Abstract
Background
To determine the validity of the lactate threshold (LT) and maximal oxygen uptake () 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). 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 measured during each GXT () as well as between each LT and MLSS. and LT data were analysed using mean difference (MD) and intraclass correlation (ICC).
Results
The value from GXT1 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. from GXT3, 4, 7, 10 underestimated by ~1–5 mL.kg-1.min-1. Many of the traditional LT methods were not valid and a newly developed Modified Dmax method derived from GXT4 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 and LT. It is also apparent that and LT cannot be determined in a single GXT, even with the inclusion of a VEB.
Citation: Jamnick NA, Botella J, Pyne DB, Bishop DJ (2018) Manipulating graded exercise test variables affects the validity of the lactate threshold and . PLoS ONE 13(7):
e0199794.
https://doi.org/10.1371/journal.pone.0199794
Editor: Øyvind Sandbakk, Norwegian University of Science and Technology, NORWAY
Received: April 30, 2018; Accepted: June 13, 2018; Published: July 30, 2018
Copyright: © 2018 Jamnick et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The data underlying this study have been uploaded to the Open Science Framework and are accessible using the following link: https://osf.io/293ns/.
Funding: Funding was provided by the Graduate Research Office (PhD Student Budget) at Victoria University. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations:
LT,
lactate threshold; GXT,
graded exercise testing; ,
maximal oxygen uptake; OBLA,
onset of fixed blood lactate accumulation; MLSS,
maximal lactate steady state; VEB,
verification exhaustive bout; BMI,
body mass index; ,
maximum power output; ,
highest measured oxygen uptake value; RCP,
respiratory compensation point; RCPMLSS,
estimate of the maximal lactate steady state via respiratory compensation point; B + mmol.L-1,
blood lactate concentration increases above baseline value(s); ModDmax,
modified Dmax; Exp-Dmax,
exponential Dmax; Log-Poly-ModDmax,
Log-log Modified Dmax; Log-Exp-ModDmax,
Log-log Exponential Modified Dmax; CV,
coefficient of the variation; ES,
effect size; r,
Pearson product moment correlation; ICC,
intraclass correlation; SEM,
standard error of the measurement
Description
This study assesses how GXT protocol design influences the determination of V˙O2peak and LT.