Onset of metabolic acidosis (Anaerobic Threshold) as a criterion measure of submaximum fitness

The purpose of the present study was to investigate use of the onset of metabolic acidosis (anaerobic threshold) as a criterion measure of submaximum fitness. [Vdot]O₂ max and the onset of metabolic acidosis (using gas exchange variables;) were determined. Twenty-eight subjects completed, without work decrement, a submaximum work task of 300 kgm.min^-1 for an 8-minute duration. Matching individuals with respect to [Vdot]O₂ max (within 30 ml·min^-1) yielded 11 matched pairs. These pairs were divided with respect to [Vdot]O₂ uptake at the point of metabolic acidosis ([Vdot]O₂-AT). This resulted in significant differences in [Vdot]O₂-AT (X difference = 254 ml, p `.05) between the equal [Vdot]O<sub>2</sub> max groups. Examining submaximum exercise responses revealed that the group with higher [Vdot]O<sub>2</sub>-AT values took up oxygen to steady state at a faster rate (p `.05), exhibited a slightly lower steady state [Vdot]O₂ value, and showed a tendency for a faster rate of [Vdot]O₂ uptake during recovery to baseline values. Dividing the 28 subjects into high and low [Vdot]O₂-AT groups, regardless of [Vdot]O₂ max (X difference for [Vdot]O₂-AT = 367 ml, p `.05), resulted in a faster rate of oxygen uptake to a lower steady state [Vdot]O<sub>2</sub> value (p `.05) during the submaximum exercise bout for the high [Vdot]O₂-AT group. In addition, the high [Vdot]O₂-AT group produced fewer exercise and recovery Kcal (p `.05) than the low [Vdot]O₂-AT group during submaximum exercise. It was concluded that the onset of metabolic acidosis may be a better measure for evaluating submaximum fitness than [Vdot]O₂ max.