title: Longitudinal Changes in Hip Strength and Range of Motion in Female Youth Soccer Players: Implications for ACL Injury, A Pilot Study.
abstract: BACKGROUND
  Risk of anterior cruciate ligament (ACL) injuries in young female athletes increases with age, appearing to peak during maturation. Changes in hip muscle strength and range of motion (ROM) during this time may contribute to altered dynamic movement patterns that are known to increase risk of ACL injuries. Understanding the longitudinal changes in hip strength and ROM is needed to develop appropriate interventions to reduce the risk of ACL injuries.
  
  
  OBJECTIVE
  To examine the longitudinal changes in hip strength and ROM in female youth soccer players.
  
  
  METHODS
  Longitudinal descriptive study.
  
  
  METHODS
  Field setting.
  
  
  METHODS
  14 female youth soccer athletes (14.1 ± 1.1 y, 165.8 ± 5.3 cm, 57.5 ± 9.9 kg) volunteered as part of a multiyear risk factor screening project.
  
  
  METHODS
  Clinical measures of hip strength and ROM were collected annually over 3 consecutive years. Passive hip internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) ROM were measured with a digital inclinometer. Isometric hip ABD and extension (EXT) strength were evaluated using a hand-held dynamometer. Separate repeated-measures ANOVAs compared hip strength and ROM values across 3 consecutive years (P < .05).
  
  
  RESULTS
  As youth female soccer players increased in age, there were no changes in normalized hip ABD (P = .830) or EXT strength (P = .062) across 3 consecutive years. Longitudinal changes in hip ROM were observed with increases in hip IR (P = .001) and ABD (P < .001), while hip ADD (P = .009) and ER (P < .001) decreased.
  
  
  CONCLUSIONS
  Anatomical changes at the hip occur as youth female soccer players increase in age. While there are no changes in hip strength, there is an increase in hip IR and ABD ROM with a concomitant decrease in hip ER and ADD ROM. The resulting asymmetries in hip ROM may decrease the activation and force producing capabilities of the hip muscles during dynamic activities, contributing to altered lower extremity mechanics known to increase the risk of ACL injuries.
authors.forename: Anh-Dung
authors.initials: AD
authors.lastname: Nguyen
authors.forename: Emma F
authors.initials: EF
authors.lastname: Zuk
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Baellow
authors.forename: Kate R
authors.initials: KR
authors.lastname: Pfile
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: DiStefano
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Boling
mesh_terms: D000293:Adolescent; D000070598:Anterior Cruciate Ligament Injuries / Q000517:prevention & control*; D056352:Athletes; D001696:Biomechanical Phenomena; D005260:Female; D006615:Hip / Q000502:physiology*; D006801:Humans; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology; D010865:Pilot Projects; D016059:Range of Motion, Articular; D012399:Rotation; D012916:Soccer
keywords: adolescent athletes; knee ligament injury; risk factors