Interoception during incremental exercise

Most established interoceptive accuracy tasks (e.g., heartbeat counting; Schandry, 1981) are performed at rest and focus on a single bodily domain, but there are no protocols that repeatedly assess interoception from low intensity to exhaustion across cardiac and respiratory domains, relative to aerobic capacity. The current protocol is novel compared to established interoceptive accuracy tasks in three ways: (1) interoception is assessed during exercise, across a continuum from low intensity to volitional exhaustion; (2) the cardiac and respiratory domains are assessed at the same timepoints, which allows for within-person comparisons between bodily domains; and (3) exercise intensity is normalized to individual aerobic capacity, so that interoceptive trajectories can be compared between participants with different fitness levels. The protocol makes it possible to compare participants’ perception of their heart rate and breathing frequency with measured values during incremental exercise. The protocol can be embedded in a standard CPET, and only requires a laptop and an external numeric keypad in addition to the usual test equipment. The current protocol describes the assessment of interoception (i.e., the perception of internal bodily signals) before and during an incremental cardiopulmonary exercise test (CPET). At the start of the test, participants complete a 25-second heartbeat tracking task while seated at rest on the cycle ergometer. During the test, participants estimate their current heart rate (HR) and breathing frequency (BF), and provide a rating of perceived exertion (RPE), every three minutes and once more at volitional exhaustion. Perceived HR and BF are compared with simultaneously recorded physiological data to quantify interoceptive accuracy as a function of exercise intensity. Exercise intensity is expressed relative to the peak oxygen uptake of each participant (%VO2peak).