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Maximal Oxygen Uptake (maximal + oxygen_uptake)
Selected AbstractsDoes aerobic fitness influence microvascular function in healthy adults at risk of developing Type 2 diabetes?DIABETIC MEDICINE, Issue 4 2005A. R. Middlebrooke Abstract Aim To investigate whether aerobic fitness is associated with skin microvascular function in healthy adults with an increased risk of developing Type 2 diabetes. Methods Twenty-seven healthy normal glucose-tolerant humans with either a previous diagnosis of gestational diabetes or having two parents with Type 2 diabetes and 27 healthy adults who had no history of diabetes were recruited. Maximal oxygen uptake was assessed using an incremental exercise test to exhaustion. Skin microvascular function was assessed using laser Doppler techniques as the maximum skin hyperaemic response to a thermal stimulus (maximum hyperaemia) and the forearm skin blood flow response to the iontophoretic application of acetylcholine (ACh) and sodium nitroprusside. Results Maximal oxygen uptake was not significantly different in the ,at-risk' group compared with healthy controls. Maximum hyperaemia was reduced in those ,at risk' (1.29 ± 0.30 vs. 1.46 ± 0.33 V, P = 0.047); however, the peak response to acetylcholine or sodium nitroprusside did not differ in the two groups. A significant positive correlation was demonstrated between maximal oxygen uptake and maximum hyperaemia (r = 0.52, P = 0.006 l/min and r = 0.60, P = 0.001 ml/kg/min) and peak ACh response (r = 0.40, P = 0.04 l/min and r = 0.47, P = 0.013 ml/kg/min) in the ,at-risk' group when expressed in absolute (l/min) or body mass-related (ml/kg/min) terms. No significant correlations were found in the control group. Conclusions In this ,at-risk' group with skin microvascular dysfunction maximal oxygen uptake was not reduced compared with healthy controls. However, in the ,at-risk' group alone, individuals with higher levels of aerobic fitness also had better microvascular and endothelial responsiveness. [source] Cardiorespiratory fitness and body mass index values in 9-year-old rural Norwegian childrenACTA PAEDIATRICA, Issue 4 2009GK Resaland Abstract Aim: To describe cardiorespiratory fitness and body mass index (BMI) values in a representative population of 9-year-old Norwegian children in two rural communities and compare present values with previous findings. Methods: Two hundred and fifty-nine 9-year-old children were invited, and 256 participated in this study. Maximal oxygen uptake was directly measured during a continuous progressive treadmill protocol. Body mass and height were also measured. Results: The mean ± SD relative maximal oxygen uptake was 52.8 ± 6.5 for boys and 46.9 ± 7.2 mL/kg/min for girls. Eight percent of the boys and 16.8% of the girls were classified as overweight, and 1.6% of the boys and 6.9% of the girls as obese. Mean age, body mass, height and Ponderal index were not significantly different between sexes. Girls had a higher BMI than boys (p = 0.05). Conclusion: Compared to earlier Norwegian studies, children's BMI values seem to have increased substantially. This increase is most pronounced in girls. When assessing these differences using the PI, this increase is less marked. Comparing maximal oxygen uptake data with that in earlier Nordic studies, there is no evidence that fitness has declined among 9-year olds. However, the limitations of the few earlier studies make reliable comparisons difficult. [source] Mechanisms of exercise-induced improvements in the contractile apparatus of the mammalian myocardiumACTA PHYSIOLOGICA, Issue 4 2010O. J. Kemi Abstract One of the main outcomes of aerobic endurance exercise training is the improved maximal oxygen uptake, and this is pivotal to the improved work capacity that follows the exercise training. Improved maximal oxygen uptake in turn is at least partly achieved because exercise training increases the ability of the myocardium to produce a greater cardiac output. In healthy subjects, this has been demonstrated repeatedly over many decades. It has recently emerged that this scenario may also be true under conditions of an initial myocardial dysfunction. For instance, myocardial improvements may still be observed after exercise training in post-myocardial infarction heart failure. In both health and disease, it is the changes that occur in the individual cardiomyocytes with respect to their ability to contract that by and large drive the exercise training-induced adaptation to the heart. Here, we review the evidence and the mechanisms by which exercise training induces beneficial changes in the mammalian myocardium, as obtained by means of experimental and clinical studies, and argue that these changes ultimately alter the function of the whole heart and contribute to the changes in whole-body function. [source] Cerebral oxygenation is reduced during hyperthermic exercise in humansACTA PHYSIOLOGICA, Issue 1 2010P. Rasmussen Abstract Aim:, Cerebral mitochondrial oxygen tension (PmitoO2) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO2) combined with