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Sex differences in heel pad stiffness during in vivo loading and unloading

Ugbolue, Ukadike C.; Yates, Emma L.; Wearing, Scott C.; Gu, Yaodong; Lam, Wing-Kai; Valentin, Stephanie; Baker, Julien S.; Dutheil, Frédéric; Sculthorpe, Nicholas F.


Ukadike C. Ugbolue

Emma L. Yates

Scott C. Wearing

Yaodong Gu

Wing-Kai Lam

Julien S. Baker

Frédéric Dutheil

Nicholas F. Sculthorpe


Due to conflicting data from previous studies a new methodological approach to evaluate heel pad stiffness and soft tissue deformation has been developed. The purpose of this study was to compare heel pad (HP) stiffness in both limbs between males and females during a dynamic unloading and loading activity. Ten males and 10 females volunteered to perform three dynamic trials to unload and load the HP. The dynamic protocol consisted of three continuous phases: foot flat (baseline phase), bilateral heel raise (unloading phase) and foot flat (loading phase) with each phase lasting two seconds. Six retroreflective markers (3 mm) were attached to the skin of the left and right heels using a customised marker set. Three-dimensional motion analysis cameras synchronised with force plates collected the kinematic and kinetic data throughout the trials. Three-way repeated measures ANOVA together with a Bonferroni post hoc test were applied to the stiffness and marker displacement datasets. On average, HP stiffness was higher in males than females during the loading and unloading phases. ANOVA results revealed no significant differences for the stiffness and displacement outputs with respect to sex, sidedness or phase interactions (p > .05) in the X, Y and Z directions. Irrespective of direction, there were significant differences in stiffness between the baseline and unloading conditions (p < .001) but no significant differences between the baseline and loaded conditions (p = 1.000). Post hoc analyses for the marker displacement showed significant differences between phases for the X and Z directions (p < .032) but no significant differences in the Y direction (p > .116). Finally, females portrayed lower levels of mean HP stiffness whereas males had stiffer heels particularly in the vertical direction (Z) when the HP was both unloaded and loaded. High HP stiffness values and very small marker displacements could be valuable indicators for the risk of pathological foot conditions.

Journal Article Type Article
Acceptance Date Mar 30, 2020
Online Publication Date Jul 23, 2020
Publication Date 2020-09
Deposit Date Feb 8, 2023
Publicly Available Date Feb 8, 2023
Journal Journal of Anatomy
Print ISSN 0021-8782
Electronic ISSN 1469-7580
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 237
Issue 3
Pages 520-528
Keywords bilateral heel raise, foot flat, kinematics and kinetics, marker displacement, plantar flexion


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