Why we feel how we feel: Investigating cerebral blood flow during exercise

Abstract

University of South Australia, Australia Introduction: The underlying mechanisms of why we feel how we feel during exercise remain unknown and until recently have been methodologically problematic to investigate. Local cerebral blood flow (which reflects activity of the frontal cortex [FC]) can be measured using Near Infrared Spectroscopy (NIRS), and is suitable for use during exercise. The objective of this study is to examine affective responses (i.e. feeling good or feeling bad) and activity in areas of the FC during exercise standardised tometabolic processes (i.e. gas exchange thresholds). Methods: In a fully repeated measures design, participants (n=25, 25.6 years, range21–34) completed an incremental exercise test to volitional exhaustion. Affective responses (using the Feeling Scale; range +5 [very good] to −5 [very bad]) and changes in cerebral oxygenation (O2Hb), deoxygenation (HHb), blood volume (tHb) and haemoglobin difference (HbDiff =O2Hb−HHb), were measured (micromolars; m) from the right (Areas 1–4R) and left (Areas 5–8L) FC (corresponding to Brodmann’s Areas 8,10 and 46) using multi-channel NIRS. Averages were taken at ventilatory threshold (VT), respiratory compensation point (RCP) and exhaustion (END). Results: A one-way Time (Pre-, VT, RCP, END) ANOVA indicated a significant (p<0.05) decline in affect (feeling good to bad) from Pre(M± SD, 2.4±1.1), to VT (1.5±1.0), RCP (−.8±1.7), and END (−2±1.8). A multivariate ANOVA revealed significant (p<0.05) Intensity (3; VT, RCP, END) by Area (8; 1–4R, 5–8L) interactions for O2Hb, tHb and HbDiff. From VT to END, HbDiff increased in Area 6L (+1.7±4.9) compared to Area 1R (−1.3±5.7). From RCP to END, O2Hb declined in Area 1R (−.8±2.2) whereas O2Hb and tHb increased in Area 4R (+1.4±2.5 and +3.2±3.6, respectively). At RCP, Areas 1R (O2Hb, HbDiff) and 6L (HbDiff); and at END, Areas 4R (O2Hb, tHb) and 6L (HbDiff) were associated with feeling bad (range r=−0.44, p<0.02 and −0.61 p<0.01). Discussion: Differential patterns of activity and asymmetry in the FC at exercise intensities above VT are associated with howwe feel during exercise. On-going research is exploring other potential sources of influence i.e. dispositional traits and the effect of intervention strategies on FC activity during exercise to further understand why we feel how we feel.