hyperventilation-induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE). Methods:, This study evaluated the effect of heat stress during exercise on PmitoO2 calculated based on a Kety-Schmidt-determined CBF and the arterial-to-jugular venous oxygen differences in eight males [27 ± 6 years (mean ± SD) and maximal oxygen uptake (VO2max) 63 ± 6 mL kg,1 min,1]. Results:, The CBF, CMRO2 and PmitoO2 remained stable during 1 h of moderate cycling (170 ± 11 W, ,50% of VO2max, RPE 9,12) in normothermia (core temperature of 37.8 ± 0.4 °C). In contrast, when hyperthermia was provoked by dressing the subjects in watertight clothing during exercise (core temperature 39.5 ± 0.2 °C), PmitoO2 declined by 4.8 ± 3.8 mmHg (P < 0.05 compared to normothermia) because CMRO2 increased by 8 ± 7% at the same time as CBF was reduced by 15 ± 13% (P < 0.05). During exercise with heat stress, RPE increased to 19 (19,20; P < 0.05); the RPE correlated inversely with PmitoO2 (r2 = 0.42, P < 0.05). Conclusion:, These data indicate that strenuous exercise in the heat lowers cerebral PmitoO2, and that exercise capacity in this condition may be dependent on maintained cerebral oxygenation. [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] Exercise-induced growth hormone response in euglycaemia and hyperglycaemia in patients with Type 1 diabetes mellitusDIABETIC MEDICINE, Issue 2 2010S. Jenni Diabet. Med. 27, 230,233 (2010) Abstract Aims, To compare exercise-induced growth hormone (GH) response in patients with Type 1 diabetes during stable euglycaemic and hyperglycaemic conditions. Methods, We conducted a randomized, controlled, single-blinded cross-over trial in seven male patients with well-controlled Type 1 diabetes. The patients cycled twice for 120 min at a level of 55,60% maximal oxygen uptake. Euglycaemia was at 5.0 mmol/l, hyperglycaemia at 11.0 mmol/l. Results, Area under the curve of GH (AUCGH) during exercise was significantly higher during euglycaemia [1430 ng ml,1 min, 95% confidence interval (CI) 703,2910] compared with hyperglycaemia (1061 ng ml,1 min, 95% CI 538,2091, P = 0.02). Conclusions, In patients with Type 1 diabetes, GH concentrations during moderate aerobic exercise during stable hyperglycaemic conditions are significantly lower compared with euglycaemia. These findings are compatible with preserved glucose-mediated GH regulation during exercise in individuals with well-controlled Type 1 diabetes. [source] Does aerobic fitness influence microvascular function in healthy adults at risk of developing Type 2 diabetes?DIABETIC MEDICINE, Issue 4 2005A. R. Middlebrooke Abstract Aim To investigate whether aerobic fitness is associated with skin microvascular function in healthy adults with an increased risk of developing Type 2 diabetes. Methods Twenty-seven healthy normal glucose-tolerant humans with either a previous diagnosis of gestational diabetes or having two parents with Type 2 diabetes and 27 healthy adults who had no history of diabetes were recruited. Maximal oxygen uptake was assessed using an incremental exercise test to exhaustion. Skin microvascular function was assessed using laser Doppler techniques as the maximum skin hyperaemic response to a thermal stimulus (maximum hyperaemia) and the forearm skin blood flow response to the iontophoretic application of acetylcholine (ACh) and sodium nitroprusside. Results Maximal oxygen uptake was not significantly different in the ,at-risk' group compared with healthy controls. Maximum hyperaemia was reduced in those ,at risk' (1.29 ± 0.30 vs. 1.46 ± 0.33 V, P = 0.047); however, the peak response to acetylcholine or sodium nitroprusside did not differ in the two groups. A significant positive correlation was demonstrated between maximal oxygen uptake and maximum hyperaemia (r = 0.52, P = 0.006 l/min and r = 0.60, P = 0.001 ml/kg/min) and peak ACh response (r = 0.40, P = 0.04 l/min and r = 0.47, P = 0.013 ml/kg/min) in the ,at-risk' group when expressed in absolute (l/min) or body mass-related (ml/kg/min) terms. No significant correlations were found in the control group. Conclusions In this ,at-risk' group with skin microvascular dysfunction maximal oxygen uptake was not reduced compared with healthy controls. However, in the ,at-risk' group alone, individuals with higher levels of aerobic fitness also had better microvascular and endothelial responsiveness. [source] The training stimulus experienced by the leg muscles during cycling in humansEXPERIMENTAL PHYSIOLOGY, Issue 6 2009Jamie S. McPhee Considerable variability exists between people in their health- and performance-related adaptations to conventional endurance training. We hypothesized that some of this variability might be due to differences in the training stimulus received by the working muscles. In 71 young sedentary women we observed large variations in the ratio of one-leg cycling muscle aerobic capacity to two-leg cycling whole-body maximal oxygen uptake (; Ratio1:2; range 0.58,0.96). The variability in Ratio1:2 was primarily due to differences between people in one-leg (r= 0.71, P < 0.0005) and was not related to two-leg (r= 0.15, P= 0.209). Magnetic resonance imaging (n= 30) and muscle biopsy sampling (n= 20) revealed that one-leg was mainly determined by muscle volume (r= 0.73, P < 0.0005) rather than muscle fibre type or oxidative capacity. A high one-leg was associated with favourable lipoprotein profiles (P= 0.033, n= 24) but this was not the case for two-leg . Calculations based on these data suggest that conventional two-leg exercise at 70% requires subjects with the lowest Ratio1:2 to work their legs at 60% of single-leg , whilst those with the highest Ratio1:2 work their legs at only 36% of maximum. It was concluded that endurance training carried out according to current guidelines will result in highly variable training stimuli for the leg muscles and variable magnitudes of adaptation. These conclusions have implications for the prescription of exercise to improve health and for investigations into the genetic basis of muscle adaptations. [source] Cardiovascular Exercise Training Extends Influenza Vaccine Seroprotection in Sedentary Older Adults: The Immune Function Intervention TrialJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 12 2009Jeffrey A. Woods PhD OBJECTIVES: To determine whether cardiovascular exercise training resulted in improved antibody responses to influenza vaccination in sedentary elderly people who exhibited poor vaccine responses. DESIGN: Single-site randomized parallel-arm 10-month controlled trial. SETTING: University of Illinois at Urbana-Champaign. PARTICIPANTS: One hundred forty-four sedentary, healthy older (69.9 ± 0.4) adults. INTERVENTIONS: Moderate (60,70% maximal oxygen uptake) cardiovascular exercise was compared with flexibility and balance training. MEASUREMENTS: The primary outcome was influenza vaccine response, as measured according to hemagglutination inhibition (HI) anti-influenza antibody titer and seroprotective responses (HI titer ,40). Secondary measures included cardiovascular fitness and body composition. RESULTS: Of the 160 participants enrolled, 144 (90%) completed the 10-month intervention with excellent compliance (,83%). Cardiovascular, but not flexibility, exercise intervention resulted in improvements in indices of cardiovascular fitness, including maximal oxygen uptake. Although not affecting peak (e.g., 3 and 6 weeks) postvaccine anti-influenza HI titers, cardiovascular exercise resulted in a significant increase in seroprotection 24 weeks after vaccination (30,100% dependent on vaccine variant), whereas flexibility training did not. CONCLUSION: Participants randomized to cardiovascular exercise experienced improvements in influenza seroprotection throughout the entire influenza season, whereas those in the balance and flexibility intervention did not. Although there were no differences in reported respiratory tract infections, the exercise group exhibited reduced overall illness severity and sleep disturbance. These data support the hypothesis that regular endurance exercise improves influenza vaccine responses. [source] Pinealectomy reduces hepatic and muscular glycogen content and attenuates aerobic power adaptability in trained ratsJOURNAL OF PINEAL RESEARCH, Issue 1 2007Cristina das Neves Borges-Silva Abstract:, The current study emphasizes the crucial role of the pineal gland on the effects of chronic training in different tissues focusing on carbohydrate metabolism. We investigated the maximal oxygen uptake (aerobic power), muscle and liver glycogen content, and also the enzymes involved in the carbohydrate metabolism of rat adipose tissue. Pinealectomized and sham-operated adult male Wistar rats were distributed into four groups: pinealectomized (PINX) untrained, pinealectomized trained, control untrained and control trained. The maximal oxygen uptake capability was assayed before and after the training protocol by indirect open circuit calorimetry. The rats were killed after 8 wk of training. Blood samples were collected for glucose and insulin determinations. The glycogen content was assayed in the liver and muscle. Maximal activities of epididymal adipose tissue enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase, citrate synthase and malic enzyme) as well as adipocyte size were determined. The exercise training in control animals promoted an increase in the aerobic power and in liver glycogen content but caused a reduction in the malic enzyme activity in adipose tissue. However, PINX trained animals, in contrast to trained controls, showed a decrease in the aerobic power and in liver and muscle glycogen content, as well as an increase in the activity of the adipocyte enzymes involved in carbohydrate metabolism. In conclusion, these data show that the pineal gland integrity is necessary for the homeostatic control of energy metabolism among adipose, muscle and hepatic tissues. The pinealectomized animals showed alterations in adaptive responses of the maximal oxygen uptake to training. Therefore, the pineal gland must be considered an influential participant in the complex adaptation to exercise and is involved in the improvement of endurance capacity. [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] Airway limitation and exercise intolerance in well-regulated myasthenia gravis patientsACTA NEUROLOGICA SCANDINAVICA, Issue 2010A. Elsais Elsais A, Johansen B, Kerty E. Airway limitation and exercise intolerance in well-regulated myasthenia gravis patients. Acta Neurol Scand: 2010: 122 (Suppl. 