66
Improved Respiratory Muscle Endurance of Highly Trained Cyclists and the Effects on Maximal Exercise Performance M. S. Fairbarn, K. C. Coutis, R. L. Pardy, D. C. McKenzie Departments of Sports Science & Family Practice and Pulmonary Research Laboratory, University of British Columbia, Vancouver, B.C., Canada
Indroduction
M S. Fairbarn, K. C. Coutts, R. L. Pardy, D. C. McKenzie, Improved Respiratory Muscle Endurance of Highly Trained Cyclists and the Effects on Maximal Exercise Performance. mt J Sports Med, Vol 12, No 1, pp 66—70, 1991.
Accepted: April 20, 1990
Insufficient respiratory muscle endurance (RME) may be one of the factors limiting ventilation during
peak athletic performance. Our purpose was to determine whether the RME of highly trained cyclists could be enhanced and if so, to determine the effects of improved RME on their maximal exercise performance. Ten male cyclists (maximal oxygen consumption (VO2max) > 60 mlkg 5 began the study by peforming 3 tests. These were VO2max, RME measured as maximal sustainable ventilatory capac-
ity (MSVC) and maximal exercise endurance (tlim) measured by an endurance cycling test to exhaustion at 90% of their maximal power output. Five subjects then completed 4 weeks of isocapnic hyperpnea training (16 session) and 5 subjects were controls. Following this training
interval, each subject repeated the initial tests. After the
RME training, the MSVC increased from 155 11 to 174 12 1/mm (p = 0.004) for the training subjects while there was no change in the controls (155 26 and 150 34 1/mm). There were no changes for any of the 10 subjects in
either the maximal exercise performance (VO2max = 66.1 4.7 to 66.5 4.8 mlkg 5 or the maximal exercise endurance (tlim=335±79 to 385± 158 see). In conclusion, 4 weeks of respiratory muscle endurance training increased respiratory muscle endurance but had no effect on the maximal cycling performance of highly trained cyclists.
Exercise scientists generally have not thought that the ventilatory system was a limiting factor to peak athletic
performance. However, respiratory muscle fatigue has been demonstrated following both voluntary hyperpnea (1) and marathon running in normal humans (9). Exercise performance decreased following a long-term hyperpnea regimen which caused respiratory muscle fatigue (10), and maximal ventilation decreased following 60 minutes of exhausting exercise (3). Theoretically then, it is possible that the ventilatory system might contribute to exercise limitation during very intense exercise where high minute ventilation is maintained. The significance of hypoventilation during intense exercise was demonstrated during a study (5) where athletes breathing air while running on a treadmill developed hypoxemia, but when the exercise was repeated breathing a HE:02 mixture, they had higher minute ventilation and the hypoxemia was preveted. If respiratory muscle fatigue does indeed contribute to such activities, respiratory training could hypothetically result in improved exercise performance (15). There is good evidence that respiratory muscle endurance can indeed be increased in normal humans. This has been achieved both by an intense exercise running program (13) and by specific voluntary hyperpnea training of the respiratory muscles (2, 6, 8, 12). In two of these studie, the effects of the increased respiratory muscle endurance on exercise performance was examined. In both the normal elderly (2) and moderately trained athletes (12), there was no effect of the increased respiratory muscle endurance on exercise performance. To date, there have been no studies to examine whether or not the respiratory muscle endurance of highly trained ath-
letes can be improved by specific respiratory muscle hyperpnea training. Furthermore, it is not known whether exercise performance in such individuals is improved by specific respiratory muscle training.
Key words
Thus, the first purpose of this study was to train
respiratory muscles, endurance, maximal oxygen consumption, maximal sustained ventilatory capacity
the respiratory muscles of highly trained endurance athletes (cyclists) using a protocol that mimicked the high ventilation achieved in exercise. The second purpose of this study was to determine the effects of respiratory muscle endurance training on exercise performance. Methods and Procedures
tnt. J. Sports Med. 12(1991)66—70 GeorgThieme Verlag Stuttgart New York
Ten well-trained male cyclists volunteered for this study. The three criteria for inclusion in the study were:
Downloaded by: University of British Columbia. Copyrighted material.
