Functional Threshold Power in Cyclists: Validity of the Concept and Physiological Responses

Abstract

Functional threshold power is defined as the highest power output a cyclist can maintain in a quasi-steady state for approximately 60 min (FTP). In order to improve practicality for regular evaluations, FTP could theoretically be determined as 95% of the mean power output in a 20-min time trial (FTP). This study tested this assumption and the validity of FTP and FTP against the individual anaerobic threshold (IAT). Twenty-three trained male cyclists performed an incremental test to exhaustion, 20- and 60-min time trials, and a time to exhaustion at FTP. Power output, heart rate and oxygen uptake representing FTP, FTP and IAT were not different (p>0.05), and large to very large correlations were found (r=0.61 to 0.88). Bland-Altman plots between FTP, FTP and IAT showed small bias (-1 to -5 W), but large limits of agreement ([-40 to 32 W] to [-62 to 60 W]). Time to exhaustion at FTP was 50.9±15.7 min. In conclusion, FTP and FTP should not be used interchangeably on an individual basis and their validity against IAT should be interpreted with caution.

Maximal Lactate Steady State Versus the 20-Minute Functional Threshold Power Test in Well-Trained Individuals: “Watts” the Big Deal?

“…Thus, caution is warranted when comparing POs at MLSS and CP in relation to that derived from FTP testing. Given the great variability in measures of FTP compared to other markers of critical intensity, caution should be exerted before using FTP95% as one size fits all approach to predicting critical intensities of exercise 7 .…”

“…This is pertinent as many regard MLSS to be the criterion measure for tolerable exercise 2 . Furthermore, although cross-sectional comparisons between FTP95% and other markers of performance have been made [5][6][7]9 , no study has evaluated the ability or sensitivity of the FTP95% test to track changes in fitness level on a longitudinal basis.…”

Reliability of the Functional Threshold Power in Competitive Cyclists

“…It is also the key metric in a series of calculations of training load and exercise intensity (i.e., training stress score [TSS], intensity factor [IF]) [6]. Moreover, FTP is used as an indirect and practical estimate of the anaerobic threshold (AnT) and maximal lactate steady state (MLSS) [7][8][9]. Due to the long test duration (i.e., 60 min), it was suggested that the FTP might be determined as 95 % of the mean PO in a 20-min TT (FTP 20 ) [6].…”

“…The first step is the specific 45-min warm-up, which includes a maximum effort 5-min TT [6]. To the best of our knowledge, Borszcz et al [7,8] and Valenzuela et al [10] are the only studies that have used the warm-up recommended by the authors [6]. Others have not used this section of the protocol [11][12][13].…”

“…Others have not used this section of the protocol [11][12][13]. Borszcz et al [7] reported high blood lactate concentrations ([La]) before the start of the test (6.5 ± 2.9 mmol • L − 1 ). Therefore, the FTP 20 warm-up protocol is not in accordance with the recent warm-up guidelines, which suggested a duration of about 20 min and a [La] of < 3 mmol • L − 1 at the end [14].…”