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Respiratory Exchange Ratio (respiratory + exchange_ratio)
Selected AbstractsIncreased fat oxidation and regulation of metabolic genes with ultraendurance exerciseACTA PHYSIOLOGICA, Issue 1 2007J. W. Helge Abstract Aim:, Regular endurance exercise stimulates muscle metabolic capacity, but effects of very prolonged endurance exercise are largely unknown. This study examined muscle substrate availability and utilization during prolonged endurance exercise, and associated metabolic genes. Methods:, Data were obtained from 11 competitors of a 4- to 5-day, almost continuous ultraendurance race (seven males, four females; age: 36 ± 11 years; cycling o2peak: males 57.4 ± 5.9, females 48.1 ± 4.0 mL kg,1 min,1). Before and after the race muscle biopsies were obtained from vastus lateralis, respiratory gases were sampled during cycling at 25 and 50% peak aerobic power output, venous samples were obtained, and fat mass was estimated by bioimpedance under standardized conditions. Results:, After the race fat mass was decreased by 1.6 ± 0.4 kg (11%; P < 0.01). Respiratory exchange ratio at the 25 and 50% workloads decreased (P < 0.01) from 0.83 ± 0.06 and 0.93 ± 0.03 before, to 0.71 ± 0.01 and 0.85 ± 0.02, respectively, after the race. Plasma fatty acids were 3.5 times higher (from 298 ± 74 to 1407 ± 118 ,mol L,1; P < 0.01). Muscle glycogen content fell 50% (from 554 ± 28 to 270 ± 25 nmol kg,1 d.w.; n = 7, P < 0.01), whereas the decline in muscle triacylglycerol (from 32 ± 5 to 22 ± 3 mmol kg,1 d.w.; P = 0.14) was not statistically significant. After the race, muscle mRNA content of lipoprotein lipase and glycogen synthase increased (P < 0.05) 3.9- and 1.7-fold, respectively, while forkhead homolog in rhabdomyosarcoma, pyruvate dehydrogenase kinase 4 and vascular endothelial growth factor mRNA tended (P < 0.10) to be higher, whereas muscle peroxisome proliferator-activated receptor , co-activator-1, mRNA tended to be lower (P = 0.06). Conclusion:, Very prolonged exercise markedly increases plasma fatty acid availability and fat utilization during exercise. Exercise-induced regulation of genes encoding proteins involved in fatty acid recruitment and oxidation may contribute to these changes. [source] Impact of carbohydrate supplementation during endurance training on glycogen storage and performanceACTA PHYSIOLOGICA, Issue 2 2009L. Nybo Abstract Aim:, Glucose ingestion may improve exercise endurance, but it apparently also influences the transcription rate of several metabolic genes and it alters muscle metabolism during an acute exercise bout. Therefore, we investigated how chronic training responses are affected by glucose ingestion. Methods:, In previously untrained males performance and various muscular adaptations were evaluated before and after 8 weeks of supervised endurance training conducted either with (n = 8; CHO group) or without (n = 7; placebo) glucose supplementation. Results:, The two groups achieved similar improvements in maximal oxygen uptake and peak power output during incremental cycling (both parameters elevated by 17% on average) and both groups lost ,3 kg of fat mass during the 8 weeks of training. An equal reduction in respiratory exchange ratio (0.02 units) during submaximal exercise was observed in both groups. Beta-hydroxyacyl-CoA-dehydrogenase activity was increased in both groups, however, to a larger extent in the placebo group (45 ± 11%) than CHO (23 ± 9%, P < 0.05). GLUT-4 protein expression increased by 74 ± 14% in the placebo group and 45 ± 14% in CHO (both P < 0.05), while resting muscle glycogen increased (P < 0.05) to a larger extent in the placebo group (96 ± 4%) than CHO (33 ± 2%). Conclusion:, These results show that carbohydrate supplementation consumed during exercise training influences various muscular training adaptations, but improvements in cardiorespiratory fitness and reductions in fat mass are not affected. [source] Cardiopulmonary responses of asthmatic children to exercise: Analysis of systolic and diastolic cardiac functionPEDIATRIC PULMONOLOGY, Issue 3 2007Bulent Alioglu MD Abstract The aim of this study was to evaluate aerobic exercise capacity, cardiac features and function in a group of asthmatic