Effect of simulated weightlessness on exercise-induced anaerobic threshold

Ventilation (VE), CO2 output (VCO2), oxygen uptake (VO2), respiratory exchange ratio (R), and the ventilatory equivalents for VO2 and VCO2 were measured during graded exercise before and after 10 d of continuous bed rest (BR) in the -6 degrees head-down position to determine the effect of deconditioning on the anaerobic threshold (AT), i.e., the highest workrate or VO2 which was achieved without evidence of lactic acidosis, as judged from the profile of ventilatory and gas exchange responses. Ten healthy male subjects performed a supine graded cycle ergometer test before (pre) and after (post) BR which consisted of 4 min of unloaded pedaling at 60 rpm followed by an increased workrate of 15 W X min-1 until volitional fatigue (max). VE, VCO2, VO2, R, VE/VO2 and VE/VCO2 were measured every 30 s and used collectively to identify the AT. Plasma (PV) and blood (BV) volumes were measured pre- and post-BR by T-1824. Following BR, VO2max decreased from 2.42 +/- 0.17 to 2.25 +/- 0.13 L X min-1 (7.0%, p less than 0.05). BR significantly (p less than 0.05) reduced the AT from 1.26 +/- 0.09 to 0.95 +/- 0.05 L X min-1 VO2; from 52.2 +/- 2.0 to 42.6 +/- 1.6% VO2max; and from 93 +/- 9 to 65 +/- 6 W. A correlation coefficient (r) of -0.11 (NS) was found between the change in VO2max and change in AT. A decrease in BV of 8.8% (p less than 0.05) was due to the 11.0% reduction in PV; red cell volume remained constant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventilatory and plasma lactate response with different exercise protocols: a comparison of methods

The purpose of this study was to compare the methods used to identify abrupt changes in ventilation or plasma lactate (LA) during exercise. Ten males randomly performed a 1-, 3-, and 5-min, 30-W incremental cycle ergometer test to fatigue. The first change in VE and VCO2 relative to VO2 (ventilation threshold, VT1) was determined from plots of VE, VE X VO2-1, and excess CO2 vs VO2. Data were also analyzed for a second change in VE (VT2) relative to both VCO2 and VO2 using plots of VE and VE X VCO2(-1) vs VO2 and semi-log plots of VE X VO2(-1) and VE X VCO2(-1) vs VO2. Arterialized blood samples were taken each 1.0, 1.5, or 2.5 min for the 1-, 3-, and 5-min tests, respectively, to determine the LA threshold (LT) and the onset of blood lactate accumulation (4 mM, OBLA) and 1, 2, 5, 7.5, and 10 min after all tests to calculate the individual anaerobic threshold (IAT). At weekly intervals, subjects also exercised for 10 min at eight different power outputs (W) to define the onset of plasma lactate accumulation (OPLA). Results showed that VO2max was significantly higher for the 1-min (3.88 l X min-1)vs the 3- or 5-min tests (3.65 l X min-1). With increasing W duration, VT1 from either VE or VE X VO2-1 vs VO2 were similar (1.77 vs 1.72 l X min-1) but significantly lower using excess CO2 (1.23 l X min-1) . VO2 at LT (1.62 l X min-1) and OPLA (1.73 l X min-1) were similar to VT1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventilatory and gas exchange responses during heavy constant work-rate exercise.

