Manipulating graded exercise test variables affects the validity of the lactate threshold and [Image: see text]

BACKGROUND: To determine the validity of the lactate threshold (LT) and maximal oxygen uptake ([Image: see text] ) determined during graded exercise test (GXT) of different durations and using different LT calculations. Trained male cyclists (n = 17) completed five GXTs of varying stage length (1, 3, 4, 7 and 10 min) to establish the LT, and a series of 30-min constant power bouts to establish the maximal lactate steady state (MLSS). [Image: see text] was assessed during each GXT and a subsequent verification exhaustive bout (VEB), and 14 different LTs were calculated from four of the GXTs (3, 4, 7 and 10 min)—yielding a total 56 LTs. Agreement was assessed between the highest [Image: see text] measured during each GXT ([Image: see text] ) as well as between each LT and MLSS. [Image: see text] and LT data were analysed using mean difference (MD) and intraclass correlation (ICC). RESULTS: The [Image: see text] value from GXT(1) was 61.0 ± 5.3 mL(.)kg(-1.)min(-1) and the peak power 420 ± 55 W (mean ± SD). The power at the MLSS was 264 ± 39 W. [Image: see text] from GXT(3, 4, 7, 10) underestimated [Image: see text] by ~1–5 mL(.)kg(-1.)min(-1). Many of the traditional LT methods were not valid and a newly developed Modified D(max) method derived from GXT(4) provided the most valid estimate of the MLSS (MD = 1.1 W; ICC = 0.96). CONCLUSION: The data highlight how GXT protocol design and data analysis influence the determination of both [Image: see text] and LT. It is also apparent that [Image: see text] and LT cannot be determined in a single GXT, even with the inclusion of a VEB.