The influence of blood lactate sample site on exercise prescription

The aims of this study were, firstly to determine the level of agreement between the fingertip and earlobe for the measurement of blood lactate, and secondly, to examine whether these sample sites may be used interchangeably when distinguishing lactate parameters routinely used in the physiological assessment and exercise prescription. Twenty healthy males performed an incremental cycle ergometry step test. Capillary blood samples were taken simultaneously at the end of each increment from the ear lobe and fingertip to determine blood lactate concentration. Power output and heart rate at different lactate parameters (LT, LT1, 2 mmol.L-1 and 4 mmol.L-1) were calculated from the lactate values. The average bias in blood lactate concentration measured from the fingertip and earlobe was 9.2% with 95% of measures differing by between -24.9 and 58.7%. There were no significant differences between sample sites (P = 0.201), however there was a strong positive relationship (R² = 0.9455). At the different lactate parameters there were no differences in determining heart rate (except at 4 mMol.L-1 (P = 0.028), equating to 2 bpm) and power output between sample sites. In conclusion, this high level of agreement and negligable differences in prescribing exercise using power output and heart rate from commonly used lactate parameters, determined from the ear lobe and fingertip indicate that these sample sites could be used interchangeably for physiological assessment during cycle ergometry.