Maximal power output during incremental cycling test is dependent on the curvature constant of the power-time relationship

The aim of this study was to investigate whether the maximal power output (Pmax) during an incremental test was dependent on the curvature constant (W') of the power-time relationship. Thirty healthy male subjects (maximal oxygen uptake = 3.58 ± 0.40 L·min(-1)) performed a ramp incremental cycling test to determine the maximal oxygen uptake and Pmax, and 4 constant work rate tests to exhaustion to estimate 2 parameters from the modeling of the power-time relationship (i.e., critical power (CP) and W'). Afterwards, the participants were ranked according to their magnitude of W'. The median third was excluded to form a high W' group (HIGH, n = 10), and a low W' group (LOW, n = 10). Maximal oxygen uptake (3.84 ± 0.50 vs. 3.49 ± 0.37 L·min(-1)) and CP (213 ± 22 vs. 200 ± 29 W) were not significantly different between HIGH and LOW, respectively. However, Pmax was significantly greater for the HIGH (337 ± 23 W) than for the LOW (299 ± 40 W). Thus, in physically active individuals with similar aerobic parameters, W' influences the Pmax during incremental testing.

Does 75% of the difference between VO2 at lactate threshold and VO2max lie at the severe-intensity domain in well-trained cyclists?

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

HYPERLACTEMIA INDUCTION MODES AFFECT THE LACTATE MINIMUM POWER AND PHYSIOLOGICAL RESPONSES IN CYCLING

Zagatto, AM, Padulo, J, Muller, PTG, Miyagi, WE, Malta, ES, and Papoti, M. Hyperlactemia induction modes affect the lactate minimum power and physiological responses in cycling. J Strength Cond Res 28(10): 2927-2934, 2014The aim of this study was to verify the influence of hyperlactemia and blood acidosis induction on lactate minimum intensity (LMI). Twenty recreationally trained males who were experienced in cycling (15 cyclists and 5 triathletes) participated in this study. The athletes underwent 3 lactate minimum tests on an electromagnetic cycle ergometer. The hyperlactemia induction methods used were graded exercise test (GXT), Wingate test (WAnT), and 2 consecutive Wingate tests (2 x WAnTs). The LMI at 2 x WAnTs (200.3 +/- 25.8 W) was statistically higher than the LMI at GXT (187.3 +/- 31.9 W) and WAnT (189.8 +/- 26.0 W), with similar findings for blood lactate, oxygen uptake, and pulmonary ventilation at LMI. The venous pH after 2 x WAnTs was lower (7.04 +/- 0.24) than in (p <= 0.05) the GXT (7.19 +/- 0.05) and WAnT (7.19 +/- 0.05), whereas the blood lactate response was higher. In addition, similar findings were observed for bicarbonate concentration [HCO3] (2 x WAnTs lower than WAnT; 15.3 +/- 2.6 mmol center dot L-1 and 18.2 +/- 2.7 mmol center dot L(-)1, respectively) (p <= 0.05). However, the maximal aerobic power and total time measured during the incremental phase also did not differ. Therefore, we can conclude that the induction mode significantly affects pH, blood lactate, and [HCO3] and consequently they alter the LMI and physiological parameters at LMI.

Máxima fase estável de lactato sanguíneo e potência crítica em ciclistas bem treinados

