Mouthful Misjudgements: How Exercise Alters Internal Volume Estimation

An individual’s perceived ability to act is mediated by internal body-related and environmental factors. During tasks where relevant body parts are not visible, individuals mainly rely on subjective self-perceptions influenced by anthropometric factors and energy states such as fatigue that has shown to alter perceived affordances (e.g., distance or hill slope). This study builds on evidence that physical fatigue affects perception in body-related tasks by manipulating energy states on individuals’ ability to estimate their oral volume capacity. Participants (N=21) were divided between two experimental groups who completed a 10-minute stationary cycling task at a High or Low rate. The High-fatigue group biked at the equivalent of 85% of their maximal heart rate (i.e., 220-age), while the Low-fatigue group biked at 50%. The Borg Rating of Perceived Exertion (RPE) Scale, ranging from 6-20, was used to determine participants' subjective effort levels. To assess the impact of exercise-induced fatigue on perceived oral cavity volume, participants poured into a cup the amount of water they believed they could maximally hold in their mouth. Findings indicate that the High group had a significant increase (p < .05) in their estimations of oral volume from before to after exercise, whereas the Low group showed no significant change (p > .05). As estimates were already inflated before exercising, the High group further exaggerated perceived mouth volumes afterward. These results suggest that bouts of physical exertion can distort internal capacity judgements, possibly due to increased thirst or reduced accuracy in sensing internal bodily limits.