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Context: Chronic ankle instability (CAI) is characterized by repeated ankle sprains, which have been linked to postural instability. Therefore, it is important for clinicians to identify individuals with CAI who can benefit from rehabilitation.Objective: To assess the likelihood that CAI participants will exhibit impaired postural stability and that healthy control participants will exhibit better test performance values.Design: Case-control study. Setting: Laboratory.Patients or Other Participants: People with CAI (n ¼ 17, age ¼ 23 6 4 years, height ¼ 168 6 9 cm, weight ¼ 68 6 12 kg) who reported ankle ''giving-way'' sensations and healthy volunteers (n ¼ 17, age ¼ 23 6 3 years, height ¼ 168 6 8 cm, weight ¼ 66 6 12 kg).Intervention(s): Participants performed 7 balance tests: Balance Error Scoring System (BESS), time in balance, foot lift, single-legged stance on a force plate, Star Excursion Balance Test, side hop, and figure-of-8 hop.Main Outcome Measure(s): Balance was quantified with errors (score) for the BESS, length of time balancing (seconds) for time-in-balance test, frequency of foot lifts (score) for foot-lift test, velocity (cm/s) for all center-of-pressure velocity measures, excursion (cm) for center-of-pressure excursion measures, area (cm 2 ) for 95% confidence ellipse center-of-pressure area and center-of-pressure rectangular area, time (seconds) for anteriorposterior and medial-lateral time-to-boundary (TTB) measures, distance reached (cm) for Star Excursion Balance Test, and time (seconds) to complete side-hop and figure-of-8 hop tests. We calculated area-under-the-curve values and cutoff scores and used the odds ratio to determine if those with and without CAI could be distinguished using cutoff scores.Results: We found significant area-under-the-curve values for 4 static noninstrumented measures, 3 force-plate measures, and 3 functional measures. Significant cutoff scores were noted for the time-in-balance test (25.89 seconds), foot-lift test (5), single-legged stance on the firm surface (3 errors) and total (14 errors) on the BESS, center-of-pressure resultant velocity (1.56 cm/s), standard deviations for medial-lateral (1.56 seconds) time-to-boundary and anterior-posterior (3.78 seconds) time-to-boundary test, posteromedial direction on the Star Excursion Balance Test (0.91), side-hop test (12.88 seconds), and figure-of-8 hop test (17.36 seconds).Conclusions: Clinicians can use any of the 10 significant measures with their associated cutoff scores to identify those who could benefit from rehabilitation that reestablishes postural stability.

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Background and Purpose. Scapular muscle performance evaluated with a handheld dynamometer (HHD) has been investigated only in people without shoulder dysfunction for test-retest reliability of data obtained with a single scapular muscle test. The purpose of this study was to assess the reliability, error, and validity of data obtained with an HHD for 4 scapular muscle tests in subjects with shoulder pain and functional loss. Subjects and Methods. Subjects (N=40) with shoulder pain and functional loss were tested bymeasuring the kilograms applied with an HHD during 3 trials for muscle tests for the lower trapezius, upper trapezius, middle trapezius, and serratus anterior muscles. Concurrently, surface electromyography (sEMG) data were collected for the 4 muscles. The same procedures were performed 24 to 72 hours after the initial testing by the same tester. Muscle tests were performed 3 times, and the results were averaged for data analysis. Results. Intraclass correlation coefficients for intratester reliability of measurements of isometricforce obtained using an HHD ranged from .89 to .96. The standard error of the measure (90% confidenceinterval [CI]) ranged from 1.3 to 2.7 kg; the minimal detectable change (90% CI) ranged from 1.8 to 3.6 kg. Construct validity assessment, done by comparing the amounts of isometric muscle activity (sEMG) for each muscle across the 4 muscle tests, revealed that the muscle activity of the upper trapezius and lower trapezius muscles washighest during their respective tests. Conversely, the isometric muscle activity of the middle trapezius and serratus anterior muscles was not highest during their respective tests. Discussion and Conclusion. In people with shoulder pain and functional loss, the intrarater reliability and error over 1 to 3 days were established using an HHD for measurement of isometric force for the assessment of scapular muscle performance. Error values can be used to make decisions regarding individual patients. Construct validity was established for the lower and upper trapezius muscle tests; therefore, these tests are advocated for use. However, construct validity was not demonstrated for the serratus anterior and middle trapezius muscle tests as performed in this study. Further investigation of these muscle tests is warranted.

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