Maximal Oxygen Uptake Rate Research Articles

Muscle Oxygen Saturation of Master??s Triathletes/Duathletes Similar to that of Younger Athletes

1411 Many current masters' endurance athletes have been exercise training for 20–30 years, longer than that of most previously studied athletes. As individuals age typically maximum oxygen uptake and heart rate decrease as does muscle mass and respiratory capacity. However, training has been shown to maintain maximum stroke volume and a-vO2 difference, while also enhancing muscle respiratory ability. PURPOSE: To determine if muscle oxygen saturation of experienced master's endurance athletes was similar to that of younger endurance trained athletes. METHODS: Six male master triathletes/duathletes (MA; mean age = 57.0 ± 2.4 years) with at least 20 years of continuous training (mean = 24.2 ± 4.9 years) were compared to 6 younger triathletes/duathletes (YA; mean age = 32.3 ± 5.7 years). All athletes performed an incremental exercise test involving five, 6-minute stages. This was followed by a maximal running test (MAX). During the tests, oxygen uptake variables, blood lactate, and muscle oxygen saturation (StO2) of the gastrocnemius through near-infrared spectroscopy (NIRS) were determined. RESULTS: Running speed at lactate breakpoint (BRK) was significantly lower for the MA (7.9 ± 0.6 mph) than for the YA (9.1 ± 1.0 mph). Both BRK and MAX oxygen uptake were similar between the two groups of subjects. BRK heart rate was significantly less for the MA (MA = 156.5 ± 14.1 bpm, YA = 168.0 ± 7.2 bpm), while lactate was significantly greater (MA = 3.9 ± 0.8 mM, YA = 3.1 ± 0.7 mM). StO2 was not different between the two groups at BRK (MA = 65.2 ± 9.4%, YA = 56.2 ± 9.4%), nor at MAX (MA = 50.1 ± 9.9%, YA = 39.5 ± 11.0%). The small sample size probably was the cause of the StO2 values not being significantly different, as all of the MA values were greater than those of the YA. CONCLUSION: The master's athletes had similar if not greater muscle oxygenation when compared to that of the younger athletes probably due to the longevity of their training. This study was funded by Hutchinson Technology Incorporated, Hutchinson, MN

Determination of external and internal mass transfer limitation in nitrifying microbial aggregates.

In this article we present a study of the effects of external and internal mass transfer limitation of oxygen in a nitrifying system. The oxygen uptake rates (OUR) were measured on both a macro-scale with a respirometric reactor using off-gas analysis (Titrimetric and Off-Gas Analysis (TOGA) sensor) and on a micro-scale with microsensors. These two methods provide independent, accurate measurements of the reaction rates and concentration profiles around and in the granules. The TOGA sensor and microsensor measurements showed a significant external mass transfer effect at low dissolved oxygen (DO) concentrations in the bulk liquid while it was insignificant at higher DO concentrations. The oxygen distribution with anaerobic or anoxic conditions in the center clearly shows major mass transfer limitation in the aggregate interior. The large drop in DO concentration of 22-80% between the bulk liquid and aggregate surface demonstrates that the external mass transfer resistance is also highly important. The maximum OUR even for floccular biomass was only attained at much higher DO concentrations (approximately 8 mg/L) than typically used in such systems. For granules, the DO required for maximal activity was estimated to be >20 mg/L, clearly indicating the effects of the major external and internal mass transfer limitations on the overall biomass activity. Smaller aggregates had a larger volumetric OUR indicating that the granules may have a lower activity in the interior part of the aggregate.

