Home About us Contact
|
Home About us Contact | ||
|
|
||
Submaximal Exercise (submaximal + exercise)
Selected AbstractsImpact 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] Nitric oxide synthase inhibition in Thoroughbred horses augments O2 extraction at rest and submaximal exercise, but not during short-term maximal exerciseEQUINE VETERINARY JOURNAL, Issue S36 2006M. MANOHAR Summary Reason for performing study: Work is required to establish the role of endogenous nitric oxide (NO) in metabolism of resting and exercising horses. Objectives: To examine the effects of NO synthase inhibition on O2 extraction and anaerobic metabolism at rest, and during submaximal and maximal exertion. Methods: Placebo and NO synthase inhibition (with N,-nitro-L-arginine methyl ester [l -NAME] administered at 20 mg/kg bwt i.v.) studies were performed in random order, 7 days apart on 7 healthy, exercise-trained Thoroughbred horses at rest and during incremental exercise leading to 120 sec of maximal exertion at 14 m/sec on a 3.5% uphill grade. Results: At rest, NO synthase inhibition significantly augmented the arterial to mixed-venous blood O2 content gradient and O2 extraction as mixed-venous blood O2 tension and saturation decreased significantly. While NO synthase inhibition did not affect arterial blood-gas tensions in exercising horses, the exercise-induced increment in haemoglobin concentration and arterial O2 content was attenuated. In the l -NAME study, during submaximal exercise, mixed-venous blood O2 tension and haemoglobin-O2 saturation decreased to a greater extent causing O2 extraction to increase significantly. During maximal exertion, arterial hypoxaemia, desaturation of haemoglobin and hypercapnia of a similar magnitude developed in both treatments. Also, the changes in mixed-venous blood O2 tension and haemoglobin-O2 saturation, arterial to mixed-venous blood O2 content gradient, O2 extraction and markers of anaerobic metabolism (lactate and ammonia production, and metabolic acidosis) were not different from those in the placebo study. Conclusion: Endogenous NO production augments O2 extraction at rest and during submaximal exertion, but not the during short-term maximal exercise. Also, NO synthase inhibition does not affect anaerobic metabolism at rest or during exertion. Potential relevance: It is unlikely that endogenous NO release modifies aerobic or anaerobic metabolism in horses performing short-term maximal exertion. [source] Effects of phlebotomy on haemodynamic characteristics during exercise in Standardbred trotters with red cell hypervolaemiaEQUINE VETERINARY JOURNAL, Issue 4 2001P. FUNKQUIST Summary Five Standardbred trotters with red cell hypervolaemia (RCHV) were compared before and after removal of approximately 22% (36 ml/kg bwt) of the total blood volume in order to evaluate the haemodynamic responses, haemorheological alterations and oxygen transport during exercise to fatigue. Data were recorded during submaximal exercise at 4 different speeds on a treadmill and then during continued running at the highest speed step until fatigue. Oxygen uptake (V,O2), pulmonary artery pressure (PAP), systemic artery pressure (SAP), heart rate (HR), haematocrit and haemoglobin concentrations (Hb) were measured. Arteriovenous O2 content difference (C(a-v,)O2), pulmonary vascular resistance (PVR) and total systemic resistance (TSR) were calculated. Whole blood and plasma viscosity and erythrocyte aggregation tendency were determined with a rotational viscometer. Endoscopy was performed after exercise. ANOVA was used for statistical analysis. Phlebotomy resulted in a decrease in haematocrit and Hb during the course of exercise. Blood and plasma viscosity were lower and erythrocyte aggregation tendency was higher after phlebotomy. Throughout exercise, including submaximal work and continued running to fatigue, PAP, SAP, PVR, TSR and C(a-v,)O2 were lower after phlebotomy. HR was higher after phlebotomy during submaximal exercise. Oxygen delivery and VO2 were lower after phlebotomy in the period from submaximal exercise to fatigue. Run time to fatigue was shorter after phlebotomy. Four horses showed exercise-induced pulmonary haemorrhage (EIPH) before phlebotomy and the degree of bleeding was diminished but not abolished after phlebotomy. The reductions in PVR, TSR, PAP and SAP after phlebotomy were probably a result of reduced blood viscosity. In conclusion, although a 22% reduction in blood volume improved the haemodynamic and haemorheological parameters and the degree of EIPH, it was found that RCHV trotters have to rely on high oxygen delivery to the working muscles for maintenance