PROTOCOL STAGE DURATION EFFECT ON LACTATE THRESHOLD DURING INTERMITTENT CYCLE ERGOMETRY

1863 The purpose of this study was to determine if stage duration has an effect on lactate threshold determination during intermittent graded exercise testing on a cycle ergometer. Thirteen volunteer subjects (age = 26.2±4.6 yrs, VO2max = 3652±489 ml·min-1) completed incremental exercise tests, on an electronically braked cycle ergometer (Ergoline 800), at exercise stage durations of 2 (2m), 4 (4m), and 6 minutes (6m) in a randomized order. For each protocol, 60 second rests were imposed between work stages during which blood was sampled and analyzed for whole blood lactate (BLA). Lactate threshold was identified in two manners: (1) as the first increase of 1.0 mmol·1-1 after which BLA continued to increase by 1.0 mmol·1-1 or greater (TLA1) and (2) as the point at which BLA first attained or exceeded 4.0 mmol·1-1 (TLA4). Lactate thresholds were expressed as absolute power in Watts, as VO2 in ml·min-1, and as heart rate (HR) in b·min-1. The 2m protocol was carried to maximum effort, while the 4m and 6m protocols were terminated once both TLA criteria were satisfied. Repeated measures ANOVA with Newman-Keuls post hoc tests were employed in data analyses. Both TLA1 and TLA4 occurred at a higher power output for 2m(233±49 W) versus 4m (183±39 W) and 6m (175±39 W), but not for 4m versus 6m. When expressed as VO2 or HR, lactate thresholds were not significantly different among 2m, 4m, or 6m. TLA4 occurred at a significantly higher power output and VO2 than TLA1 for any protocol stage duration. When expressed as HR, TLA4 was significantly higher than TLA1 for 4m and 6m, but not for 2m. Based upon these results, it was concluded that: (1) stage durations of 2 minutes or less may result in overestimation of lactate threshold expressed as absolute power output, and (2) the methodology for determining lactate threshold, TLA1 versus TLA4, influences the threshold value regardless of the mode of expression or protocol stage duration.