72-77, DOI: 10.1080/01952307.1990.11735823 To link to this article: http://dx.doi.org/10.1080/01952307.1990.11735823
Published online: 02 Jun 2016.
Submit your article to this journal
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yscm19 Download by: [Australian Catholic University]
Date: 19 August 2017, At: 00:49
PHYSIOLOGIC RESPONSES OF ELITE PARAPLEGIC ROAD RACERS TO PROLONGED EXERCISE* Steven P. Hooker, Ph.D., Christine L. Wells, Ph.D.*
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
ABSTRACT The purpose of this study was to determine cardiopulmonary and selected metabolic responses in spinal cord injured (SCI) paraplegics during prolonged arm crank exercise (ACE). Six male and one female elite SCI paraplegic (T4-12 lesions) road racers performed 40 continuous minutes of ACE at 60% of peak ACE oxygen uptake (V02). Blood samples (30 ml) were collected via antecubital venipuncture at rest and minutes 20 and 40 of ACE for determinations of hemoglobin, hematocrit, serum free fatty acid (FFA), and blood lactate (LA) concentrations. No significant differences were observed over time for V02 or pulmonary ventilation. Heart rate recorded at minutes 30 and 40 was significantly elevated' above HR at minutes 10 and 20 of ACE indicating the presence of an upward drift in HR in paraplegics performing prolonged ACE. Compared to rest, LA concentration was significantly higher at minute 20 and remained relatively stable thereafter. A significant increase in FFA concentration at minute 40 combined with a significant decline in the respiratory exchange ratio suggested a preference for lipid substrate utilization by exercising muscle as ACE continued. The data indicate that the autonomic sympathetic nervous system impairment associated with paraplegia had no apparent adverse effects on cardiopulmonary or metabolic adjustments to prolonged ACE in these well-trained subjects. KEY WORDS: spinal cord injury, arm crank ergometry, oxygen uptake, heart rate, respiratory exchange ratio, free fatty acid, lactate, plasma volume. INTRODUCTION
Whereas physiologic responses in able-bodied subjects performing prolonged exercise have been well-documented,1.2 only three studies have reported physiologic responses to prolonged exercise in spinal cord injured (SCI) subjects.3-5 This is unfortunate since traumatic SCI impairs autonomic sympathetic nervous system function which could result in inadequate cardiopulmonary and metabolic adjustments to exercise. 6 In addition, there are a growing number of SCI persons participating in prolonged upper-body exercise during recreational and competitive sporting events. In able-bodied persons, sympathetic nervous system outflow increases during physical activity to augment oxygen and energy substrate delivery to exercising muscle? The proper mobilization and delivery of oxygen and energy substrates to active muscle is crucial for optimal aerobic exercise performance. Indeed, inadequate substrate availability has been linked to onset of fatigue during prolonged exercise.8·9 In addition, inadequate oxygen delivery to exercising muscle will result in a greater reliance on anaerobic metabolism for energy production and has•Exercise and Sport Research Institute, Arizona State University Tempe,AZ Address reprint requests to: Steven P. Hooker, Ph.D. Research and Development (151), Veterans Affairs Medical Center, 4100 W. Third Street Dayton, OH 45428 (513) 268-6511, X2880 Some information in this paper appeared in abstract form in the 1989 ASIA Abstract Digest.
72
ten onset of fatigue. 1 Traumatic SCI limits sympathetic neural activation which may affect subsequent availability of oxygen and energy substrates, and therefore, adversely affect prolonged exercise performance. Thus, the purpose of the present study was to characterize the pattern of cardiopulmonary and selected metabolic responses in SCI persons during prolonged exercise. Although not necessarily representative of the average SCI population, competitive paraplegic road racers were selected as subjects since they are frequently exposed to bouts of prolonged upper-body exercise. In addition, arm crank exercise (ACE) was employed because this exercise mode is commonly prescribed for rehabilitation of SCI patients and highly reproducible during exercise testing. METHODS
Subjects Seven (6 male, 1 female) elite paraplegic road racers with T4-T12 lesions participated in the study. Subject characteristics were (mean± SO) 35.0 ± 6.1 years of age and 61.6 ± 5.7 kg of body weight. Each subject had incurred a traumatic SCI within the past 8-14 years, and five were diagnosed as neurologically complete with respect to loss of infralesional motor and sensory function. At the time of the study, each subject was actively training for and competing in the Open Division of the 1987 Invacare Cup Road Racing Series.
