Measuring ultrasound images of abdominal and lumbar multifidus muscles in older adults: A reliability study

Measurement reliability of the L4/5 lumbar multifidus (MF) muscles is high in older adults, but few studies have investigated measurement reliability of the abdominal and upper lumbar MF muscles in this age group. Objectives To determine measurement reliability of abdominal and lumbar MF muscles from a single ultrasound (US) image in older adults. Methods Resting thickness of rectus abdominis and obliquus externus, resting and contracted thickness of obliquus internus, transversus abdominis and lumbar MF, and resting cross-sectional area (CSA) of MF levels (L2-5) were obtained from US images of 92 community-dwelling older adults (aged 65–89 years). Measurements of images were undertaken by an experienced rater and repeated 7–10 days later for intra-rater, and by a second expert rater for inter-rater calculations. Intra-rater reliability was estimated for all muscles. Inter-rater reliability was estimated for all abdominal muscles and for L5 multifidus. Reliability was estimated by intraclass correlation coefficients (ICC). Results Intra-rater ICC(3,1) and inter-rater ICC(2,1) of resting thickness measures of all muscles and CSA of MF were ≥0.86. The ICCs for percentage thickness change were ≥0.76 for the abdominal muscles, and ≥0.42 for MF. Conclusions Measurement reliability of US imaging for abdominal and MF muscle thickness and MF CSA was high, and consistent with previous findings for younger adults. Reliability of percentage thickness change was lower suggesting caution is needed when using this as an outcome measure or study factor among older adults.