title: Hip-Extensor Strength, Trunk Posture, and Use of the Knee-Extensor Muscles During Running.
abstract: BACKGROUND
  Diminished hip-muscle performance has been proposed to contribute to various knee injuries.
  
  
  OBJECTIVE
  To determine the association between hip-extensor muscle strength and sagittal-plane trunk posture and the relationships among hip-extensor muscle strength and hip- and knee-extensor work during running.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Musculoskeletal biomechanical laboratory.
  
  
  METHODS
  A total of 40 asymptomatic recreational runners, 20 men (age = 27.1 ± 7.0 years, height = 1.74 ± 0.69 m, mass = 71.1 ± 8.2 kg) and 20 women (age = 26.2 ± 5.8 years, height = 1.65 ± 0.74 m, mass = 60.6 ± 6.6 kg), participated.
  
  
  METHODS
  Maximum isometric strength of the hip extensors was assessed using a dynamometer. Sagittal-plane trunk posture (calculated relative to the global vertical axis) and hip- and knee-extensor work (sum of energy absorption and generation) during the stance phase of running were quantified while participants ran over ground at a controlled speed of 3.4 m/s. We used Pearson product moment correlations to examine the relationships among hip-extensor strength, mean sagittal-plane trunk-flexion angle, hip-extensor work, and knee-extensor work.
  
  
  RESULTS
  Hip-extensor strength was correlated positively with trunk-flexion angle (r = 0.55, P < .001) and hip-extensor work (r = 0.46, P = .003). It was correlated inversely with knee-extensor work (r = -0.39, P = .01). All the correlations remained after adjusting for sex.
  
  
  CONCLUSIONS
  Our findings suggest that runners with hip-extensor weakness used a more upright trunk posture. This strategy led to an overreliance on the knee extensors and may contribute to overuse running injuries at the knee.
authors: Department of Physical Therapy, California State University, Long Beach;|Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles.
authors: Hsiang-Ling
authors: HL
authors: Teng
authors: Christopher M
authors: CM
authors: Powers
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D001696:Biomechanical Phenomena; D005260:Female; D006615:Hip / Q000033:anatomy & histology / Q000502:physiology; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007718:Knee Injuries / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D007719:Knee Joint / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular; D012420:Running / Q000502:physiology*; D013223:Statistics as Topic; D060726:Torso / Q000502:physiology
keywords: energetics; gait; kinetics