title: The Role of Arch Compression and Metatarsophalangeal Joint Dynamics in Modulating Plantar Fascia Strain in Running.
abstract: Elastic energy returned from passive-elastic structures of the lower limb is fundamental in lowering the mechanical demand on muscles during running. The purpose of this study was to investigate the two length-modulating mechanisms of the plantar fascia, namely medial longitudinal arch compression and metatarsophalangeal joint (MPJ) excursion, and to determine how these mechanisms modulate strain, and thus elastic energy storage/return of the plantar fascia during running. Eighteen runners (9 forefoot and 9 rearfoot strike) performed three treadmill running trials; unrestricted shod, shod with restricted arch compression (via an orthotic-style insert), and barefoot. Three-dimensional motion capture and ground reaction force data were used to calculate lower limb kinematics and kinetics including MPJ angles, moments, powers and work. Estimates of plantar fascia strain due to arch compression and MPJ excursion were derived using a geometric model of the arch and a subject-specific musculoskeletal model of the plantar fascia, respectively. The plantar fascia exhibited a typical elastic stretch-shortening cycle with the majority of strain generated via arch compression. This strategy was similar in fore- and rear-foot strike runners. Restricting arch compression, and hence the elastic-spring function of the arch, was not compensated for by an increase in MPJ-derived strain. In the second half of stance the plantar fascia was found to transfer energy between the MPJ (energy absorption) and the arch (energy production during recoil). This previously unreported energy transfer mechanism reduces the strain required by the plantar fascia in generating useful positive mechanical work at the arch during running.
authors.affiliation: School of Sport Science Exercise and Health, The University of Western Australia, Crawley, Perth, Western Australia, Australia.
authors.forename: Kirsty A
authors.initials: KA
authors.lastname: McDonald
authors.affiliation: School of Sport Science Exercise and Health, The University of Western Australia, Crawley, Perth, Western Australia, Australia.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Stearne
authors.affiliation: School of Sport Science Exercise and Health, The University of Western Australia, Crawley, Perth, Western Australia, Australia.
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Alderson
authors.affiliation: Willetton Podiatry, Willetton, Perth, Western Australia, Australia.
authors.forename: Ian
authors.initials: I
authors.lastname: North
authors.affiliation: School of Sport Science Exercise and Health, The University of Western Australia, Crawley, Perth, Western Australia, Australia.
authors.forename: Neville J
authors.initials: NJ
authors.lastname: Pires
authors.affiliation: School of Sport Science Exercise and Health, The University of Western Australia, Crawley, Perth, Western Australia, Australia.|Biomechanics Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, State College, Pennsylvania, United States of America.
authors.forename: Jonas
authors.initials: J
authors.lastname: Rubenson
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005205:Fascia / Q000502:physiology*; D005528:Foot / Q000502:physiology; D061826:Foot Orthoses; D006801:Humans; D008297:Male; D008683:Metatarsophalangeal Joint / Q000502:physiology*; D008954:Models, Biological; D012420:Running / Q000502:physiology*; D013314:Stress, Mechanical