JAm Paraplegia Soc Vol13 No 4
October 1990
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
The test protocols and procedures were approved by the University Human Subjects Research Review Committee. Each subject gave written consent after being informed of experimental procedures, purpose of the study, and any potential benefits and risks of the experiments. Procedures A Monark Rehab Trainer (Monark-Crescent AB, Varberg, Sweden) was used for all ACE tests. This device was mounted on an adjustable steel frame similar to that previously described. 10 The crank axis was adjusted to mid-sternum level and the arms were positioned 90 degrees from the body, with slight elbow flexion in the extended position. Subjects were instructed to maintain a cranking cadence of 70 RPM. A visual display of cadence was provided during each test with a digital meter attached to the ergometer. All subjects initially completed a continuous, graded ACE test to volitional fatigue for determinations of peak power output (PO) and peak oxygen uptake (V02). One or two days following the maximaleffort tests, all subjects performed 40 continuous minutes of ACE at a PO associated with 60% of peak V02. Simple regression equations derived from the PO versus vo2 data generated during the maximal-effort tests were used to determine the appropriate PO for the prolonged tests. Physiological variables During the 40-minute ACE tests, the subjects breathed through a two-way Daniels valve for 2 minutes each, beginning at minutes 8, 18, 28, and 38. Expired air was collected in a S-liter chamber from which a sample of air was continuously drawn. Expired 02 and carbon dioxide (C02) content were analyzed with applied Electrochemistry S-3A and Beckman LB-2 analyzers, respectively. Expired gas volumes were measured with a Parkinson-Cowan CD4 gas meter fitted with a rotary potentio~eter. From these measures, pulmonary ventilation (VE, 1min-1, BTPS), V02 (lmin-1, STPD), C02 production CVC02, 1min-1, STPD), and respiratory exchange ratio (RER) were calculated with a computerized metabolic measurement program. Heart rate (HR) was continuously monitored and recorded for 15 seconds at minutes 10, 20, 30, and 40 with a Hewlett-Packard ECG oscilliscope-cardio-tachometer unit. The subjects came to the laboratory in the morning following an overnight fast and reported not having used caffeine, nicotine, or medications at least 8 hours preceding any test as requested. Blood (30 ml) was collected via antecubital venipuncture following 20 minutes of rest in a seated position (minute 0) and during ACE at minutes 20 and 40. To allow for blood collection during ACE, the subject momentarily
October 1990
stopped cranking with one arm, but continued to crank with the contralateral arm. During this time, a technician assisted with arm cranking to maintain a steady work rate. An aliquote portion of each blood sample was placed in two test tubes and one microtube. Blood lactate (LA) concentration was immediately determined from the blood aliquote in the microtube with an automated LA analyzer (YSI Model 23L, Yellow Springs, OH). One test tube was centrifuged for 30 minutes after which serum was removed. This serum sample was kept on ice until frozen at -40°C and subsequently analyzed for free fatty acid (FFA) concentration with a test kit (WAKO Pure Chemical Industries, Dallas, TX) utilizing an in vitro enzymatic colormetric technique. The remaining test tube was centrifuged for 15 minutes, refrigerated, and transported to a local facility (National Health Laboratories, Tempe, AZ) for determinations of hemoglobin (Hb) and hematocrit (Hct). Each variable was analyzed in duplicate, and serum samples for each subject were analyzed in one assay. Inter-assay and intra-assay variability ranged from 3-7% for FFA and 1-2% for LA, HB, and Hct. Changes in plasma volume (~PV) were determined from Hb and Hct concentrations using the method of Dill and Costill. 11 The effects of the change in ~PV upon changes in the absolute concentrations of LA and FFA were determined with equations developed by HillP Statistical Treatment Cardiopulmonary, metabolic, and plasma volume data were statistically analyzed with one-way, repeated-measures analysis of variance (ANOVA) and Tukey post hoc tests. The alpha level of significance was established as .05. RESULTS Mean values for peak PO, absolute V02 (l·min- 1), relative V02 (ml kg-1min- 1), HR, and RER elicited by Table 1. Peak values for power output and physiologic responses during the graded arm crank exercise test in paraplegic road racers (n=7). Mean± SD.