Microbial Activity of Gravel Intertidal Zone for Purification of Polluted Near Shore Water

Microbial activity of biofilm formed on the surface of gravels from intertidal zone was estimated using an aerobic respirometer system, and compared with that of suspended marine microorganisms contained in a near shore water, The maximum oxygen uptake rate of the suspended marine microorganisms was 0.15mg<TEX>$O_2$</TEX>/L/hr, indicating the potential of purification of polluted near shore water. For the gravels from the intertidal zone, the maximum uptake rate of oxygen was affected by the vertical positions, but their gross value was 0.77mg <TEX>$O_2$</TEX>/L/hr, which was around 5.1 times higher than the purification potential of polluted near shore water by the microorganisms contained in the near shore water. The nitrogen removed by the gravels from the intertidal zone and the marine microorganisms was about 1/20-1/39 times of the total consumption of oxygen, which was similar to that of the phosphate. The gravel intertidal zone contained lots of particulate organics, over than that in the near shore water, and this was confirmed from the large difference between total oxygen consumption and the removed soluble COD in the microbial activity test. This indicates that the gravel intertidal zone plays an important role in controlling the non-point source pollutants from land, as well as self-purification of polluted near shore water by trapping and degrading the particulate organics.

Aerobic degradation of the azo dye acid red 151 in a sequencing batch biofilter

The azo dye acid red 151 (AR151) was aerobically biodegraded in a sequencing batch biofilter packed with a porous volcanic rock. AR151 was used as the sole source of carbon and energy for acclimated microorganisms. Acclimation was followed using the degradation time and the oxygen uptake rate. A maximal oxygen uptake rate of 0.5 mg O2/(lmin) was obtained. Mineralization studies showed that 73% (as carbon) of the initial azo dye was transformed to CO2 by the consortia. A maximal substrate degradation rate of 247 mg AR151/(lreactord) was obtained. Color removal was up to 99% using an initial concentration of 50 mg AR151/l. Anaerobic tests suggested that in the interior of the porous material, anaerobic biotransformations can occur, contributing from 14% to 16% of the decoloration of the azo dye.

Response surface methodological approach for inclusion of perfluorocarbon in actinorhodin fermentation medium

The combined effects of perfluorocarbon and glucose concentrations on actinorhodin production by Streptomyces coelicolor A3(2) were studied in a 2-l bioreactor using response surface methodology. A 2 2 full-factorial central composite design was employed for experimental design and analysis of the results. The optimum PFC and glucose concentrations were found to be 42.7% and 12.25 g/l, respectively. In these conditions, actinorhodin concentration of 60 mg/l with a biomass concentration of 1.9 g/l, a maximum volumetric oxygen uptake rate of 180 mgO 2/l h and a glucose consumption rate of 0.110 g glucose/l h was attained. These results are in close agreement with the model predictions.

Heart rate, oxygen uptake, and energy cost of ascending and descending the stairs.

This study describes the heart rate and oxygen uptake responses during, and the intensity and caloric cost of, ascending and descending a public-access staircase. Subjects were initially assessed for their maximum oxygen uptake and heart rate on a treadmill in the laboratory. For field measurements, subjects ascended (N = 103) and descended (N = 49) 11 stories of 180 steps, each step of 15 cm in height, for a total vertical displacement of 27.0 m. The mean oxygen uptake and heart rate during the last 30 s of ascending were 33.5 +/- 4.8 mL.kg(-1).min(-1) and 159 +/- 15 beats.min(-1), respectively. During the descent, oxygen uptake and heart rate during the last 30 s of the climb were 17.0 +/- 3.8 mL.kg(-1).min(-1) and 107 +/- 18 beats.min(-1), respectively. The estimated gross energy expended during ascending and descending were 19.7 and 9.0 kcal, or equivalent to an intensity of 9.6 and 4.9 metabolic equivalents (METs), respectively (or 10.2 and 5.2 kcal.min(-1), respectively). The caloric cost of stepping up and down a step was calculated to be 0.11 and 0.05 kcal, respectively. Stair-climbing exercise using a local public-access staircase met the minimum requirements for cardiorespiratory benefits and can therefore be considered a viable exercise for most people and suitable for promotion of physical activity.

Human aerobic performance: too much ado about limits to V(O(2)).

