Background　The　human　heel　pad　is　a　complex　biological　structure　consisting　of　the　fat　pad　and　the　skin.　The　mechanical　properties　of　the　skin　layer　are　of　significant　importance　to　the　load-bearing　function　of　the　heel　pad　and　human　locomotion.　The　condition　of　the　heel　skin　is　also　directly　associated　with　some　medical　conditions　such　as　heel　ulcers　that　may　become　a　site　for　the　skin　breakdown,　which　is　the　most　common　precursor　to　lower　extremity　amputation　among　persons　with　diabetes.　It　is　essential　to　develop　a　detailed　understanding　of　the　properties　of　the　heel　skin　layer　and　its　effect　on　hind　foot　biomechanics　during　heel　strike.　Objectives　This　work　aims　to　gain　a　better　insight　into　the　biomechanical　behaviour　of　the　heel　skin　layer　through　a　combined　experimental　and　numerical　study.　The　main　objective　is　to　characterise　the　biomechanical　responses　of　the　hind　foot　system　during　heel　strike　with　potential　variation　of　the　skin　stiffness　based　on　a　subject-specific　finite　element　(FE)　model　and　biomechanical　testing.　Methods　A　three-dimensional　(3D)　FE　model　of　the　human　hind　foot　incorporating　a　separate　heel　skin　layer　was　developed　based　on　subject-specific　medical　images.　An　inverse　FE　analysis　of　the　in　vivo　indentation　test　was　carried　out　to　study　the　nonlinear　material　property　of　the　heel　skin.　The　FE　model　was　then　used　to　study　the　deformation　of　the　hind　foot　during　heel　strike　in　comparison　with　the　plantar　pressure　measurement　results　and　to　establish　the　effects　of　stiffness　of　the　heel　skin　on　the　stress　and　pressure　distributions.　Results　The　FE　foot　model　with　subject-specific　heel　skin　properties　was　successfully　used　to　predict　the　deformation　of　the　hind　foot　during　heel　strike,　and　the　results　showed　good　agreements　with　biomechanical　pressure　measurements.　The　results　showed　that　the　high　pressure　and　stress　in　the　heel　skin　appeared　in　the　centre　region　during　a　heel　strike.　Heel　skin　stiffness　sensitivity　studies　showed　that　an　increase　in　the　skin　stiffness　had　a　limited　effect　on　the　stress　and　contact　pressure　of　the　hind　foot　bones,　but　caused　a　slight　increase　in　the　skin　stresses,　while　skin　softening　caused　a　decrease　in　the　peak　plantar　pressure　and　its　distribution　pattern　changed.　In　addition,　the　results　also　suggest　that　skin　softening　may　cause　a　higher　stress　level　in　the　bones　and　ligaments.　Conclusion　The　nonlinear　parameter　of　the　heel　skin　has　been　successfully　predicted　from　in　vivo　indentation　tests　based　on　a　subject-specific　FE　model.　Skin　properties＇　sensitivity　tests　clearly　showed　that　the　stiffness　of　the　heel　skin　could　have　a　direct　effect　on　the　biomechanics　of　the　hind　foot.　The　results　suggest　that　individuals　with　a　pathologically　stiffened　heel　skin　could　exert　an　increase　in　the　heel　pressure,　which　may　potentially　lead　to　skin　breakdown　or　ulcer.