Haematological parameters and muscle oxygen saturation in elite male speed skaters during a 2-min time trial

Purpose This study analysed the relationship between haematological indices and near-infrared spectroscopy (NIRS) parameters, as they are rarely explored. Methods Nineteen elite male speed skaters performed a 2-min cycling time trial (TT) during which muscle oxygen saturation (SmO 2 ) and local haemoglobin concentration (tHb muscle ) were continuously monitored using NIRS. Haematological parameters was evaluated through (1) total haemoglobin mass (tHb mass ), plasma volume (PV), blood volume (BV), and red cell volume (RCV), using the carbon monoxide (CO) rebreathing method, and (2) complete blood count from venous blood samples. Exploratory correlation and regression analyses were conducted to investigate potential associations between the variables. Results Baseline SmO 2 was not associated with any parameters, whereas tHb muscle was positively correlated with RCV, BV, and PV ( p < 0.05). SmO₂ values exhibited three distinct phases: a descent and plateau during the TT, followed by an ascent during recovery. None of the haematological variables explained SmO 2 variability in the entire cohort. After dividing the participants based on the median of haematological variables into low and high groups, regression analyses showed that dichotomised tHb mass ( p < 0.01), BV ( p < 0.01), and PV ( p < 0.05) explained the variability of SmO 2 only in the linear part of the descent phase. During recovery, half-time of local muscle reoxygenation correlated negatively with relative values of PV, BV ( p < 0.05) and tHb mass ( p < 0.06). Conclusions Haematological status, irrespective of the assessment method, did not appear to influence either resting SmO 2 or SmO₂ kinetics during the time trial. However, muscle reoxygenation dynamics may be associated with haematological parameters obtained via the CO rebreathing method.