Abstract
PurposeTime to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W′) of the power–duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W′.MethodsEleven trained cyclists completed a series of TTE tests to establish CP and W′ under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test.ResultsPerceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P < 0.05), without a change in perceived physical fatigue (P > 0.05). PE was significantly higher during TTE in the MF condition (P < 0.05). Pre-post blood lactate accumulation was significantly lower after each TTE in MF condition (P < 0.05). HR was not significant different between conditions (P > 0.05). Neither cognitive task induced any change in CP (MF 253 ± 51 vs. CON 247 ± 58W; P > 0.05), although W′ was significantly reduced in the MF condition (MF 22.8 ± 4.5 vs. CON 29.3 ± 6.3 kJ; P < 0.01).ConclusionMF has no effect of CP, but reduces the W′ in trained cyclists. Lower lactate accumulation during TTE tests following MF suggests that cyclists were not able to fully expend W′ even though they exercised to volitional exhaustion.
Highlights
The critical power (CP) concept is based upon a mathematical model of the hyperbolic relationship between work done and time to exhaustion (TTE)
When endurance exercise was performed 5% above the CP, V O2 continued to increase until V O2 was reached, and blood lactate continued to rise until the participants were no longer able to exercise
A significant interaction effect of condition × time point (P = 0.04) was found with greater levels of perceived physical fatigue being evident after the Time to exhaustion (TTE) tests in both conditions (Fig. 2b)
Summary
The critical power (CP) concept is based upon a mathematical model of the hyperbolic relationship between work done and time to exhaustion (TTE). Since the early work of Monod and Scherer (1965), it has been accepted that the hyperbolic relationship is reflective of physiological responses to endurance exercise, where CP represents the highest sustainable rate of aerobic metabolism Poole et al (1988) demonstrated that if endurance exercise is performed at the CP, following the initial “fundamental” increase in oxygen consumption (V O2,) a delayed steady state is achieved within a few minutes. The increase in V O2 is replicated by the blood lactate response, which following an initial rise at the start of endurance exercise, stabilizes after some minutes. The curvature constant of the model is known as the W′ and represents the amount of work that can be performed above the CP, regardless of the chosen work rate above CP (Moritani et al 1981; Monod and Scherrer 1965; Poole et al 1988). W′ has been attributed to the depletion of intramuscular phosphocreatine (PCr) and glycogen with accumulation of fatigue-related muscle metabolites including hydrogen ion (H+) and inorganic phosphate (Pi) (Fitts 1994)
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