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

Abstract

Purpose: Functional threshold power (FTP), determined as 95% of the average power during a 20-min time trial, is suggested as a practical test for the determination of the maximal lactate steady state (MLSS) in cycling. Therefore, the objective of the present study was to determine the validity of FTP in predicting MLSS. Methods: A total of 15 cyclists, 7 classified as trained and 8 as well trained (mean [SD] maximal oxygen uptake 62.3 [6.4] mL·kg−1·min−1, maximal aerobic power 329 [30] W), performed an incremental test to exhaustion, an FTP test, and several constant-load tests to determine the MLSS. The bias ± 95% limits of agreement (LoA), typical error of the estimate (TEE), and Pearson coefficient of correlation (r) were calculated to assess validity. Results: For the power-output measures, FTP presented a bias ± 95% LoA of 1.4% ± 9.2%, a moderate TEE (4.7%), and nearly perfect correlation (r = .91) with MLSS in all cyclists together. When divided by training level, the bias ± 95% LoA and TEE were higher in the trained group (1.4% ± 11.8% and 6.4%, respectively) than in the well-trained group (1.3% ± 7.4% and 3.0%, respectively). For the heart-rate measurement, FTP presented a bias ± 95% LoA of −1.4% ± 8.2%, TEE of 4.0%, and very large correlation (r = .80) with MLSS. Conclusion: Therefore, trained and well-trained cyclists can use FTP as a noninvasive and practical alternative to estimate MLSS.

Power Assessment in Road Cycling: A Narrative Review

“…Similar findings have been obtained in another study, in which FTP and LT were closely linked in trained cyclists but not in recreational cyclists [24]. The PO obtained from FTP 20-min testing does not seem to correlate with all the other LT methods [24,26,27], except for fixed blood lactate concentrations of 4.0 mmol/L (r = 0.88, p < 0.001) [46]. On the other hand, another FTP testing duration has been attempted in several scientific studies.…”

“…Allen and Coggan's work [19] is widely considered as the reference for power meter-based training in the practical field and has, therefore, been chosen as the unifying thread for the current review. However, it should be highlighted that the authors did not provide a sufficient scientific basis to support their assumptions and the research that has attempted to validate their theories has had varying degrees of success [19,[24][25][26][27]. FTP is also used as a reference for establishing seven different training zones and, additionally, the testing protocol provides information about the riders' power profile, which can help in their classification according to their strengths and weaknesses [28].…”

Physiological Predictors of Competition Performance in CrossFit Athletes

“…Only those participants who performed all the WODs were included in analyses. Participants were divided by the median into a low (LP) and a high-performance (HP) group attending to the final ranking as described elsewhere [3,25,26].…”

The Application of Critical Power, the Work Capacity above Critical Power (W′), and Its Reconstitution: A Narrative Review of Current Evidence and Implications for Cycling Training Prescription

“…The adoption of FTP as the de facto standard for performance measurement and tracking including amongst professional cyclists [ 121 ] has led to recent investigations into its physiological basis. As a measure of endurance performance FTP correlates strongly against other such endurance measures [ 122 , 123 , 124 , 125 , 126 , 127 , 128 ], but was not found to be an interchangeable or surrogate measure of lactate threshold [ 122 , 125 , 126 , 129 , 130 ], CP [ 131 ], respiratory compensation point [ 132 ], or MLSS [ 124 , 133 ] (see Table 2 ). This is unsurprising given that FTP is a measure of performance over an arbitrary chosen one-hour duration, which sits unquestionably within the confines of the heavy intensity domain, and as such does not align to any known physiological markers, thresholds or boundaries which define such laboratory-derived measurements [ 13 ].…”

“…This is unsurprising given that FTP is a measure of performance over an arbitrary chosen one-hour duration, which sits unquestionably within the confines of the heavy intensity domain, and as such does not align to any known physiological markers, thresholds or boundaries which define such laboratory-derived measurements [ 13 ]. Furthermore, to avoid the psychological factors that can affect fatigue over a 60-min trial, FTP is almost always estimated from a shorter 20-min test by scaling average power to 95% [ 120 , 121 , 122 , 123 , 124 , 125 , 126 , 129 , 134 ], or even an 8- min test scaling average power to 90% [ 129 , 130 ]. Thus, whilst FTP being in the heavy intensity domain will not deplete W′, the value is estimated from test protocols in the severe domain which expend an unknown amount of W′, further questioning its validity as either a performance measure or physiological proxy.…”