Human endurance performance is often evaluated on the basis of the maximal rate of oxygen uptake during exercise (V(O(2)max)). Methods for overcoming limits to V(O(2)max) are touted as means for increasing athletic endurance performance. Here, we argue that the respiratory system is well designed for delivering O(2) to meet O(2) demands and that no single factor is rate-determining for O(2) uptake. We show that V(O(2)max) can vary 5000-fold among mammals, while any limitation to O(2) delivery by a single component of the respiratory system affects V(O(2)max) by 10% or less. Attempts to increase O(2) delivery by enhancing one step in the respiratory system are shown to have little effect. Blood doping, hyperoxia and O(2) supplementation of high-altitude natives all raise O(2) availability substantially to the working muscles, but these treatments increase V(O(2)max) only minimally. Finally, we argue that O(2) uptake is only one of a number of properties important to human aerobic performance.

Determining the maximum acceptable work duration for high-intensity work.

The aim of this study was to determine the maximum acceptable work duration (MAWD) for high-intensity work. Thirty young individuals participated in this study. Their maximum oxygen uptake (VO2max) and maximum work rate (MWR) were assessed first. Each subject then performed two cycling tests (60% and 70% MWR) on two separate days. Oxygen uptake and heart rate data were collected throughout the test. The results indicate that the MAWD in the 60% MWR test (18.8 min) was about threefold greater than the MAWD in the 70% MWR test (6.5 min). The MAWD was inversely correlated with the relative workload indices: relative oxygen uptake (RVO2; r = -0.82, P < 0.001) and relative heart rate (RHR; r = -0.79, P < 0.001). The RVO2 was defined as the elevation in oxygen uptake from the resting level as a percentage of the difference between maximum and resting oxygen uptake. The RHR was defined as the elevation in heart rate from the resting level as a percentage of the difference between maximum and restingheart rate. Furthermore, more than 80% of the variations were explained by the exponential decrease regression model for predicting MAWD using the above two variables. The findings of this study can provide useful information for the design of high-intensity jobs.

A validation of the 10-meter incremental shuttle walk test as a measure of aerobic power in cardiac and rheumatoid arthritis patients

MacSween A, Johnson NJL, Armstrong G, Bonn J. A validation of the 10-meter incremental shuttle walk test as a measure of aerobic power in cardiac and rheumatoid arthritis patients. Arch Phys Med Rehabil 2001;82:807-10. Objective: To validate a simple, clinically relevant, and inexpensive test of aerobic power—the 10-meter incremental shuttle walk test (SWT)—in 2 separate patient populations. Design: Two-sample validity study. Setting: Physiotherapy department of major hospital in the United Kingdom. Patients: Convenience samples of rheumatoid arthritis (RA) patients (n = 10) and cardiac patients (n = 10). Intervention: Subjects were attached to a portable respiratory gas analyzer to measure oxygen uptake. They walked around an oval 10-meter course, starting at 0.5m/s, with velocity gradually increased by.17m/s increments for as long as they could, for up to 12 minutes. Main Outcome Measures: A subject's maximal rate of oxygen uptake during exercise (V̇O2max) established with linear extrapolation was regressed against the number of shuttles completed (distance walked). An earlier study (n = 28) showed high levels of reliability and validity with linear extrapolation. Results: No significant linear relationship was found between V̇O2max and the number of shuttles completed (R2; RA subjects = 9.7%, cardiac subjects =.03%, p >.05). Conclusion: These results do not support use of the SWT as a representative measure of aerobic power. Despite this finding, the advantages of developing a clinically viable alternative to costly laboratory testing warrants further study of the SWT in patient groups.