PURPOSE: At constant work-rates below the gas exchange threshold (VO(2 theta)), VO(2) normally achieves steady-state values within 3 min, whereas at heavier work-rates, VO(2) may continue to rise. The VO(2) response to heavy exercise can be described by a three-exponential model with the slow phase usually commencing 2-3 min after the onset of exercise. The aim of our study was to estimate precisely the VO(2), VCO(2), VE and f(C) required for above-VO(2 theta) exercise from the relationship of the specific variable to work-rate below VO(2 theta) and to compare this with the actual value achieved. METHODS: Nine cyclists performed five constant work-rates of 8 min duration, four below VO(2 theta) (40, 80, 120, 160 W) and one midway between VO(2 theta) and VO(2max) (295 +/- 34 W). The VO(2), VCO(2), VE and f(C) were averaged for the final 2 min of each below-VO(2 theta) test and were found to be linear with respect to work-rate (average r2 >0.95). Variables for the above-VO(2 theta) work-rate were predicted by extrapolation and compared with the actual measured values at the end of the exercise bout. RESULTS: VO(2) exceeded the predicted value by 0.48 +/- 0.21 L x min(-1) (12.4 +/- 5.1%), VCO(2) by 0.78 +/- 0.26 L x min(-1) (23.2 +/- 7.2%), VE by 40.3 +/- 16.3 L x min(-1) (51.0 +/- 23.1%), and f(C) by 12.2 +/- 12.5 beats x min(-1) (8.8 +/- 9.3%), all P < 0.0001 except f(C) P < 0.02, paired t-test. The point at which VO(2) during above-VO(2 theta) exercise exceeded the predicted value (145.7 +/- 64.9 s) agreed with the point at which the slow component of VO(2) began, as determined by nonlinear regression analysis (131.5 +/- 44.3 s, P = NS, ANOVA). CONCLUSION: There is an excessive metabolic response to heavy exercise over and above that predicted by extrapolation from light-moderate exercise and this excess VO(2) approximates on average to the slow phase of a three-compartment exponential model.     

The ventilatory threshold, heart rate, and endurance performance: relationships in elite cyclists

The purpose of this study was to investigate the validity of the ventilatory response during incremental exercise as indication of endurance performance during prolonged high-intensity exercise under field test conditions in elite cyclists. The ventilatory threshold (VT) was assessed in 14 male elite cyclists (age 22.4+/-3.4 years, height 181+/-6 cm, weight 69.2+/-6.8 kg, VO2max 69+/-7 ml x min(-1) x kg(-1)) during an incremental exercise test (20 W x min(-1)). Heart rate and oxygen uptake were assessed at the following ventilatory parameters: 1. Steeper increase of VCO2 as compared to VO2 (V-slope-method); 2. Respiratory exchange ratio (RQ)=0.95 and 1.00; 3. VE/VO2 increase without a concomitant VE/VCO2 (VE/VO2 method). Three weeks following the laboratory tests, the ability to maintain high-intensity exercise was determined during a 40 km time trial on a bicycle. During this time trial the mean heart rate (HR(TT)) and the road racing time (TT) were assessed. The V-slope-method and the VE/VO2 method showed significant correlations with TT (V-slope: r = -0.82; p<0.001; 90% interval of confidence = +/-82 sec; VE/VO2: r=-0.81; p<0.01; 90% interval of confidence = +/-81 sec). Heart rate at the ventilatory parameters and at the maximum heart rate (HRmax) showed significant correlations with HR(TT). The V-slope-method is the preferred method to predict heart rate during prolonged high-intensity exercise (r=0.93; p<0.0001; 90% interval of confidence: +/-4.8 beats x min(-1)). For predicting heart rate during prolonged high-intensity exercise using an incremental exercise test (20 W x min(-1)), without the knowledge of ventilatory parameters, we recommend using the regression formula: H(TT)=0.84 x Hmax + 14.3 beats x min(-1) (r=0.85; p<0.001).     

Reliability of the VmaxST portable metabolic measurement system

The purpose of this study was to evaluate the reliability of the VmaxST portable metabolic measurement system. Forty-five healthy adults (age = 25.7 +/- 5.9 yr; height = 171.8 +/- 9.1 cm; weight = 69.6 +/- 12.8 kg; VO2peak) = 40.7 ml/kg/min; percent fat = 21.7 +/- 11.0) performed two separate and identical exercise routines on different days consisting of treadmill walking at 2.0 mph (53.6 m/min), 3.0 mph (80.5 m/min), and 4.0 mph (107.3 m/min) and running at 6.0 mph (160.9 m/min). VE and gas exchange were measured continuously breath-to-breath. A random effects model on log-transformed data yielded coefficients of variation (CV) and intraclass correlation coefficients (ICC) for VO2 and VE of 5.2 - 7.6 %, and 0.77 - 0.92, respectively, for all walking and running trials. For VCO2, CVs were higher (10 - 12 %) and ICCs lower (0.70 - 0.81). Ordinary least squares regression between the individual difference scores and the individual mean scores for VE, VO2 and VCO2, respectively, indicated no systematic bias (all p > 0.05). Bland-Altman analysis also illustrated no systematic bias between repeated measurements. The VmaxST provides reliable measurements of VO2 and VE during walking and running eliciting VE and VO2 at least up to approximately 56 and 2.2 l/min, respectively. The system appears to be less reliable for measuring VCO2.     