children who underwent medical treatment. Dynamic exercise testing was done to evaluate aerobic exercise capacity. Echocardiography was performed to identify the effects that asthma-induced pulmonary changes have on respiratory and cardiac function in these patients. The study involved 20 asthmatic children (aged 7,16 years) who were followed at our hospital and 20 age- and sex-matched, healthy control subjects. Sixteen of the asthma cases were moderate and four were severe. All 40 subjects underwent similar series of assessments: multiple modes of echocardiography, treadmill stress testing, pulmonary function testing. The means for forced expiratory volume in 1 sec, forced expiratory flow 25,75%, maximal voluntary ventilation and inspiratory capacity were all significantly higher in the control group. The patient group had significantly lower mean maximal oxygen uptake and mean endurance time than the controls but there were no significant differences between the groups with respect to respiratory exchange ratio or the ventilatory threshold. The control group means for ejection fraction, fractional shortening, left ventricular mass, and left ventricular mass index were significantly higher than the corresponding patient group results. Children with moderate or severe asthma have lower aerobic capacity than healthy children of the same age. The data suggest that most of these children have normal diastolic cardiac function, but exhibit impaired systolic function and have lower LVM than healthy peers of the same age. Pediatr Pulmonol. 2007; 42:283,289. © 2007 Wiley-Liss, Inc. [source] A comparison of physiological variables in aged and young women during and following submaximal exerciseAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2009Michael R. Deschenes Previously, we have examined how aging affects the physiological responses of men to endurance exercise. In the present investigation, we aimed to extend our assessment of the influence of aging on exercise-induced responses by focusing on women. Ten young (20.3 ± 0.3 years; mean ± SE) and 10 aged (75.5 ± 1.2 years) women performed 30 min of cycling at 60,65% of their predetermined peak oxygen uptake. Data for respiratory exchange ratio (RER), heart rate, blood pressure, rectal temperature, and plasma metabolites were collected before exercise, at the 15th and 30th min of exercise, and at 5 and 15 min postexercise. A two-way, repeated measures ANOVA with main effects of age and time was conducted on each variable. Our findings showed that age affected exercise-induced responses of each variable quantified. Although RER, heart rate, temperature, and lactate were significantly (P < 0.05) higher among young women, blood pressure and glucose values were greater among aged women. Moreover, unlike previous results noted among men where age-related differences primarily occurred during postexercise recovery, in women the effect of aging was detected during exercise itself. The data presented here indicate that aging impacts physiological responses of women to prolonged endurance exercise even when relative intensity (% of peak oxygen uptake) is held constant. Combined with our earlier study on men, these findings suggest that gender interacts with aging to determine whether age-related differences are manifested during exercise itself, or during postexercise recovery. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] The effect of antecedent fatiguing activity on the relationship between perceived exertion and physiological activity during a constant load exercise taskPSYCHOPHYSIOLOGY, Issue 5 2007Roger Eston Abstract This study assessed the relationship between the rate of change of the rating of perceived exertion (RPE), physiological activity, and time to volitional exhaustion. After completing a graded exercise test, 10 participants cycled at a constant load equating to 75% of peak oxygen uptake (V, O2peak) to exhaustion. Participants performed two further constant load exercise tests at 75%V, O2peak in a fresh state condition within the next 7 days. The RPE was regressed against time and percentage of the time (%time) to volitional exhaustion in both conditions. Despite a lower respiratory exchange ratio (RER) and higher heart rate at