Improvement of antibiotic production by increased oxygen solubility through the addition of perfluorodecalin

AbstractA perfluorocarbon (PFC), namely perfluorodecalin, was added to fermentation medium to increase the medium's oxygen solubility. The antibiotic concentration obtained in the absence of PFC was 45 mg dm−3, whereas it was 90 mg dm−3 in the presence of 10% (v/v) PFC. On the other hand, biomass concentration decreased from 5.7 kg m−3 to 2.9 kg m−3 by adding 10% PFC. The use of PFC in the fermentation medium also reduced the formation of mycelial pellets. The values of the mass transfer coefficient, kLa, measured in the medium with PFC were found to be in the range of 122–175 h−1 during the active growth phase which were two to three times higher than those in the medium containing no PFC. Furthermore, the maximum oxygen uptake rates obtained at the stationary phase with and without PFC were 7 mmol dm−3 h−1 and 4.9 mmol dm−3 h−1, respectively. The actual effect of PFC on actinorhodin fermentation was demonstrated by applying different operational strategies to the system.© 2001 Society of Chemical Industry

Validation of a new model for aerobic organic solids decomposition: simulations with substrate specific kinetics

This study is a synthesis of substrate specific kinetics and a mass and energy model to predict the process dynamics of the aerobic degradation of synthetic food waste (SFW). The model is validated against pilot scale experimental data obtained from two previous studies. In all the observations the model tended to over predict values of the state variables. The maximum rates of oxygen uptake, cumulative oxygen uptake, and the maximum process temperature were all over predicted. The sensitivity of the model to two key parameters, the specific O 2 uptake, γ O 2 , and the respiration quotient, β r, was also investigated. It was noted that the smaller values of respiration quotient produced better estimates later in the process. The maximum rate of O 2 uptake was insensitive to changes in specific oxygen uptake rate at low aeration rates and more sensitive at high aeration rates. Discrepancies between the model predictions and actual data are explained by the violations of basic assumptions of homogeneous bed conditions.

The reaction of young coho Oncorhynchus kisutch to declining oxygen levels during long-term exposure

The respiration of coho salmon, Oncorhynchus kisutch, weighing between 20 and 45 g was measured at gradually declining oxygen levels and at temperatures ranging between 14 and 17 °C. The maximum and minimum oxygen concentrations tested were 235 and 41 μmol/L, respectively. Respiration rates were measured for 24 h at 235 μmol/L before the oxygen concentration was lowered stepwise to 157 and 81 μmol/L. In one single trial, the oxygen level was lowered to 66, 53, and 41 μmol/L. Respiration was highly variable in time. Peak activities always occurred during the night. The standard metabolic rate at normoxic conditions was estimated to be around 4 μmol oxygen/g/h. The highest rates reached values close to 15 μmol oxygen/g/h. At reduced oxygen levels the standard oxygen demand slightly increased to 4.5 μmol oxygen/g/h, indicating a higher demand for vital metabolic functions. Due to the decrease of swimming activity, the maximum oxygen uptake rates dropped to < 8 μmol oxygen/g/h below 81 μmol/L oxygen concentration. Under long-term conditions, physiological and behavioural adaptations play an important role for survival and need to be considered for the design and operation of fish farm facilities.

Non-steroidal anti-inflammatory drugs and renal response to exercise: a comparison of indomethacin and nabumetone

