Trunk flexors and extensors muscular performances in healthy subjects and low back pain patients

Demoulin Christophe, Sac Delphine, Serre Laurent

Department of Physical Medicine and Rehabilitation, University of Liege

ISEPK – B21, Allée des Sports 4, B-4000 LIEGE – SART TILMAN, Belgium

Objectives:

Compare common field tests assessing trunk extensor or abdominal muscles, verify the reproducibility of the tests and compare chronic low back pain (CLBP) patients and matched healthy volunteers with regard to performances.

Methods:

The experimental design comprised two experiments. Both protocols consisted in 3 groups of 20 subjects (10 men, 10 women): a student group, a CLBP group (pain duration > 1 year) and a control group (without back pain history). Several anthropometric measures were taken in the student group.

In experiment 1: Trunk extensor muscles performances of the student group were assessed on 2 separate days with various tests (Sorensen test, Ito test, repetitive arch-up test). The two other groups performed one single session including twice the Sorensen test followed by once the repetitive arch-up test.

In experiment 2: Abdominal muscles performances were evaluated in each group. Students participated in two sessions including a dynamic strength test and 2 different static endurance tests, respectively described by Hyytiainen et al. and McQuade et al.. The two other groups performed one single session including the strength test followed by twice the McQuade test.

Results:

In experiment 1, the Sorensen test showed satisfactory intra- and inter-session reproducibility: in the student group, coefficients of variation (CV) ranged from 4.6% to 12.5 %. CLBP patients demonstrated higher CV indicating fear of pain during their first Sorensen test (particularly in women). In comparison to the control group, CLBP patients had decreased endurance performances (particularly males in the Sorensen test) although the perceived exertion was similar.

In experiment 2, the intra- and inter-session reproducibility appeared better for the McQuade test (CV respectively reaching 9.9 % and 12.2 %) than for the Hyytiainen test (CV were respectively 17.7 % and 22.3 %). This latter test caused slightly more cases of back pain and the position appeared more difficult to be maintained. The dynamic strength test showed good reproducibility (CV intra- and intersession = 5 %). When comparing CLBP and control groups, it appeared that although the difference did not appear significant (p>0.05), male and female patients presented decreased abdominal endurance.

Patients did not display a reduction of abdominal strength.

Conclusions:

The Sorensen test as well as the static endurance abdominal test described by McQuade appeared reproducible and safe to assess CLBP patients. According to the results of both experiments, CLBP patients present decreased trunk muscles endurance performances, especially trunk extensors in males.