of maximal performance. [source] Are Hormonal Responses to Exercise in Young Men with Down's Syndrome Related to Reduced Endurance Performance?JOURNAL OF NEUROENDOCRINOLOGY, Issue 5 2008V-A. Bricout The aim of the present study was to analyse whether hormonal responses could explain an exercise limitation in Down's syndrome (DS). Fourteen young men with DS (mean age 22.5 ± 0.7 years) and 15 controls (CONT, mean age 22.5 ± 0.3 years) participated in the study. During a treadmill submaximal incremental test, blood samples were collected for determination of hormonal and metabolic variables. Compared to CONT, DS individuals showed lower VO2max (P < 0.05), and lower duration of submaximal incremental exercise (P < 0.001). At rest, DS individuals showed greater catecholamines, insulin and leptin values (P < 0.05), but lower testosteronemia and cortisolemia (P < 0.05), compared to CONT. During submaximal incremental tests, catecholamines and cortisol were not increased, whereas the insulin concentration of DS individuals was significantly higher (P < 0.01) compared to CONT. Glycaemia increased significantly at the end of submaximal incremental test for CONT but not for DS individuals (P < 0.01). Maximal fat oxidation was lower (P < 0.01), whereas non-esterified fatty acids concentrations rose significantly during submaximal exercise in DS individuals. These results indicate an altered hormonal response to exercise in DS individuals. This endocrine profile at rest and during exercise may limit endurance performance in DS individuals. [source] Plasma Thyroid Hormone Concentrations in Dogs Competing in a Long-Distance Sled Dog RaceJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 4 2003David L. Panciera Plasma thyroxine (T4), 3,5,3,-triiodothyronine (T3), total protein, and albumin concentrations were measured in 15 dogs both before and after completion, and in an additional 16 dogs before and 24 dogs after completion, of a long-distance sled dog race. The plasma T4 concentration (mean ± SD) decreased significantly from 18.2 ± 5.4 nmol/L before to 14.3 ± 3.5 nmol/L after the race in dogs evaluated at both times and decreased significantly from 21.8 ± 10.5 nmol/L before to 15.8 ± 4.9 nmol/L after the race in dogs sampled only before or only after the race. The mean plasma T3 concentrations in dogs measured twice decreased significantly from 1.20 ± 0.48 nmol/L before to 0.74 ± 0.42 nmol/L after the race, as well as in dogs measured either before (1.28 ± 0.36 nmol/L) or after (0.69 ± 0.28 nmol/L) the race, respectively. Plasma total protein and albumin concentrations decreased significantly after completion of the race. No significant change was noted in 4 control dogs that did not compete in the race and were tested during a similar time period. The plasma concentrations of T4 and T3 were lower than the normal reference range established for this laboratory in 23 and 39%, respectively, of Alaskan sled dogs tested before the race. Plasma thyroid hormone concentrations frequently are below normal in conditioned Alaskan sled dogs and are further reduced after prolonged submaximal exercise. [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] Left ventricular torsion and untwisting during exercise in heart transplant recipientsTHE JOURNAL OF PHYSIOLOGY, Issue 10 2009Ben T. Esch Left ventricular (LV) rotation is the dominant deformation during relaxation and links systole with early diastolic recoil. LV torsion and untwisting rates during submaximal exercise were compared between heart transplant recipients (HTRs), young adults and healthy older individuals to better understand impaired diastolic function in HTRs. Two dimensional and colour M-mode echocardiography with speckle-tracking analysis were completed in eight HTRs (age: 61 ± 9 years), six recipient age-matched (RM, age: 60 ± 11 years), and five donor age-matched (DM, age: 35 ± 8 years) individuals (all males) at rest and during submaximal cycle exercise. LV peak torsion, peak rate of untwisting and peak intraventricular pressure gradients (IVPGs) were examined. LV torsion increased with exercise in DMs (6.5 ± 5.6 deg, P < 0.05), but not in RMs (,2.6 ± 7.0 deg) or HTRs (,0.9 ± 4.4 deg). The change from rest to exercise in the peak rate of untwisting was significantly greater for DMs (,2.1 ± 0.5 rads s,1, P < 0.05) compared to RMs (,0.7 ± 1.3 rads s,1) and HTRs (,0.2 ± 0.9 rads s,1). The amount of untwisting occurring prior to mitral valve opening substantially declined with exercise in RMs and HTRs only. The change in IVPGs was 1.3-fold greater in DMs versus HTRs or RMs (P > 0.05). Peak LV torsion and untwisting are blunted during