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Cycle Test (cycle + test)
Selected AbstractsCerebral oxygenation decreases during exercise in humans with beta-adrenergic blockadeACTA PHYSIOLOGICA, Issue 3 2009T. Seifert Abstract Aim:, Beta-blockers reduce exercise capacity by attenuated increase in cardiac output, but it remains unknown whether performance also relates to attenuated cerebral oxygenation. Methods:, Acting as their own controls, eight healthy subjects performed a continuous incremental cycle test to exhaustion with or without administration of the non-selective beta-blocker propranolol. Changes in cerebral blood flow velocity were measured with transcranial Doppler ultrasound and those in cerebral oxygenation were evaluated using near-infrared spectroscopy and the calculated cerebral mitochondrial oxygen tension derived from arterial to internal jugular venous concentration differences. Results:, Arterial lactate and cardiac output increased to 15.3 ± 4.2 mm and 20.8 ± 1.5 L min,1 respectively (mean ± SD). Frontal lobe oxygenation remained unaffected but the calculated cerebral mitochondrial oxygen tension decreased by 29 ± 7 mmHg (P < 0.05). Propranolol reduced resting heart rate (58 ± 6 vs. 69 ± 8 beats min,1) and at exercise exhaustion, cardiac output (16.6 ± 3.6 L min,1) and arterial lactate (9.4 ± 3.7 mm) were attenuated with a reduction in exercise capacity from 239 ± 42 to 209 ± 31 W (all P < 0.05). Propranolol also attenuated the increase in cerebral blood flow velocity and frontal lobe oxygenation (P < 0.05) whereas the cerebral mitochondrial oxygen tension decreased to a similar degree as during control exercise (delta 28 ± 10 mmHg; P < 0.05). Conclusion:, Propranolol attenuated the increase in cardiac output of consequence for cerebral perfusion and oxygenation. We suggest that a decrease in cerebral oxygenation limits exercise capacity. [source] Central and peripheral cardiovascular adaptations to exercise in endurance-trained childrenACTA PHYSIOLOGICA, Issue 2 2002S. NOTTIN ABSTRACT Stroke volume (SV) response to exercise depends on changes in cardiac filling, intrinsic myocardial contractility and left ventricular afterload. The aim of the present study was to identify whether these variables are influenced by endurance training in pre-pubertal children during a maximal cycle test. SV, cardiac output (Doppler echocardiography), left ventricular dimensions (time,movement echocardiography) as well as arterial pressure and systemic vascular resistances were assessed in 10 child cyclists (VO2max: 58.5 ± 4.4 mL min,1 kg,1) and 13 untrained children (UTC) (VO2max: 45.9 ± 6.7 mL min,1 kg,1). All variables were measured at the end of the resting period, during the final minute of each workload and during the last minute of the progressive maximal aerobic test. At rest and during exercise, stroke index was significantly higher in the child cyclists than in UTC. However, the SV patterns were strictly similar for both groups. Moreover, the patterns of diastolic and systolic left ventricular dimensions, and the pattern of systemic vascular resistance of the child cyclists mimicked those of the UTC. SV patterns, as well as their underlying mechanisms, were not altered by endurance training in children. This result implied that the higher maximal SV obtained in child cyclists depended on factors influencing resting SV, such as cardiac hypertrophy, augmented myocardium relaxation properties or expanded blood volume. [source] The effect of an Ni,Cr protective layer on cyclic oxidation of Ti3AlJOURNAL OF MICROSCOPY, Issue 1 2006I. CVIJOVI Summary The effect of an 80Ni,20Cr (at.%) metallic coating on the cyclic oxidation behaviour of a Ti3Al-based alloy with the composition Ti,25Al,11Nb (at.%) was investigated in this study. Cyclic oxidation tests were carried out in air at 600 °C and 900 °C for 120 h. For one cycle test, the specimens were held for 24 h at test temperature and then furnace-cooled to room temperature. The oxidation rate was determined by plotting the mass gain per unit surface area of the specimen vs. exposure time. The morphology and composition of the oxidation products were characterized on the cross-section of the specimens by scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy. The oxidation scale forms during exposure at both 600 °C and 900 °C. TiO2 is the main oxide component, whereas the Al2O3 layer appears only discontinuously. The remarkable improvement in oxidation resistance at 900 °C was attributed to the chemical composition and structure of the scale formed on the 80Ni,20Cr coating. [source] Strength Degradation and Failure Mechanisms of Electron-Beam Physical-Vapor-Deposited Thermal Barrier CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2001James A. Ruud Failure mechanisms were determined for electron-beam physical-vapor-deposited thermal barrier coating (TBC) systems from the degradation of mechanical properties and microstructural changes in a furnace cycle test. Bond strength degradation for TBCs resulted from the initiation and growth of interfacial delamination defects between the yttria-stabilized zirconia topcoat and the thermally grown alumina (TGO). It is proposed that defects started from concave depressions in the bondcoat surface created by the grit-blast-cleaning process and that defect growth was driven by the reduction in compressive strain in the TGO as the alumina deformed into and displaced the bondcoat during the cooling cycles. Inclusion