Percentage Of Oxygen Consumption Research Articles

Hydrolyzed whey protein enriched with glutamine dipeptide attenuates skeletal muscle damage and improves physical exhaustion test performance in triathletes.

To investigate the effects of hydrolyzed whey protein enriched with glutamine dipeptide on the percentage of oxygen consumption, second ventilatory threshold, duration and total distance covered, and skeletal muscle damage during an exhaustion test in elite triathletes. The study was a randomized, double-blinded, placebo-controlled, crossover trial. Nine male triathletes performed a progressive incremental test on a treadmill ergometer (1.4 km h-1·3 min-1) 30 min after ingesting either 50 g of maltodextrin plus four tablets of 700 mg hydrolyzed whey protein enriched with 175 mg of glutamine dipeptide diluted in 250 ml of water (MGln) or four tablets of 700 mg maltodextrin plus 50 g maltodextrin diluted in 250 ml of water (M). Each athlete was submitted to the two dietary treatments and two corresponding exhaustive physical tests with an interval of one week between the interventions. The effects of the two treatments were then compared within the same athlete. Maximal oxygen consumption, percentage of maximal oxygen consumption, second ventilatory threshold, and duration and total distance covered were measured during the exhaustion test. Blood was collected before and immediately after the test for the determination of plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities and lactate concentration (also measured 6, 10, and 15 min after the test). Plasma cytokines (IL-6, IL-1β, TNF-α, IL-8, IL-10, and IL-1ra) and C-reactive protein levels were also measured. A single dose of MGln increased the percentage of maximal oxygen consumption, second ventilatory threshold duration, and total distance covered during the exhaustion test and augmented plasma lactate levels 6 and 15 min after the test. MGln also decreased plasma LDH and CK activities indicating muscle damage protection. Plasma cytokine and C-reactive protein levels did not change across the study periods. Conditions including overnight fasting and a single dose of MGln supplementation resulted in exercising at a higher percentage of maximal oxygen consumption, a higher second ventilatory threshold, blood lactate levels, and reductions in plasma markers of muscle damage during an exhaustion test in elite triathletes. These findings support oral glutamine supplementation's efficacy in triathletes, but further studies require.

Maximal versus sub-maximal effort during cardiopulmonary exercise testing in adults with congenital heart disease: outcome analysis of short-term cardiac-related events.

Peak respiratory exchange ratio is an objective marker of patient effort during cardiopulmonary exercise testing. We evaluated exercise variables in 175 adult congenital heart disease patients and the impact of respiratory exchange ratio on the prognostic value of exercise variables for short-term cardiac-related events. Of 175 patients, 110 completed the exercise test with a peak respiratory exchange ratio of ≥1.10 and the remaining 65 had a peak respiratory exchange ratio of <1.10. Peak oxygen consumption, the percentage of oxygen consumption at the ventilatory threshold, peak heart rate, percentage predicted peak heart rate, double product, oxygen uptake efficiency slope, and the number of patients with exercise oscillatory ventilation were reduced significantly in patients with a respiratory exchange ratio of <1.10 compared to those with a respiratory exchange ratio of ≥1.10. After a median follow-up of 21 months, total cardiac-related events occurred in 37 (21%) patients. Multivariate Cox proportional hazard analysis showed that the percentage predicted peak oxygen consumption, and oxygen uptake efficiency slope were independent predictors of cardiac-related events only in patients with a peak respiratory exchange ratio of ≥1.10. Sub-maximal exercise performance can be preserved in adult congenital heart disease patients. The percentage predicted oxygen consumption and the oxygen uptake efficiency slope are two independent predictors for short-term cardiac-related events in adult congenital heart disease patients.

