Reproducibility of lactate markers during 4 and 8 min stage incremental running: A pilot study

ObjectivesThis study examined the reproducibility of speed corresponding to specific lactate markers during incremental treadmill running of normal and prolonged stage durations.DesignNineteen healthy participants (14 male, 5 female) performed repeated, incremental treadmill running trials of 4 and 8 min stages on separate days to examine the test–retest reproducibility of speed at lactate markers. Two trials were completed for each duration in a randomised order.MethodsFingertip blood samples drawn upon stage completion were analysed for plasma lactate, then used to determine running speed at: 2.0, 3.5, and 4.0 mmol l−1 fixed blood lactate accumulations (FBLA), a 1 mmol l−1 rise from baseline, and the markers: the deviation maximum (Dmax), the Dmax of the second curve derivative (D2Lmax), the lactate threshold (LT) and log–log LT.ResultsThe 2.0 mmol l−1 FBLA reported the lowest mean bias between 4 min trials (−0.06 km h−1), with the narrowest limits of agreement (LoA) (−1.78 to 1.66 km h−1). The Dmax had the second lowest bias (0.14 km h−1), D2Lmax the second narrowest LoA (−1.93 to 2.90 km h−1). For 8 min stages, the 1 mmol l−1 rise demonstrated, low mean bias (−0.13 km h−1) and narrowest LoA (−1.22 to 0.97 km h−1) between trials.ConclusionsThis preliminary report suggests the reproducibility of running speed at lactate summary markers is influenced by stage duration for incremental treadmill running. Varied marker reproducibility between 4 and 8 min stages indicates different blood lactate response, and therefore workload calculation, according to stage length. Consideration of marker construct is recommended.