the start of the exercise bout in the fatigued condition, there were no differences in RPE at the onset or completion of exercise. As expected, the rate of increase in RPE was greater in the fatigued condition, but there were no differences when expressed against %time. Results suggest that RPE is set at the start of exercise using a scalar internal timing mechanism, which regulates RPE by altering the gain of the relationship with physiological parameters such as heart rate and RER when these are altered by previous fatiguing exercise. [source] Mechanisms by which systemic salbutamol increases ventilationRESPIROLOGY, Issue 2 2006Antony E. TOBIN Background and objective: Salbutamol (SAL) has systemic effects that may adversely influence ventilation in asthmatic patients. The authors sought to determine the magnitude of this effect and mechanisms by which i.v. SAL affects ventilation. Methods: A prospective study of nine healthy subjects (eight men, one woman; age 23 ± 1.4 years (SD)) was undertaken. Each subject received i.v. SAL at 5, 10 and 20 µg/min each for 30 min at each dose and was observed for 1 h post infusion. Minute ventilation (V,E), oxygen consumption (V,O2), CO2 production (V,CO2), occlusion pressure (P0.1), heart rate, blood pressure, respiratory rate, glucose, arterial blood gases, lactate and potassium (K+) were recorded at baseline and at 30-min intervals. The effect of 100% oxygen on V,E and P0.1 during SAL infusion at 20 µg/min was observed. Results are expressed as mean ± SEM. Results: V,E was significantly increased at 20 µg/min SAL (37.8 ± 12.1%, P = 0.01), as were V,O2 (22.5 ± 5.1%, P < 0.01) and V,CO2 (40.9 ± 10.6%, P < 0.01). Ventilation was in excess of metabolic needs as demonstrated by a rise in the respiratory exchange ratio (0.87 ± 0.03 to 0.99 ± 0.04, P < 0.05). Serum lactate rose by 124 ± 30.4% from baseline to 20 µg/min (1.1 ± 0.1 to 2.3 ± 0.25 mmol/L, P < 0.01) and base excess decreased (0.89 ± 0.56 to vs. ,1.75 ± 0.52 mmol/L, P < 0.01) consistent with a lactic acidosis contributing to the excess ventilation. There was no significant differences in V,E or P0.1 with FIO2 = 1.0, suggesting peripheral chemoreceptor stimulation was not responsible for the rise in V,E. At 20 µg/min SAL, K+ fell significantly from baseline (3.8 ± 0.06 to 2.8 ± 0.09 mmol/L, P < 0.001). Conclusion: Systemic SAL imposes ventilatory demands by increasing metabolic rate and serum lactate. This may adversely affect patients with severe asthma with limited ventilatory reserve. [source] Cardiorespiratory effects of warm water immersion in elderly patients with chronic heart failureCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2005Åsa Cider Summary Background:, Hydrotherapy might be included in the rehabilitation of patients with chronic heart failure (CHF), but little is known about the acute cardiorespiratory reaction in warm water. The aim of this study was to assess the acute cardiorespiratory effect of immersion in warm water, in a clinical setting, in elderly patients with CHF compared with healthy age and sex matched persons. Methods:, Twelve patients (three females) with CHF, NYHA II,III, age 64 ± 6 years, and 12 healthy subjects were studied. Cardiorespiratory changes, on land and in a temperature-controlled swimming pool (33,34°C) were assessed during rest and exercise, in a sitting position, using continuous gas analyses. Results:, There were no significant differences, land versus water, in carbon dioxide production, total ventilation, respiratory frequency, respiratory exchange ratio, heart rate or blood pressure in either of the groups. A significant difference was found in oxygen uptake, at rest, land versus water in patients with CHF in comparison with healthy subjects (,0·2 ± 0·4 versus +0·3 ± 0·6 ml kg,1 min,1, P<0·01). Oxygen kinetics (,) increased significantly (P = 0·01) in both groups during exercise in water. Conclusion:, Hydrotherapy was well tolerated and the vast majority of the cardiorespiratory responses, during warm water immersion in a clinical setting, are similar in patients with CHF compared with healthy subjects. However, further larger studies, are needed to better understand the physiological reactions during hydrotherapy. [source] | |||||||||||||