Influence of work rate incremental rate on the exercise responses in patients with COPD

PURPOSE: The peak work rate (Wpeak) measured during a progressive stepwise exercise test is commonly used to select the target training intensity for an exercise training program. In healthy subjects, a greater Wpeak is achieved when a faster rate of increase in work rate is used, whereas VO2 peak is independent of the rate of increase in work rate. This effect might be even more pronounced in chronic obstructive pulmonary disease (COPD) patients, in whom the VO2 kinetics during exercise are slower compared with healthy subjects. METHODS: To investigate this, we studied 10 COPD patients (9 M/1 F, age: 65+/-5 yr [mean +/- SD], FEV1: 33+/-8%). They underwent, on separate days, three stepwise exercise tests on an ergocycle. For each test, increments of 5, 10, or 20 W x min(-1) were used in random order; the investigator was blinded as to which increment was used. VO2, VCO2, heart rate (HR), minute ventilation (VE), breathlessness and leg fatigue at rest, at each work rate, and at maximal capacity were obtained. RESULTS: Wpeak averaged 40+/-13, 53+/-14, and 66+/-19 W for the 5-, 10-, and 20-W protocol, respectively (P < 0.001), whereas VO2 peak was comparable at 0.96+/-0.16, 1.02+/-0.18, and 1.03+/-0.20 L x min(-1). As the rate of increase in work rate became faster, the VO2/work rate relationship shifted to the right. This is exemplified by the VO2 at 40 W, which averaged 0.98+/-0.06, 0.90+/-0.09, and 0.83+/-0.10 L x min(-1) for the 5-, 10-, and 20-W protocol, respectively (P < 0.05). Similar observations were made for the relationship between HR, VE, and symptom scores, and work rate. There was no significant differences in peak values for HR and VE, and symptoms scores. CONCLUSIONS: We conclude that the work rate incremental rate influences the Wpeak achieved, whereas the peak values for VO2, HR, VE, and symptom scores remain comparable. These findings have practical implications for the exercise evaluation of patients with COPD.     

Smoking effect on exercise response kinetics of oxygen uptake and related variables

The effects of smoking on the kinetics of oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (Ve) and heart rate (HR) in the transition from rest to steady-state submaximal exercise was investigated in 6 female and 4 male smokers (32 +/- 8 yrs). The subjects underwent two counter-balanced treadmill tests at 60% of their maximal VO2, lasting 10 min each: one following a 24-hr smoking abstinence, and one immediately after smoking three cigarettes without prior abstinence. Physiological variables were measured at rest and every 30 sec throughout each test. The time required for a given variable to rise from its respective resting baseline to half of its steady-state value (t1/2) was calculated for VO2, VCO2, Ve and HR. Smoking abstinence was associated with t1/2 values of 32 +/- 8, 42 +/- 12, 43 +/- 10, and 30 +/- 9 sec for VO2, VCO2, Ve, and HR, respectively. Smoking significantly (p less than 0.01) lengthened those values to 51 +/- 12, 58 +/- 11, 54 +/- 8, and 41 +/- 10 sec. Concurrently, smoking raised the baseline (resting) values of HR (p less than 0.01) and of Ve, VCO2, O2 pulse (O2P), and both systolic and diastolic blood pressures (p less than 0.05). During steady-state exercise only HR values were elevated by smoking (p less than 0.01), while O2P values were lowered (p less than 0.05). These findings indicate that smoking considerably retards physiological responses to submaximal exercise.     

