A comparison of lactate kinetics, minute ventilation and acid-base balance as measures of the anaerobic threshold

The aim of this study was to assess whether changes in blood bicarbonate HCO ₃ ^- and blood lactate levels La could be more accurate predictors of endurance performance than the anaerobic threshold (AT) as described by either the ventilatory threshold (VT), individual anaerobic threshold (IAT) or onset of blood lactate accumulation (OBLA). Twelve healthy male, elite junior and senior rowers (Mean±SE) age: 23.27plusmn;1.8yr, body mass: 79.6±3.9kg, height: 183.9±1.4cm and VO _2max: 63.7±3.4ml.kg ^-1.min ^-1 participated in the study. The power output for OBLA, VT and IAT were all calculated according to standard incremental exercise protocols and calculations. The metabolic threshold (MT) was calculated by utilising the intersection of the HCO ₃ ^- and La curves plotted on the same graph. The times to exhaustion at each of the power outputs for each threshold point were then undertaken by the rowers. The analysis of variance revealed a significant difference between the power data (p<0.0001). The power outputs [Watts (W)] were; OBLA, 236±9.4; IAT, 219±6.5; MT, 291±9.8; VT, 247±9.6. In all subjects the MT was the highest power output. When the subjects rowed at these selected power outputs fatigue occurred at 6.64±0.20min at the MT, while at the VT they rowed for 14.29±0.34min. At OBLA they rowed for 16.02±0.49min and finally at the IAT they rowed for 27.5±0.25min. The results indicate that the MT gives a significantly higher reading in terms of power output than any of the other methods and a shorter time to fatigue. The other methods were similar in terms of power output but when related to exercise time there were significant differences between them.