Abstract
Int.J.SportsMed. 12 (1991) 67
ImprovedRespiratory Muscle Endurance of Highly Trained Cyclists and the Effects
maximal oxygen consumption (VO2max) greater than 60 mlkg 1min normal values for spirometry, and an active participation in cycling events. Since the subjects were known to be highly fit athletes and both the experimental and control subjects were matched for fitness, quantifying the amount of aerobic training during this study was not included in the protocol. However, subjects were asked to report any substantial changes in their cycling training. In addition, testing of all subjects was completed while the cycling competitions were being held on a regular schedule. Informed consent was obtained from each subject. Five subjects were assigned to the training group and five to the control group. The three tests used to evaluate the effect of the isocapnic hyperpnea training were: the maximal sustainable ventilatory capacity test (MSVC), a maximal incremental cycle ergometer test, and an endurance cycle test at 90% of the maximal power during the VO2max test. Each of these tests was performed by all subjects both before and after the four-week training period for the experi-
P A - Pump B — Air Plow Meter C — Mixing Chember D—
CO2 Cylinder
Spirometer 9 I F — Aneathnit Bag 5 I o — ln.pired Gag Analyzer H • 2—way Valve & Mouthpiece H
I — Pneumotachograph
I — Expired On Analyzore K — Microcomputer
training programs and were required to record the number of kilometers per week that they cycled.
Fig. 1 Ventilatory endurance apparatus for respiratory muscle endurance testing and training. Arrows indicate direction of airflow.
Maximal Incremental Cycle Test other.
The initial maximal incremental cycle test was used both to ensure that subjects had a VO2max greater than 60 mlkg — min1 and to measure maximal exercise ventilation (VEmax). The test following training was an index of whether the aerobic fitness of the subjects had changed during the project as well as a measure of the effectiveness of the isocapnic hyperpnea training. The incremental cycle test was performed on an electronically braked cycle ergometer (Mijnhardt, Holland) using a ramp protocol beginning at 0 watts and increasing by 30 watts per minute. Expired gas was measured and analyzed by either a Medical Graphics system with the associated 2001 software package or with a separate system consisting of oxygen and C02 analyzers (Beckman OM 11, LB2,FulJerton, CA), and a heated pneumotachograph (Fleisch, Switzerland) to calculate minute ventilation. Each of the analysers were Calibrated with air and calibration gases before and after each test. Data was processed on-line by an IBM microcomputer.
Heart rate (HR) was recorded using direct lead ECG (Lifepack 6, Physio Control Canada, Agincourt, Ontario). Criteria for attaining VO2max was a plateau in V02 with an in-
creased workload, a respiratory exchange ratio greater than 1.15, and HR greater than 180 beats per minute (90% predicted maximum heart rate). Maximum Sustained Ventilatory Capacity (MSVC)
The MSVC test was used to measure respiratory muscle endurance; this was determined by measuring the maximum ventilation the subjects could sustain for 10 minutes (2). As a warm up to the test, the subjects breathed on
the ventilatory endurance apparatus (see below) for two minutes at 50% of their maximal exercise ventilation (VEmax) followed by one minute of rest. During the first two minutes of the test the air flow was gradually increased from the warm-up
level to the maximum ventilation that the subjects could tolerate for the next 8 minutes. To ensure the baseline MSVC values were maximal, the test was peformed by each subject until two tests, separated by 48 hours, were within 5% of each
The mean ventilation reached during the last eight
minutes of the highest test was the baseline measurement.
Ventilatory Endurance Apparatus
The ventilatory endurance apparatus (Fig. 1) was designed to allow isocapnic hyperpnea for both testing and training the endurance of the respiratory muscles. On the inspired side of the circuit, a vacuum pump (Bodine Electric,
Chicago, IL) supplied a variable air flow which passed through an air flow meter (Vacumetrics, Ventrua, CA) and then into a 13.5-litre mixing chamber. 100% CO2 was added at the rate of 3.4 to 4.25 1/mm to maintain the fractional concen-
tration of mixed expired C02 (FECO2) at each subject's predetermined resting level. A 9-liter Respirometer (Collins, Boston, MA) provided the visual reference for the target ventilation for the subject. The subject was instructed to keep a mark on the bell of the respirometer below the water reservoir level. A 5-litre anesthesia bag was included on the inspired side of the system to provide a dampening effect. Distal to this bag was a sampling tube connected to a CO2 analyzer (Medical Graphics, St. Paul, MN) to measure the fractional concen-
tration of inspired C02 (FICO2). The subject breathed through a low-resistance 2-way valve (Hans Rudolph K.C., MO) and the expired gas passed through a heated pneumotachograph (Model 3 Fleisch, Switzerland) to calculate minute ventilation. A temperature gauge recorded expired gas temperature. Ventilation was processed on line by an IBM microcomputer (Armonk, N. Y.). The gas analyzer was calibrated using air and calibration gas before each test. The pneumotachograph was calibrated at the maximum volume of 230 1/mm as measured by air flow meter. The resistance of the circuit was 0.035cm H2O/l/min.
