title: Biomechanical measures in participants with shoulder pain: Intra-rater reliability.
abstract: Biomechanical measures are used to characterize the mechanisms of treatment for shoulder pain. The objective was to characterize test-retest reliability and measurement error of shoulder surface electromyographic(sEMG) and kinematic measures. Individuals(n = 12) with subacromial pain syndrome were tested at 2 visits. Five repetitions of shoulder scapular plane elevation were performed while collecting sEMG of the upper trapezius(UT), middle trapezius(MT), lower trapezius(LT), serratus anterior(SA) middle-deltoid, and infraspinatus muscles during ascending and descending phases. Simultaneously, electromagnetic sensors measured 3-dimensional kinematics of scapular internal/external rotation, upward/downward rotation, posterior/anterior tilt, and clavicular elevation/depression and clavicular protraction/retraction. Kinematic and sEMG variables were reduced for the total phase of ascending and descending elevation (30°-120°, 120°-30°), at 30° intervals for sEMG, and at every 30° discrete kinematic angle. The intraclass correlation coefficients(ICC) ranged from 0.08 to 0.99 for sEMG and 0.23-0.95 for kinematics. Correspondingly, the standard error of the measurement(SEM) and minimal detectable change(MDC) for sEMG measures varied from 2.3% to 103.8% of a reference contraction(REF-contraction). For kinematics, the SEM and MDC varied from 1.4° to 5.9°. Between-day reliability was good to very good, except for scapular internal/external rotation kinematics, and sEMG for the LT, UT, and SA. sEMG error values were highest (>25%REF-contraction) for most of the LT, UT, and SA variables. Kinematic error values indicate changes or differences of 2°-3° are meaningful, except for upward/downward rotation and internal/external rotation with MDCs of 4°-6°. Generally, data from the total phase of movement had better reliability and lower error than the data from sEMG interval or kinematic discrete angles.
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA 90089, USA. Electronic address: lmichene@usc.edu.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Michener
authors.affiliation: Department of Physical Therapy, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Elmore
authors.affiliation: Department of Physical Therapy, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Darter
authors.affiliation: School of Kinesiology, Marshall University, Huntington, WV 25755, USA.
authors.forename: Mark K
authors.initials: MK
authors.lastname: Timmons
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D015203:Reproducibility of Results; D017006:Rotator Cuff / Q000503:physiopathology*; D012540:Scapula / Q000503:physiopathology*; D019534:Shoulder Impingement Syndrome / Q000503:physiopathology* / Q000534:rehabilitation*; D020069:Shoulder Pain / Q000503:physiopathology* / Q000534:rehabilitation*
keywords: Electromyography; Impingement syndrome; Kinematics; Rotator cuff; Scapula