Relation between anaerobic threshold and maximal oxygen consumption during graded treadmill exercise

The ratio of anaerobic threshold (AT) to maximal oxygen consumption (Max VO2), which is referred to as relative AT, was evaluated in six athletic students (S), 12 normal male subjects (N) and 39 patients with chronic heart disease (C). Group C was categorized in three subgroups according to the New York Heart Association functional class (CI: 10, CII: 16 and CIII: 13 patients). The symptomatic-maximal graded treadmill exercise test was performed and respiratory parameters were measured by R1500S Autoaerobics. AT was determined as the oxygen consumption (VO2) at which a linear relationship between pulmonary ventilation and VO2 was lost during progressive exercise. All subjects performed maximal exertion until they were limited by either shortness of breath or leg fatigue. AT (ml/min/kg) was 36.4 +/- 6.0, 25.9 +/- 5.7, 21.4 +/- 4.5, 16.3 +/- 4.0 and 11.1 +/- 2.6, and MaxVO2 (ml/min/kg) was 77.3 +/- 6.5, 47.6 +/- 10.2, 29.5 +/- 6.1, 22.5 +/- 5.8 and 15.5 +/- 3.1, respectively, in group S, N, CI, CII and CIII (p less than 0.01 between each group). Relative AT(%) was 46.8 +/- 4.4, 54.9 +/- 7.2, 72.1 +/- 6.4, 73.0 +/- 8.6 and 72.6 +/- 8.7, respectively, in groups S, N, CI, CII and CIII (p less than 0.01 between S and N, between N and CI-CIII, between S and CI-III). The anaerobic threshold appeared at mid-point in the graded symptomatic maximal exercise test. However, the appearance of AT relative to the maximal oxygen consumption varied from 47 to 73% in the study groups tested. AT appeared relatively early in normal subjects compared to cardiac subjects.