Ultrasound Characteristics of the Deep Abdominal Muscles During the Active Straight Leg Raise Test

Abstract 

Teyhen DS, Williamson JN, Carlson NH, Suttles ST, O'Laughlin SJ, Whittaker JL, Goffar SL, Childs JD. Ultrasound characteristics of the deep abdominal muscles during the active straight leg raise test.

Objective

To determine whether changes in the transversus abdominis (TrA) and internal oblique (IO) muscles, as seen on ultrasound imaging, during the active straight leg raise (ASLR) test differ between subjects with and without unilateral lumbopelvic pain.

Design

Cross-sectional, case-control study.

Setting

Clinical laboratory.

Participants

Subjects (n=15) with unilateral symptoms in the lumbopelvic region and age-matched and sex-matched control subjects (n=15).

Interventions

Bilateral measurements of the deep abdominal muscles (TrA and IO) were obtained simultaneously using ultrasound imaging to compare the percent change in muscle thickness from rest with (1) immediately on raising, (2) after a 10-second hold, and (3) within 5 seconds after returning the lower extremity to the plinth.

Main Outcome Measure

Percent change in muscle thickness of both muscles from rest to the other 3 time intervals during the ASLR test.

Results

The 3-way group × side measured × time and 2-way side measured × time interactions were not significant for either the TrA (P≥.34) or the IO (P≥.14) muscles. The 2-way interaction group × time was significant for both the TrA (P=.003) and the IO (P=.02) muscles. On lifting the lower extremity, the control group demonstrated a 23.7% and 11.2% increase in TrA and IO muscle thickness, respectively, while those with lumbopelvic pain demonstrated a 6.4% and 5.7% increase in TrA and IO muscle thickness, respectively.

Conclusions

Although subjects with unilateral lumbopelvic pain demonstrated a smaller increase in muscle thickness, during the ASLR test there appears to be a symmetrical response in both of the deep abdominal muscles regardless of which lower extremity is lifted during the ASLR test or the unilateral nature of the symptoms. This study attests to the potential construct validity of using the ASLR test to assess different motor control strategies of the TrA and IO muscles in subjects with unilateral lumbopelvic pain.

Key Words: Low back pain, Rehabilitation

List of Abbreviations: ASLR, active straight leg raise, CI, confidence interval, ICC, intraclass correlation coefficient, IO, internal oblique, MDC, minimal detectable change, TrA, transversus abdominis, USI, ultrasound imaging