exercise in HTRs and RMs compared to DMs. These factors may contribute to the impaired diastolic filling found in HTRs during exercise. Similarities between HTRs and RMs during exercise suggest functional accelerated ageing of the cardiac allograft. [source] Prior heavy exercise eliminates slow component and reduces efficiency during submaximal exercise in humansTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005K. Sahlin We investigated the hypothesis that the pulmonary oxygen uptake slow component is related to a progressive increase in muscle lactate concentration and that prior heavy exercise (PHE) with pronounced acidosis alters kinetics and reduces work efficiency. Subjects (n= 9) cycled at 75% of the peak for 10 min before (CON) and after (AC) PHE. was measured continuously (breath-by-breath) and muscle biopsies were obtained prior to and after 3 and 10 min of exercise. Muscle lactate concentration was stable between 3 and 10 min of exercise but was 2- to 3-fold higher during AC (P < 0.05 versus CON). Acetylcarnitine (ACn) concentration was 6-fold higher prior to AC and remained higher during exercise. Phosphocreatine (PCr) concentration was similar prior to exercise but the decrease was 2-fold greater during AC than during CON. The time constant for the initial kinetics (phase II) was similar but the asymptote was 14% higher during AC. The slow increase in between 3 and 10 min of exercise during CON (+7.9 ± 0.2%) was not correlated with muscle or blood lactate levels. PHE eliminated the slow increase in and reduced gross exercise efficiency during AC. It is concluded that the slow component cannot be explained by a progressive acidosis because both muscle and blood lactate levels remained stable during CON. We suggest that both the slow component during CON and the reduced gross efficiency during AC are related to impaired contractility of the working fibres and the necessity to recruit additional motor units. Despite a pronounced stockpiling of ACn during AC, initial kinetics were not affected by PHE and PCr concentration decreased to a lower plateau. The discrepancy with previous studies, where initial oxidative ATP generation appears to be limited by acetyl group availability, might relate to remaining fatiguing effects of PHE. [source] Influence of nitric oxide synthase inhibition on pulmonary O2 uptake kinetics during supra-maximal exercise in humansTHE JOURNAL OF PHYSIOLOGY, Issue 2 2004Daryl P. Wilkerson We have recently reported that inhibition of nitric oxide synthase (NOS) with NG -nitro- l -arginine methyl ester (l -NAME) accelerates the ,phase II' pulmonary O2 uptake kinetics following the onset of moderate and heavy intensity submaximal exercise in humans. These data suggest that the influence of nitric oxide (NO) on mitochondrial function is an important factor in the inertia to aerobic respiration that is evident in the transition from a lower to a higher metabolic rate. The purpose of the present study was to investigate the influence of l -NAME on pulmonary kinetics following the onset of supra-maximal exercise, where it has been suggested that O2 availability represents an additional limitation to kinetics. Seven healthy young men volunteered to participate in this study. Following an incremental cycle ergometer test for the determination of , the subjects returned on two occasions to perform a ,step' exercise test from a baseline of unloaded cycling to a work rate calculated to require 105%, preceded either by systemic infusion of l -NAME (4 mg kg,1 in 50 ml saline) or 50 ml saline as a control (Con). Pulmonary gas exchange was measured on a breath-by-breath basis throughout the exercise tests. The duration of ,phase I' was greater with l -NAME (Con: 14.0 ± 2.1 versusl -NAME: 16.0 ± 1.6 s; P= 0.03), suggestive of a slower cardiovascular adaptation following the onset of exercise. However, the phase II time constant was reduced by 44% with l -NAME (Con: 36.3 ± 17.3 versusl -NAME: 20.4 ± 8.3 s; P= 0.01). The accumulation of blood lactate during exercise was also reduced with l -NAME (Con: 4.0 ± 1.1 versusl -NAME: 2.7 ± 2.1 mm; P= 0.04). These data indicate that skeletal muscle NO production represents an important limitation to the acceleration of oxidative metabolism following the onset of supra-maximal exercise in humans. [source] Phosphocreatine degradation in type I and type II muscle fibres during submaximal exercise in man: effect of carbohydrate ingestionTHE JOURNAL OF PHYSIOLOGY, Issue 1 2001Kostas Tsintzas 1The aim of this study was to examine the effect of carbohydrate (CHO) ingestion on changes in ATP and phosphocreatine (PCr) concentrations in different muscle fibre types during prolonged running and relate those changes to the degree of glycogen depletion. 