O principal objetivo deste estudo foi comparar a intensidade correspondente à máxima fase estável de lactato (MLSS) e a potência crítica (PC) durante o ciclismo em indivíduos bem treinados. Seis ciclistas do sexo masculino (25,5 ± 4,4 anos, 68,8 ± 3,0kg, 173,0 ± 4,0cm) realizaram em diferentes dias os seguintes testes: exercício incremental até a exaustão para a determinação do pico de consumo de oxigênio (VO2pico) e sua respectiva intensidade (IVO2pico); cinco a sete testes de carga constante para a determinação da MLSS e da PC; e um exercício até a exaustão na PC. A MLSS foi considerada com a maior intensidade de exercício onde a concentração de lactato não aumentou mais do que 1mM entre o 10º e o 30º min de exercício. Os valores individuais de potência (95, 100 e 110% IVO2pico) e seu respectivo tempo máximo de exercício (Tlim) foram ajustados a partir do modelo hiperbólico de dois parâmetros para a determinação da PC. Embora altamente correlacionadas (r = 0,99; p = 0,0001), a PC (313,5 ± 32,3W) foi significantemente maior do que a MLLS (287,0 ± 37,8W) (p = 0,0002). A diferença percentual da PC em relação à MLSS foi de 9,5 ± 3,1%. No exercício realizado na PC, embora tenha existido componente lento do VO2 (CL = 400,8 ± 267,0 ml.min-1), o VO2pico não foi alcançado (91,1 ± 3,3 %). Com base nesses resultados pode-se concluir que a PC e a MLSS identificam diferentes intensidades de exercício, mesmo em atletas com elevada aptidão aeróbia. Entretanto, o percentual da diferença entre a MLLS e PC (9%) indica que relação entre esses dois índices pode depender da aptidão aeróbia. Durante o exercício realizado até a exaustão na PC, o CL que é desenvolvido não permite que o VO2pico seja alcançado.

Effect of aerobic training status on both maximal lactate steady state and critical power

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

PHYSIOLOGICAL and PERCEIVED EXERTION RESPONSES AT INTERMITTENT CRITICAL POWER and INTERMITTENT MAXIMAL LACTATE STEADY STATE

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

There is no anaerobic work capacity replenishment at critical power intensity: An indirect evidence

Aim. - This study aimed to test if investigate whether the anaerobic work capacity is replenished while exercising at critical power intensity. Then, a known exercise duration, which demands high anaerobic energy contribution, was compared to intermittent exercise duration with passive and active (cycling at critical power intensity) rest periods.Methods. - Nine participants performed five sessions of testing. From the 1st to the 3rd sessions, individuals cycled continuously at different workloads (P-high, P-intermediate and P-low) in order to estimate the critical power and the anaerobic work capacity. The 4th and 5th sessions were performed in order to determine the influence of anaerobic work capacity replenishment oil exercise duration. They consisted of manipulating the resting type (passive or active) between two cycling efforts. The total exercise duration was determined by the sum of the two cycling efforts duration.Results. - The exercise duration under passive resting condition (408.0 +/- 42.0 s) was longer (p<0.05) than known exercise duration at P-intermediate (T-intermediate = 305.8 +/- 30.5 s) and than exercise duration performed under active resting conditions (T-active = 304.4 +/- 30.7s). However, there was no significant difference between T-intermediate and T-active.Conclusion. - These results demonstrated indirect evidence that the anaerobic work capacity is not replenished while exercising at critical power intensity. (C) 2008 Elsevier Masson SAS. All rights reserved.

The highest intensity and the shortest duration permitting attainment of maximal oxygen uptake during cycling: effects of different methods and aerobic fitness level

The aims of this study were: (1) to verify the validity of previous proposed models to estimate the lowest exercise duration (T (LOW)) and the highest intensity (I (HIGH)) at which VO(2)max is reached (2) to test the hypothesis that parameters involved in these models, and hence the validity of these models are affected by aerobic training status. Thirteen cyclists (EC), eleven runners (ER) and ten untrained (U) subjects performed several cycle-ergometer exercise tests to fatigue in order to determine and estimate T (LOW) (ET (LOW)) and I (HIGH) (EI (HIGH)). The relationship between the time to achieved VO(2)max and time to exhaustion (T (lim)) was used to estimate ET (LOW). EI (HIGH) was estimated using the critical power model. I (HIGH) was assumed as the highest intensity at which VO2 was equal or higher than the average of VO(2)max values minus one typical error. T (LOW) was considered T (lim) associated with I (HIGH). No differences were found in T (LOW) between ER (170 +/- 31 s) and U (209 +/- 29 s), however, both showed higher values than EC (117 +/- 29 s). I (HIGH) was similar between U (269 +/- 73 W) and ER (319 +/- 50 W), and both were lower than EC (451 +/- 33 W). EI (HIGH) was similar and significantly correlated with I-HIGH only in U (r = 0.87) and ER (r = 0.62). ET (LOW) and T (LOW) were different only for U and not significantly correlated in all groups. These data suggest that the aerobic training status affects the validity of the proposed models for estimating I (HIGH).