Use of facemask and mouthpiece to assess constant-workrate exercise capacity in COPD

PURPOSE: To compare the response to constant-workrate cycling exercise between the mouthpiece and the facemask in patients with chronic obstructive pulmonary disease (COPD). METHODS: Ten patients with COPD (FEV1: 48 +/- 14% pred, mean +/- SD) performed two symptom-limited constant-workrate cycling exercise tests at 80% of their predetermined peak exercise capacity. One test was performed using a mouthpiece and the other with a facemask, in a random order. The endurance time to constant-workrate exercise was compared between the two interfaces. VO2, VCO2, ventilation (VE), inspiratory capacity, dyspnea Borg score, and heart rate responses during exercise were also compared. RESULTS: Endurance time was similar between the two interfaces (mean difference +/- SD, 30 +/- 74 s, P = 0.23). Except for the end-exercise values, which were lower with the facemask, the VO2, VCO2, and VE responses to submaximal exercise were similar between the two interfaces. Perception of dyspnea, inspiratory capacity, and heart rate kinetics were similar during the two exercise tests. No clear preference about either interface was expressed by the patients. CONCLUSION: The mouthpiece and the facemask can be used with comparable results to determine the endurance time to constant-workrate cycling exercise in patients with COPD. Compared with the mouthpiece, the end-exercise values for VO2, VCO2, and VE were underestimated when a facemask was used. The similar responses in heart rate and symptom perception suggest that this could be due to an air leak at end-exercise with the facemask.     

Exercise performance following intense, short-term ventilatory work

Evidence exists to indicate that prolonged ventilatory work fatigues respiratory muscles and may limit exercise tolerance. However, the effects of short-duration, high-intensity ventilatory work on subsequent exercise remains in question. We tested the hypothesis that intense short-term volitional hyperpnea would result in respiratory muscle fatigue and would therefore hinder subsequent exercise tolerance. Pulmonary function was determined in ten healthy, male subjects before and after two constant load exercise tests to exhaustion on a cycle ergometer. Test 1 was a preliminary test to determine VO2max, peak exercise VE, and peak exercise power output. Test 2 was a constant load (85% peak power output) exercise test to exhaustion. Test 3 was identical to test 2 but was preceded by 10 min of volitional, isocapnic hyperpnea (85% of peak exercise V.E) at a controlled frequency and tidal volume. Pulmonary function measures (FVC, FEV1, FEV1/FVC, and peak flow) were not significantly (P less than 0.05) altered by the volitional hyperpnea. Ventilation and gas exchange variables (VO2, VE, f, end-tidal PO2 and PCO2, VE/VO2, VE/VCO2, %SaO2) during exercise and time to exhaustion were not significantly (P less than 0.05) different between treatments. These experiments failed to show any effect of short-term ventilatory work on pulmonary function or subsequent exercise performance.     

Metabolic and cardiorespiratory responses relative to the anaerobic threshold

The present study has compared the metabolic and cardiorespiratory responses for two groups of male subjects during 20 min of exercise at the anaerobic threshold (AT), at AT + 1/3, and at AT + 2/3 of the difference (delta) between AT and VO2max. A log-log transformation of the lactate (LA)-power output relationship was used to define AT and divide subjects into a high (N = 7, AT = 51.9 +/- 1.5% VO2max) and low (N = 5; AT = 41.9 +/- 1.8% VO2max) AT group. No differences were observed between groups during exercise at AT for VE.VO2-(1), VE.VCO2(-1), pH, pCO2, blood LA, and plasma strong ions Na+, K+, and Cl-. Although blood LA values were significantly elevated for the low AT subjects (2.3 +/- 0.6 mmol.l-1) compared with the high AT group (1.0 +/- 0.1 mmol.l-1) during exercise at AT + 1/3 delta, no other differences between groups were noted. In contrast, marked differences were observed between groups during exercise at AT + 2/3 delta. The high AT group showed no change in VE (79.1 +/- 4.8 l.min-1), pH (7.367 +/- 0.01), pCO2 (37.3 +/- 1.2 mm Hg), and blood LA (2.9 +/- 0.3 mmol.l-1) during the final 10 min of the 20 min exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise capacity of cardiac asymptomatic hereditary hemochromatosis subjects

