A comparison of head motion and prefrontal haemodynamics during upright and recumbent cycling exercise

The aim of this observational study was to compare head motion and prefrontalhaemodynamics during exercise using three commercial cycling ergometers. Participants (n=12) completed an incremental exercise test to exhaustion duringupright, recumbent and semi-recumbent cycling. Head motion (using accelerometry), physiological data (oxygen uptake, end-tidal carbon dioxide [PETCO2] andheart rate) and changes in prefrontal haemodynamics (oxygenation, deoxygenation and blood volume using near infrared spectroscopy [NIRS]) were recorded.Despite no difference in oxygen uptake and heart rate, head motion was higherand PETCO2was lower during upright cycling at maximal exercise (P<005). Analyses of covariance (covariates: head motionP>005; PETCO2,P<001) revealed that prefrontal oxygenation was higher during semi-recumbent than recumbentcycling and deoxygenation and blood volume were higher during upright than recumbent and semi-recumbent cycling (respectively;P<005). This work highlights the robustness of the utility of NIRS to head motion and describes the potential postural effects upon the prefrontal haemodynamic response duringupright and recumbent cycling exercise.