Evaluation of the best-designed graded exercise test to assess peak treadmill speed

This study examined the influence of different speed increments during treadmill exercise tests on peak treadmill speed (Vpeak) and its relationship with a 1-h treadmill running performance. 18 male recreational and amateur runners (10-km running pace: 10–15 km·h−1) performed, in an alternate order, 3 continuous incremental exercise tests with different speed increments (0.5, 1.0 and 2.0 km·h−1) on a motorized treadmill to determine Vpeak. Thereafter they undertook a 1-h time trial on a treadmill. Vpeak was determined as either (a) the highest speed that could be maintained for a complete minute (Vpeak-60 s), (b) the speed of the last complete stage (Vpeak-C), or (c) the speed of the last complete stage added to the product of the speed increment and the completed fraction of the incomplete stage (Vpeak-P). The Vpeak values were highly influenced by the different speed-incremented rates and the Vpeak-P determined during the protocol comprising speed increments of 1 km·h−1 presented the highest correlation with 1-h time trial performance (r=0.89). The results suggest that a protocol with speed increments comprising 1 km·h−1 and with a 3-min stage duration should be used as standard for the determination of Vpeak to assess aerobic fitness and predict endurance performance in recreational runners. Furthermore, the Vpeak-P should be used for the determination of Vpeak.

Estudo de diferentes protocolos para a determinação do lactato mínimo em eqüinos em exercício: comparação com a máxima fase estável de lactato

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reliability of peak running speeds obtained from different incremental treadmill protocols

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reproducibility of heart rate and rating of perceived exertion values obtained from different incremental treadmill tests

Objective The present study aimed to examine the reproducibility of heart rate (HR) and rating of perceived exertion (RPE) values obtained during different incremental treadmill tests. Equipment and methods Twenty male, recreational, endurance-trained runners (10-km running pace: 10–15 km·h−1) performed, in a counterbalanced order, three continuous incremental exercise tests with different speed increments (0.5 km·h−1, 1 km·h−1 and 2 km·h−1). Thereafter, each participant performed the three tests again, maintaining the same order as before. The reproducibility of the HR and RPE values were analyzed for all protocols during submaximal intensities (8, 10, 12, and 14 km·h−1). In addition, it was examined the reproducibility of maximal HR (HRmax) and peak RPE (RPEpeak). Results The variability of both the HR and RPE values showed a tendency to decrease over the stages during the incremental test and was not or slightly influenced by the incremental test design. The HR at 14 km·h−1 and HRmax presented the highest reproducibility (CV < 2%). In contrast, the submaximal RPE values showed higher variability indices (i.e., CV > 5.0%). In conclusion, the HR values were highly reproducible during the stages of the incremental test, in contrast to the RPE values that presented limited reproducibility.

Comparison of the lactate minimum speed and the maximal lactate steady state to determine aerobic capacity in purebred Arabian horses

AIM: To compare five different protocols for estimating the lactate minimum speed (LMS) with that for estimating the maximal lactate steady state (MLSS) in Arabian horses, in order to obtain a more rapid method for monitoring aerobic capacity and prescribing training schedules. METHODS: Eight purebred Arabian horses were conditioned to exercise on a treadmill for 12 days then submitted to three to five exercise sessions to determine the MLSS. Blood samples were collected from a jugular catheter at specific intervals for measurement of lactate concentrations. The MLSS was the velocity maintained during the last 20 minutes of constant submaximal exercise, at which the concentration of lactate increased by no more than 1.0 mmol/L. The LMS test protocols (P1 - P5) included a warm-up period followed by a high-intensity gallop. The speed was then reduced to 4 m/s, and the incremental portion of the test was initiated. In P1, P2, and P3, the velocity increment was 0.5 m/s, and the duration of each incremental stage was three, five and seven minutes, respectively. In P4 and P5, the velocity increments were 1.0 and 1.5 m/s, respectively, and the duration of the stages was fixed at five minutes each. A second-degree polynomial function was fitted to the lactate-velocity curve, and the velocity corresponding to the lowest concentration of lactate was the LMS. RESULTS: Only the mean LMS determined by P1 and P2 did not differ from the velocity determined by the MLSS test (p > 0.1). There was a strong correlation (r >0.6) between P1 and the MLSS velocity. A limits of agreement plot revealed that the best agreement occurred between the MLSS test and P1 (mean bias = 0.14 m/s), followed by P2 (bias = -0.22 m/s). The lactate concentrations associated with the various LMS protocols did not differ. CONCLUSIONS: This study shows the variation between protocols of the LMS test for determining the onset of blood lactate accumulation but also reveals that, at least for Arabian horses, the P1 protocol of the LMS has good agreement with the MLSS. © 2013 Copyright New Zealand Veterinary Association.

Genetic associations between flight speed and growth traits in Nellore cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Performance of aerodynamic baffles in cylindrical grinding analyzed on the basis of air layer pressure and speed

Over the years, grinding has been considered one of the most important manufacturing processes. Grinding is a high precision process, and the loss of a single workpiece in this stage of the production is unacceptable, fir the value added to the material is very high due to many processes it has already undergone prior to grinding. This study aims to contribute toward the development of an experimental methodology whereby the pressure and speed of the air layer produced by the high rotation of the grinding wheel is evaluated with and without baffles, i.e., in an optimized grinding operation and in a traditional one. Tests were also carried out with steel samples to check the difference in grinding wheel wear with and without the use of baffles.