Blood lactate and oxygen consumption in soccer players: comparison between different positions on the field

OBJECTIVE: We hypothesize that in players with better aerobic fitness, lactate production was not inhibited after high-intensity exercise, regardless of the footballer's position on the field. METHOD: Sixty professional male soccer players performed cardiopulmonary exercise tests on an ergometric treadmill; respiratory gas exchanges were monitored throughout and blood lactate levels at peak effort was measured, using a portable device. The heart rate response was determined by computerized EKG. Training sessions took place over an average of ten hours per week, and the players had 6.8 years of experience in competitive soccer; they were tested a third of way into the season. The positions tested were (centerback, fullback, midfielder and striker). RESULTS: The following results (mean ± std. dev.) were obtained: (1) peak oxygen consumption of 58.8 ± 4.5 ml.kg-1.min.-1; (2), blood peak lactate of 12.3 ± 1.6 mmol.L-1; (3) maximum heart rate of 193 ± 3.3 beats. min-1; (4); oxygen consumption at the second ventilatory threshold of 49.6 ± 5.0 mL. kg-1.min-1; (5); running speed at the second ventilatory threshold of 13.3 ± 0.8 km.h-1; (6) percentage of oxygen consumption in the second ventilatory threshold of 84 ± 6%. There was no correlation between maximum aerobic level vs. peak lactate concentration (r = -0,031; p = 0.812), nor between submaximal aerobic level vs. peak lactate concentration (r = -0.146; p = 0.335) in the positions tested. CONCLUSION: Better or worse aerobic profiles according to game positions in soccer players do not influence peak lactate levels following high-intensity exercise, and confirms the study hypothesis.

Ingesting a preworkout supplement containing caffeine, creatine, β-alanine, amino acids, and B vitamins for 28 days is both safe and efficacious in recreationally active men

The purpose of this study was to determine the safety and efficacy of consuming a preworkout supplement (SUP) containing caffeine, creatine, β-alanine, amino acids, and B vitamins for 28 days. We hypothesized that little to no changes in kidney and liver clinical blood markers or resting heart rate and blood pressure (BP) would be observed. In addition, we hypothesized that body composition and performance would improve in recreationally active males after 28 days of supplementation. In a double-blind, placebo-controlled study, participants were randomly assigned to ingest one scoop of either the SUP or placebo every day for 28 days, either 20 minutes before exercise or ad libitum on nonexercise days. Resting heart rate and BP, body composition, and fasting blood samples were collected before and after supplementation. Aerobic capacity as well as muscular strength and endurance were also measured. Significant (P < .05) main effects for time were observed for resting heart rate (presupplementation, 67.59 ± 7.90 beats per minute; postsupplementation, 66.18 ± 7.63 beats per minute), systolic BP (presupplementation, 122.41 ± 11.25 mm Hg; postsupplementation, 118.35 ± 11.58 mm Hg), blood urea nitrogen (presupplementation, 13.12 ± 2.55 mg/dL; postsupplementation, 15.24 ± 4.47 mg/dL), aspartate aminotransferase (presupplementation, 34.29 ± 16.48 IU/L; postsupplementation, 24.76 ± 4.71 IU/L), and alanine aminotransferase (presupplementation, 32.76 ± 19.72 IU/L; postsupplementation, 24.88 ± 9.68 IU/L). Significant main effects for time were observed for body fat percentage (presupplementation, 15.55% ± 5.79%; postsupplementation, 14.21% ± 5.38%; P = .004) and fat-free mass (presupplementation, 70.80 ±9.21 kg; postsupplementation, 71.98 ± 9.27 kg; P = .006). A significant decrease in maximal oxygen consumption (presupplementation, 47.28 ± 2.69 mL/kg per minute; postsupplementation, 45.60 ± 2.81 mL/kg per minute) and a significant increase in percentage of oxygen consumption per unit time at which ventilatory threshold occurred (presupplementation, 64.38% ± 6.63%; postsupplementation, 70.63% ± 6.39%) and leg press one-repetition maximum (presupplementation, 218.75 ± 38.43 kg; postsupplementation, 228.75 ± 44.79 kg) were observed in the SUP only. No adverse effects were noted for renal and hepatic clinical blood markers, resting heart rate, or BP. Supplements containing similar ingredients and doses should be safe for ingestion periods lasting up to 28 days in healthy, recreationally trained, college-aged men.

