Individuals with functional ankle instability took significantly longer to stabilize than individuals with stable ankles after a single-leg jump landing. Differences between groups were not detected with mean sway measured during single-leg stance.

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.

Although 10 measures identified group differences, M/L GRF SD and A/P time to stabilization were the most accurate in discriminating between ankle groups. These results provide evidence for choosing these GRF measures for evaluating static and dynamic balance deficits associated with FAI.

Context:Functional ankle instability (FAI) is difficult to identify and quantify.Objective:To compare joint position sense (JPS), time to stabilization (TTS), and electromy-ography (EMG) of ankle musculature in recreational athletes with and without FAI.Design:Case-control compared withttests and ANOVAs.Setting:Sports medicine research laboratory.Participants:20 recreational athletes.Main Outcome Measures:Passive angle reproduction, TTS, and mean EMG amplitude of the tibialis anterior, peroneals, lateral gastrocnemius, and soleus muscles during single-leg-jump landing.Results:No differences in JPS or medial-lateral TTS measures between groups. Significantly longer anterior-posterior TTS (P< .05) in the unstable ankle group. The stable ankle group had significantly higher mean EMG soleus amplitude after landing (P< .05). No other significant differences were found for mean EMG amplitudes before or after landing.Conclusions:Subjects with FAI demonstrated deficits in landing stability and soleus muscle activity during landing that may represent chronic adaptive changes following injury.

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.

Coordination training can improve dynamic postural instabilities associated with FAI. SR stimulation might be an alternative therapy for FAI, as this stimulation might improve dynamic postural stability more quickly and to a greater extent than coordination training without SR stimulation.

The AJFAT was an excellent assessment tool for discriminating between ankle groups, whereas RV time to stabilization was a fair assessment tool. Although both assessments discriminated between ankle groups, the AJFAT more accurately discriminated between groups than the RV time to stabilization did. Future researchers should confirm these findings using a prospective research design.

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.