A SIMPLIFIED APPROACH TO ESTIMATING THE MAXIMAL LACTATE STEADY-STATE

The exercise intensity associated with an elevated but stable blood la ctate (HLa) concentration during constant load work (the maximal stead y state, MSS) has received attention as a candidate for the ''optimal' ' exercise intensity for endurance training. Identification of MSS ord inarily demands direct measurement of HLa or respiratory metabolism. T he purpose of this study was to test the ability of heart rate (I-IR) to identify MSS during steady state exercise, similar to that used in conventional exercise prescription. Trained runners (n = 9) and cyclis ts (n = 12) performed incremental and steady state exercise. MSS was d efined as the highest intensity in which blood lactate concentration i ncreased < 1.0 mM from minutes 10 to 30. The next higher intensity wor kbout completed was defined as >MSS. HR models related to the presence or absence of steady state conditions were developed from the upper 9 5 % confidence interval of MSS and the lower 95 % confidence interval of >MSS. Cross validation of the model to predict MSS was performed us ing 21 running and 45 cycling exercise bouts in a separate group. Usin g the MSS upper 95 % confidence interval model 84% and 76% of workbout s were correctly predicted in cyclists and runners, respectively. Usin g the >MSS lower 95 % confidence interval model, 76 % and 81 % of work bouts were correctly predicted in cyclists and runners, respectively. Prediction errors tended to incorrectly predict non-steady state condi tions when steady state had occurred (16/26) (62%). We conclude that u se of these simple HR models may predict MSS with sufficient accuracy to be useful when direct HLa measurement is not available.