Comparison of methods for the determination of the intensity of the aerobic training for young individuals

Laboratorio de Biociencias da Motricidade Humana Campus Universitario BR 101 s/no Lagoa Nova Natal RN CEP 59072-970 ABSTRACT: Introduction: In order to determine the intensity of aerobic exercise the anaerobic threshold and the respiratory compensation are used as referential; respectively, these physiologic markers are, generally, located at 50% and 80% of the maximal oxygen uptake (VO2max). To compare the values to the percentages of 50, 60, 70 and 80%, calculated through the HRR and VO2R equations corresponding to the oxygen consumption obtained by direct method. Materials and Methods: The sample was composed by 11 men and 10 women: mean age, 21.43 ± 2.82 years, body weight, 64.86 ± 12.17kg; and stature, 170.05 ± 9.12cm, performing maximal treadmill test, and the oxygen consumption obtained by the metabolic analyzer. To determine the percentages, we have used the mean values corresponding to the studied intensities according to the respective interval time relative to the percentage of oxygen consumption. Results: The measured intensities showed signifi cant difference (p > 0.05) for every reference values. The mean values calculate by HRR showed a tendency to underestimate the intensities, while the values calculated by VO2R showed a tendency to overestimate the intensities. Conclusion: Both intensity determination methods of aerobic training showed signifi cative difference, but they need to be adjusted in the equations. Thus, it is recommended the use of HRR in the determination of the intensities.

AGE‐RELATED DECLINE IN MAXIMAL OXYGEN CAPACITY: CONSEQUENCES FOR PERFORMANCE OF EVERYDAY ACTIVITIES

To the Editor: Routine activities of daily living in young and adult individuals only induce a minimal challenge on maximal capacity, but with increasing age, less physically demanding tasks require increasingly more of the maximal physical capacity. The latter may make it almost impossible for a significant proportion of old subjects to perform even light activities of daily living (ADLs). A minimum aerobic threshold for independent living appears to fluctuate between 13 and 15 mL oxygen/min per kg, which has been suggested as a minimum requirement for successfully coping with everyday tasks.1,2 Interestingly, men have higher muscle mass and aerobic capacity than women, which may explain why men perform better in ADLs than women and why women in general are functionally dependent for about 4 years longer than men.3 This difference between the sexes may render old women more vulnerable because their maximal functional capacity may fall below the threshold of successful independent living. This study determined maximal oxygen uptake and the relative effort assessed as oxygen consumption necessary to perform selected everyday activities such as stair climbing, dressing, walking, and vacuuming in different age cohorts of women. Nine young (aged 32.2±1.7), eight middle-aged (54.1±1.3), and eight old (77.4±1.8) Danish women participated in the study. They all reported normal level of physical activity for Danish women such as daily walking, bicycling, or gardening. Maximal aerobic capacity was measured as maximal oxygen uptake (VO2max) using a progressive, maximal test on a Cybex cycle ergometer. Oxygen, carbon dioxide, ventilation, and respiratory exchange ratio were continuously analyzed using an on-line system (Innovision AMIS 2001, INNOVISION, Odense, Denmark).4 Oxygen consumption during everyday activities was performed during walking at a self-selected speed, dressing, stair climbing, and vacuuming (Figure 1). After 6 minutes of repetitive movements, expired air was collected in Douglas bags and analyzed for oxygen and carbon dioxide on a Beckmann analyzer. Maximal oxygen uptake and oxygen consumption during stair climbing, walking, dressing, and vacuuming in the three age groups of healthy community-dwelling women. Significant differences were observed between all three groups in VO2max and VO2max relative to body weight. Relative effort expressed as the percentage of oxygen consumption (l/min) during an everyday activity in relation to VO2max (l/min) increased with age in all everyday activities. Significant differences were observed between all groups. Absolute values of oxygen (l/min) used in the different everyday activities revealed no significant differences between the groups. Elderly women experience oxygen consumption during everyday activities near their VO2max, whereas middle-aged and young subjects possess a more significant margin between these two parameters. VO2max is reported to decrease 5% to 15% after age 25.5 The present study revealed an even more significant decrease of 29% between the young and the middle-aged groups (∼14.5%/decade) and 27% between the middle-aged and the old groups (∼10.8%/decade) in this parameter. Furthermore, the old women in this study were active and lived independently, in spite of this, the VO2max per kg of body weight was perilously close to the critical threshold claimed to be between 13 and 15 mL or O2/min per kg.1,2 It is important to notice that these data are cross-sectional and may not only reflect a biological change in VO2max, but also cultural and lifestyle differences. In the present study, all women were able to perform the four different everyday activities, but the elderly women had to make significantly higher efforts. During performance of the different everyday activities, no significant changes were observed in oxygen uptake between any of the groups, indicating that the same amount of oxygen is demanded for the same everyday activity independent of age, and significant changes were found in all activities between all groups in the relative effort of performance, demonstrating that older women perform these four everyday activities closer to their maximal capacity than younger subjects. Even very old subjects are able to increase their VO2max through regular training, which will optimize physical function and independence.4,6,7 Furthermore, a high VO2max demonstrates decrease in the risk of developing lifestyle diseases such as diabetes mellitus, osteoporosis, hypertension, cardiovascular diseases, and depression and even increase psychological well-being.8 In conclusion, oxygen consumption during performance of everyday activities was similar in the different age groups of women. In contrast, a significant age-related decline in VO2max was noticed. This narrows the window during aging between demand and capacity of oxygen consumption that makes everyday tasks such as stair climbing, walking, dressing, and vacuuming difficult—and finally impossible—to perform.

