The Reliability of Lactate Measurements During Exercise

The purpose of this study was to establish the reliability of lactate threshold (LT) measurement across days. Twelve endurance-trained males aged 21 - 44 years participated in the study. Blood lactate concentration in capillary whole blood was measured at rest and at completion of 5 minute stages on a treadmill at 60 %, 65 %, 71 %, 77 %, 83 % and 89 % of VO₂max during 3 separate days of testing. Velocity at LT (LT_VEL), oxygen consumption at LT (LT_VO2), and heart rate at LT (LT_HR) are determined using each of the following criteria: fixed lactate concentrations of 2.0 mmol, 2.5 mmol, and 4.0 mmol, the breakpoint of the lactate-intensity curve, 1 mmol above rest, and 1 mmol above exercise baseline. A one factor repeated measures AMOVA model was used to calculate intraclass reliability coefficients across the 3 testing sessions. Confidence intervals (95 %) were calculated around the point estimates of reliability for each LT criterion. Intraclass correlation coefficients ranged from 0.98 to 0.99 LT_VEL (SEM 0.06 to 0.14 km · hr^-1). from 0.91 to 0.96 for LT_VO2 (SEM 0.34 to 0.72 ml · kg^-1 · min^-1), and from 0.75 to 0.96 for LT_HR (SEM 0.7 to 1.9 beats · min^-1). These results support the reliability of LT_VEL, LT_VO2, and LT_HR measurement.

Lactate threshold - reliability