FAI is associated with impaired balance. Due to the relatively large effect sizes and simplicity of use of time in balance and foot lifts, we recommend that further research should establish their clinical validity and clinical cutoff scores.

The authors compared leg stiffness (K VERT ), muscle activation, and joint movement patterns between 11 men and 10 women during hopping. Physically active and healthy men and women performed continuous 2-legged hopping at their preferred rate and at 3.0 Hz. Compared with men, women demonstrated decreased K VERT ; however, after the authors normalized for body mass, gender differences in K VERT were eliminated. In comparison with men, women also demonstrated increased quadriceps and soleus activity, as well as greater quadriceps-to-hamstrings coactivation ratios. There were no significant gender differences for joint movement patterns (p > .05). The relationship between the observed gender differences in muscle recruitment and the increased risk of anterior cruciate ligament injury in women requires further study. KeywordsACL; quadriceps; coactivation; hop; jump Females' anterior cruciate ligament (ACL) injury rates are 2.0 to 9.7 times greater than are males' ACL injury rates

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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.

Evaluating balance can be an important part of the rehabilitation protocol of an athletic injury. One purpose of this study was to determine the intertester and intratester reliability scores of single-leg stability on a platform of gradually decreasing stability using the Biodex Stability System (BSS). The second purpose was to determine intertester and intratester reliability scores of subject foot placement on the BSS. Subjects (N= 19) underwent a familiarization session on Day 1 that included five 30-s balance tests on the BSS. In each of the five tests, platform stability gradually decreased over the 30 s. Subjects were tested without footwear at all times. On the second day, each subject was tested twice by the same investigator and once by a second investigator using the same 30-s test. Investigator tests were counterbalanced to eliminate order effects. Intertester intraclass correlations (ICCs) ranged from .70 to .42 for stability index and from .93 to .54 for foot placement. Intratester ICCs ranged from .82 to .43 for stability index and from .81 to .55 for foot placement. The overall stability index scores were the most reliable stability scores (.82 for intratester and .70 for intertester). A 30-s, single-leg, gradually decreasing platform stability test appears to be highly reliable when performed on the BSS.

The purpose of this study was to determine whether participants with functional ankle instability have deficits in force sense reproduction compared to uninjured participants. Twenty participants with no history of injury and 20 with functional ankle instability volunteered for this investigation. Participants in the instability group had a history of at least one ankle sprain and frequent episodes of giving way. Ankle force sense testing was performed at 10, 20, and 30% of eversion maximal voluntary isometric contraction. Ten trials were performed at each force. Absolute and variable errors were then calculated. We observed significant (p < 0.05) main effects for group for absolute and variable errors. Force sense absolute error was significantly greater in the functionally unstable ankles (3.7 AE 2.2 N) compared to uninjured ankles (2.8 AE 1.1 N). Variable error was also significantly greater in the functionally unstable ankles (3.2 AE 1.8 N) than the uninjured ankles (2.4 AE 0.8 N). Functional ankle instability is associated with deficits in an individual's ability to accurately reproduce a given force. This deficit may impair an individual's ability to set appropriate muscle force levels to provide stability to the joint. ß