Acid-base balance in three theoretical models of anaerobic threshold

Few theoretical models for anaerobic threshold assessment are truly axiomatic and causative. The main goal of the present study was to compare three kinds of such theoretical models that are widely used to assess the anaerobic threshold. Ten subjects (mean ± SD: age, 23 ± 1 yrs ; weight, 61.2 ± 4.9 kg; VO2 max = 37.6 ± 2.8 mL·kg-1 ·min-1) were exposed to the original graded exercise test (GXT) to determine Wasserman’s Anaerobic Threshold (AT), Stegmanan’s Individual Anaerobic Threshold (IAT), and Mader’s 4 mmol·L-1 Anaerobic Threshold (4mM). Then, they were submitted to three square wave tests (SWT), one for each anaerobic threshold workload, in order to compare acid-base balance and metabolic parameters at each workload. Repetitive two-way ANOVA with Green-House correction for alpha inflation and HSD-Tukey post hoc tests were used for statistical comparisons among AT, IAT, and 4mM, GXT and SWT and their interactions (P≤0.05). The 4mM anaerobic threshold occurs at higher values (Workload = 142 ± 16 W) than the threshold based on the AT (Workload = 86 ± 11 W) or the IAT (Workload = 95 ± 8 W) approach. The AT model shows the lowest mean squared error (watt/lactate curve), the strongest correlation with VO2 max and the least disturbance in acid-base balance during the SWT. The findings indicate that the Wasserman’s AT theory for anaerobic threshold offered better predictions than both the IAT and the 4mM models.