Is the Functional Threshold Power Interchangeable With the Maximal Lactate Steady State in Trained Cyclists?

Area of Science:

• Sports Science
• Exercise Physiology
• Cycling Performance Analysis

Background:

• Maximal lactate steady state (MLSS) is a key indicator of endurance performance in cycling.
• Functional threshold power (FTP), derived from a 20-minute time trial, is a practical alternative for estimating MLSS.
• The validity of FTP for predicting MLSS requires further investigation.

Purpose of the Study:

• To determine the validity of functional threshold power (FTP) in predicting maximal lactate steady state (MLSS) in trained and well-trained cyclists.
• To compare the accuracy of FTP in estimating MLSS across different training levels.

Main Methods:

• Fifteen cyclists (7 trained, 8 well-trained) underwent an incremental test, an FTP test, and multiple constant-load tests to establish MLSS.
• Statistical analyses included bias ± 95% limits of agreement (LoA), typical error of the estimate (TEE), and Pearson correlation coefficient (r).

Main Results:

• FTP demonstrated a strong correlation (r = .91) with MLSS for power output, with a bias of 1.4% ± 9.2% and TEE of 4.7%.
• The well-trained group showed better agreement between FTP and MLSS (bias ± 95% LoA: 1.3% ± 7.4%; TEE: 3.0%) compared to the trained group.
• For heart rate, FTP showed a bias of -1.4% ± 8.2%, TEE of 4.0%, and a correlation of r = .80 with MLSS.

Conclusions:

• Functional threshold power (FTP) is a valid and practical noninvasive method for estimating MLSS in both trained and well-trained cyclists.
• FTP provides a reliable alternative to direct MLSS testing for practical training applications.