PURPOSE: The exercise capacity of cardiac asymptomatic subjects with hereditary hemochromatosis (HH) has not been well described. In this study, we tested whether the iron overload associated with HH affected exercise capacity with a case control study design. METHODS: Forty-three HH and 21 normal control subjects who were New York Heart Association functional class I underwent metabolic stress testing using the Bruce protocol at the clinical center of the National Institutes of Health. Exercise capacity was assessed with minute ventilation (.VE), oxygen uptake (.VO2), and carbon dioxide production (.VCO2) using a breath-by-breath respiratory gas analyzer. RESULTS: The exercise capacity of HH subjects was not statistically different from that of control subjects (exercise time 564 +/- 135 vs 673 +/- 175 s, P = 0.191; peak .VO2 29.6 +/- 6.4 vs 32.5 +/- 6.7 mL.kg(-1).min(-1), P = 0.109; ventilatory threshold 19.0 +/- 3.4 vs 21.0 +/- 5.0 mL.min(-1).kg(-1), P = 0.099; data are for HH vs control subjects). Ventilatory efficiency was comparable between groups (.VE/.VCO2 slope 23.7 +/- 3.2 vs 23.4 +/- 4.2, P = 0.791). No significant correlation between the markers of iron levels and the markers of exercise capacity was noted. Iron depletion by 6-month phlebotomy therapy in 18 subjects who were newly diagnosed did not affect exercise testing variables (exercise time 562 +/- 119 vs 579 +/- 118 s, P = 0.691; peak .VO2 29.5 +/- 3.7 vs 29.1 +/- 4.7 mL.kg(-1).min(-1), P = 0.600; ventilatory threshold 18.5 +/- 2.8 vs 17.9 +/- 3.8 mL.kg(-1).min(-1), P = 0.651; data are from before and after phlebotomy therapy). Abnormal ischemic electrocardiographic responses and complex arrhythmias were more frequently seen in HH subjects. CONCLUSIONS: The aerobic exercise capacity of asymptomatic HH subjects seems not to be statistically different from that of normal subjects. The iron levels do not seem to affect exercise capacity in asymptomatic HH subjects.     

Does exercise alter anaerobic threshold in coronary artery disease during beta blockade?

The effect of propranolol on cardiac patients undergoing exercise training is reported to increase exercise tolerance and maximum oxygen uptake (VO2 max) but its effect on anaerobic threshold (AT) is unknown. It was the purpose of this study to determine the role of exercise training with propranolol on AT in patients with coronary artery disease (CAD). Eight men and one woman with significant (CAD) were selected for this study. Each patient completed a maximum treadmill stress test (MTST) following the Bruce protocol on propranolol 40-160 mg/day as a control study. Cardiorespiratory variables were measured at rest and at each stage of the treadmill test. These patients underwent an exercise training programme for 12-16 weeks on the same dose of propranolol. Training sessions were for a minimum of 30-40 minutes, 3 times a week, with training heart rate of 75%-85% of the pretraining peak heart rate. Training heart rate ranged from 98 to 128 beats/min. They were retested with a MTST after the training programme, on the same dose of propranolol. AT was calculated noninvasively by measuring respiratory variables every 30 seconds in relation to work increment. AT was identified by measuring the time course of VE, VCO2, VE/VO2, etc. in relation to incremental work. The mean values of VO2, O2P and % VO2 max at AT before and after training on propanolol were as follows: VO2 = 1.43 L/min +/- .25 and 1.86 L/min +/- .44, O2P = 14.35 +/- 2.40 and 18.73 +/- 4.00 ml/beat, % of VO2 max = 68.20 +/- 6.31 and 73.59 +/- 5.84. The mean changes of VO2 O2P, and % of VO2 max were + 0.43 L/min +/- 0.20 (P < .003), + 4.38 +/- 2.55 (P < .003) and +/- 5.07% +/- 4.84 (P < .001). After exercise training on propanolol, the mean peak exercise tolerance time and absolute VO2 max increased by 2.8 min (from 9.0 to 11.8 min) (P < .001) and 22.7% (P < .007), respectively. We conclude that the increase in anaerobic threshold in patients with coronary artery disease may be due to improvement in VO2 max, increased stroke volume, and peripheral O2 extraction.     