Nabumetone, a newer non-steroidal anti-inflammatory drug (NSAID) which preferentially blocks cyclo-oxygenase-2 activity, may be less nephrotoxic than indomethacin. This study tested whether nabumetone has effects different from those of indomethacin on exercise-induced changes in renal function and the renin-aldosterone system. In a randomized fashion, ten subjects were studied after indomethacin (100 mg), nabumetone (1 g) or no medication (control) administered orally at 22.00 hours on the day before each study day, and again at 8.00 hours upon arrival at the laboratory. Renal function was studied at baseline, during graded 20-min exercise sessions at 25%, 50% and 75% of the maximal oxygen uptake rate, and subsequently during two 1-h recovery periods. Heart rate, arterial blood pressure, cardiac output and plasma catecholamines at rest and during exercise were not altered by indomethacin or nabumetone. Indomethacin decreased urinary rates of excretion of 6-oxo-prostaglandin F(1alpha) (6-oxo-PGF(1alpha)) and thromboxane B(2) in all study periods. Nabumetone decreased 6-oxo-PGF(1alpha) excretion during and after exercise. Excretion rates for PGE(2) did not change. Neither indomethacin nor nabumetone changed baseline values or exercise-induced decreases in renal plasma flow or glomerular filtration rate. Indomethacin, but not nabumetone, decreased sodium excretion, urine flow rate and free water clearance. The renal response to exercise, however, remained unchanged. In contrast with nabumatone, indomethacin decreased the plasma renin concentration. Thus, during exercise, nabumetone may decrease the excretion of 6-oxo-PGF(1alpha) by inhibition of cyclo-oxygenase-1 or by inhibition of specific exercise-induced activation of cyclo-oxygenase-2, or both. None of the drugs changed the renal response to exercise. Inhibition by indomethacin of angiotensin II and thromboxane A(2) synthesis may, during exercise, counterbalance renal vasoconstriction caused by blockade of vasodilatory prostaglandins.

Respiration of Aquatic and Terrestrial Amphibian Embryos

Respiratory constraints on the structure of single eggs and egg masses have affected the mode of amphibian reproduction in water and in air. Aquatic eggs generally require less oxygen, develop faster, and hatch earlier, but these characteristics are related to small ovum size. A comparison of two species of aquatic and terrestrial breeding frogs with similarly sized ova shows no differences in hatching stage, maximum rate of oxygen uptake, oxygen conductance of the egg capsule, or P o2 difference across the capsule. However, the aquatic species develops about 2.4 times faster and tolerates lower environmental P o2, suggesting adaptation for development in ephemeral water. Modelling of diffusive oxygen transport into a single aquatic egg shows that a large amount of jelly (or a boundary layer) around the capsule may not greatly restrict gas exchange, if the inner radius of the capsule is large. However, gelatinous egg masses that contain other embryos that compete for oxygen are therefore limited in size, unless the eggs are ventilated by convection of water among them. Aquatic egg are often suspended in masses above the substrate, promoting oxygen movement into the mass from all directions. Terrestrial egg masses are more diffusion limited, because gravity and surface tension collapse them, preventing convection between the eggs, and restricting the source for oxygen diffusion. Terrestrial embryos are often larger than their aquatic counterparts and have higher demands for oxygen. Terrestrial conditions have selected for adaptations that reduce respiratory competition between embryos, for example, separating of embryos by large volumes of jelly or reducing the number of eggs in a clutch. The size of foam nests is unlimited, because oxygen for each embryo is supplied directly from the foam.

Influence of structurally different lipid emulsions on human neutrophil oxygen radical production.

The aim of this study was to evaluate immunomodulatory properties of lipid emulsions applied in parenteral nutrition by measuring neutrophil oxygen radical production (the 'respiratory burst') after lipid incubation. Neutrophils, isolated from the blood of 10 healthy individuals, were incubated in medium or in lipid emulsions in a physiological concentration (2.5 mmol L-1) containing long-chain [Intralipid (LCT)], mixed medium and long-chain [Lipofundin (LCT/MCT)] or structured triglycerides (SL). After washing and stimulation with phorbol 12-myristate 13-acetate (PMA) or serum-treated zymosan (STZ) particles, the respiratory burst was evaluated by measuring maximum oxygen uptake, superoxide and hydrogen peroxide production rates and chemiluminescence. Unlike LCT and SL, LCT/MCT increased PMA- and STZ-induced oxygen uptake rate by 45% and 31% respectively (both P = 0.006 compared with medium) as well as superoxide (+56%, P = 0.006) and hydrogen peroxide (+14%, P = 0.04) production, within 5 min after stimulation. Increased LCT/MCT-mediated early respiratory burst was confirmed by decreased PMA- (-65%) and STZ-stimulated (-54%) chemiluminescence peak time (time after stimulation to peak) in combination with unchanged peak height (maximum rate of radical production). Late respiratory burst (within 2 h) of LCT/MCT, indicated by overall luminescence (overall radical production), remained unchanged (PMA) or decreased (STZ, P = 0.02). The addition of 2.5 mmol L-1 LCT/MCT or MCT emulsion to unstimulated neutrophils, in contrast to LCT and SL, resulted in significant luminescence. Early neutrophil respiratory burst is accelerated by the LCT/MCT emulsion Lipofundin, whereas LCT (Intralipid) and structured lipid emulsions exert no effect. MCT-containing emulsions, contrary to LCT and structured lipid emulsions, can induce oxygen radical production in unstimulated neutrophils.