Endurance Cycle Test Each subject performed a cycle ride to exhaustion at a power which represented 90% of the maximum work rate previously achieved during the incremental cycle test. The purpose fo the endurance cycle test was to simulate a competi-
Downloaded by: University of British Columbia. Copyrighted material.
mental subjects. Subjects continued their regular aerobic
M. S. Fairbarn, K. C. Coutts, R. L. Pardy, D. C. McKenzie
mt. J. Sports Med. 12 (1991) 200
Table 1 Anthropometric Data for 10 Subjects (Mean SD) Experimental
Control
(n=5)
(n=5)
174
Weight (kg)
69
7.7 6.2 Age (yr)
22
2.7 FVC (liters)
5.5
FEy1 (liters)
0.9 4.4 0.3
MVV12 (1/mm)
206 15
'I
178
3.8 73 6.8 23 4.0 5.7 0.7
4.8 0.6 215 20
FVC = Forced vital capacity FEV1 = Forced expiratory volume in one second MW12 = Maximal voluntary ventilation in 12 seconds.
tive cycle ride while standardizing the external environment. Previous experience in this laboratory with similar subjects has shown that the approximate time for a test at this work level
E 160
0 so
140 0s
> 120 A
4
2
6
10
8
time (mm)
Pre-Exp. (n—SI
—
— Pre-Con.
(n..5(
Post.-Exp.
(n5)
-. A Post-Con.
(n5(
Fig. 2 Mean ventilation for each minute during the MSVC test for both the experimental and control groups pre- and post-training period. The mean of the last 8 minutes of the MSVC was greater for the experimental group (—A—) post training.
is from 6 to 10 minutes, a duration similar to the MSVC test and
isocapnic hyperpnea training times. Following a 3-minute warm-up, resistance was increased over 10 seconds until the predetermined work rate was attained. From this point, expired minute ventilation (VEtlim) was recorded as well as the time to exhaustion (tlim). The criterion for the end of the test was the inability to maintain the minimum pedal frequency of 60 rpm for 3 consecutive revolutions. Subjects were not aware of the elapsed time.
the eighth training session, the duration of both the work and rest intervals was increased to 10 minutes each.
Statistical Analysis
Analysis of variance was used to test the similarity of the experimental and control groups prior to respiratory muscle endurance training for the following variables: age, height, weight, FYC, FEVi, MVV12, MSVC, VO2max,
Pulmonary Function Tests
VEmax, tlim, and VEthm.
Pulmonary function tests were performed to
To determine the effects of the respiratory muscle endurance training, the mean group pre- and posttraining differences were tested by multiple analysis of vari-
ensure normal spirometry of the subjects. Forced vital capacity (FVC), forced expiratory volume in one second (FEVi), and maximal voluntary ventilation in 12 seconds (M\TV12)
were measured and analyzed using the Medical Graphics computerized spirometer system (St. Paul, MN) with the associated 1070 software package.
Respiratory Muscle Endurance Training Protocol
To improve the endurance performance of the respiratory muscles, a volume overload technique, isocapnic hyperpnea, was selected. The subjects attended three or four training sessions per week for a total of 16 sessions. Each session consisted of three 8-minute work intervals of isocapnic
hyperpnea alternated with 8-minute intervals of rest. The training overload was a combination of increasing both ventilation and duration of the work intervals. Initially, the target ventilation for each work interval was the ventilation each subject achieved during the initail MSVC test with the remainder of each training session at the maximum tolerable ventilation. Progressively, the subjects were able to maintain this target ventilation for each of the three work intervals. To provide a training stimulus, the target ventilation was then increased to a level that could only be maintained for the first work interval of a training session and the subject's new goal was to maintain this larger ventilation for all three work intervals. Following
ance for the variables in the following groups: 1. Pulmonary functions: FVC, FEY1, MYV 2. Maximal aerobic capacity test: VO2max, VEmax 3. Endurance cycle test: turn, VEtlim.
