La_max: determining the optimal test duration for maximal lactate formation rate during all-out sprint cycle ergometry

This study aimed to ascertain the optimal test duration to elicit the highest maximal lactate formation rate ( $$ La_max), whilst exploring the underpinning energetics, and identifying the optimal blood lactate sampling period.

Fifteen trained to well-trained males (age 27 ± 6 years; peak power: 1134 ± 174 W) participated in a randomised cross-over design completing three all-out sprint cycling tests of differing test durations (10, 15, and 30 s). Peak and mean power output (W and W^.kg^-1), oxygen uptake, and blood lactate concentrations were measured. $$ La_max and energetic contributions (phosphagen, glycolytic, and oxidative) were determined using these parameters.

The shortest test duration of 10 s elicited a significantly (p = 0.003; p < 0.001) higher $$ La_max (0.86 ± 0.17 mmol^.L^-1.s^-1; 95% CI 0.802-0.974) compared with both 15 s (0.68 ± 0.18 mmol^.L^-1.s^-1; 95% CI 0.596-0.794) and 30 s (0.45 ± 0.07 mmol^.L^-1.s^-1; 95% CI 0.410-0.487). Differences in $$ La_max were associated with large effect sizes (d = 1.07, d = 3.15). We observed 81% of the PCr and 53% of the glycolytic work completed over the 30 s sprint duration was attained after 10 s. BLa_maxpost were achieved at 5 ± 2 min (t_test 10 s), 6 ± 2 min (t_test 15 s), and 7 ± 2 min (t_test 30 s), respectively.

Our findings demonstrated a 10 s test duration elicited the highest $$ La_max. Furthermore, the 10 s test duration mitigated the influence of the oxidative metabolism during all-out cycling. The optimal sample time to determine peak blood lactate concentration following 10 s was 5 ± 2 min.