Reproducibility of Ultrasound Measurement of Transversus Abdominis During Loaded, Functional Tasks in Asymptomatic Young Adults

ObjectiveTo examine the reproducibility of repeat tests of ultrasound imaging (USI) measurement of transversus abdominis (TrA) activation in a single group of asymptomatic adults performing reaching and lifting tasks before and after abdominal drawing-in technique (ADIM) training in the supine position with TrA USI biofeedback.DesignClinical measurement, longitudinal reliability study.SettingUniversity laboratory.ParticipantsFive male (age, 20.6 ± 4.8 years; body mass index, 25.8 ± 4.5) and 8 female (age, 18.3 ± 0.5 years; body mass index, 24.4 ± 3.3) healthy college students.InterventionsNot applicable.Main Outcome MeasuresReliability and precision of minimum, maximum, and percentage of change in TrA thickness measures were examined on recorded cine loop images obtained via USI (B-mode, 7.5 MHz) for 13 asymptomatic adults. Thickness changes of the TrA muscle were measured at rest and during contraction while performing 5 functional, loaded tasks on 3 repeat tests during 3 testing sessions (ie, before ADIM training and 5 minutes and 5 months after ADIM training). The percent thickness change of TrA was calculated as [(thicknessmax – thicknessmin)/thicknessmin] × 100. Reproducibility was examined by using intraclass correlation coefficients (ICC2,k), standard error of measurement (error variance formula), and repeated-measures analysis of variance.ResultsRanges of ICC and standard error of measurement values for 3 repeat tests per testing session were high and precise for single measures of minimum thickness per task (session 1: 0.68-0.93, 0.24-0.37 mm; session 2: 0.62-0.87, 0.28-0.44 mm; session 3: 0.79-0.84, 0.43-0.56 mm) and for composite measures of maximum thickness (session 1: 0.93, 0.25 mm; session 2: 0.94, 0.37 mm; session 3: 0.95, 0.64 mm) and percent change in thickness (session 1: 0.81, 12%; session 2: 0.94, 14%; session 3: 0.94, 15%). Repeated-measures analysis of variance indicated significant effects for subjects, but not repeat tests.ConclusionsThis study produced acceptable reproducibility of USI measures of TrA during loaded functional activities.