Functional threshold power is not a valid marker of the maximal metabolic steady state

Purpose: Functional Threshold Power (FTP) has been considered a valid alternative to other performance markers that represent the upper boundary of the heavy intensity domain. However, such a claim has not been empirically 6 examined from a physiological perspective.

Method: This study examined the blood lactate and VO2 response when exercising at and 15 W above the FTP 9 (FTP+15W). Thirteen cyclists participated in the study. The VO2 was recorded continuously throughout FTP and FTP+15W, with blood lactate measured before the test, every 10 minutes and at task failure. Data were subsequently analysed using two-way ANOVA.

Results: The time to task failure at FTP and FTP+15W were 33.7 ± 7.6 and 22.0 ± 5.7 minutes (p < 0.001), respectively. The VO2peak was not attained when exercising at FTP+15W (VO2peak: 3.61 ± 0.81 vs FTP+15W 3.33 ± 0.68 L·min-1, p < 0.001). The VO2 stabilised during both intensities. However, the end test blood lactate corresponding to FTP and FTP+15W was significantly different (6.7 ± 2.1 mM vs 9.2 ± 2.9 mM; p < 0.05).

Conclusion: The VO2 response corresponding to FTP and FTP+15W suggests that FTP should not be considered a threshold marker between heavy and severe intensity.