title: Step frequency and lower extremity loading during running.
abstract: The purpose of the present study was to ascertain whether increase in step frequency at a given velocity during running reduces the lower extremity loading variables, which is associated with tibial stress fracture in runner. We hypothesized that the lower extremity loading variables at a given speed would be minimized at around +15% f step. 10 male subjects were asked to run at 2.5 m/s on a treadmill-mounted force platform. 5 step frequencies were controlled using a metronome: the preferred, below preferred (-15 and -30%) and above preferred (+15 and +30%). From the vertical ground reaction force, we measured following lower extremity loading variables; vertical impact peak (VIP), vertical instantaneous loading rate (VILR) and vertical average loading rate (VALR). We found that there were significant differences in lower extremity loading variables among 5 step frequency conditions. Furthermore, quadratic regression analyses revealed that the minimum loading variable frequencies were 17.25, 17.55, and 18.07% of preferred step frequency for VIP, VILR and VIAR, respectively. Thus, adopting a step frequency greater than one's preferred may be practical in reducing the risk of developing a tibial stress fracture by decreasing lower extremity loading variables.
authors.affiliation: Research Institute, National Rehabilitation Center for Persons with Disabilities, Department of Rehabilitation for the Movement Functions, Tokorozawa, Japan. hobara-hiroaki@rehab.go.jp
authors.forename: H
authors.initials: H
authors.lastname: Hobara
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: M
authors.initials: M
authors.lastname: Sakaguchi
authors.forename: T
authors.initials: T
authors.lastname: Sato
authors.forename: K
authors.initials: K
authors.lastname: Nakazawa
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D015775:Fractures, Stress / Q000517:prevention & control*; D005684:Gait; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D012044:Regression Analysis; D012420:Running / Q000293:injuries* / Q000502:physiology; D013978:Tibial Fractures / Q000517:prevention & control*; D016474:Weight-Bearing