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Purpose: This study aimed 1) to examine the accuracy with which W′ reconstitution (W′REC) is estimated by the W′ balance (W′BAL) models after a 3-min all-out cycling test (3MT), 2) to determine the effects of a 3MT on the power–duration relationship, and 3) to assess whether accounting for changes in the power–duration relationship during exercise improved estimates of W′REC. Methods: The power–duration relationship and the actual and estimated W′REC were determined for 12 data sets extracted from our laboratory database where participants had completed two 3MT separated by 1-min recovery (i.e., control [C-3MT] and fatigued [F-3MT]). Results: Actual W′REC (6.3 ± 1.4 kJ) was significantly overestimated by the W′BAL·ODE (9.8 ± 1.3 kJ; P < 0.001) and the W′BAL·MORTON (16.9 ± 2.6 kJ; P < 0.001) models but was not significantly different to the estimate provided by the W′BAL·INT (7.5 ± 1.5 kJ; P > 0.05) model. End power (EP) was 7% lower in the F-3MT (263 ± 40 W) compared with the C-3MT (282 ± 44 W; P < 0.001), and work done above EP (WEP) was 61% lower in the F-3MT (6.3 ± 1.4 kJ) compared with the C-3MT (16.9 ± 3.2 kJ). The size of the error in the estimated W′REC was correlated with the reduction in WEP for the W′BAL·INT and W′BAL·ODE models (both r > −0.74, P < 0.01) but not the W′BAL·MORTON model (r = −0.18, P > 0.05). Accounting for the changes in the power–duration relationship improved the accuracy of the W′BAL·ODE and W′BAL·MORTON, but they remained significantly different to actual W′REC. Conclusions: These findings demonstrate that the power–duration relationship is altered after a 3MT, and accounting for these changes improves the accuracy of the W′BAL·ODE and the W′BAL·MORTON, but not W′BAL·INT models. These results have important implications for the design and use of mathematical models describing the energetics of exercise performance. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate effects of concurrent and independent administration of dietary nitrate (NO3−), administered as NO3–-rich beetroot juice (BR; ~12.4 mmol of NO3−), and N-acetylcysteine (NAC; 70 mg·kg−1) on physiological responses during prolonged exercise and subsequent high-intensity exercise tolerance. Sixteen recreationally active males supplemented with NO3–-depleted beetroot juice (PL) or BR for 6 days and ingested an acute dose of NAC or maltodextrin (MAL) 1 h prior to performing 1 h of heavy-intensity cycling exercise immediately followed by a severe-intensity time-to-exhaustion (TTE) test in four conditions: 1) PL+MAL, 2) PL+NAC, 3) BR+MAL and 4) BR+NAC. Pre-exercise plasma [NO3−] and nitrite ([NO2−]) were elevated following BR+NAC and BR+MAL (both P < 0.01) compared with PL+NAC and PL+MAL; plasma [cysteine] was increased in PL+NAC and BR+NAC (both P < 0.01) compared to PL+MAL. Muscle excitability declined over time during the prolonged cycling bout in all conditions but was better preserved in PL+NAC compared to BR+NAC (P < 0.01) and PL+MAL (P < 0.05). There was no effect of supplementation on subsequent TTE. These findings indicate that co-ingestion of BR and NAC does not appreciably alter physiological responses during prolonged heavy-intensity cycling or enhance subsequent exercise tolerance. [ABSTRACT FROM AUTHOR]

Purpose: To investigate whether oxygen-uptake (...) kinetics and simulated 4-km cycling performance are synergistically improved by prior "priming" exercise and an all-out starting strategy. Methods: Nine men completed 4 target work trials (114 ± 17 kJ) to assess ... kinetics and cycling performance in a repeated-measures, crossover experimental design. Trials were initiated with either a 12-s all-out start or a self-selected start and preceded by prior severe-intensity (70%Δ) priming exercise or no priming exercise. Results: The ... mean response time (MRT) was lower (indicative of faster ... kinetics) in the all-out primed condition (20 ± 6 s) than in the all-out unprimed (23 ± 6 s), self-paced-unprimed (42 ± 13 s), and self-paced-primed (42 ± 11 s) trials (P < .05), with the ... MRT also lower in the all-out unprimed than the self-paced unprimed and self-paced primed trials (P < .05). Trial-completion time was shorter (performance was enhanced) in the all-out primed trial (402 ± 14 s) than in the all-out unprimed (408 ± 14 s), self-paced unprimed (411 ± 16 s), and self-paced primed (411 ± 19 s) trials (P < .05), with no differences between the latter 3 trials. Conclusions: The findings from this study suggest that combining severe-intensity priming exercise with a short-duration all-out starting strategy can expedite the adjustment of ... and lower completion time during a cycling performance trial to a greater extent than either intervention administered independently. These results might have implications for optimizing performance in short-duration high-intensity competitive events such as a 4-km cycling time trial. [ABSTRACT FROM AUTHOR]

