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M. Travis Byrd, Jonathan Robert Switalla, Joel E. Eastman, Brian J. Wallace, Jody L. Clasey and Haley C. Bergstrom

The critical-power (CP) (and critical force) test of Monod and Scherrer involved dynamic, intermittent, static, and continuous muscle actions for isolated movements of synergic muscle groups including the forearm flexors, forearm extensors, and leg flexors. 1 This test involves local muscle work

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Bettina Karsten, Jonathan Baker, Fernando Naclerio, Andreas Klose, Antonino Bianco and Alfred Nimmerichter

Critical power (CP) is defined as the highest sustainable rate of aerobic metabolism without a continuous loss of homeostasis. 1 It separates power-output (PO) intensities, for which exercise tolerance is predictable (PO > CP), from those of longer sustainable durations (PO < CP). The second

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Taylor K. Dinyer, M. Travis Byrd, Ashley N. Vesotsky, Pasquale J. Succi and Haley C. Bergstrom

The critical power (CP) model was originally developed as a 2-parameter linear model to examine the relationship between total work and time to exhaustion ( T lim ) for dynamic, continuous isometric, and intermittent isometric contractions of a muscle or local muscle group (less than one-third the

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Samantha G. Fawkner and Neil Armstrong

The purpose of this study was to examine methods of assessing Critical Power (CP) with children. Eight boys and 9 girls (10.3 – 0.4 yrs) completed 3 cycle tests in one day, each at a different constant power output predicted to induce fatigue in 2 to 15 min. Time to exhaustion was recorded, and order of the tests was randomized, with 3 hours recovery between tests. The children repeated these tests and 2 additional tests with at least 24 hr recovery between each test. CP was determined using least squares linear regression analysis of the power — t−1 relationship, for the single day (CP1), the 5 tests from different days (CP2), and the repeated 3 tests from different days (CP3). The 95% limits of agreement (range of percentage differences) were −15.4 to 13.1% (CP1 v CP2), −16.8 to 13.5% (CP1 v CP3), and −8.4 to 6.7% (CP2 v CP3). CP is a robust measure even when only 3 tests are completed in a single day and may be used to provide a simple and useful parameter of exercise intensity for constant load exercise with children.

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Anni Vanhatalo, Andrew M. Jones and Mark Burnley

The critical power (CP) is mathematically defined as the power-asymptote of the hyperbolic relationship between power output and time-to-exhaustion. Physiologically, the CP represents the boundary between the steady-state and nonsteady state exercise intensity domains and therefore may provide a more meaningful index of performance than other well-known landmarks of aerobic fitness such as the lactate threshold and the maximal O2 uptake. Despite the potential importance to sports performance, the CP is often misinterpreted as a purely mathematical construct which lacks physiological meaning and only in recent years has this concept begun to emerge as valid and useful technique for monitoring endurance fitness. This commentary defines the basic principles of the CP concept, outlines its importance to high-intensity exercise performance, and provides an overview of the current methods available for its assessment. Interventions including training, pacing and prior exercise can be used to alter the parameters of the power-time relationship. A future challenge lies in optimizing such interventions in order to positively affect the parameters of the power-time relationship and thereby enhance sports performance in specific events.

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David W. Hill, Robert P. Steward Jr. and Cindy J. Lane

The purpose of this study was to evaluate use of the critical power concept with swimmers ages 8 to 18 years. Critical velocity (CV) and anaerobic swimming capacity (ASC) were determined from the results of three short time trials (n = 86) or competition swims (n = 60). Data fit the critical power model well, as evidenced by high R2 and low SEE of CV and ASC estimates. CV was correlated with velocity in an endurance swim (r ≥ 0.86) and ASC was correlated with peak lactate (r ≥ 0.69). Thus, even in very young swimmers, CV and ASC provide mode-specific indices of endurance and anaerobic capacity, respectively.

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Len Parker Simpson and Mehdi Kordi

Purpose:

Typically, accessing the asymptote (critical power; CP) and curvature constant (W′) parameters of the hyperbolic power–duration relationship requires multiple constant-power exhaustive-exercise trials spread over several visits. However, more recently single-visit protocols and personal power meters have been used. This study investigated the practicality of using a 2-trial, single-visit protocol in providing reliable CP and W′ estimates.

Methods:

Eight trained cyclists underwent 3- and 12-min maximal-exercise trials in a single session to derive (2-trial) CP and W′ estimates. On a separate occasion a 5-min trial was performed, providing a 3rd trial to calculate (3-trial) CP and W′.

Results:

There were no differences in CP (283 ± 66 vs 282 ± 65 W) or W′ (18.72 ± 6.21 vs 18.27 ± 6.29 kJ) obtained from either the 2-trial or 3-trial method, respectively. After 2 familiarization sessions (completing a 3- and a 12-min trial on both occasions), both CP and W′ remained reliable over additional separate measurements.

Conclusions:

The current study demonstrates that after 2 familiarization sessions, reliable CP and W′ parameters can be obtained from trained cyclists using only 2 maximal-exercise trials. These results offer practitioners a practical, time-efficient solution for incorporating power–duration testing into applied athlete support.

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Jason C. Bartram, Dominic Thewlis, David T. Martin and Kevin I. Norton

Purpose:

New applications of the critical-power concept, such as the modeling of intermittent-work capabilities, are exciting prospects for elite cycling. However, accurate calculation of the required parameters is traditionally time invasive and somewhat impractical. An alternative single-test protocol (3-min all-out) has recently been proposed, but validation in an elite population is lacking. The traditional approach for parameter establishment, but with fewer tests, could also prove an acceptable compromise.

Methods:

Six senior Australian endurance track-cycling representatives completed 6 efforts to exhaustion on 2 separate days over a 3-wk period. These included 1-, 4-, 6-, 8-, and 10-min self-paced efforts, plus the 3-min all-out protocol. Traditional work-vs-time calculations of CP and anaerobic energy contribution (W′) using the 5 self-paced efforts were compared with calculations from the 3-min all-out protocol. The impact of using just 2 or 3 self-paced efforts for traditional CP and W′ estimation was also explored using thresholds of agreement (8 W, 2.0 kJ, respectively).

Results:

CP estimated from the 3-min all-out approach was significantly higher than from the traditional approach (402 ± 33, 351 ± 27 W, P < .001), while W′ was lower (15.5 ± 3.0, 24.3 ± 4.0 kJ, P = .02). Five different combinations of 2 or 3 self-paced efforts led to CP estimates within the threshold of agreement, with only 1 combination deemed accurate for W′.

Conclusions:

In elite cyclists the 3-min all-out approach is not suitable to estimate CP when compared with the traditional method. However, reducing the number of tests used in the traditional method lessens testing burden while maintaining appropriate parameter accuracy.

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Alan Chorley, Richard P. Bott, Simon Marwood and Kevin L. Lamb

Cycle races are often characterized by the ability of competitors to perform repeated surges of severe intensity efforts (“attacks”) interspersed with short recovery periods. The critical power (CP) model first introduced by Monod and Scherrer 1 offers an objective physiological framework for the

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Jason C. Bartram, Dominic Thewlis, David T. Martin and Kevin I. Norton

The hyperbolic relationship between maximal work rate and duration in humans was first described by A.V. Hill in 1925. 1 Approximately 40 years later, the concept was given a mathematical framework and became the critical power (CP) model. 2 Now commonly used today, the model describes a subject