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

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 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.

Fingertip blood samples drawn upon stage completion were analysed for plasma lactate, then used to determine running speed at: 2.0, 3.5, and 4.0 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 (D2L(max)), the lactate threshold (LT) and log-log LT.

The 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)), D2L(max) 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.

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 8 min stages indicates different blood lactate response, and therefore workload calculation, according to stage length. Consideration of marker construct is recommended.