of yttrium in the substrate resulted in a doubling of the furnace cycle life of the TBCs because of enhanced fracture toughness of the TGO-bondcoat interface. [source] A diagnostic cycle test for McArdle's diseaseANNALS OF NEUROLOGY, Issue 4 2003John Vissing MD We investigated whether the second wind phenomenon (ie, a decrease in heart rate and perceived exertion during exercise) is pathognomonic for McArdle's disease. Twenty-four patients with McArdle's disease, 17 healthy subjects, and 25 patients with other inborn errors of muscle metabolism cycled a constant workload for 15 minutes. In McArdle's disease patients, heart rate consistently decreased by 35 ± 3 beats per minute from the 7th to the 15th minute of exercise, whereas heart rate increased progressively with exercise in all 42 control subjects. The findings indicate that cycling at a moderate, constant workload provides a specific, sensitive, and simple diagnostic test for McArdle's disease. Ann Neurol 2003;54:539-542 [source] Dynamic compressive properties of porcine temporomandibular joint discEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2003Eiji Tanaka This study aimed to evaluate the effect of the strain frequency and amplitude on the compressive properties of the porcine temporomandibular joint disc and to determine the time-dependent changes associated with energy dissipation. Seven discs were used for compressive cycle tests, including various frequencies and magnitudes of compressive strain. Each experiment consisted of 25 cycles of loading and unloading. Hysteresis and the instantaneous and steady moduli were calculated. All specimens showed a clear hysteresis and repeatable stress,strain relationships within 19 cycles. The hysteresis at the initial cycle ranged between 35% and 62%, and gradually decreased in subsequent cycles. The instantaneous modulus became larger when the strain frequency and the strain amplitude increased. The steady modulus was approximately one-third of the instantaneous one. It was concluded that the disc has an energy-dissipating function during dynamic compression. [source] Physical training and testing in patients with chronic obstructive pulmonary diseaseTHE CLINICAL RESPIRATORY JOURNAL, Issue 1 2007Ragnheišur Harpa Arnardóttir Abstract Introduction:, The effects of different training modes need to be investigated further in patients with chronic obstructive pulmonary disease (COPD). Both advanced laboratory tests and field tests are used in patients with COPD to evaluate effects of interventions such as pulmonary rehabilitation. Aims:, The overall aims of the studies were to investigate the effects of different training modalities on exercise capacity and on health-related quality of life (HRQoL) in patients with moderate or severe COPD and, further, to explore two of the physical field tests used in pulmonary rehabilitation, the 12-min walk test and the incremental shuttle walking test (ISWT). Materials and Methods:, Patients with moderate or severe COPD were included. In study I (n = 57), the 12-min walk test was performed three times within 1 week. Exercise-induced hypoxemia (EIH) was assessed by pulse oximeter and was defined as SpO2 < 90%. In study II (n = 93), performance on ISWT was compared to performance on two different cycle tests. In study III (n = 42), the effects of two different combination training programmes were compared when training twice a week for 8 weeks. One programme was mainly based on endurance training (group A), and the other was based on resistance training and on callisthenics (group B). In study IV (n = 60), endurance training with interval resistance was compared to endurance training with continuous resistance. Results:, In study I, the 12-min walking distance (12MWD) did not increase on retesting in patients with EIH, but increased significantly on retesting in the non-EIH patients. In study II, the ISWT was as good a predictor of peak exercise capacity (W peak) as peak oxygen uptake (VO2 peak) was. In study III, W peak and 12MWD increased in group A but not in group B. HRQoL, anxiety and depression were unchanged in both groups. Ratings of perceived exertion at rest were significantly lower in group A than in group B after training and during 12 months of follow-up. Twelve months post training, 12MWD was back to baseline in group A, but was significantly shorter than at baseline in group B. Patients with moderate and severe COPD responded to training in the same way. In study IV, both interval and continuous endurance training increased W peak, VO2 peak, peak exhaled carbon dioxide (VCO2 peak) and 12MWD. Likewise, HRQoL, dyspnoea during activities of daily life, anxiety and depression improved similarly in both groups. At a fixed, sub-maximal workload (isotime), the interval training reduced oxygen cost and ventilatory demand significantly more than the continuous training did. Conclusions:, EIH affects the retest effects on 12MWD. W peak can be predicted from an ISWT similarly well as from VO2 peak. A short training programme can improve W peak and 12MWD when based mainly on endurance training. Both patients with moderate and severe COPD respond to training in the same way. A short endurance training intervention can possibly delay decline in 12MWD for 1 year. Both interval and continuous endurance training improves physical performance and HRQoL. Interval training lowers the energy cost of sub-maximal work more than continuous training does. [source] | ||||||||||