STUDY DESIGN: Block-counterbalanced, repeated-measures crossover study. OBJECTIVES: To assess scapular upward rotation positional adaptations to experimentally induced subacromial pain. BACKGROUND: Existing subacromial pathology is often related to altered scapular kinematics during humeral elevation, such as decreased upward rotation and posterior tilting. These changes have the potential to limit subacromial space and mechanically impinge subacromial structures. Yet, it is unknown whether these changes are the cause or result of injury and what the acute effects of subacromial pain on scapular upward rotation may be. METHODS: Subacromial pain was induced via hypertonic saline injection in 20 participants, aged 18 to 31 years. Scapular upward rotation was measured with a digital inclinometer at rest and at 30°, 60°, 90°, and 120° of humeral elevation during a painful condition and a pain-free condition. Repeated-measures analyses of variance were conducted for scapular upward rotation position, based on condition (pain or control) and humeral position. Post hoc testing was conducted with paired t tests as appropriate. RESULTS: Scapular upward rotation during the pain condition was significantly increased (range of average increase, 3.5°-7.7°) compared to the control condition at all angles of humeral elevation tested. CONCLUSION: Acute subacromial pain elicited an increase in scapular upward rotation at all angles of humeral elevation tested. This adaptation to acute experimental pain may provide protective compensation to subacromial structures during humeral elevation.

J Orthop Sports Phys Ther 2013;43(4):199-203. Epub 14 January 2013. doi:10.2519/jospt.2013.4276

KEY WORDS: experimental shoulder pain, impingement syndrome, rotator cuff

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

STUDY DESIGN: Cross-sectional, controlled laboratory study. OBJECTIVES: To determine whether thigh muscle isokinetic torque patterns and activity, measured by electromyography (EMG), of individuals with hamstring injury differ from control individuals. BACKGROUND: Neuromuscular control during thigh muscle strength assessment following hamstring injuries has not been reported. METHODS: Fifteen athletes with prior hamstring injury (hamstring-injured group [HG]) were compared to 15 uninjured athletes (control group [CG]). The injuries were incurred 6 weeks to 12 months prior to participation, and all injured athletes had returned to at least partial training. Participants performed 5 isokinetic concentric extensor, concentric flexor, and eccentric flexor torque tests at 60°/s in the seated position. Peak torque was determined for each contraction type, as well as average torque for each of 4 time-based movement quartiles. EMG root-mean-squares were calculated in these movement quartiles for the biceps femoris and medial hamstrings. RESULTS: No significant differences were found for peak torque for all contractions, when comparing HG injured and uninjured sides to CG bilateral averages. The HG injured limb eccentric flexor torque was significantly lower in the fourth quartile (approximately 25° to 5° knee flexion, hamstring lengthened range) compared to the CG bilateral average (P = .025). Eccentric flexor biceps femoris and hamstrings EMG root-mean-squares of the HG injured and the uninjured sides were significantly lower in the second to fourth quartiles (towards the lengthened range), compared to the CG bilateral averages (P<.05). CONCLUSION: Decreased strength and EMG activation in a lengthened hamstrings range for the athletes with prior hamstring injury suggested a change in neuromuscular control. Lengthened range assessment of isokinetic eccentric flexor torque may be useful for the assessment of athletes with a prior injury; however, results should be confirmed with prospective studies.

J Orthop Sports Phys Ther 2011;41(5):354-363, Epub 2 February 2011. doi:10.2519/jospt.2011.3268

KEY WORDS: dynamometry, EMG, electromyography, strain