The influence of running speed and sex on running economy is unclear and may have been confounded by measurements of oxygen cost that do not account for known differences in substrate metabolism, across a limited range of speeds, and differences in performance standard. Therefore, this study assessed the energy cost of running over a wide range of speeds in high-level and recreational runners to investigate the effect of speed (in absolute and relative terms) and sex (men vs women of equivalent performance standard) on running economy. To determine the energy cost (kcal • kg-1 ⋅ km-1) of submaximal running, speed at lactate turn point (sLTP), and maximal rate of oxygen uptake, 92 healthy runners (high-level men, n = 14; high-level women, n = 10; recreational men, n = 35; recreational women, n = 33) completed a discontinuous incremental treadmill test. There were no sex-specific differences in the energy cost of running for the recreational or high-level runners when compared at absolute or relative running speeds (P > .05). The absolute and relative speed--energy cost relationships for the high-level runners demonstrated a curvilinear U shape with a nadir reflecting the most economical speed at 13 km/h or 70% sLTP. The high-level runners were more economical than the recreational runners at all absolute and relative running speeds (P < .05). These findings demonstrate that there is an optimal speed for economical running, there is no sex-specific difference, and high-level endurance runners exhibit better running economy than recreational endurance runners. [ABSTRACT FROM AUTHOR]

Purpose: We tested the hypotheses that a highly cushioned running shoe (HCS) would 1) improve incremental exercise performance and reduce the oxygen cost (Oc) of submaximal running, and 2) attenuate the deterioration in Oc elicited by muscle damage consequent to a downhill run. Methods: Thirty-two recreationally active participants completed an incremental treadmill test in an HCS and a control running shoe (CON) for the determination of Oc and maximal performance. Subsequently, participants were pair matched and randomly assigned to one of the two footwear conditions to perform a moderate-intensity running bout before and 48 h after a 30-min downhill run designed to elicit muscle damage. Results: Incremental treadmill test performance was improved (+5.7%; +1:16 min:ss; P < 0.01) in the HCS when assessed in the nondamaged state, relative to CON. This coincided with a significantly lower Oc (−3.2%; −6 mL·kg−1·km−1; P < 0.001) at a range of running speeds and an increase in the speed corresponding to 3 mM blood lactate (+3.2%; +0.4 km·h−1; P < 0.05). As anticipated, the downhill run resulted in significant changes in biochemical, histological, and perceptual markers of muscle damage, and a significant increase in Oc (+5.2%; 10.1 mL·kg−1·km−1) was observed 48 h post. In the presence of muscle damage, Oc was significantly lower in HCS (−4.6%; −10 mL·kg−1·km−1) compared with CON. Conclusions: These results indicate that HCS improved incremental exercise performance and Oc in the absence of muscle damage and show, for the first time, that despite worsening of Oc consequent to muscle damage, improved Oc in HCS is maintained. [ABSTRACT FROM AUTHOR]

Purpose: To assess whether combining prior "priming" exercise with an all-out pacing strategy is more effective at improving oxygen-uptake (...O2) kinetics and cycling performance than either intervention administered independently. Methods: Nine men completed target-work cycling performance trials using a self-paced or all-out pacing strategy with or without prior severe-intensity (70%Δ) priming exercise. Breath-by-breath pulmonary VO2 and cycling power output were measured during all trials. Results: Compared with the self-paced unprimed control trial (22 ± 5 s), the VO2 mean response time (MRT) was shorter (...O2 kinetics were faster) with all-out pacing (17 ± 4 s) and priming (17 ± 3 s), with the lowest ...O2 MRT observed when all-out pacing and priming were combined (15 ± 4 s) (P < .05). However, total O2 consumed and end-exercise ...O2 were only higher than the control condition in the primed trials (P < .05). Similarly, cycling performance was improved compared with control (98 ±11 s) in the self-paced primed (93 ± 8 s) and all-out primed (92 ± 8 s) trials (P < .05) but not the all-out unprimed trial (97 ± 5 s; P > .05). Conclusions: These findings suggest that combining an all-out start with severe-intensity priming exercise additively improves VO2 MRT but not total O2 consumption and cycling performance since these were improved by a similar magnitude in both primed trials relative to the self-paced unprimed control condition. Therefore, these results support the use of priming exercise as a precompetition intervention to improve oxidative metabolism and performance during short-duration high-intensity cycling exercise, independent of the pacing strategy adopted. [ABSTRACT FROM AUTHOR]

Purpose: To determine the accuracy of critical power (CP) and Wʹ (the curvature constant of the power-duration relationship) derived from self-paced time-trial (TT) prediction trials using mobile power meters to predict 16.1-km road cycling TT performance. This study also aimed to assess the agreement between functional threshold power (FTP) and CP. Methods: Twelve competitive male cyclists completed an incremental test to exhaustion, a FTP test and 4-5 self-paced TT bouts on a stationary bike within the lab, and a 16.1 km road TT, using mobile power meters. Results: CP and Wʹ derived from the power-duration relationship closely predicted TT performance. The 16.1-km road TT completion time (26.7 ± 2.2 min) was not significantly different from and was significantly correlated with the predicted time-to-completion (27.5 ± 3.3 min, r = 0.89, P < 0.01). CP and FTP were not significantly different (275 ± 40 W vs. 278 ± 42 W, P > 0.05); however, the limits of agreement between CP and FTP were 30 to -36 W. Discussion: The findings of this study indicate that CP and Wʹ determined using mobile power meters during maximal, self-paced TT prediction trials can be used to accurately predict 16.1-km cycling performance, supporting the application of the CP and Wʹ for performance prediction. However, the limits of agreement were too large to consider FTP and CP interchangeable. [ABSTRACT FROM AUTHOR]