Physiological responses and perceptions of exertion in a step aerobics session

The aims of this study were to establish the cardiovascular and metabolic demands of a university step aerobics session entitled ‘Uni-Step’ performed at three step heights, and to evaluate the use of heart rate and ratings of perceived exertion for the estimation of exercise intensity during this mode. Ten female participants in step aerobics (meanVO2max = 47.7,= 6.8 ml.kg-1.min-1) performed a 40-min Uni-Step routine on steps of height 6, 8 and 10 inches (15.2, 20.3 and 25.4 cm). Oxygen uptake, heart rate and ratings of perceived exertion were recorded throughout each test. Maximum oxygen uptake (VO2max) and maximum heart rate were measured using a continuous treadmill protocol. The mean intensities were 45.6%, 51.6% and 56.2% VO2max for the 6-,8- and 10-inch steps respectively. The mean percent heart rate reserves were 57.2%, 63.6% and 70.1% at these three heights respectively. Correlations indicated a weak relationship between % VO2max and ratings of perceived exertion for the 6-and 8-inch steps (r = 0.61 and 0.66 respectively) but a stronger one for the 10-inch step (r = 0.79). Uni-Step performed on the two highest steps was of a sufficient relative intensity to improve or maintain the cardiovascular fitness of participants in this study. The lowest step may be useful for participants of lower fitness. Heart rate overestimated the metabolic cost of Uni-Step at all three step heights and therefore caution is advised if used to predict intensity. Low correlations between % VO2max and ratings of perceived exertion at the two lower step heights indicate that ratings of perceived exertion may have limited utility in prescribing training intensity.

Latitudinal variation in the abundance and oxidative capacities of muscle mitochondria in perciform fishes

The abundance, distribution and oxidative capacities of mitochondria have been investigated in the red pectoral fin adductor muscles of fish (Order Perciformes) that use a predominantly labriform style of swimming. Mediterranean Sea species from the families Labridae, Serranidae, Sparidae and Antarctic Nototheniidae and non-Antarctic Nototheniidae and Channichthyidae were studied. Sub-Antarctic species from the Beagle Channel, Tierra del Fuego, included the pelagic haemoglobin-less icefish (Champsocephalus esox) and the robalo (Eleginops maclovinus), which occurs as far north as 35 degrees S. In Champsocephalus esox, the mitochondrial volume density of red muscle was 0.51 and mitochondrial cristae surface density (43. 9 microm2 microm-3) was higher than reported for Antarctic icefishes. In the red-blooded, active pelagic or semi-pelagic species, mitochondrial volume density was within the range 0.27-0.33 regardless of habitat temperature. Amongst less active demersal species, mitochondrial volume density ranged from 0.29-0.33 in polar species to 0.08-0.13 in Mediterranean species. In Antarctic species and Champsocephalus esox, myofibrils occurred in ribbons or clusters one fibril thick entirely surrounded by mitochondria. The volume density of intracellular lipid droplets was not correlated with activity patterns or habitat temperature. In a comparison of Eleginops maclovinus caught in summer (approximately 10 degrees C) and winter (approximately 4 degrees C), mitochondrial volume density did not differ, whereas the surface density of mitochondrial clusters was higher in summer fish. The temperature-dependence of the state 3 respiration rate of isolated mitochondria with pyruvate as substrate was described by a single quadratic relationship for all species, indicating no significant up-regulation of the maximum rate of oxygen uptake per milligram mitochondrial protein in Antarctic species. Our results support the conclusion that increasing the volume and surface density of mitochondrial clusters is the primary mechanism for enhancing the aerobic capacity of muscle in cold-water fish.