Power Output (W) Oxygen Uptake (1·min. 1) Oxygen Uptake Heart Rate (bt.
(1"kg-1min. 1)
min. 1)
Respiratory Exchange Ratio
136.00
±
17.00
2.60
±
.54
42.30
±
7.00
178.00
±
10.00
1.14
±
.09
the SCI paraplegics during the graded ACE test are presented in Table 1. The mean valuesforV02, VE,HR,RER,andrelative exercise intensity(% peak V02) at each data collection
JAm Paraplegia Soc Vol13 No 4
73
Table 2. Values for physiologic responses and relative exercise intensity during prolonged arm crank exercise. Mean (±SO).
DATA COLLECTION INTERVAL Min 18-20 Min 28-30
Min 8-10 Oxygen up-take 1.50 ± (1· min -1 ) Pulmonary 34.10 ± Ventilation (1-min- 1 ) Heart rate 124.00 ± (b-min- 1) RER 0.90 ± %Peak V02 58.20 ±
Min 38-40
0.25
1.56 ± 0.30
1.60 ± 0.27
1.62 ± 0.35
5.90
34.80 ± 8.00
36.60 ± 8.00
34.90 ± 8.50
16.00
130.00 ± 16.00
134.00 ± 19.00a
139.00 ± 15.ooa,b
0.05 4.50
0.89 ± 0.05 59.80± 3.60
0.86 ± 0.06a,b
0.85 ± 0.06a,b
61.70± 4.70
62.00 ± 5.60
Downloaded by [Australian Catholic University] at 00:49 19 August 2017
REA = respiratory exchange ratio % peak V02 = percent peak oxygen uptake a significantly different from minute 8-10 (P s .05) b significantly different from minute 18-20 (P s .05)
interval are given in Table 2. The mean relative exercise intensity attained was 60.5 ± 1.7 per cent. No significant changes were observed for V02, VE, or relative exercise intensity during prolonged ACE tests after minute 10. These data indicate the subjects were in a relative physiologic steady-state throughout the prolonged ACE bout. A significant increase in HR occurred during the 40 minutes of ACE. The mean HR at minute 30 was significantly higher than at minute 10, and the mean HR at minute 40 was significantly higher than at minutes 10 and 20. A significant decrease in RER was observed over time during the40-minute ACE test. The mean RER for minutes 30 and 40 were each significantly less than at minutes 10 and 20. Compared to rest, mean LA concentration was significantly elevated by ACE at both minutes 20 and 40. However, there was no significant difference in LA con-
centration between minutes 20 and 40 of ACE (Fig. 1). The mean FFA concentration at minute 20 was not significantly different than at rest. By minute 40 of ACE, however, the mean FFAconcentration was significantly higher than at rest and at minute 20 (Fig. 2). Prolonged ACE resulted in a 6.7-6.9% mean decrease in .1PV. The relative .1PV, however, was not significantly different between minutes 20 and 40 of ACE (Fig 3). The relative .1PV was of insufficient magnitude to account for the changes observed in the absolute LA and FFA concentrations during prolonged ACEP Therefore, the changes in LA and FFA concentrations were primarily due to physiologic effects of prolonged ACE other than changes in PV.
1.5
SERUM FREE FATTY ACID
BLOOD LACTATE
(mmor·r1)
1
0.5
0
10
20
30
40
0
Fig 1. Blood lactate concentration (mean± SO) in spinal cord injured paraplegics during prolonged arm crank exercise. • Denotes significantly higher concentration than at rest (Ps .05).
74
10
20
30
40
TIME (minutes)
TIME (minutes)
Fig 2. Serum-free fatty acid concentration (mean± SO) in spinal cord injured paraplegics during prolonged arm crank exercise. ·oenotes significantly higher concentration than at rest and minute 20 (P
