Complexity of spatiotemporal plantar pressure patterns during everyday behaviours

Abstract

The human foot sole is the primary interface with the external world during balance and walking, and also provides important tactile information on the state of contact. However, prior stud- ies on plantar pressure have focused mostly on summary metrics such as overall force or centre of pressure under limited condi- tions. Here, we recorded spatiotemporal plantar pressure pat- terns with high spatial resolution while participants completed a wide range of daily activities, including balancing, locomotion, and jumping tasks. Contact area differed across task categories, but was only moderately correlated with the overall force expe- rienced by the foot sole. The centre of pressure was often located outside the contact area or in locations experiencing relatively low pressure, and therefore a result of disparate contact regions spread widely across the foot. Non-negative matrix factorisation revealed low-dimensional spatial complexity that increased dur- ing interaction with unstable surfaces. Additionally, pressure patterns at the heel and metatarsals decomposed into separately located and robustly identifiable components, jointly capturing most variance in the signal. These results suggest optimal sen- sor placements to capture task-relevant spatial information and provide insight into how pressure varies spatially on the foot sole during a wide variety of natural behaviours.

Mechanoreceptor sensory feedback is impaired by pressure induced cutaneous ischemia on the human foot sole and can predict cutaneous microvascular reactivity

“…We demonstrated that localized skin ischemia on the foot sole of a healthy individual generates significant changes to skin sensitivity. As hypothesized, this change in skin sensitivity was localized to high pressure foot regions (Cleland et al, 2023) and coincided with locations where blood flow was drastically reduced during loading (3MT and heel). The Mean ± SD of PORH Peak for each site across the foot sole for a 15% body weight load (light gray) or a 50% body weight (dark gray) load.…”

“…We demonstrated that localized skin ischemia on the foot sole of a healthy individual generates significant changes to skin sensitivity. As hypothesized, this change in skin sensitivity was localized to high pressure foot regions ( Cleland et al, 2023 ) and coincided with locations where blood flow was drastically reduced during loading (3MT and heel). The sensitivity of the medial arch, which experiences very little plantar pressure during stance-like loading, did not generate a PORH response, and did not experience any significant changes to skin sensitivity.…”

“…Previous work found that in upright stance, the blood flow in the heel is occluded with as little as 15% BW ( Chang et al, 1996 ). However, the heel experiences ~20% body weight with bipedal quiet stance ( Cleland et al, 2023 ). Therefore, the decline in sensitivity generated in the current work is particularly concerning because it suggests that quiet standing for prolonged periods (>10 min), even at low magnitudes of body weight (15% BW) can impair cutaneous sensitivity.…”

“…Three sites on the foot sole were examined in this study. Two of the sites, the heel and third metatarsal head (3MT), experience higher plantar pressures in standing and gait, while the medial arch (MA) is typically a lower plantar pressure site ( Goffar et al, 2013 ; Helili et al, 2021 ; Cleland et al, 2023 ). We chose to examine the 3MT as it is a common region for foot ulcerations in pathologies such as diabetic neuropathy ( Caselli et al, 2002 ; Petersen et al, 2020 ) and experiences the greatest peak pressure during gait ( Melai et al, 2011 ; Kim et al, 2019 ) which is a direct predictor of ulcer formation ( Pu et al, 2018 ).…”

Texture perception at the foot sole: comparison between walking, sitting, and to the hand

“…The force applied to a surface is especially important when judging roughness (Hollins and Risner, 2000;Lederman and Taylor, 1972), with higher forces leading to greater roughness ratings (Lederman and Taylor, 1972;. As the foot regularly experiences forces exceeding three times body mass (Cleland et al, 2023;McKay et al, 2017), materials may be perceived as much rougher at the foot sole than at the hand. Investigating texture perception on the foot sole is important, because textures might provide important clues about the stability of a given surface.…”