Whilst modelling the power-duration relationship permits the estimation of CP to 1 W, we remind the reader that experimental evidence suggests that CP occurs within a range provided by the 95% confidence limits of the CP estimate. This review also highlights that CP differs from the maximal lactate steady state (MLSS) and uses this to support the assertion that CP is therefore not a valid indicator of the maximal metabolic steady state (MMSS). Therefore, we propose that an appraisal of the CP concept based on how long exercise "at" CP can be maintained is a fundamentally flawed endeavour. [Extracted from the article]

Purpose: The parameters of the power-duration relationship (i.e., the critical power, CP, and the curvature constant, W′) may theoretically predict maximal performance capability for exercise above the CP. The CP and Wʹ are associated with the parameters of oxygen uptake ( $${\dot{\text{V}}}$$ O) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and Wʹ derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance. Methods: Thirty subjects (males, n = 28; females, n = 2) performed a ramp incremental test, and 3-5 CWR prediction trials for the determination of the CP and Wʹ. Multiple ramp incremental tests and corresponding CP and Wʹ estimates were available for some subjects such that in total 51 ramp test performances were predicted. Results: The ramp incremental test performance (729 ± 113 s) was overestimated by the CP and Wʹ estimates derived from the best (751 ± 114 s, P < 0.05) and worst (749 ± 111 s, P < 0.05) individual fits of CWR prediction trial data. The error in the prediction was inversely correlated with the magnitude of the Wʹ for the best ( r = −0.56, P < 0.05) and worst individual fits ( r = −0.36, P < 0.05). Conclusions: The overestimation of ramp incremental performance suggests that the CP and Wʹ derived from different work-rate forcing functions, thus resulting in different $${\dot{\text{V}}}$$ O kinetics, cannot be used interchangeably. The present findings highlight a potential source of error in performance prediction that is of importance to both researchers and applied practitioners. [ABSTRACT FROM AUTHOR]

The parameters of the power-duration relationship for severe-intensity exercise (i.e., the critical power (CP) and the curvature constant ( W′)) are related to the kinetics of pulmonary O2 uptake, which may be altered by pacing strategy. We tested the hypothesis that the CP would be higher when derived from a series of self-paced time-trials (TT) than when derived from the conventional series of constant work-rate (CWR) exercise tests. Ten male subjects (age, 21.5 ± 1.9 years; mass, 75.2 ± 11.5 kg) completed 3-4 CWR and 3-4 TT prediction trial protocols on a cycle ergometer for the determination of the CP and W′. The CP derived from the TT protocol (265 ± 44 W) was greater ( P < 0.05) than the CP derived from the CWR protocol (250 ± 47 W), while the W′ was not different between protocols (TT: 18.1 ± 5.7 kJ, CWR: 20.6 ± 7.4 kJ, P > 0.05). The mean response time of pulmonary O2 uptake was shorter during the TTs than the CWR trials (TT: 34 ± 16, CWR: 39 ± 19 s, P < 0.05). The CP was correlated with the total O2 consumed in the first 60 s across both protocols ( r = 0.88, P < 0.05, n = 20). These results suggest that in comparison with the conventional CWR exercise protocol, a self-selected pacing strategy enhances CP and improves severe-intensity exercise performance. The greater CP during TT compared with CWR exercise has important implications for performance prediction, suggesting that TT completion times may be overestimated by CP and W′ parameters derived from CWR protocols. [ABSTRACT FROM AUTHOR]

The maximal lactate steady state (MLSS) and the critical power (CP) are two widely used indices of the highest oxidative metabolic rate that can be sustained during continuous exercise and are often considered to be synonymous. However, while perhaps having similarities in principle, methodological differences in the assessment of these parameters typically result in MLSS occurring at a somewhat lower power output or running speed and exercise at CP being sustainable for no more than approximately 20–30 min. This has led to the view that CP overestimates the 'actual' maximal metabolic steady state and that MLSS should be considered the 'gold standard' metric for the evaluation of endurance exercise capacity. In this article we will present evidence consistent with the contrary conclusion: i.e., that (1) as presently defined, MLSS naturally underestimates the actual maximal metabolic steady state; and (2) CP alone represents the boundary between discrete exercise intensity domains within which the dynamic cardiorespiratory and muscle metabolic responses to exercise differ profoundly. While both MLSS and CP may have relevance for athletic training and performance, we urge that the distinction between the two concepts/metrics be better appreciated and that comparisons between MLSS and CP, undertaken in the mistaken belief that they are theoretically synonymous, is discontinued. CP represents the genuine boundary separating exercise in which physiological homeostasis can be maintained from exercise in which it cannot, and should be considered the gold standard when the goal is to determine the maximal metabolic steady state. [ABSTRACT FROM AUTHOR]