Exercise performance in elite male and female sailors.

In order to evaluate the physiological profile of elite competitive sailors, and to determine if sailors revealed any seasonal variation in their exercise capacity over a 9 month period, results from female sailors (n = 6), and male sailors ("hikers" n = 8 and "non-hikers" n = 7) were compared with male physical education students (n = 8). Maximal oxygen uptake rate (VO2max) determined on treadmill did not differ between male sailors and control subjects (61.4 +/- 2.0 vs 64.9 +/- 1.4 ml O2/min.kg, mean +/- SE) and did not change with time in elite sailors (p > 0.05). Isometric endurance for abdominal and back muscles was similar for all groups. The isometric muscle endurance in a hiking bench was markedly greater in "hikers" [time: 218 sec (91-426) mean, range] compared to control subjects [time: 98 sec (48-188)], male "non-hikers", and female sailors (p < 0.05). Hiking endurance in "hikers" did not change over the 9 month observation period. Furthermore, dynamic arm performance ("all-out" in 60 sec) was higher in "hikers" compared to all other groups. Elite sailors who perform hiking activity ("hikers") show an enhanced performance in a functional arm test and higher endurance in a hiking-bench compared to "non-hiking" elite sailors and a control group matched for age, weight and fitness. Furthermore sailors did not show any seasonal variation in their VO2max or isometric endurance over a 9 month period.

Effects of daily mild supine exercise on physical performance after 20 days bed rest in young persons

To investgate the effects of daily mild supine exercise on physical performance capacity identified as maximal oxygen uptake rate (VO 2max) after 20 days bed-rest, 3 male students performed a supine pedaling at 40 % intensity of VO 2max for one hour every day, while 6 male and 5 female students were control. Before and after the bed-rest, muscle mass and strength of exercising leg and cardio-vascular responses during −40 mmHg lower body negative pressure (LBNP) and moderate upright cycling exercise were measured. Despite the exercise programme VO 2max was similarly decreased to the control subjects after the bed-rest. The delta VO 2max was correlated to delta % left ventricular fractional shortening during LBNP, and also % delta VO 2max to % delta stroke volume of the moderate exercise (both p<0.05). The exercise programme should be too weak to maintain cardiovascular functions and thus to present the decrease in VO 2max against pro-longed bed-rest as well as weightlessness stress.

THE ROLE OF CARDIOPULMONARY EXERCISE TESTING IN LUNG AND HEART-LUNG TRANSPLANTATION

Cardiopulmonary exercise testing in recipients of lung and heart-lung transplants demonstrates significant restoration of exercise tolerance to individuals severely disabled by their underlying cardiopulmonary disease. Recipients can perform moderate levels of activity compatible with a normal lifestyle. Considerable exercise limitation, however, remains in most recipients as measured by maximum oxygen uptake and work rate, despite substantial improvement and often normalization in resting cardiopulmonary function. The amount of exercise limitation observed in recipients of single-lung, bilateral-lung, and heart-lung transplants is interestingly similar, and the pattern of limitation is somewhat stereotyped. Ventilatory abnormalities are never limiting. Gas exchange abnormalities are sometimes seen (especially in single-lung transplant recipients) but generally are not limiting. Cardiac dysfunction is sometimes seen (particularly in heart-lung transplant recipients) but also does not appear to be limiting. Peripheral factors limiting exercise (which may include abnormalities in the peripheral circulation and peripheral neuromuscular structure and function) are almost universally seen and are probably the primary determinant of exercise limitation in these patients. At present, the relative contributions of various peripheral factors to exercise limitation are unclear. Further study may help elucidate these issues.