n South African Journal of Sports Medicine - The prediction of endurance performance from work rates at fixed blood lactate concentrations is a mathematical not a physiological phenomenon - a novel hypothesis : review article

Volume 17, Issue 3
  • ISSN : 1015-5163
  • E-ISSN: 2078-516X



Traditionally it is accepted that physiological mechanisms underpin the oft-demonstrated highly significant relationship between work rates at fixed blood lactate concentrations of 4 mmol.l&lt;sup&gt;-1&lt;/sup&gt; (WR<sub>fblc</sub>) and endurance performance (EP). The objective of this paper was to suggest an alternative nonphysiological mechanism for the ability of WR&lt;sub&gt;fblc&lt;/sub&gt; to predict EP. Important observations are that WR&lt;sub&gt;fblc&lt;/sub&gt; occur at a constant percentage of maximum work rate (WR<sub>max</sub>) in trained athletes and there are high correlations between WR<sub>fblc</sub>, WR&lt;sub&gt;max&lt;/sub&gt; and EP. These observations suggest that WR&lt;sub&gt;fblc&lt;/sub&gt; is a marker of WR<sub>max</sub>. Using data from published reports, the association between WR&lt;sub&gt;fblc&lt;/sub&gt; and EP is dramatically reduced after removing the effect of WR<sub>max</sub>. Furthermore, the between-subject variation in slopes (first derivative of exponential plus constant function) at fixed blood lactate concentrations is significantly associated with WR&lt;sub&gt;fblc&lt;/sub&gt;/WR&lt;sub&gt;max&lt;/sub&gt; ratios with exponential but not linear relationships using the same blood lactate concentration - work rate data. This paper argues that WR&lt;sub&gt;fblc&lt;/sub&gt; is related to EP through its relationship with WR<sub>max</sub>, and contends that the relationship between WR&lt;sub&gt;fblc&lt;/sub&gt; and EP is not causal because of physiological mechanisms, specifically skeletal muscle metabolism. The WR<sub>fblc</sub>- EP relationship is rather the result of the peculiar properties of the exponential relationship between blood lactate concentrations and incremental work rate. Re-analyses of existing data sets with valid measures of WR&lt;sub&gt;max&lt;/sub&gt; and homogeneous and heterogeneous samples in terms of endurance performance, to confirm or reject this hypothesis, are warranted.

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