Analysis of variance was used to determine the significance of the difference in the MSVC test between the groups. The data analysis was performed using the statistical package, SYSTAT, version 4 (16). The level of significance for each test was P
Improved Respiratory Muscle Endurance of Highly Trained Cyclists and the Effects on Maximal Exercise Performance M. S. Fairbarn, K. C. Coutis, R. L. Pardy, D. C. McKenzie Departments of Sports Science & Family Practice and Pulmonary Research Laboratory, University of British Columbia, Vancouver, B.C., Canada
Indroduction
M S. Fairbarn, K. C. Coutts, R. L. Pardy, D. C. McKenzie, Improved Respiratory Muscle Endurance of Highly Trained Cyclists and the Effects on Maximal Exercise Performance. mt J Sports Med, Vol 12, No 1, pp 66—70, 1991.
Accepted: April 20, 1990
Insufficient respiratory muscle endurance (RME) may be one of the factors limiting ventilation during
peak athletic performance. Our purpose was to determine whether the RME of highly trained cyclists could be enhanced and if so, to determine the effects of improved RME on their maximal exercise performance. Ten male cyclists (maximal oxygen consumption (VO2max) > 60 mlkg 5 began the study by peforming 3 tests. These were VO2max, RME measured as maximal sustainable ventilatory capac-
ity (MSVC) and maximal exercise endurance (tlim) measured by an endurance cycling test to exhaustion at 90% of their maximal power output. Five subjects then completed 4 weeks of isocapnic hyperpnea training (16 session) and 5 subjects were controls. Following this training
interval, each subject repeated the initial tests. After the
RME training, the MSVC increased from 155 11 to 174 12 1/mm (p = 0.004) for the training subjects while there was no change in the controls (155 26 and 150 34 1/mm). There were no changes for any of the 10 subjects in
either the maximal exercise performance (VO2max = 66.1 4.7 to 66.5 4.8 mlkg 5 or the maximal exercise endurance (tlim=335±79 to 385± 158 see). In conclusion, 4 weeks of respiratory muscle endurance training increased respiratory muscle endurance but had no effect on the maximal cycling performance of highly trained cyclists.
Exercise scientists generally have not thought that the ventilatory system was a limiting factor to peak athletic
performance. However, respiratory muscle fatigue has been demonstrated following both voluntary hyperpnea (1) and marathon running in normal humans (9). Exercise performance decreased following a long-term hyperpnea regimen which caused respiratory muscle fatigue (10), and maximal ventilation decreased following 60 minutes of exhausting exercise (3). Theoretically then, it is possible that the ventilatory system might contribute to exercise limitation during very intense exercise where high minute ventilation is maintained. The significance of hypoventilation during intense exercise was demonstrated during a study (5) where athletes breathing air while running on a treadmill developed hypoxemia, but when the exercise was repeated breathing a HE:02 mixture, they had higher minute ventilation and the hypoxemia was preveted. If respiratory muscle fatigue does indeed contribute to such activities, respiratory training could hypothetically result in improved exercise performance (15). There is good evidence that respiratory muscle endurance can indeed be increased in normal humans. This has been achieved both by an intense exercise running program (13) and by specific voluntary hyperpnea training of the respiratory muscles (2, 6, 8, 12). In two of these studie, the effects of the increased respiratory muscle endurance on exercise performance was examined. In both the normal elderly (2) and moderately trained athletes (12), there was no effect of the increased respiratory muscle endurance on exercise performance. To date, there have been no studies to examine whether or not the respiratory muscle endurance of highly trained ath-
letes can be improved by specific respiratory muscle hyperpnea training. Furthermore, it is not known whether exercise performance in such individuals is improved by specific respiratory muscle training.
Key words
Thus, the first purpose of this study was to train
respiratory muscles, endurance, maximal oxygen consumption, maximal sustained ventilatory capacity
the respiratory muscles of highly trained endurance athletes (cyclists) using a protocol that mimicked the high ventilation achieved in exercise. The second purpose of this study was to determine the effects of respiratory muscle endurance training on exercise performance. Methods and Procedures
tnt. J. Sports Med. 12(1991)66—70 GeorgThieme Verlag Stuttgart New York
Ten well-trained male cyclists volunteered for this study. The three criteria for inclusion in the study were:
Downloaded by: University of British Columbia. Copyrighted material.
