STUDY DESIGN: Randomized, repeated-measures crossover design. OBJECTIVES: To determine the interrater reliability of directional-bias assessment and to investigate its validity for predicting immediate changes in dynamic postural stability and muscle performance following directionally biased exercises. BACKGROUND: Directional bias in dynamic postural stability deficits may be associated with outcome following intervention. METHODS: Two researchers independently assessed 33 participants, each with a history of more than 1 unilateral lower-limb injury, for directional bias. Interrater reliability was evaluated with the kappa coefficient and a prevalence-adjusted and bias-adjusted kappa coefficient. Participants were randomly allocated to perform matched-bias (MB) or unmatched-bias (UB) exercises first, in 2 crossover groups. Two outcome measures, time to stabilization and rebound hopping, were assessed before and following each exercise intervention, using a force plate. Crossover trial data were analyzed by t tests for period, interaction, and treatment effects, and repeated-measures analyses of variance were used to investigate differences between baseline, MB, and UB. RESULTS: Interrater reliability of directional-bias assessment was substantial (κ = 0.75; prevalence-adjusted and bias-adjusted κ = 0.76). Following MB exercises, medial/lateral time to stabilization and time on the ground during rebound hopping were significantly shorter (P = .01 and P = .05, respectively) compared with UB exercises. Compared with baseline, pairwise change in anterior/posterior time to stabilization (P = .008) improved following MB, whereas time in the air decreased following UB (P = .036). CONCLUSION: Directional-bias assessment demonstrates substantial reliability, and outcomes suggest validity for predicting immediate improvements following matched directionally biased exercises.

J Orthop Sports Phys Ther 2012;42(8):676-687. doi:10.2519/jospt.2012.3790

KEY WORDS: dance medicine, exercise therapy, rehabilitation