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The relationship between anaerobic threshold, excess CO² and blood lactate in elite marathon runners Hearst, William Edward


The purpose of this study was to investigate the use of excess CO₂ (ExCO₂) as a determinant of the anaerobic threshold (AT) and the subsequent relationship to blood lactate (La). Four highly trained marathon runners (x values, age=30.6 years; % body fat= 8.2; VO₂max = 6 8 ml-kg⁻¹min⁻¹) volunteered to participate in this study. Metabolic and respiratory exchange variables were assessed by an open circuit method utilizing a Beckman metabolic measurement cart interfaced on-line with a Hewlitt Packard 3052A data acquisition system. VO₂max and the treadmill velocity at the threshold of anaerobic metabolism (V[sub=tam]) were obtained from a progressive, treadmill run (.81 kph. > min.) until volitional fatigue. V[sub=tam] (Kilometers per hour, Kph) was calculated from the point of .a non-linear increase in ExCO₂. Subjects performed set treadmill runs of 10 minutes on alternate days. Variations (latin square) included runs at V[sub=tam], V[sub=tam+1], [sub=tam+2], and [sub=tam-1]. Analysis of variance with preplanned orthogonal comparisons and Scheffe post hoc contrasts were used to determine the effects of the treadmill variations on La and ExCO₂. There was no significance found between V[sub=tam] and V[sub=tam-1] for La or ExCO₂. Significance (p < .05) was evident with V[sub=tam]< [sub=tam+1, V[sub=tam]< [sub=tam+2] for La and V[sub=tam]< [sub=tam+2] for ExCO₂. An overall correlation of .89 (p <. 005) demonstrated a high positive relationship between ExCO₂ and La. Findings indicate V[sub=tam] to be a critical point in determining the anaerobic threshold in marathoners, and performance above this demarcation results in a state of anaerobiosis.

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