Maximal lactate steady state, critical power and EMG during cycling

Abstract

We hypothesised that: (1) the maximal lactate steady state (MLSS), critical power (CP) and electromyographic fatigue threshold (EMG(FT)) occur at the same power output in cycling exercise, and (2) exercise above the power output at MLSS (P-MLSS) results in continued increases in oxygen uptake (VO(2)), blood lactate concentration ([La]) and integrated electromyogram (iEMG) with time. Eight healthy subjects [mean (SD) age 25 (3) years, body mass 72.1 (8.2) kg] performed a series of laboratory tests for the determination of MLSS, CP and EMG(FT). The CP was determined from four exhaustive trials of between 2 and 15 min duration. The MLSS was determined as the highest power output at which the increase in blood [La] was less than 1.0 mM across the last 20 min of a series of 30-min trials. The EMG(FT) was determined from four trials of 2 min duration at different power outputs. The surface electromyogram was recorded continuously from the vastus lateralis muscle. The CP was significantly higher than the P-MLSS [242 (25) vs. 222 (23) W; P<0.05], although the two variables were strongly correlated (r=0.95; P<0.01). The EMG(FT) could not be determined in 50% of the subjects. Blood [La], VO(2) and minute ventilation all increased significantly with time for exercise at power outputs above the P-MLSS. In conclusion, the P-MLSS, and not the CP, represents the upper limit of the heavy exercise domain in cycling. During exercise above the P-MLSS, there is no association between changes in iEMG and increases in VO(2) and blood [La] with time.

Oxygen uptake kinetics as a determinant of sports performance

“…Theoretically, however, it is the critical power that represents the maximal sustainable power output defined above, and this parameter has therefore been suggested to represent the boundary between the heavy and severe exercise intensity domains (Poole, Ward, Gardner, & Whipp, 1988). The critical power is notionally equivalent to the power output at the so-called ''maximal lactate steady state'' (for discussion, see Pringle & Jones, 2002;Smith & Jones, 2001). The above outline poses two important questions: First, why does the lactate threshold correlate with endurance performance, even though athletes consistently exceed the threshold during races?…”

A single test for the determination of parameters of the speed–time relationship for running

“…The 1/time model has commonly been utilized for parameter determination (Brickley et al, 2002, Ferguson et al, 2007, Ferguson et al, 2010, Pringle and Jones, 2002 …”

“…The power-time relationship has been observed in cycling (Barker et al, 2006, Gaesser and Wilson, 1988, Hill et al, 1995, Housh et al, 1989, Miura et al, 1999, Miura et al, 2000, Miura et al, 2009, Neder et al, 2000, Poole et al, 1988, Poole et al, 1990, Pringle and Jones, 2002, Smith et al, 1999, rowing (Cheng et al, 2012, Hill et al, 2003, Kendall et al, 2011, knee-extension (Burnley, 2009), and running (Bull et al, 2008, Hughson et al, 1984, Smith and Jones, 2001) where a substitute for power is used when necessary. CP is associated with the muscle's aerobic power (Gaesser and Wilson, 1988, Gaesser et al, 1995, Jenkins and Quigley, 1992, McLellan and Cheung, 1992, Miura et al, 1999, Miura et al, 2000, Moritani et al, 1981, Moritani et al, 1981, Poole et al, 1990, while W` represents predominantly 'anaerobic' characteristics (Ferguson et al, 2007, Ferguson et al, 2010, Gaesser and Wilson, 1988, Jenkins and Quigley, 1992, Miura et al, 1999, Miura et al, 2000, Moritani et al, 1981, Poole et al, 1990 and is determined, in part, by intramuscular energy stores of phosphate, glycogen, and oxygen (Miura et al, 1999…”

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

“…Durante o ciclismo estacionário de alta intensidade, a relação entre a potência externa gerada (P) e o seu respectivo tempo máximo de exercício (Tlim) tem sido frequentemente descrita por um modelo hiperbólico de dois parâmetros (equação 1) (1,2) . A assíntota e o grau da curvatura dessa relação têm sido identificados como "potência crítica" (PC) e "capacidade de trabalho anaeróbio" (CTAn), respectivamente.…”

“…As naturezas aeróbia e anaeróbia da PC e CTAn, respectivamente, têm sido exaustivamente confirmadas por diferentes delineamentos experimentais (2)(3)(4) . Uma importante implicação da determinação da PC, tanto para a prescrição do exercício aeróbio bem como na elaboração de delineamentos experimentais, é a identificação do limite entre o domínio pesado e severo de exercício.…”