title: Primary and secondary effects of real-time feedback to reduce vertical loading rate during running.
abstract: Gait modifications are often proposed to reduce average loading rate (AVLR) during running. While many modifications may reduce AVLR, little work has investigated secondary gait changes. Thirty-two rearfoot runners [16M, 16F, 24.7 (3.3) years, 22.72 (3.01) kg/m2, >16 km/week] ran at a self-selected speed (2.9 ± 0.3 m/s) on an instrumented treadmill, while 3D mechanics were calculated via real-time data acquisition. Real-time visual feedback was provided in a randomized order to cue a forefoot strike (FFS), a minimum 7.5% decrease in step length, or a minimum 15% reduction in AVLR. AVLR was reduced by FFS (mean difference = 26.4 BW/s; 95% CI = 20.1, 32.7; P < 0.001), shortened step length (8.4 BW/s; 95% CI = 2.9, 14.0; P = 0.004), and cues to reduce AVLR (14.9 BW/s; 95% CI = 10.2, 19.6; P < 0.001). FFS, shortened step length, and cues to reduce AVLR all reduced eccentric knee joint work per km [(-48.2 J/kg*m; 95% CI = -58.1, -38.3; P < 0.001), (-35.5 J/kg*m; 95% CI = -42.4, 28.6; P < 0.001), (-23.1 J/kg*m; 95% CI = -33.3, -12.9; P < 0.001)]. However, FFS and cues to reduce AVLR also increased eccentric ankle joint work per km [(54.49 J/kg*m; 95% CI = 45.3, 63.7; P < 0.001), (9.20 J/kg*m; 95% CI = 1.7, 16.7; P = 0.035)]. Potentially injurious secondary effects associated with FFS and cues to reduce AVLR may undermine their clinical utility. Alternatively, a shortened step length resulted in small reductions in AVLR, without any potentially injurious secondary effects.
authors.affiliation: Department of Physical Therapy, East Carolina University, Greenville, NC, USA.
authors.forename: M
authors.initials: M
authors.lastname: Baggaley
authors.affiliation: Department of Physical Therapy, East Carolina University, Greenville, NC, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Willy
authors.affiliation: Department of Physical Therapy, East Carolina University, Greenville, NC, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Meardon
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology*; D005545:Forefoot, Human / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D012420:Running / Q000293:injuries / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Tibial stress fracture; cadence; foot strike; gait modification