Body-awareness relies on the representation of both interoceptive and exteroceptive percepts coming from one's body. However, the exact relationship and possible interaction of interoceptive and exteroceptive systems for body-awareness remain unknown. We sought to understand for the first time, to our knowledge, the interaction between interoceptive and exteroceptive awareness of the body. First, we measured interoceptive awareness with an established heartbeat monitoring task. We, then, used a multi-sensory-induced manipulation of body-ownership (e.g. Rubber Hand Illusion (RHI)) and we quantified the extent to which participants experienced ownership over a foreign body-part using behavioural, physiological and introspective measures. The results suggest that interoceptive sensitivity predicts the malleability of body representations, that is, people with low interoceptive sensitivity experienced a stronger illusion of ownership in the RHI. Importantly, this effect was not simply owing to a poor proprioceptive representation or differences in autonomic states of one's body prior to the multi-sensory stimulation, suggesting that interoceptive awareness modulates the online integration of multi-sensory body-percepts.

Cardiac interoception, the ability to sense and process cardiac afferent signals, has been shown to improve after a single session of acute physical exercise. However, it remains unclear whether repetitive engagement in physical exercise over time leads to long-term changes in cardiac interoceptive accuracy and neural activity associated with the processing of afferent cardiac signals. In this study, we aimed to investigate this hypothesis through two cross-sectional studies, categorizing participants as highor low fit based on physical fitness (Study I) or self-reported physical activity levels (Study II). Interoception was assessed using the Heart-Evoked Potential (Studies I and II), the Heartbeat Counting task (Study II), and the Rubber Hand Illusion (Study II). Despite consistent between-group differences in electrocardiogram recordings in both studies, there were not statistically significant between-group differences in any of the measures of interoception. Consequently, our results do not provide evidence to support the notion that regular physical exercise leads to an increase in cardiac interoception.