Faster kinetics of VO2 during arm exercise with circulatory occlusion of the legs

Occlusion of the nonworking leg muscles prior to the onset of supine arm exercise was examined for an effect on the kinetics of respiratory gas exchange (VO2 and VCO2), ventilation (VE), and heart rate (HR). Seven subjects performed arm cycling at 40 W (two females) or 50 W (five males) for 8 min following 4 min of "0" W pedaling. Six repetitions of each of uncuffed and cuffed leg conditions were averaged for individual subject analysis. The VO2 kinetics were significantly faster in the cuffed than the uncuffed condition (mean response time 66.0 +/- 26.4 vs 81.2 +/- 37.5 s, P less than 0.04). The kinetics of VCO2, VE, and HR were not affected by occlusion. It is concluded that the faster VO2 kinetics with the prior occlusion of nonworking leg muscles was a consequence of increased availability of oxygen to the working arm muscles at the onset of exercise.     

Pulmonary ventilation in relation to oxygen uptake and carbon dioxide production during incremental load work

The purposes of the present investigation were: (1) to describe the relationships between exercise pulmonary ventilation (VE) and oxygen uptake (VO2) and VE and carbon dioxide production (VCO2), (2) to determine the % VO2 max at the lowest ventilatory equivalent of oxygen (VEO2), and (3) to examine the relationship between the % VO2 max at the lowest VEO2 and maximal aerobic power (VO2 max). During incremental load work, VE increased exponentially in relation to elevations in VO2 and VCO2. Differentiation of the VE to VO2 exponential equation gives the minimum slope of the equation and corresponds to the lowest ventilatory equivalent for oxygen. In our subjects, VO2 max (mean +/- SD) was 3.84 +/- 0.71 l . min-1, and VO2 at the lowest VEO2 was 1.70 +/- 0.32 l . min-1. The VO2 at the lowest VEO2 was 44.3 +/- 4.0% VO2 max (range 37% to 53% VO2 max). The correlation coefficient (r) between VO2 at the lowest VEO2 and VO2 max was 0.90, while the r between % VO2 max at the lowest VEO2 and VO2 max was -0.24.     

Comparison of 6-min "all-out" and incremental exercise tests in elite oarsmen

A high aerobic capacity is an important criterion for rowing success. Two exercise protocols, the 6-min "all-out" (6M-AO) and progressive incremental (PI) tests, have been used to evaluate physiological performance in rowers and to select team members. We measured heart rate (HR), minute ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) every 30 s, and obtained ratings of perceived exertion (RPE) from 12 candidates for the 1983 United States Men's Lightweight Rowing Team. Testing was randomized and each oarsman performed a different test on the rowing ergometer on consecutive days. For the group, age was 23 +/- 2 yr (mean +/- SD), height was 183 +/- 3 cm, and weight was 72.2 +/- 1.4 kg. Peak physiological values were achieved in the first 2 min of exercise for the 6M-AO test, but in the last 2 min for the PI test. There were no statistically significant differences among peak values for HR, VE, VO2, VCO2, and RPE with each test. The peak ventilatory equivalent for oxygen (VE/VO2) was also similar. The onset of anaerobic metabolism was observed at 83 +/- 4% of peak VO2 during the PI test, while anaerobic metabolism has been shown to occur within the first minute of the 6M-AO test. We conclude that physiological values at peak exercise were similar for the 6M-AO and PI tests. Because the onset of anaerobic metabolism can only be determined by noninvasive means using the PI test, this method of testing is preferable for the physiological assessment of rowing performance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Normoxic and acute hypoxic exercise tolerance in man following acetazolamide

