Blood lactate concentrations are mildly affected by mobile gas exchange measurements

We sought to investigate the effects of wearing a mobile respiratory gas analysis system during a treadmill test on blood lactate (bLa) concentrations and commonly applied bLa thresholds. A total of 16 recreational athletes (31±3 years, VO2max: 58±6 ml · min(-1) · kg(-1)) performed one multistage treadmill test with and one without gas exchange measurements (GEM and noGEM). The whole bLa curve, the lactate threshold (LT), the individual anaerobic thresholds according to Stegmann (IATSt) and Dickhuth (IATDi), and a fixed bLa concentration of 4 mmol ∙ l(-1) (OBLA) were evaluated. The bLa curve was shifted slightly leftward in GEM compared to noGEM (P<0.05), whereas the heart rate response was not different between conditions (P=0.89). There was no difference between GEM and noGEM for LT (2.61±0.34 vs. 2.64±0.39 m · s(-1), P=0.49) and IATSt (3.47±0.42 vs. 3.55±0.47 m · s(-1), P=0.12). However, IATDi (3.57±0.39 vs. 3.66±0.44 m · s(-1), P<0.01) and OBLA (3.85±0.46 vs. 3.96±0.47 m · s(-1), P<0.01) occurred at slower running velocities in GEM. The bLa response to treadmill tests is mildly affected by wearing a mobile gas analysis system. This also applies to bLa thresholds located at higher exercise intensities. While the magnitude of the effects is of little importance for recreational athletes, it might be relevant for elite athletes and scientific studies.