Abstract
Int.J.SportsMed. 12 (1991) 67
ImprovedRespiratory Muscle Endurance of Highly Trained Cyclists and the Effects
maximal oxygen consumption (VO2max) greater than 60 mlkg 1min normal values for spirometry, and an active participation in cycling events. Since the subjects were known to be highly fit athletes and both the experimental and control subjects were matched for fitness, quantifying the amount of aerobic training during this study was not included in the protocol. However, subjects were asked to report any substantial changes in their cycling training. In addition, testing of all subjects was completed while the cycling competitions were being held on a regular schedule. Informed consent was obtained from each subject. Five subjects were assigned to the training group and five to the control group. The three tests used to evaluate the effect of the isocapnic hyperpnea training were: the maximal sustainable ventilatory capacity test (MSVC), a maximal incremental cycle ergometer test, and an endurance cycle test at 90% of the maximal power during the VO2max test. Each of these tests was performed by all subjects both before and after the four-week training period for the experi-
P A - Pump B — Air Plow Meter C — Mixing Chember D—
CO2 Cylinder
Spirometer 9 I F — Aneathnit Bag 5 I o — ln.pired Gag Analyzer H • 2—way Valve & Mouthpiece H
I — Pneumotachograph
I — Expired On Analyzore K — Microcomputer
training programs and were required to record the number of kilometers per week that they cycled.
Fig. 1 Ventilatory endurance apparatus for respiratory muscle endurance testing and training. Arrows indicate direction of airflow.
Maximal Incremental Cycle Test other.
The initial maximal incremental cycle test was used both to ensure that subjects had a VO2max greater than 60 mlkg — min1 and to measure maximal exercise ventilation (VEmax). The test following training was an index of whether the aerobic fitness of the subjects had changed during the project as well as a measure of the effectiveness of the isocapnic hyperpnea training. The incremental cycle test was performed on an electronically braked cycle ergometer (Mijnhardt, Holland) using a ramp protocol beginning at 0 watts and increasing by 30 watts per minute. Expired gas was measured and analyzed by either a Medical Graphics system with the associated 2001 software package or with a separate system consisting of oxygen and C02 analyzers (Beckman OM 11, LB2,FulJerton, CA), and a heated pneumotachograph (Fleisch, Switzerland) to calculate minute ventilation. Each of the analysers were Calibrated with air and calibration gases before and after each test. Data was processed on-line by an IBM microcomputer.
Heart rate (HR) was recorded using direct lead ECG (Lifepack 6, Physio Control Canada, Agincourt, Ontario). Criteria for attaining VO2max was a plateau in V02 with an in-
creased workload, a respiratory exchange ratio greater than 1.15, and HR greater than 180 beats per minute (90% predicted maximum heart rate). Maximum Sustained Ventilatory Capacity (MSVC)
The MSVC test was used to measure respiratory muscle endurance; this was determined by measuring the maximum ventilation the subjects could sustain for 10 minutes (2). As a warm up to the test, the subjects breathed on
the ventilatory endurance apparatus (see below) for two minutes at 50% of their maximal exercise ventilation (VEmax) followed by one minute of rest. During the first two minutes of the test the air flow was gradually increased from the warm-up
level to the maximum ventilation that the subjects could tolerate for the next 8 minutes. To ensure the baseline MSVC values were maximal, the test was peformed by each subject until two tests, separated by 48 hours, were within 5% of each
The mean ventilation reached during the last eight
minutes of the highest test was the baseline measurement.
Ventilatory Endurance Apparatus
The ventilatory endurance apparatus (Fig. 1) was designed to allow isocapnic hyperpnea for both testing and training the endurance of the respiratory muscles. On the inspired side of the circuit, a vacuum pump (Bodine Electric,
Chicago, IL) supplied a variable air flow which passed through an air flow meter (Vacumetrics, Ventrua, CA) and then into a 13.5-litre mixing chamber. 100% CO2 was added at the rate of 3.4 to 4.25 1/mm to maintain the fractional concen-
tration of mixed expired C02 (FECO2) at each subject's predetermined resting level. A 9-liter Respirometer (Collins, Boston, MA) provided the visual reference for the target ventilation for the subject. The subject was instructed to keep a mark on the bell of the respirometer below the water reservoir level. A 5-litre anesthesia bag was included on the inspired side of the system to provide a dampening effect. Distal to this bag was a sampling tube connected to a CO2 analyzer (Medical Graphics, St. Paul, MN) to measure the fractional concen-
tration of inspired C02 (FICO2). The subject breathed through a low-resistance 2-way valve (Hans Rudolph K.C., MO) and the expired gas passed through a heated pneumotachograph (Model 3 Fleisch, Switzerland) to calculate minute ventilation. A temperature gauge recorded expired gas temperature. Ventilation was processed on line by an IBM microcomputer (Armonk, N. Y.). The gas analyzer was calibrated using air and calibration gas before each test. The pneumotachograph was calibrated at the maximum volume of 230 1/mm as measured by air flow meter. The resistance of the circuit was 0.035cm H2O/l/min.
