Relationship Between Blood Lactate Response to Exercise and Endurance Performance in Competitive Female Master Cyclists

The blood lactate response to graded exercise and its relationship to performance in the field was examined in highly competitive female master cyclists. Thirteen women, age 47.5 ± 2.2 yr (mean ± SE), all of whom were United States Cycling Federation (USCF) competitors, underwent laboratory testing for aerobic capacity (VO₂max) and lactate threshold (LT), and field testing for performance in 13.5 km and 20 km time-trials. The mean VO₂max of the subjects (50.6 ± 2.7 ml · kg^-1 · min^-1) was approximately 10 % higher than that previously reported for other age-matched female athletes and correlated moderately (r = -0.67) with age. Maximal heart rate was unrelated to age (r = -0.25, p > 0.05). Blood lactate concentration (BLC) while time-trialing was significantly higher than that at the LT (2.86 ± 0.17mmol · l^-1) for both the 13.5 km (7.59 mmol · l^-1, p < 0.0001), and the 20 km trials (6.99 mmol · l^-1, p < 0.002). The LT occurred at a mean power output of 168 ±11.3 Wand 66 % of VO₂max. The VO₂ corresponding to a BLC of 4.0 mmol · l^-1 (LT4) was 72 % of VO₂max. As expected, time-trial performance was highly correlated with VO₂max (r = -0.85); however, regression analysis indicated that power output at the lactate threshold was the best laboratory predictor of performance (13.5 km: r2 = 0.83; 20 km: r2 = 0.78). Relative to maximal heart rate, heart rate at LT (88 % HR_max) was significantly (p<0.05) lower than time-trial heart rate (92 - 94 % HR_max). The cyclists in this study have higher aerobic capacities and maximal heart rates than those previously reported for other age-matched female athletes and are able to cycle for extended periods at blood lactate concentrations significantly higher than those at the lactate threshold. Traditional methods of exercise prescription, particularly when using age-estimates of maximal heart rate, underestimate training intensities required to be above the LT in female master cyclists.

Key words

Blood lactate - cardiovascular fitness - cycling - exercise - women