190): 12,17. © 2010 John Wiley & Sons A/S. Objectives,,, Myasthenia gravis (MG) is an autoimmune disease of neuromuscular synapses, characterized by muscular weakness and reduced endurance. Remission can be obtained in many patients. However, some of these patients complain of fatigue. The aim of this study was to assess exercise capacity and lung function in well-regulated MG patients. Patients and methods,,, Ten otherwise healthy MG patients and 10 matched controls underwent dynamic spirometry, and a ramped symptom-limited bicycle exercise test. Spirometric variables included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and maximum voluntary ventilation (MVV). Exercise variables included maximal oxygen uptake (VO2 max), anaerobic threshold (VO2 AT) maximum work load (W), maximum ventilation (VE max), and limiting symptom. Results,,, Myasthenia gravis patients had significantly lower FEV1/FVC ratio than controls. This was more marked in patients on acetylcholine esterase inhibitors. On the contrary, patients not using acetylcholine esterase inhibitors had a significantly lower exercise endurance time. Conclusion,,, Well-regulated MG patients, especially those using pyridostigmine, tend to have an airway obstruction. The modest airway limitation might be a contributing factor to their fatigue. Patients who are not using acetylcholinesterase inhibitor seem to have diminished exercise endurance in spite of their clinically complete remission. [source] Cardiorespiratory fitness and body mass index values in 9-year-old rural Norwegian childrenACTA PAEDIATRICA, Issue 4 2009GK Resaland Abstract Aim: To describe cardiorespiratory fitness and body mass index (BMI) values in a representative population of 9-year-old Norwegian children in two rural communities and compare present values with previous findings. Methods: Two hundred and fifty-nine 9-year-old children were invited, and 256 participated in this study. Maximal oxygen uptake was directly measured during a continuous progressive treadmill protocol. Body mass and height were also measured. Results: The mean ± SD relative maximal oxygen uptake was 52.8 ± 6.5 for boys and 46.9 ± 7.2 mL/kg/min for girls. Eight percent of the boys and 16.8% of the girls were classified as overweight, and 1.6% of the boys and 6.9% of the girls as obese. Mean age, body mass, height and Ponderal index were not significantly different between sexes. Girls had a higher BMI than boys (p = 0.05). Conclusion: Compared to earlier Norwegian studies, children's BMI values seem to have increased substantially. This increase is most pronounced in girls. When assessing these differences using the PI, this increase is less marked. Comparing maximal oxygen uptake data with that in earlier Nordic studies, there is no evidence that fitness has declined among 9-year olds. However, the limitations of the few earlier studies make reliable comparisons difficult. [source] Improving exercise capacity, 6 wk training tends to reduce circulating endothelin after heart transplantationCLINICAL TRANSPLANTATION, Issue 6 2004Stèphane Doutreleau Abstract:, Short-term survival is no longer the pivotal issue after heart transplantation but, most heart-transplant (Htx) patients still present with increased circulating endothelin-1 (ET) and reduced exercise capacity. ET-1 limits both exercise-induced vasodilation and blood flow redistribution toward acting muscles and might be accessible to training. This study was performed to investigate the effect of training on ET-1 and whether an eventual training-induced improvement in exercise capacity may be related to reduced baseline or exercise circulating ET-1 in Htx patients. Five Htx patients performed a maximal bicycle exercise test and an endurance exercise test before and after a training program of 18 exercises sessions during 6 wk. ET-1 was determined by radioimmunoassay at rest, end endurance exercise and 30 min recovery, before and after training. Training improved significantly Htx's maximal oxygen uptake (+13.1 ± 4.8%; p < 0.05) and also reduced significantly the endurance exercise-induced heart rate increase. Resting ET-1 was increased in Htx (5.98 ± 1.88 vs. 1.61 ± 0.25 pmol/L in controls; p < 0.01) but although ET-1 modulation might participate in training-induced beneficial effects, training failed to modulate either resting or exercise ET-1 plasma level. Training-induced improvement in exercise capacity might not mainly due to decreased ET-1 after heart transplantation. Further supporting the usefulness of training, these preliminary data suggest that improved exercise capacity may not be mainly due to decreased ET-1 in Htx patients. Further, larger scale studies will be needed to investigate whether an impaired nitric oxide pathway stimulation might explain such results and whether a longer training program can reduce local ET-1, arising from working muscles after heart transplantation. [source] | |||||||||||||