title: Foot strike pattern differently affects the axial and transverse components of shock acceleration and attenuation in downhill trail running.
abstract: Trail runners are exposed to a high number of shocks, including high-intensity shocks on downhill sections leading to greater risk of osseous overuse injury. The type of foot strike pattern (FSP) is known to influence impact severity and lower-limb kinematics. Our purpose was to investigate the influence of FSP on axial and transverse components of shock acceleration and attenuation during an intense downhill trail run (DTR). Twenty-three trail runners performed a 6.5-km DTR (1264m of negative elevation change) as fast as possible. Four tri-axial accelerometers were attached to the heel, metatarsals, tibia and sacrum. Accelerations were continuously recorded at 1344Hz and analyzed over six sections (~400 steps per subject). Heel and metatarsal accelerations were used to identify the FSP. Axial, transverse and resultant peak accelerations, median frequencies and shock attenuation within the impact-related frequency range (12-20Hz) were assessed between tibia and sacrum. Multiple linear regressions showed that anterior (i.e. forefoot) FSPs were associated with higher peak axial acceleration and median frequency at the tibia, lower transverse median frequencies at the tibia and sacrum, and lower transverse peak acceleration at the sacrum. For resultant acceleration, higher tibial median frequency but lower sacral peak acceleration were reported with forefoot striking. FSP therefore differently affects the components of impact shock acceleration. Although a forefoot strike reduces impact severity and impact frequency content along the transverse axis, a rearfoot strike decreases them in the axial direction. Globally, the attenuation of axial and resultant impact-related vibrations was improved using anterior FSPs.
authors.affiliation: Laboratory of Exercise Physiology, University Savoie Mont Blanc, Le Bourget-du-Lac, France; Amer Sports Footwear Laboratory of Biomechanics and Exercise Physiology, Salomon SAS, Annecy, France. Electronic address: marlene.giandolini@salomon.com.
authors.forename: Marlene
authors.initials: M
authors.lastname: Giandolini
authors.affiliation: Laboratory of Exercise Physiology, University Savoie Mont Blanc, Le Bourget-du-Lac, France; Amer Sports Footwear Laboratory of Biomechanics and Exercise Physiology, Salomon SAS, Annecy, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Horvais
authors.affiliation: Laboratory of Exercise Physiology, University of Lyon, Saint Etienne, France.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Rossi
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.
authors.forename: Guillaume Y
authors.initials: GY
authors.lastname: Millet
authors.affiliation: Laboratory of Exercise Physiology, University Savoie Mont Blanc, Le Bourget-du-Lac, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Samozino
authors.affiliation: Laboratory of Human Motricity, Education Sport and Health, University of Nice Sophia Antipolis, Nice, France.
authors.forename: Jean-Benoît
authors.initials: JB
authors.lastname: Morin
mesh_terms: D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D006801:Humans; D008297:Male; D008682:Metatarsal Bones / Q000502:physiology; D008875:Middle Aged; D012420:Running / Q000502:physiology*; D012447:Sacrum / Q000502:physiology; D013977:Tibia / Q000502:physiology; D014732:Vibration
keywords: Antero-posterior acceleration; Downhill running; Foot strike; Resultant acceleration; Vertical acceleration