EFFECTS of PREFERRED and NONPREFERRED MUSIC on CONTINUOUS CYCLING EXERCISE PERFORMANCE

The aim of this study was to investigate the effects of preferred and nonpreferred music on exercise distance, Heart Rate (HR), and Rating of Perceived Exertion (RPE) during continuous cycling exercise performed at high intensity Fifteen participants performed five test sessions During two sessions, they cycled with fixed workload on ergometer to determine the Critical Power (Cl') intensity Then, they performed three more sessions cycling at CP intensity listening to Preferred Music, listening to Nonpreferred Music, and No Music The HR responses in the exercise sessions did not differ among all conditions However, the RPE was higher for Nonpreferred Music than in the other conditions The performance under Preferred Music (9 8 +/- 4 6km) was greater than under Nonpreferred Music (7 1 +/- 3 5km) conditions Therefore, listening to Preferred Music during continuous cycling exercise at high intensity can Increase the exercise distance, and individuals listening to Nonpreferred Music can perceive more discomfort caused by the exercise

Indexes of power and aerobic capacity obtained in cycle ergometry and treadmill running: comparisons between sedentary, runners, cyclists and triathletes

The objectives of this study were: a) to determine, in a cross-sectional manner, the effect of aerobic training on the peak oxygen uptake, the intensity at O2peak and the anaerobic threshold (AnT) during running and cycling; and b) to verify if the transference of the training effects are dependent on the analized type of exercise or physiological index. Eleven untrained males (UN), nine endurance cyclists (EC), seven endurance runners (ER), and nine triathletes (TR) were submitted, on separate days, to incremental tests until voluntary exhaustion on a mechanical braked cycle ergometer and on a treadmill. The values of O2peak (ml.kg-1.min-1) obtained in running and cycle ergometer (ER = 68.8 ± 6.3 and 62.0 ± 5.0; EC = 60.5 ± 8.0 and 67.6 ± 7.6; TR = 64.5 ± 4.8 and 61.0 ± 4.1; UN = 43.5 ± 7.0 and 36.7 ± 5.6; respectively) were higher in the group that presented specific training in the modality. The UN group presented the lower values of O2peak, regardless of the type of exercise. This same behavior was observed for the AnT (ml.kg-1.min-1) determined in running and cycle ergometer (ER = 56.8 ± 6.9 and 44.8 ± 5.7; EC = 51.2 ± 5.2 and 57.6 ± 7.1; TR = 56.5 ± 5.1 and 49.0 ± 4.8; UN = 33.2 ± 4.2 and 22.6 ± 3.7; respectively). It can be concluded that the transference of the training effects seems to be only partial, independently of the index (O2peak, IO2peak or AnT) or exercise type (running or cycling). In relation to the indices, the specificity of training seems to be less present in the O2peak than in the IO2peak and the AnT.

Production grinding burn detection using acoustic emission and electric power signals

This work uses a monitoring system based on a PC platform, where the acoustic emission and electric power signals generated during the grinding process are used to investigate superficial burning occurrence in a surface grinding operation using two types of steel, three grinding conditions and an Al203 vitrified grinding wheel. Acoustic emission signals on the workpiece and grinding power were measured during a surface plunge operation until the grinding burn happened. From the results the standard deviation of the acoustic emission signal and the maximum electric power were calculated for each grinding pass. The proposed DPO parameter is the product between the power level and acoustic emission standard deviation. The results show that both signals can be used for burning detection, and the parameter DPO is the best indicator for the burning studied in this work. This can be explained by the high dispersion of the acoustic emission RMS level associated to the high power consumption when the grinding wheel lose its sharpness.