2Five male subjects performed two runs at 70 % maximum oxygen uptake (V,O2,max), 1 week apart. Each subject ingested 8 ml (kg body mass (BM)),1 of either a placebo (Con trial) or a 5.5 % CHO solution (CHO trial) immediately before each run and 2 ml (kg BM),1 every 20 min thereafter. In the Con trial, the subjects ran to exhaustion (97.0 ± 6.7 min). In the CHO trial, the run was terminated at the time coinciding with exhaustion in the Con trial. Muscle samples were obtained from the vastus lateralis before and after each trial. 3Carbohydrate ingestion did not affect ATP concentrations. However, it attenuated the decline in PCr concentration by 46 % in type I fibres (CHO: 20 ± 8 mmol (kg dry matter (DM)),1; Con: 34 ± 6 mmol (kg DM),1; P < 0.05) and by 36 % in type II fibres (CHO: 30 ± 5 mmol (kg DM),1; Con: 48 ± 6 mmol (kg DM),1; P < 0.05). 4A 56 % reduction in glycogen utilisation in type I fibres was observed in CHO compared with Con (117 ± 39 vs. 240 ± 32 mmol glucosyl units (kg DM),1, respectively; P < 0.01), but no difference was observed in type II fibres. 5It is proposed that CHO ingestion during exhaustive running attenuates the decline in oxidative ATP resynthesis in type I fibres, as indicated by sparing of both PCr and glycogen breakdown. The CHO-induced sparing of PCr, but not glycogen, in type II fibres may reflect differential recruitment and/or role of PCr between fibre types. [source] Exercise Training Improves Aerobic Capacity and Skeletal Muscle Function in Heart Transplant RecipientsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 4 2009M. Haykowsky The aim of this study was to examine the effects of 12 weeks of supervised aerobic and strength training (SET) versus no-training (NT) on peak aerobic power (VO2peak), submaximal exercise left ventricular (LV) systolic function, peripheral vascular function, lean tissue mass and maximal strength in clinically stable heart transplant recipients (HTR). Forty-three HTR were randomly assigned to 12 weeks of SET (n = 22; age: 57 ± 10 years; time posttransplant: 5.4 ± 4.9 years) or NT (n = 21; age: 59 ± 11 years; time posttransplant: 4.4 ± 3.3 years). The change in VO2peak (3.11 mL/kg/min, 95% CI: 1.2,5.0 mL/kg/min), leg and total lean tissue mass (0.78 kg, 95% CI: 0.31,1.3 kg and 1.34 kg, 95% CI: 0.34,2.3 kg, respectively), chest-press (10.4 kg, 95% CI: 5.2,15.5 kg) and leg-press strength (34.7 kg, 95% CI: 3.7,65.6 kg) were significantly higher after SET versus NT. No significant change was found for submaximal exercise LV systolic function or brachial artery endothelial-dependent or -independent vasodilation. Supervised exercise training is an effective intervention to improve VO2peak, lean tissue mass and muscle strength in HTR. This training regimen did not improve exercise LV systolic function or brachial artery endothelial function. [source] Protective effects of long term dietary restriction on swimming exercise-induced oxidative stress in the liver, heart and kidney of ratCELL BIOCHEMISTRY AND FUNCTION, Issue 2 2007Cenk Aydin Abstract In this study, we evaluated the hypothesis that long term dietary restriction would have beneficial effects on the oxidative stress and antioxidant enzyme systems in liver, heart and kidney in adult male rats undergoing different intensities of swimming exercise. Sixty male, Sprague,Dawley rats were assigned as either dietary restricted on every other week day (DR) or fed ad libitum (AL) groups, and each group was further subdivided into sedentary, endurance swimming exercise training (submaximal exercise) and exhaustive swimming exercise (maximal exercise) groups. Animals in the submaximal exercise group swam 5 days/week for 8 weeks, while maximal exercise was performed as an acute bout of exercise. In parallel with the increase in the intensity of the exercise, the degree of lipid peroxidation and protein oxidation were increased in both the DR and AL groups; however the rate of increase was lower in the DR group. Reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) enzyme activities were lower in the DR group than in the AL group. In parallel with the increase in exercise intensity, GSH and GR enzyme activities decreased, whereas an increase was observed in GSH-Px enzyme activity. In conclusion, the comparison between the DR and AL groups with the three swimming exercise conditions shows that the DR group is greatly protected against different swimming exercise-induced oxidative stress compared with the AL group. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||