The influence of the regression model and final speed criteria on the reliability of lactate threshold determined by the Dmax method in endurance-trained runners

• Published in: Applied physiology, nutrition, and metabolism nutrition, and metabolism, 2016-10, Vol.41 (10), p.1039-1044
• Main Authors: Camargo Alves, Júlio César, Segabinazi Peserico, Cecília, Nogueira, Geraldo Angelo, Machado, Fabiana Andrade
• Format: Article
• Language: English
• Subjects: Adult; anaerobic threshold; Athletes; Brazil; Cardiorespiratory Fitness; course; Ear Auricle; Endurance; Exercise; Exercise Test; exponential-plus-constant; Heart Rate; Humans; Kinetics; Lactic Acid - blood; Male; Metabolism; Methods; Models, Statistical; Physical Endurance; Physiological aspects; Regression Analysis; Reproducibility of Results; reproductibilité des résultats; Running; régression exponentielle avec constante; régression par polynôme du troisième degré; seuil anaérobie; Studies; third-order polynomial; Track and field athletes; Velocity
• ISSN: 1715-5312; 1715-5320
• DOI: 10.1139/apnm-2016-0075

Few studies verified the reliability of the lactate threshold determined by Dmax method (LT Dmax ) in runners and it remains unclear the effect of the regression model and the final speed on the reliability of LT Dmax . This study aimed to examine the test–retest reliability of the speed at LT Dmax in runners, considering the effects of the regression models (exponential-plus-constant vs third-order polynomial) and final speed criteria (complete vs proportional). Seventeen male, recreational runners performed 2 identical incremental exercise tests, with increments of 1 km·h –1 each for 3 min on treadmill to determine peak treadmill speed (V peak ) and lactate threshold. Earlobe capillary blood samples were collected during rest between the stages. The V peak was defined as the speed of the last complete stage (complete final speed criterion) and as the speed of the last complete stage added to the fraction of the incomplete stage (proportional final speed criterion). Lactate threshold was determined from exponential-plus-constant and from third-order polynomial regression models with both complete and proportional final speed criteria and from fixed blood lactate level of 3.5 mmol·L −1 (LT 3.5mM ). The LT Dmax obtained from the exponential-plus-constant regression model presented higher reliability (coefficient of variation (CV) ≤ 3.7%) than the LT Dmax calculated from the third-order polynomial regression model (CV ≤ 5.8%) and LT 3.5mM (CV = 5.4%). The proportional final speed criterion is more appropriate when using the exponential-plus-constant regression model, but less appropriate when using the third-order polynomial regression model. In conclusion, exponential-plus-constant using the proportional final speed criterion is preferred over LT 3.5mM and over third-order polynomial regression model to determine a reliable LT Dmax .