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Low reproducibility of many lactate markers during incremental cycle exercise
  1. R Hugh Morton1,
  2. Stephen R Stannard1,
  3. Bartholomew Kay2
  1. 1Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
  2. 2Department of Sport and Exercise Science, University of Auckland, Auckland, New Zealand
  1. Correspondence to Dr R Hugh Morton, School of Sport and Exercise, Massey University, PO Box 11222, Palmerston North 4442, New Zealand; h.morton{at}massey.ac.nz

Abstract

Reports on reproducibility of lactate markers usually considered only two trials. The authors assessed reproducibility of power output at seven markers in 11 fit subjects over at least six trials under tightly controlled conditions. Subjects undertook incremental exercises (50 W start, +50 W every 3 min to exhaustion) on a cycle ergometer. At each trial blood lactate concentration was determined at rest and within the final 30 s of each stage. The Rest+1, 2.0 and 4.0 mmol/l markers were determined by interpolation, the D-max and nadir using a quadratic model and the lactate slope index using an exponential plus constant model, and a visual turnpoint was determined empirically. Intraclass correlations and coefficients of variation assessed reproducibility. Power output at all markers differed significantly between subjects, but not between trials. Intraclass correlation coefficients were respectively 0.799, 0.794, 0.807, 0.903, 0.677, 0.769 and 0.648, and corresponding standard errors of measurement 11.9, 9.2, 9.1, 2.5, 9.2, 10.8 and 24.7 W. Statistical powers of detecting a 30 W increment at these markers were 0.30, 0.43, 0.42, 0.98, 0.58, 0.38 and 0.18 respectively. These results indicate that only the D-max marker has good reproducibility and that it alone can identify small but meaningful changes in training status with sufficient statistical power.

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Footnotes

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the Massey University Human Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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