title: Regulation of step frequency in transtibial amputee endurance athletes using a running-specific prosthesis.
abstract: Running specific prostheses (RSP) are designed to replicate the spring-like behaviour of the human leg during running, by incorporating a real physical spring in the prosthesis. Leg stiffness is an important parameter in running as it is strongly related to step frequency and running economy. To be able to select a prosthesis that contributes to the required leg stiffness of the athlete, it needs to be known to what extent the behaviour of the prosthetic leg during running is dominated by the stiffness of the prosthesis or whether it can be regulated by adaptations of the residual joints. The aim of this study was to investigate whether and how athletes with an RSP could regulate leg stiffness during distance running at different step frequencies. Seven endurance runners with an unilateral transtibial amputation performed five running trials on a treadmill at a fixed speed, while different step frequencies were imposed (preferred step frequency (PSF) and -15%, -7.5%, +7.5% and +15% of PSF). Among others, step time, ground contact time, flight time, leg stiffness and joint kinetics were measured for both legs. In the intact leg, increasing step frequency was accompanied by a decrease in both contact and flight time, while in the prosthetic leg contact time remained constant and only flight time decreased. In accordance, leg stiffness increased in the intact leg, but not in the prosthetic leg. Although a substantial contribution of the residual leg to total leg stiffness was observed, this contribution did not change considerably with changing step frequency. Amputee athletes do not seem to be able to alter prosthetic leg stiffness to regulate step frequency during running. This invariant behaviour indicates that RSP stiffness has a large effect on total leg stiffness and therefore can have an important influence on running performance. Nevertheless, since prosthetic leg stiffness was considerably lower than stiffness of the RSP, compliance of the residual leg should not be ignored when selecting RSP stiffness.
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. Electronic address: l.oudenhoven@vumc.nl.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Oudenhoven
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Boes
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; CORAL - Centre for Orthopaedic Research Alkmaar, Orthopaedic Outpatient Department, Noordwest Ziekenhuisgroep, The Netherlands.
authors.forename: Laura
authors.initials: L
authors.lastname: Hak
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Gert S
authors.initials: GS
authors.lastname: Faber
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; Heliomare Research and Development, Wijk aan Zee, The Netherlands.
authors.forename: Han
authors.initials: H
authors.lastname: Houdijk
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000674:Amputees; D001186:Artificial Limbs; D056352:Athletes; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D019919:Prosthesis Implantation; D012420:Running / Q000502:physiology*; D055815:Young Adult
keywords: Leg stiffness; Lower limb prosthesis; Natural frequency; Running; Spring-mass model