Correlation between the cerebral oxyhaemoglobin signal and physiological signals during cycling exercise: A near- infrared spectroscopy study

Abstract

Near-infrared spectroscopy (NIRS) is a widely used noninvasive method for measuring human brain activation based on the cerebral haemodynamic response. However, systemic changes can influence the signal’s parameters. Our study aimed to investigate the relationships between NIRS signals and skin blood flow (SBF) or blood pressure during dynamic movement. Nine healthy volunteers (mean age, 21.3 ± 0.7 years; 6 women) participated in this study. The oxyhaemoglobin (O 2 Hb) signal, SBF, and mean arterial pressure (MAP) were measured while the volunteers performed multi-step incremental exercise on a bicycle ergometer, at workloads corresponding to 30, 50, and 70 % of peak oxygen consumption (VO2 peak) for 5 min. The Pearson’s correlation coefficients for the O2 Hb signal and SBF at 50 and 70 % VO2 peak were 0.877 (P < 0.01) and −0.707 (P < 0.01), respectively. The correlation coefficients for O2 Hb and MAP during warm-up, 30 % VO2 peak, and 50 % VO2 peak were 0.725 (P < 0.01), 0.472 (P < 0.01), and 0.939 (P < 0.01), respectively. Changes in the state of the cardiovascular system influenced O2 Hb signals positively during low and moderate-intensity exercise, whereas a negative relationship was observed during high-intensity exercise. These results suggest that the relationship between the O2 Hb signal and systemic changes is affected by exercise intensity.