Using Blood Lactate and pH Parameters to Predict Time Trial Performance During Cycling Ergometry

Lactate/lactic acid accumulation has traditionally been viewed as a contributing factor to metabolic acidosis and fatigue during high-intensity exercise. These associations have led to the use of lactate threshold working capacity as an indicator of performance in competitive endurance events. However, current evidence suggests that lactate production does not contribute to acidosis and that work rate at lactate threshold may not accurately reflect performance in competitions featuring sustained, high-intensity efforts. PURPOSE: The purpose of this investigation was to evaluate relationships between power outputs at blood lactate threshold, blood maximal lactate steady state, blood pH threshold, and the average power output during a simulated 20 km time trial each determined on a bicycle ergometer. METHODS: Subjects (N = 13) were trained male and female cyclists and triathletes all permanent residents of moderate altitude (1525-2225). Testing was performed at 1525 or 1860 m. Power outputs were determined during a simulated 20 km time trial (PTT), at blood pH threshold (PpHT), maximal lactate steady state (PMLSS), and blood lactate threshold determined by two methods: 1) the highest power output that did not result in consecutive and continued increases in blood lactate concentrations from exercising baseline (PLT), and 2) the highest power output that did not result in consecutive and continued increases of = 1 mmol L−1 in blood lactate concentrations from exercising baseline (PLT1). RESULTS: PLT (219 ± 32 W), PLT1 (226 ± 26 W), and PMLSS (233 ± 35 W) were all significantly lower than PpHT (261 ± 29 W, P < 0.05) and PTT (257 ± 31 W, P < 0.05). No significant difference was observed between PpHT and PTT (P > 0.05). Significant relationships were observed between each of the predictors, PLT (R2 = 0.95), PLT1 (R2 = 0.77), PMLSS (R2 = 0.67), and PpHT (R2 = 0.93), when compared to PTT (P < 0.05). CONCLUSION: The results demonstrate that PTT was accurately reflected only by PpHT, and that PLT, PLT1 and PMLSS are not representative of competitive performance in 20 km time trials. However, regression equations can improve the predictive capabilities of the power outputs from blood lactate assessments on 20 km time trial performance.