Low-threshold cutaneous mechanoreceptors on the foot sole have enhanced sensitivity when skin temperature is elevated

Cutaneous mechanoreceptor input from the foot sole is critical for balance and gait, yet ageing and disease can compromise skin sensitivity, increasing risks for falls and related injuries. Heating improves perceptual sensitivity, but its direct effects on afferent firing remain unknown. This study examined how topical heating alters Aβ afferent responses to mechanical loads that closely emulate walking. Single tibial nerve afferents were recorded using microneurography and classified as fast-adapting (FA) or slowly adapting (SA), type I or II. Ramp-and-hold compressions, normalized to regional stance pressure distributions, were applied over receptive fields using a 1 cm² probe before and after heating. Dynamic (ramp) and static (hold) firing rates were compared between temperatures. Thirty-seven afferents (11 SAI, 13 SAII, 9 FAI, 4 FAII) were tested. Heating increased skin temperature by 9.5± 2.4°C (P < 0.001) and significantly elevated SAI (P = 0.001) and SAII (P < 0.001) static firing, as well as SAI (P = 0.03), SAII (P = 0.028) and FAI dynamic firing (P < 0.001). These findings provide the first direct physiological evidence that heating enhances cutaneous mechanoreceptor activity, offering mechanistic basis for previously observed improvements in perceptual sensitivity. By using gait-like compressions this work also demonstrates that the augmented encoding persists under functionally relevant conditions. Together these findings reveal that heating amplifies static and dynamic mechanoreceptor responses in ways essential to postural control, supporting heat-based stimulation as a practical, non-invasive strategy for improving plantar feedback and reducing fall risk. KEY POINTS: The sole of the foot contains touch receptors that provide critical information for balance and walking, which decline with age and disease, increasing fall risk. Heating can improve touch perception, but the underlying mechanisms are unclear. Single nerve fibre activity from the foot sole was recorded in healthy young adults while applying natural, walking-like loads before and after skin heating. Heating increased nerve activity in three classes of touch receptors, enhancing sensitivity during application of pressure (dynamic) and steady pressure (static). Static activity relays standing balance input, whereas dynamic activity relays gait and slip feedback. Notably in dynamic receptors increases in heat-related nerve activity were more prevalent when loads were applied at faster rates. For the first time this work shows how heating differentially affects touch receptor classes and provides a physiological basis for using heat to support balance in future clinical studies.