The effect of glycogen depletion on the curvature constant parameter of the power-duration curve for cycle ergometry

Abstract

For high-intensity cycle ergometer exercise, the relation between power (P) and its tolerable duration (t) has been well characterized by the hyperbolic relationship: (P-thetaF) t = W', or P = W' (1/t)+thetaF, where thetaF may be termed the 'fatigue threshold'. The curvature constant (W') reflects a constant amount of work which is postulated to be equivalent to a finite energy store that relates to the oxygen-deficit: phosphagen pool, anaerobic glycolysis and oxygen stores. Compared to thetaF, the physiological nature of W' has received little consideration. The purpose of this study was therefore to establish the parameters of the power-duration curve (thetaF and W') for subjects in normal glycogen (NG) and glycogen depleted (GD) states. Seven healthy male subjects (aged 22 to 41 years) each performed four high-intensity square-wave exercise bouts on an electrically braked cycle ergometer under two different muscular glycogen content conditions, i.e. NG and GD states. Subjects performed the following exercise on the evening before the trial day to induce the GD state. Initially, they performed a 75-min cycling exercise at 60% of VO2max. After a 5-min rest period, they subsequently repeated a 1-min cycling bout at 115% of VO2max (separated by 1-min rest periods) until the subject could no longer maintain the prescribed pedal rate for the full minute. Subjects then reported to the laboratory after an overnight fast and performed a single high-intensity exercise bout. The GD procedure was repeated four times at 1-week intervals. In the GD state, the respiratory exchange ratio (RER) (VO2/VCO2) value during a recumbent control period prior to the trial was significantly lower than that in the NG state [GD: 0.84+/-0.02, NG: 0.94+/-0.04, mean +/- SD]. There was no significant difference for thetaF between GD and NG state [NG: 197.1+/-31.9 W, GD: 190.6+/-28.2 W]. W' in contrast was significantly reduced by the GD procedure [NG: 12.83+/-2.21 kJ, GD: 10.33+/-2.41 kJ]. The present results indicate that the muscular glycogen store seems to be an important determinant of the curvature constant (W') of the power-duration curve for cycle ergometry.

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

“…The duration that this exercise can be maintained is dependent upon the magnitude of D`, which is determined by available energy stores and their rate of depletion , Miura et al, 1999, Miura et al, 2000, as…”

“…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…”

“…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, Miura et al, 2000, Monod and Scherrer, 1965 as well as by accumulation of fatigue-inducing metabolites (Coats et al, 2003, Ferguson et al, 2007. CP demarcates the heavy-severe domain boundary in that, at or below CP a general steady state is achieved , Poole et al, 1988 , Poole et al, 1988.…”

“…For example, intervention studies typically require a minimum of eight testing sessions per subject (Barker et al, 2006, Gaesser and Wilson, 1988, Hill et al, 1995, Miura et al, 1999, Miura et al, 2000, Miura et al, 2009, Poole et al, 1990. The development of the all-out test (Burnley et al, 2006, Dekerle et al, 2006 has led to a reduction in the number of testing sessions required to determine the parameters of the power-time relationship (Vanhatalo et al, 2007), directly addressing the time consuming dilemma.…”

Influence of blood flow occlusion on muscle oxygenation characteristics and the parameters of the power-duration relationship

“…It is also evident that W= is a constant term that determines the limit of exercise tolerance (T lim ) for severe-intensity exercise (21, 55). Intramuscular energy stores (35,36,38), the accumulation of fatigue-inducing metabolites (7,18,21,28), and/or the magnitude of the severe-intensity domain (5, 51) have all been postulated to determine W=. Building evidence supports that complete utilization of W= is associated with consistent muscle phosphocreatine ([PCr]), inorganic phosphate ([P i ]), and hydrogen ion concentration ([H ϩ ]) perturbations, which may limit the amount of work performed above CP (28,43,51).…”