Changes in lateral abdominal muscle thickness during the abdominal drawing-in maneuver in those with lumbopelvic pain.

Abstract

Controlled laboratory study. To determine if changes in transversus abdominis (TrA) and internal oblique (IO) muscle thickness and side-to-side symmetry differ in individuals with and without unilateral lumbopelvic pain while at rest and during the abdominal drawing-in maneuver (ADIM). Although the ADIM has been found to produce a symmetrical change in TrA and IO muscle thickness in healthy subjects, how these muscles are activated in those with unilateral lumbopelvic pain during the ADIM remains unknown. Fifteen subjects with lumbopelvic pain and 15 age- and gender-matched control subjects were recruited. To investigate a similar subgroup of patients with lumbopelvic pain that has been used in previous research, subjects were required to have unilateral symptoms, a positive sacroiliac provocation test, and a positive active straight-leg raise test. Ultrasound images were obtained bilaterally at 2 different points during each trial of the ADIM: (1) at rest and (2) while maintaining the ADIM. Average percent change in thickness of the TrA and IO muscles was obtained over 3 trials. The percent change in thickness of the TrA was 20.9% less in those with lumbopelvic pain compared to the control group (P = .035), while the percent change in IO thickness was equivalent between groups (P = .522). No differences were observed for the TrA or IO muscles between the symptomatic and asymptomatic sides in those with (TrA, P = .263; IO, P = .172) or without (TrA, P = .780; IO, P = .635) lumbopelvic pain during the ADIM. Changes in TrA muscle thickness were greater than the IO muscle during the ADIM for both groups (P<.001). Specifically, the increases in TrA muscle thickness in those with and without lumbopelvic dysfunction were 32.7% and 47.3% greater, respectively, compared to changes in the IO muscle. Individuals with unilateral lumbopelvic pain demonstrated a smaller increase in thickness of the TrA muscle during the ADIM. This finding provides an element of construct validity for the use of the ADIM for assessing TrA muscle thickness in those with unilateral lumbopelvic pain. However, both groups demonstrated a symmetrical side-to-side change in TrA and IO muscle thickness despite the symptomatic group having unilateral symptoms. Further, we detected a preferential change in TrA muscle thickness during the ADIM in both groups.