Reliability of power output, maximal rate of capillary blood lactate accumulation, and phosphagen contribution time following 15-s sprint cycling in amateur cyclists

Based on Mader's mathematical model, the rate of capillary blood lactate concentration (νLa_max) following intense exercise is thought to reflect the maximal glycolytic rate. We aimed to investigate the reliability of important variables of Mader's model (i.e. power output, lactate accumulation, predominant phosphagen contribution time frames (t_PCr)) and resulting νLa_max values derived during and after a 15-s cycling sprint. Fifty cyclists performed a 15-s all-out sprint test on a Cyclus2 ergometer three times. The first sprint test was considered a familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine νLa_max. Test–retest analysis between T2 and T3 revealed excellent reliability for power output (P_mean and P_peak; ICC = 0.99, 0.99), ∆La and νLa_max with t_PCr of 3.5 s (ICC = 0.91, 0.91). νLa_max calculated with t_PCr = t_Ppeak (ICC = 0.87) and t_PCr = t_Ppeak–3.5% (ICC = 0.79) revealed good reliability. t_Ppeak and t_Ppeak–3.5% revealed only poor and moderate reliability (ICC = 0.41, 0.52). Power output and ∆La are reliable parameters in the context of this test. Depending on t_PCr, reliability of νLa_max varies considerably with t_PCr of 3.5 s showing excellent reliability. We recommend standardization of this type of testing especially t_PCr.