Predicting Lactate Threshold in Cyclists Using Ventilatory Threshold

Lactate threshold (LT) is an important reference point in setting training intensities for endurance athletes. Ventilatory threshold (VT) has been used as a noninvasive estimate of LT, but appears to underestimate training intensity for many athletes who often report training at intensities above VT for prolonged periods. Determining LT can be time-consuming and invasive. PURPOSE: Thus, the purpose of this study was to evaluate whether metabolic and heart rate data obtained during a noninvasive, maximal graded exercise test could be used to more accurately predict LT. METHODS: Nineteen trained cyclists (10 men, 9 women, 35 ± 2 years) performed a graded exercise test on a bicycle ergometer to determine maximal oxygen consumption (max VO2 = 55 ± 2 ml O2 •kg−1•min−1) and heart rate at the ventilatory threshold (HRVT). Ventilatory threshold was determined using the V-slope method. Cyclists returned to the laboratory on a different day to perform a lactate threshold test, consisting of 8 min stages at power outputs below, at, and above the ventilatory threshold. Steady-state heart rates were measured during each 8 min stage, and a fingerstick blood sample was obtained during the last min of each stage to measure blood lactate. The heart rate associated with the lactate threshold (HRLT) was determined using the D-max method (Cheng et al., 1992). RESULTS: The correlation between HRVT and HRLT was 0.68, indicating 46% shared variance. The best fitting model to predict HRLT included HRVT, gender, body weight, and an interaction between gender and body weight. For male cyclists, HRLT = 177.34 + (0.44 × HRVT) - (1.03 × body weight in kg). For female cyclists, HRLT = 94.85 + (0.44 · HRVT)+ (0.10 × body weight in kg). Using this model, R2 was 0.70. CONCLUSIONS: For trained cyclists, HRVT, obtained during a maximal graded exercise test, may be adjusted to more accurately predict a training heart rate that corresponds to the lactate threshold. Endurance performance is determined by a number of factors, including the intensity of exercise that may be sustained without accumulation of lactic acid. Thus, a more accurate assessment of lactate threshold may aid cyclists in their training and, potentially, enhance performance.