title: Concentric evertor strength differences and functional ankle instability: a meta-analysis.
abstract: OBJECTIVE
  To determine whether concentric evertor muscle weakness was associated with functional ankle instability (FAI).
  
  
  METHODS
  We conducted an electronic search through November 2007, limited to English, and using PubMed, Pre-CINAHL, CINAHL, and SPORTDiscus. A forward search was conducted using the Science Citation Index on studies from the electronic search. Finally, we conducted a hand search of all selected studies and contacted the respective authors to identify additional studies. We included peer-reviewed manuscripts, dissertations, and theses.
  
  
  METHODS
  We evaluated the titles and abstracts of studies identified by the electronic searches. Studies were selected by consensus and reviewed only if they included participants with FAI or chronic ankle instability and strength outcomes. Studies were included in the analysis if means and SDs (or other relevant statistical information, such as P values or t values and group n's) were reported for FAI and stable groups (or ankles).
  
  
  METHODS
  Data were extracted by the authors independently, cross-checked for accuracy, and limited to outcomes of concentric eversion strength. We rated each study for quality. Outcomes were coded as either fast or slow velocity (ie, equal to or greater than 110 degrees /s or less than 110 degrees /s, respectively).
  
  
  RESULTS
  Data included the means, SDs, and group sample sizes (or other appropriate statistical information) for the FAI and uninjured groups (or ankles). The standard difference in the means (SDM) for each outcome was calculated using the pooled SD. We tested individual and overall SDMs using the Z statistic and comparisons between fast and slow velocities using the Q statistic. Our analysis revealed that ankles with FAI were weaker than stable ankles (SDM = 0.224, Z = 4.0, P < .001, 95% confidence interval = 0.115, 0.333). We found no difference between the fast- and slow-velocity SDMs (SDM(Fast) = 0.189, SDM(Slow) = 0.244, Q = 29.9, df = 24, P = .187). Because of the small SDM, this method of measuring ankle strength in the clinical setting may need to be reevaluated.
authors.affiliation: Virginia Commonwealth University, 1015 West Main Street, PO Box, 842020, Richmond, VA 23284-2020, USA. barnold@vcu.edu
authors.forename: Brent L
authors.initials: BL
authors.lastname: Arnold
authors.forename: Shelley W
authors.initials: SW
authors.lastname: Linens
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: de la Motte
authors.forename: Scott E
authors.initials: SE
authors.lastname: Ross
mesh_terms: D016512:Ankle Injuries / Q000150:complications / Q000453:epidemiology*; D000843:Ankle Joint / Q000503:physiopathology*; D001265:Athletic Injuries / Q000150:complications / Q000453:epidemiology*; D016001:Confidence Intervals; D006801:Humans; D007593:Joint Instability / Q000453:epidemiology* / Q000209:etiology; D009119:Muscle Contraction; D053580:Muscle Strength; D018908:Muscle Weakness / Q000150:complications; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology; D016059:Range of Motion, Articular; D013180:Sprains and Strains / Q000453:epidemiology; D013223:Statistics as Topic