Endurance Cycle Test Each subject performed a cycle ride to exhaustion at a power which represented 90% of the maximum work rate previously achieved during the incremental cycle test. The purpose fo the endurance cycle test was to simulate a competi-
Downloaded by: University of British Columbia. Copyrighted material.
mental subjects. Subjects continued their regular aerobic
M. S. Fairbarn, K. C. Coutts, R. L. Pardy, D. C. McKenzie
mt. J. Sports Med. 12 (1991) 200
Table 1 Anthropometric Data for 10 Subjects (Mean SD) Experimental
Control
(n=5)
(n=5)
174
Weight (kg)
69
7.7 6.2 Age (yr)
22
2.7 FVC (liters)
5.5
FEy1 (liters)
0.9 4.4 0.3
MVV12 (1/mm)
206 15
'I
178
3.8 73 6.8 23 4.0 5.7 0.7
4.8 0.6 215 20
FVC = Forced vital capacity FEV1 = Forced expiratory volume in one second MW12 = Maximal voluntary ventilation in 12 seconds.
tive cycle ride while standardizing the external environment. Previous experience in this laboratory with similar subjects has shown that the approximate time for a test at this work level
E 160
0 so
140 0s
> 120 A
4
2
6
10
8
time (mm)
Pre-Exp. (n—SI
—
— Pre-Con.
(n..5(
Post.-Exp.
(n5)
-. A Post-Con.
(n5(
Fig. 2 Mean ventilation for each minute during the MSVC test for both the experimental and control groups pre- and post-training period. The mean of the last 8 minutes of the MSVC was greater for the experimental group (—A—) post training.
is from 6 to 10 minutes, a duration similar to the MSVC test and
isocapnic hyperpnea training times. Following a 3-minute warm-up, resistance was increased over 10 seconds until the predetermined work rate was attained. From this point, expired minute ventilation (VEtlim) was recorded as well as the time to exhaustion (tlim). The criterion for the end of the test was the inability to maintain the minimum pedal frequency of 60 rpm for 3 consecutive revolutions. Subjects were not aware of the elapsed time.
the eighth training session, the duration of both the work and rest intervals was increased to 10 minutes each.
Statistical Analysis
Analysis of variance was used to test the similarity of the experimental and control groups prior to respiratory muscle endurance training for the following variables: age, height, weight, FYC, FEVi, MVV12, MSVC, VO2max,
Pulmonary Function Tests
VEmax, tlim, and VEthm.
Pulmonary function tests were performed to
To determine the effects of the respiratory muscle endurance training, the mean group pre- and posttraining differences were tested by multiple analysis of vari-
ensure normal spirometry of the subjects. Forced vital capacity (FVC), forced expiratory volume in one second (FEVi), and maximal voluntary ventilation in 12 seconds (M\TV12)
were measured and analyzed using the Medical Graphics computerized spirometer system (St. Paul, MN) with the associated 1070 software package.
Respiratory Muscle Endurance Training Protocol
To improve the endurance performance of the respiratory muscles, a volume overload technique, isocapnic hyperpnea, was selected. The subjects attended three or four training sessions per week for a total of 16 sessions. Each session consisted of three 8-minute work intervals of isocapnic
hyperpnea alternated with 8-minute intervals of rest. The training overload was a combination of increasing both ventilation and duration of the work intervals. Initially, the target ventilation for each work interval was the ventilation each subject achieved during the initail MSVC test with the remainder of each training session at the maximum tolerable ventilation. Progressively, the subjects were able to maintain this target ventilation for each of the three work intervals. To provide a training stimulus, the target ventilation was then increased to a level that could only be maintained for the first work interval of a training session and the subject's new goal was to maintain this larger ventilation for all three work intervals. Following
ance for the variables in the following groups: 1. Pulmonary functions: FVC, FEY1, MYV 2. Maximal aerobic capacity test: VO2max, VEmax 3. Endurance cycle test: turn, VEtlim.
Analysis of variance was used to determine the significance of the difference in the MSVC test between the groups. The data analysis was performed using the statistical package, SYSTAT, version 4 (16). The level of significance for each test was P