Lipid Peroxidation and Modification of Lipid Composition in an Endothelial Cell Model of Ischemia and Reperfusion

Among the changes that accompany the development of ischemia are alterations in the composition and turnover of membrane phospholipids. To study these effects, a cell culture model was developed to facilitate accurate measurements of lipids over varying intervals of ischemia and reperfusion (I/R). In order to mimic ischemia, rabbit aortic endothelial cells were grown to confluency on collagen coated beads and the bead cultures allowed to settle to the bottom of a conical test tube or spectrofluorometric cuvette. The cell-coated beads were then resuspended in media to simulate the process of reperfusion. Survival after ischemia/reperfusion, was determined by measurements of cellular replating efficiency, and found to decrease after periods longer than three hours of ischemia (followed by 24 h of reperfusion). Plating efficiencies were reduced to nearly 50% after 5 h of ischemia followed by reperfusion. Release of LDH inversely correlated with cell survival, and lactate production, ATP levels, and extracellular H2O2 concentration were all affected by the duration of ischemia. These changes could be directly related to rates of cellular oxygen consumption which decreased by 50% after 5 h of ischemia, while the percentage of oxygen consumption not be inhibitable by cyanide, increased. Release of esterified fatty acids, which was partly inhibited by the phospholipase A2 inhibitor, mepacrine, was stimulated by increasing periods of ischemia while the incorporation of free fatty acids into phospholipids was inhibited. The incorporation of arachidonic acid was inhibited to a lesser degree than that of oleic or linoleic acids with a resulting change in phospholipid fatty acyl composition favoring greater proportions of unsaturated fatty acids. In some experiments, the effects of vitamin E or ascorbic acid administered prior to ischemia were studied. The degree of fatty acid unsaturation, fatty acid incorporation into phospholipids, and release from phospholipids into the free fatty acid pool during ischemia/reperfusion were not affected by prior administration of vitamin E or ascorbic acid. However, the extent of lipid peroxidation during ischemia was inhibited by 100 mM ascorbic acid when present during the ischemia/reperfusion period, but not by vitamin E administered for 24 h prior to ischemia. Ascorbic acid treatment, but not vitamin E, also enabled cells to recover substantial amounts of the ATP lost following prolonged ischemia. The ATP recovery corresponded to an increased cell survival and decreased lipid peroxidation. Progressive intervals of ischemia followed by reperfusion result in compromised cell respiratory activity and decreased ATP production, and decreased phospholipid acylation leading to net hydrolysis. The associated changes in phospholipid composition, and specifically increased unsaturation appear to favor peroxidation of membrane phospholipids.