Equivalence between FTP and RCP: Assessment of association, agreement and sex effect

IF 2.4 4区医学 Q2 MEDICINE, GENERAL & INTERNAL

Clinics Pub Date : 2026-01-01 Epub Date: 2026-04-29 DOI:10.1016/j.clinsp.2026.100977

Paulo Engelke , Lavínia Vivan , Vinícius Ribeiro dos Anjos Souza , Claudio Andre Barbosa de Lira , Katja Weiss , Thomas Rosemann , Beat Knechtle , Marilia Santos Andrade

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引用次数: 0

Abstract

Objectives

Functional Threshold Power (FTP) is widely used for performance evaluation and training prescription in endurance sports. Although FTP is strongly associated with power at the Respiratory Compensation Point (RCP), its interchangeability remains debated. This study examined the relationship and agreement between FTP and RCP in amateur triathletes and tested whether sex influences this relationship.

Methods

Forty-nine amateur triathletes (male and female) participated. Each athlete completed a maximal cardiorespiratory cycling test and an FTP test, separated by at least 72 h. Linear regression models were used to test the association between FTP and RCP. A regression model including the interaction term (FTP × sex), equivalent to an ANCOVA framework, was applied to assess sex effects on the FTP-RCP relationship. Agreement between methods was assessed using Bland-Altman analysis. Two-way analysis of variance (ANOVA) was performed to examine the effects of sex, test type, and their interaction on absolute power (W), power relative to total body mass, and power relative to lean mass.

Results

FTP and RCP were strongly correlated (r = 0.916; p < 0.001). The interaction term FTP × sex was not significant (β = -0.135, p = 0.524), indicating that the regression slopes do not differ between males and females. Thus, the relationship between FTP and RCP was statistically similar across sexes. However, Bland-Altman analysis revealed wide limits of agreement, indicating poor interchangeability between FTP and RCP at the individual level.

Conclusions

FTP is strongly associated with RCP, and the relationship is independent of sex. Despite this association, FTP and RCP are not interchangeable measures. Caution is warranted when using FTP as a direct surrogate for RCP in training prescription and performance assessment.

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FTP与RCP的等价性：关联度、一致性和性别效应的评估

目的功能阈值功率（FTP）被广泛应用于耐力运动的成绩评价和训练处方。尽管FTP与呼吸代偿点（RCP）的能量密切相关，但其互换性仍存在争议。本研究考察了业余铁人三项运动员FTP和RCP之间的关系和一致性，并测试了性别是否影响这种关系。方法49名业余铁人三项运动员（男、女）参加。每个运动员都完成了最大心肺循环测试和FTP测试，间隔至少72小时。使用线性回归模型来测试FTP和RCP之间的关系。采用包含交互项（FTP ×性别）的回归模型（相当于ANCOVA框架）来评估性别对FTP- rcp关系的影响。采用Bland-Altman分析评估方法间的一致性。采用双向方差分析（ANOVA）来检验性别、测试类型及其相互作用对绝对功率(W)、相对于总体重的功率和相对于瘦体重的功率的影响。结果ftp与RCP呈强相关（r = 0.916; p < 0.001）。交互作用项FTP ×性别不显著（β = -0.135, p = 0.524），表明回归斜率在雌雄之间没有差异。因此，FTP和RCP之间的关系在性别上是相似的。然而，Bland-Altman分析揭示了广泛的一致性限制，表明FTP和RCP在个体水平上的互换性较差。结论sftp与RCP有较强的相关性，且与性别无关。尽管存在这种关联，FTP和RCP是不可互换的度量。在培训处方和绩效评估中使用FTP作为RCP的直接替代品时，需要谨慎。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Clinics 医学-医学：内科

CiteScore

4.10

自引率

3.70%

发文量

129

审稿时长

52 days

期刊介绍： CLINICS is an electronic journal that publishes peer-reviewed articles in continuous flow, of interest to clinicians and researchers in the medical sciences. CLINICS complies with the policies of funding agencies which request or require deposition of the published articles that they fund into publicly available databases. CLINICS supports the position of the International Committee of Medical Journal Editors (ICMJE) on trial registration.