This study examined the reproducibility of speed corresponding to specific lactate markers during incremental treadmill running of normal and prolonged stage durations.Nineteen healthy participants (14 male, 5 female) performed repeated, incremental treadmill running trials of 4 and 8min 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.Fingertip blood samples drawn upon stage completion were analysed for plasma lactate, then used to determine running speed at: 2.0, 3.5, and 4.0mmoll −1 fixed blood lactate accumulations (FBLA), a 1mmoll −1 rise from baseline, and the markers: the deviation maximum (D max ), the D max of the second curve derivative (D2L max ), the lactate threshold (LT) and log–log LT.The 2.0mmoll −1 FBLA reported the lowest mean bias between 4min trials (−0.06kmh −1 ), with the narrowest limits of agreement (LoA) (−1.78 to 1.66kmh −1 ). The D max had the second lowest bias (0.14kmh −1 ), D2L max the second narrowest LoA (−1.93 to 2.90kmh −1 ). For 8min stages, the 1mmoll −1 rise demonstrated, low mean bias (−0.13kmh −1 ) and narrowest LoA (−1.22 to 0.97kmh −1 ) between trials.This 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 8min stages indicates different blood lactate response, and therefore workload calculation, according to stage length. Consideration of marker construct is recommended.