The influence of acetazolamide (ACZ) upon the ability to perform and sustain maximal and submaximal exercise bouts under normoxic and hypoxic conditions was examined in four groups of healthy male subjects (N = 27). ACZ (500 mg) or inert placebo (Pla) was administered prior to exercise in a quasi-randomized, double-blind, crossover fashion. ACZ was shown to lower venous pH (ACZ, 7.31 +/- 0.01, vs Pla, 7.35 +/- 0.08) and bicarbonate (ACZ, 22.4 +/- 0.27 mM, vs Pla, 25.4 +/- 0.6 mM) and to elevate urine pH (ACZ, 7.36 +/- 0.06, vs Pla, 5.84 +/- 0.19) and tended to elevate VE (P = 0.07) at rest. Peak VO2 measured using a continuous incremental protocol was unaltered in normoxia, while peak VCO2 and RER were lowered by ACZ. No significant effect of ACZ upon VO2, VCO2, RER, or heart rate (HR) was observed during submaximal exercise (75% of peak VO2) although VE was increased by 14% and time to exhaustion (EXHt) was reduced by 29%. During acute hypoxia at a simulated altitude of 4,270 m (Pbar = 446 mm Hg), no significant differences were noted in VE, VO2, VCO2, RER, HR, or arterial saturation (SaO2) at rest. Prior to exercise, venous pH (ACZ, 7.39 +/- 0.04, vs Pla, 7.44 +/- 0.007) and bicarbonate were lower with ACZ (ACZ, 21.6 +/- 0.46 mM, vs Pla, 24.2 +/- 0.25 mM), while urine pH was higher (ACZ, 7.6 +/- 0.07, vs Pla, 5.9 +/- 0.25). Other than a higher PCO2 and lower venous lactate with ACZ, no significant differences were identified at peak VO2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerobic threshold, anaerobic threshold, and maximal oxygen uptake of Japanese speed-skaters

The purpose of this study was to investigate the physiologic and metabolic parameters of speed-skaters with different training regimes and performance level and examine some physiologic prerequisites for speed-skating. The subjects were 25 male speed-skaters including members of the 1984 Japanese National Speed Skating Team whose ages ranged from 19 to 25 years. Aerobic threshold (AerT), anaerobic threshold (AnT), and VO2max were determined during a progressive bicycle ergometer exercise. The power was increased by 12.25 W every 3 min to exhaustion. AerT was determined using gas exchange variables; nonlinear increase in VE and VCO2, and peak VO2.VE-1. AnT was estimated from breakaway VE and the onset of decrease in FECO2.VO2max was measured during another incremental exercise on a bicycle ergometer. Mean AerT, AnT, and VO2max for skaters (n = 25) were 2.47 +/- 0.36.min-1 (61.1 +/- 7.2 %VO2max), 2.93 +/- 0.33.min-1 (73.4 +/- 5.9 %VO2max), and 4.06 +/- 0.42.min-1, respectively. All-arounders had higher AerT values but the same VO2max as sprinters. AnT of all-arounders was significantly higher than those of sprinters. A significant difference between the top ten elite skaters and the other skaters (n = 15) was found only in VO2max expressed as l.min-1. However, no significant correlation was noted between measured physiologic variables (AerT, AnT, and VO2max) and performances expressed as mean velocities at various events.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproducibility of ventilation of thresholds in trained cyclists during ramp cycle exercise

The reproducibility of peak cardiopulmonary exercise responses and the first (VT1) and second [VT2) ventilation thresholds was studied in sixteen endurance-trained male cyclists (mean +/- SD peak oxygen uptake [VO2 peak] = 63.3 +/- 7.1 ml x kg(-1) x min(-1)) during duplicate 30 W x min(-1) ramp cycling protocols. Expired gas sampled from a mixing chamber was analysed on-line and VT1 and VT2 were determined by computerised V-slope analysis and visually by two evaluators (test-retest reliability) and again by one of the evaluators 12 months later (intra-evaluator reliability) from 20-s-average respiratory data. The results demonstrated high intra-evaluator reliability (r = 0.91-0.97, P < 0.0001) for repeat determinations of VO2, work rate (WR) and heart rate (HR) at VT1 and VT2. No significant differences were observed between Tests 1 and 2 for any of the measured variables (P > 0.05). Test-retest intraclass reliability coefficients ranged from 0.86 to 0.98 (P < 0.0001) for VO2 peak, peak pulmonary ventilation (VE), carbon dioxide output (VCO2), HR and WR values, and measurements of VO2 and WR at VT2, and from 0.67 to 0.80 (P < 0.01) for measurements of VO2 and WR at VT1. The reliability of VT1 and VT2 was reduced when the thresholds were expressed as relative (%VO2 peak) (r = 0.67-0.70, P<0.01) rather than absolute (l x min(-1)) (r = 0.77-0.93, P<0.001) VO2 values. It was concluded that VO2 peak, peak VE, VCO2. HR and WR values, and VT2 are highly reproducible in trained cyclists using a 30 W x min(-1) ramp exercise function. However, determinations of VT1 are less reliable. Additionally, ventilation thresholds are more reliably described using absolute rather than relative VO2 values.     