Virtual instrumentation applied to the implementation of IEEE STD 1459-2000 power definitions

This paper discusses the utilization of Virtual Instrumentation to the implementation and evaluation of different power definitions, so that classical formulations and new definitions can be compared without the necessity of acquiring different power meters or analyzers. Accordingly, the definitions of IEEE Standard 1459-2000 for the measurement of power quantities under distorted and unbalanced situations, have been digitally implemented. Thus, several power and power factor components related to the decomposition of the measured voltage and current signals have been obtained. The proposed PC-based Virtual Instrument uses a high performance acquisition board and isolated sensors and transducers. All digital algorithms and routines have been implemented by means of a graphical development system. Regarding to the implementation of STD 1459, this paper also proposes several different algorithms to the required decompositions of voltage, current and power components. © 2005 IEEE.

Frequency-adjustable positive sequence detector for power conditioning applications

This paper proposes a novel and simple positive sequence detector (PSD), which is inherently self-adjustable to fundamental frequency deviations by means of a software-based PLL (Phase Locked Loop). Since the proposed positive sequence detector is not based on Fortescue's classical decomposition and no special input filtering is needed, its dynamic response may be as fast as one fundamental cycle. The digital PLL ensures that the positive sequence components can be calculated even under distorted waveform conditions and fundamental frequency deviations. For the purpose of validating the proposed models, the positive sequence detector has been implemented in a PC-based Power Quality Monitor and experimental results illustrate its good performance. The PSD algorithm has also been evaluated in the control loop of a Series Active Filter and simulation results demonstrate its effectiveness in a closed-loop system. Moreover, considering single-phase applications, this paper also proposes a general single-phase PLL and a Fundamental Wave Detector (FWD) immune to frequency variations and waveform distortions. © 2005 IEEE.

Efeito do nível do treinamento aeróbio na determinação do limite superior do domínio pesado no ciclismo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aptidão aeróbia e amplitude dos domínios de intensidade de exercício no ciclismo

INTRODUÇÃO: A determinação dos domínios de intensidade de exercício tem importantes implicações na prescrição do treino aeróbio e na elaboração de delineamentos experimentais. OBJETIVO: Analisar os efeitos do nível de aptidão aeróbia sobre a amplitude dos domínios de intensidade de exercício durante o ciclismo. MÉTODOS: Doze ciclistas (CIC), 11 corredores (COR) e oito indivíduos não treinados (NT) foram submetidos aos seguintes protocolos em diferentes dias: 1) teste progressivo para determinação do limiar de lactato (LL), consumo máximo de oxigênio (VO2máx) e sua respectiva intensidade (IVO2máx); 2) três testes de carga constante até a exaustão a 95, 100 e 110% IVO2máx para a determinação da potência crítica (PC); 3) testes até a exaustão para determinar a intensidade superior do domínio severo (Isup). As amplitudes dos domínios (moderado < LL; LL > pesado < PC; PC > severo < Isup) foram expressas como percentual da Isup (VO2). RESULTADOS: A amplitude do domínio moderado foi similar entre CIC (52 ± 8%) e COR (47 ± 4%) e significantemente maior no CIC em relação ao NT (41 ± 7%). O domínio pesado foi significantemente menor no CIC (17 ± 6%) em relação ao COR (27 ± 6%) e NT (27 ± 9%). Em relação ao domínio severo não foram encontradas diferenças significantes entre os CIC (31 ± 7%), COR (26 ± 5%) e NT (31 ± 7%). CONCLUSÃO: O domínio pesado de exercício é mais sensível a mudanças determinadas pelo nível de aptidão aeróbia, existindo a necessidade de que se atenda ao princípio da especificidade do movimento, quando se pretende obter um elevado grau de adaptação fisiológica.