Purpose To study validity and reliability of a Japanese version of the Cumberland Ankle Instability Tool and to determine the optimal cutoff score. Methods In this study, the questionnaire was cross-culturally adapted into Japanese. The psychometric properties tested in the Japanese version of the CAIT were measured for criteria validity, internal consistency and test-retest reliability in 111 collegiate soccer athletes. We also established the questionnaire cutoff score for discriminating between individuals with and without CAI. Results There was a significant correlation between the Japanese version of the CAIT and the Karlsson score (r = 0.604, p < 0.001). The questionnaire had a high internal consistency (Cronbach's α = 0.833) and reliability [intraclass correlation coefficient (ICC) = 0.826, 95% confidence interval (CI): 0.732-0.888]. The optimal cutoff score was ≤25, which was consistent with previous reports. Conclusions The Japanese version of the CAIT has been shown to be a valid and reliable questionnaire for determining the presence of CAI. We expect that researchers and clinicians will use the Japanese version of the CAIT in Japan. Implications for Rehabilitation Chronic Ankle Instability (CAI), which not only increases recurrence rate of ankle sprain but also decreases athletic performance, is a residual symptom after ankle sprain. Cumberland Ankle Instability Tool, which has the reliability and validity to assess CAI, will be critically useful in assessment procedure for CAI. It is preferable for clinicians and researchers to use the native language version of the CAIT.

BackgroundThe purpose of this study is to examine the effects of different strike forms, during cutting, on knee joint angle and lower limb muscle activity.MethodsSurface electromyography was used to measure muscle activity in individuals performing cutting manoeuvres involving either rearfoot strikes (RFS) or forefoot strikes (FFS). Three-dimensional motion analysis was used to calculate changes in knee angles, during cutting, and to determine the relationship between muscle activity and knee joint angle. Force plates were synchronized with electromyography measurements to compare muscle activity immediately before and after foot strike.ResultsThe valgus angle tends to be smaller during FFS cutting than during RFS cutting. Just prior to ground contact, biceps femoris, semitendinosus, and lateral head of the gastrocnemius muscle activities were significantly greater during FFS cutting than during RFS cutting; tibialis anterior muscle activity was greater during RFS cutting. Immediately after ground contact, biceps femoris and lateral head of the gastrocnemius muscle activities were significantly greater during FFS cutting than during RFS cutting; tibialis anterior muscle activity was significantly lower during FFS cutting.ConclusionsThe results of the present study suggest that the hamstrings demonstrate greater activity, immediately after foot strike, during FFS cutting than during RFS cutting. Thus, FFS cutting may involve a lower risk of anterior cruciate ligament injury than does RFS cutting.

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Our findings indicate the presence of an association between the CAIT-J score and TTSML, as well as postural stability deficits in collegiate soccer players with FAI during diagonal landings.

The purpose of this study was to investigate postural stability and lower leg muscular activity in male collegiate soccer players with functional ankle instability (FAI), during a diagonal landing. Twenty-two male collegiate soccer players were divided into an FAI group (n = 11) and healthy control group (n = 11). Muscle reaction times for sudden ankle inversion were measured to evaluate neuromuscular control in the peroneus longus (PL), peroneus brevis (PB), tibialis anterior (TA), gastrocnemius lateral head (GL), and gastrocnemius medial head (GM). Time to anteroposterior stabilization (TTSAP), time to mediolateral stabilization (TTSML), and activity of these muscles during a diagonal single-leg landing was measured. Reaction times in the peroneus muscles were delayed in the FAI group, compared to the control group (PL: P < 0.01, PB: P = 0.02). TTSML was increased in the FAI group, compared to the control group (P = 0.02). Muscular activity of PL, PB, and TA were reduced in the FAI group, compared to controls, during a diagonal single-leg landing (PL: P < 0.05, from 87 ms pre-initial contact [pre-IC] to 108 ms post-initial contact [post-IC], PB: P < 0.05, from 180 ms pre-IC to 123 ms post-IC, TA: P < 0.05, from 65 ms to 203 ms post-IC). Male collegiate soccer players with FAI had increased TTSML and reduced muscle activity in PL, PB, and TA during diagonal single-leg landing. It is important for clinicians to assess the postural stability and function of the lower leg muscle activity, during rehabilitation after ankle sprains.