Expiratory flow limitation confounds ventilatory response during exercise in athletes

INTRODUCTION: A significant number of highly trained endurance runners have been observed to display an inadequate hyperventilatory response to intense exercise. Two potential mechanisms include low ventilatory responsiveness to hypoxia and ventilatory limitation as a result of maximum expiratory flow rates being achieved. PURPOSE: To test the hypothesis that expiratory flow limitation can complicate determination of ventilatory responsiveness during exercise the following study was performed. METHODS/MATERIALS: Sixteen elite male runners were categorized based on expiratory flow limitation observed in flow volume loops collected during the final minute of progressive exercise to exhaustion. Eight flow limited (FL) (VO2max, 75.9+/-2.4 mL x kg(-1) x min(-1); expiratory flow limitation, 47.3+/-20.4%) and eight non-flow limited subjects (NFL) (VO2max, 75.6+/-4.8 mL x kg(-1) x min(-1); expiratory flow limitation, 0.3+/-0.8%) were tested for hypoxic ventilatory responsiveness (HVR). RESULTS: Independent groups ANOVA revealed no significant differences between FL and NFL for VO2max, VE max (136.2+/-16.0 vs 137.5+/-21.6 L x min(-1)), VE/VO2, (28.4+/-3.2 vs 27.6+/-2.9 L x lO2(-1)), VE/VCO2 (24.8+/-3.1 vs 24.4+/-2.0 L x lCO2(-1)), HVR (0.2+/-0.2 vs 0.3+/-0.1 L x %SaO2(-1)), or SaO2 at max (89.1+/-2.4 vs 86.6+/-4.1%). A significant relationship was observed between HVR and SaO2 (r = 0.92, P < or = 0.001) in NFL that was not present in FL. Conversely, a significant relationship between VE/VO2 and SaO2 (r = 0.79, P < or = 0.019) was observed in FL but not NFL. Regression analysis indicated that the HVR-SaO2 and SaO2-VE/VO2 relationships differed between groups. DISCUSSION: When flow limitation is controlled for, HVR plays a more significant role in determining SaO2 in highly trained athletes than has been previously suggested.     

The prognostic value of ventilatory efficiency with beta-blocker therapy in heart failure

PURPOSE: Beta-blockade (BB) has been shown to improve outcomes among patients with heart failure (HF). The impact this pharmacological approach has on the prognostic information gained from cardiopulmonary exercise testing (CPX) is, however, unclear. METHODS: Four hundred seventeen subjects diagnosed with HF underwent CPX. The numbers of subjects prescribed and not prescribed a BB agent were 167 and 250, respectively. Subjects were tracked for cardiac-related mortality after CPX. RESULTS: Values are reported for the no-BB versus the BB group throughout. Age (57.9 +/- 13.3 vs 55.6 +/- 12.5), peak VO2 (16.2 +/- 5.7 vs 16.5 +/- 5.5 mL x kg(-1) x min(-1)), VE/VCO2 slope (34.2 +/- 9.0 vs 33.2 +/- 7.4), and peak RER (1.07 +/- 0.16 vs 1.05 +/- 0.14) were similar between groups (P > 0.05). Multivariate Cox regression analysis revealed that the VE/VCO2 slope was the superior predictor of death in both groups (chi-square: 71.9, P < 0.001; and 18.4, P < 0.001). The optimal threshold values for VE/VCO2 slope in the no-BB and BB groups were 36.0 and 34.3, respectively. CONCLUSIONS: The results of the present study indicate that BB does not alter the prognostic value/characteristics of the VE/VCO2 slope. Findings from previous investigations examining the prognostic significance of CPX predominantly using HF groups not receiving a BB agent may, therefore, still be applicable in modern-day clinical practice.