title: A description of shock attenuation for children running.
abstract: BACKGROUND
  A growing number of children are participating in organized sport activities, resulting in a concomitant increase in lower extremity injuries. Little is known about the impact generated when children are running or how this impact is attenuated in child runners.
  
  
  OBJECTIVE
  To describe shock attenuation characteristics for children running at different speeds on a treadmill and at a single speed over ground.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Biomechanics laboratory.
  
  
  METHODS
  Eleven boys (age = 10.5 +/- 0.9 years, height = 143.7 +/- 8.3 cm, mass = 39.4 +/- 10.9 kg) and 7 girls (age = 9.9 +/- 1.1 years, height = 136.2 +/- 7.7 cm, mass = 35.1 +/- 9.6 kg) participated.
  
  
  METHODS
  Participants completed 4 running conditions, including 3 treadmill (TM) running speeds (preferred, fast [0.5 m/s more than preferred], and slow [0.5 m/s less than preferred]) and 1 overground (OG) running speed.
  
  
  METHODS
  We measured leg peak impact acceleration (LgPk), head peak impact acceleration (HdPk), and shock attenuation (ratio of LgPk to HdPk).
  
  
  RESULTS
  Shock attenuation (F(2,16) = 4.80, P = .01) was influenced by the interaction of speed and sex. Shock attenuation increased across speeds (slow, preferred, fast) for boys (P < .05) but not for girls (P > .05). Both LgPk (F(1,16) = 5.04, P = .04) and HdPk (F(1,16) = 6.04, P = .03) were different across speeds, and both were greater for girls than for boys. None of the dependent variables were influenced by the interaction of setting (TM, OG) and sex (P >or= .05). Shock attenuation (F(1,16) = 33.51, P < .001) and LgPk (F(1,16) = 31.54, P < .001) were different between TM and OG, and each was greater when running OG than on the TM, regardless of sex.
  
  
  CONCLUSIONS
  Shock attenuation was between 66% and 76% for children running under a variety of conditions. Girls had greater peak impact accelerations at the leg and head levels than boys but achieved similar shock attenuation. We do not know how these shock attenuation characteristics are related to overuse injuries.
authors.affiliation: Department of Kinesiology and Nutrition Sciences, University of Nevada, Las Vegas, Nevada 89195-3019, USA. john.mercer@unlv.edu
authors.forename: John A
authors.initials: JA
authors.lastname: Mercer
authors.forename: Janet S
authors.initials: JS
authors.lastname: Dufek
authors.forename: Brent C
authors.initials: BC
authors.lastname: Mangus
authors.forename: Mack D
authors.initials: MD
authors.lastname: Rubley
authors.forename: Kunal
authors.initials: K
authors.lastname: Bhanot
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Aldridge
mesh_terms: D000054:Acceleration; D000222:Adaptation, Physiological; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002648:Child; D002669:Child Welfare; D005080:Exercise Test; D005260:Female; D006801:Humans; D007869:Leg Injuries / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012420:Running / Q000293:injuries* / Q000502:physiology; D012737:Sex Factors; D013223:Statistics as Topic; D014732:Vibration / Q000009:adverse effects*
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