Influence of the grinding wheel's dive speed on the damage of rectified hardened steels

The world tendency is the increase of the productivity and the production of pieces more and more sophisticated, with high degree of geometric and dimensional tolerances, with good surface finish and low cost. Rectification is responsible for the final finish in the machining process of a material. However, damages generated in this production phase affect all the resources used in the previous processes. Great part of the problems happennig in the rectification process is due to the enormous temperature generated in this activity because of the machining conditions. The dive speed, which is directly related to the productivity, is considered responsible for the damages that occur during rectification, limiting its values to those that do not cause such damages. In this work, through the variation of the dive speed in the process of cylindrical grinding of type ABNT D6 steel, rationalizing the application of two cutting fluids and using a CBN (cubic boron nitrate) abrasive wheel with vitrified blond, the influence of the dive speed on the surface damages of hardened steels was evaluated. The results allowed to say that the dive speed, associated to an efficient cooling and lubrication, didn't provoke thermal damages (including heated zones, cracks and tension stresses) to the material. Residual stresses and the roughness of rectified materials presented a correlation with the machining conditions. The work concluded that it is possible to increase the productivity without provoking damages in the rectified components.

Influence of belt speed, grit sizes and pressure on the sanding of Eucalyptus grandis wood

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Power performance evaluation of an electric home fan with triac-based automatic speed control system

In order to provide a low cost system of thermal comfort, a common model of home fan, 40 cm diameter size, had its manual four-button control system replaced by an automatic speed control. The new control system has a temperature sensor feeding a microcontroller that, by using an optic coupling, DIAC or TRIAC-based circuit, varies the RMS value of the fan motor input voltage and its speed, according to the room temperature. Over a wide range of velocity, the fan net power and the motor fan input power were measured working under both control system. The temperature of the motor stator and the voltage waveforms were observed too. Measured values analysis showed that the TRIAC-based control system makes the fan motor work at a very low power factor and efficiency values. The worst case is at low velocity range where the higher fan motor stator temperatures were registered. The poor power factor and efficiency and the harmonics signals inserted in the motor input voltage wave by the TRIAC commutation procedure are correlated.

Positive leader characteristics from high-speed video observations

Based on analyses of high-speed video recordings of cloud-to-ground lightning in Brazil and the USA, the characteristics of positive cloud-to-ground (+CG) leaders are presented. The high frame rates permitted the average, 2-dimensional speeds of development along the paths of the channels to be resolved with good accuracy. The values range from 0.3 to 6.0 x 10(5) ms(-1) with a mean of 2.7 x 10(5) ms(-1). Contrary to what is usually assumed, downward +CG leader speeds are similar to downward -CG leader speeds. Our observations also show that the speeds tend to increase by a factor of 1.1 to 6.5 as they approach the ground. The presence of short duration, recoil leaders (RLs) during the development of positive leaders reveal a highly branched structure that is not usually recorded when using conventional photographic and video cameras. The existence of the RLs may help to explain observations of UHF-VHF radiation during the development of +CG flashes.

A novel HPF voltage source rectifier for variable speed refrigeration systems

A novel single-phase voltage source rectifier capable to achieve High-Power-Factor (HPF) for variable speed refrigeration system application, is proposed in this paper. The proposed system is composed by a single-phase high-power-factor boost rectifier, with two cells in interleave connection, operating in critical conduction mode, and employing a soft-switching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifier's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the EEC61000-3-2 standards. The digital controller for the output stage has been developed using a conventional voltage-frequency control (scalar V/f control), and a simplified stator oriented Vector control, in order to verify the feasibility and performance of the proposed digital controls for continuous temperature control applied at a refrigerator prototype.

Comparative Histopathological Analysis of Human Pulps after Class I Cavity Preparation with a High-Speed Air-Turbine Handpiece or Er:YAG Laser

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Application of preparative high-speed counter-current chromatography for the separation of flavonoids from the leaves of Byrsonima crassa Niedenzu (IK)

The methanolic extract of the leaves of the medicinal plant Byrsonima crassa (Malpighiaceae) contain flavonoids with antioxidant activity. They were separated in a preparative scale using high-speed counter-current chromatography. The optimum solvent system used was composed of a mixture of ethyl acetate-n-propanol-water (140:8:80 (v/v/v)) and led to a successful separation between monoglucosilated flavonoids (quercetin-3-O-alpha-L-arabinoside, quercetin-3-O-beta-D-galactoside) and the biflavonoid amentoflavone in only 3.5 h. The purities of quercetin-3-O-alpha-L-arabinoside (95 mg), quercetin-3-O-beta-D-galactoside (16 mg) and the biflavonoid amentoflavone (114 mg) were all isolated at purity over 95%. Identification was performed by H-1 NMR, C-13 NMR and UV analyses. (C) 2004 Published by Elsevier B.V.