title: Association of postural balance and isometric muscle strength in early- and middle-school-age boys.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the isometric muscle strength (IMS) and dynamic balance in early- and middle-school-age boys and to assess the strength of association between the dynamic balance scores and 6 different IMS indexes.
  
  
  METHODS
  This is a cross-sectional study of a convenience sample of 94 boys who were 6 to 10 years of age and classified into an early school age (6-8 years) group (n = 50) and a middle school age (8-10 years) group (n = 44). Balance was tested using a Biodex Balance System. Anteroposterior Stability Index, Mediolateral Stability Index, and Overall Stability Index were recorded. IMS of 11 muscle groups was measured with a handheld dynamometer and categorized into 6 different muscle strength indices.
  
  
  RESULTS
  The mean (SD) values of anteroposterior, mediolateral, and overall stability indexes observed for all study boys were 1.9 ± 1.0, 1.2 ± 0.7, and 2.5 ± 1.2 respectively. In the middle school age group, strong positive relationships were detected between the overall stability index and trunk, lower limb, anti-gravity, pro-gravity, and total strength indexes (r = -0.86/P < .001, r = -0.91/P < .001, r = -0.88/P < .001, r = -0.83/P < .001, and r = -0.84/P < .001 respectively), while no significant relationship was detected with the upper limb strength index (r = 0.159/P = .303). In the early school age group, moderate positive relationships were detected between the overall stability index and anti-gravity, lower limb, and total strength indexes (r = -0.404/P = .004, r = -0.356/P = .011, and r = -0.350/P = .013 respectively).
  
  
  CONCLUSIONS
  Dynamic balance did not appear to be mature by the age of 10 years. Better balance skills were recorded in the mediolateral direction than in the anteroposterior direction. In the middle school age group, the overall stability index had positive relationships with almost all examined muscle strength indexes excepting the upper limb strength index.
authors.affiliation: Assistant Professor, Department of Physical Therapy, College of Applied Medical Sciences, University of Dammam, Dammam, KSA. Electronic address: Alaa_ibrahim40@yahoo.com.
authors.forename: Alaa I
authors.initials: AI
authors.lastname: Ibrahim
authors.forename: Qassim I
authors.initials: QI
authors.lastname: Muaidi
authors.forename: Mohammed S
authors.initials: MS
authors.lastname: Abdelsalam
authors.forename: Ziad M
authors.initials: ZM
authors.lastname: Hawamdeh
authors.forename: Adel A
authors.initials: AA
authors.lastname: Alhusaini
mesh_terms: D000367:Age Factors; D000886:Anthropometry; D002648:Child; D003430:Cross-Sectional Studies; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D012016:Reference Values; D012494:Sampling Studies; D013647:Task Performance and Analysis
keywords: Muscle Strength; Muscle Strength Dynamometer; Postural Balance