Manipulating graded exercise test variables affects the validity of the lactate threshold and (V) over dotO(2peak)

Background To determine the validity of the lactate threshold (LT) and maximal oxygen uptake ((V) over dotO(2max)) 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). (V) over dotO(2) 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 (V) over dotO(2) measured during each GXT (V) over dotO(2peak) as well as between each LT and MLSS. (V) over dotO(2peak) and LT data were analysed using mean difference (MD) and intraclass correlation (ICC). Results The (V) over dotO(2peak) value from GXT(1) was 61.0 +/- 5.3 mL.kg(-1).min(-1) and the peak power 420 +/- 55W (mean +/- SD). The power at the MLSS was 264 +/- 39 W. (V) over dotO(2peak) from GXT(3, 4, 7, 10) underestimated (V) over dotO(2peak) by similar to 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 (V) over dotO(2peak) and LT. It is also apparent that (V) over dotO(2max) and LT cannot be determined in a single GXT, even with the inclusion of a VEB.