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Do Critical and Functional Threshold Powers Equate in Highly-Trained Athletes?
Eanna McGrath1, Nick Mahony1, Neil Fleming1
1Human Performance Laboratory, Departments of Anatomy and Physiology, School of Medicine, Trinity College Dublin, IRL.
International Journal of Exercise Science
|May 31, 2021
Summary
Critical Power (CP) and Functional Threshold Power (FTP) are not interchangeable for elite cyclists and triathletes. CP, determined via multiple trials, was significantly higher than FTP, suggesting distinct physiological underpinnings.
Area of Science:
- Exercise Physiology
- Sports Science
- Biotechnology
Background:
- Critical Power (CP) and Functional Threshold Power (FTP) are key metrics for assessing endurance performance in cyclists and triathletes.
- Understanding the interchangeability of CP and FTP is crucial for accurate training prescription and performance analysis.
- Previous research has explored these metrics, but direct comparison in highly-trained populations requires further investigation.
Purpose of the Study:
- To determine if Critical Power (CP) and Functional Threshold Power (FTP) can be used interchangeably in highly-trained cyclists and triathletes.
- To compare CP, determined using different models, with FTP.
- To investigate the physiological differences between CP and FTP in this athletic cohort.
Main Methods:
- Critical Power (CP) was determined using multiple fixed load trials with hyperbolic (Hmodel) and linear (Jmodel, Imodel) models.
- Functional Threshold Power (FTP) was assessed from a single cycling trial.
- Analysis of variance (ANOVA) and Bland-Altman plots were used to compare CP (Jmodel) and FTP.
Main Results:
- The Jmodel for CP was identified as the most appropriate for comparison with FTP.
- Significant differences were found between Jmodel CP (282 ± 53 W) and FTP (266 ± 55 W) (p < 0.001).
- Bland-Altman analysis indicated that CP and FTP are not interchangeable, with CP consistently higher than FTP by a mean bias of 16 W.
Conclusions:
- Critical Power (CP) and Functional Threshold Power (FTP) are not interchangeable for highly-trained cyclists and triathletes.
- The Jmodel for CP consistently overestimates power compared to FTP, suggesting a potential need for a correction factor.
- Further research is warranted to explore the concept of CP and FTP representing a maximal metabolic steady-state, as mechanical power at CP was significantly greater than at FTP.
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