“Comparison of abdominal and hip abductor activation between chronic low back pain and asymptomatic individuals during walking” – F. Algarni - Master Thesis, School of Physiotherapy, Dalhousie University, Canada, Feb. 2nd 2010

FS, Algarni . 2010
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جامعة دالهاوزي
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Background: An important function of the trunk and hip joint muscles is to ensure
lumbar-pelvic stability. Low back pain (LBP) patients have been shown to have
neuromuscular impairments, and walking is a good model to study neuromuscular
function as spinal stability demands are dynamically changing. There has been minimal
investigation of the abdominals and gluteus medius muscles during walking in those with
chronic low back pain (CLBP) compared to asymptomatic controls. Objectives: This
research compared abdominal and gluteus medius (GM) muscle activation amplitudes
and temporal patterns for adults with and without CLBP and investigated whether there
was coordination among muscle pairs. Methods: Data were collected from (14)
participants with a history of CLBP and (14) matched controls (CON) with no history of
LBP. Surface electrodes were placed over the anterior (EOl), middle (E02), and
posterior (E03) fibers of external oblique, internal oblique (10), and GM bilaterally using
standardized procedures. All participants walked on a pressure-sensor mat connected
with the GAITRite system to determine gait cycles during walking at a self-selected
walking speed. Normalized Root Mean Square (NRMS) amplitudes for the right stance
phase and sample ensemble average curves were calculated for each muscle site. A three
(muscle, side, group) factor mixed model analysis of variance (ANOVA) was used to
compare the NRMS amplitude for the four abdominal muscle sites from both sides of the
trunk between CLBP and CON groups. A two (group, side) factor mixed model ANOVA
design was used to compare the NRMS amplitudes of GM muscle from both sides of the
hip between the two groups. An a=0.05 level of significance was used to determine if
there were systematic differences between the level of the factors of interest. Pearson
product-moment correlation coefficient (r) was calculated to show whether there is
coordination in temporal activation patterns among muscle pairs in both groups
separately. Coefficient of variation (CV) of the ensemble average waveforms was also
calculated to quantify variability of the muscle activation pattern during walking in adults
with and without CLBP. Results: There were no significant differences (p>.05) in
abdominal and hip abductor muscle activation amplitudes between CLBP and CON
groups while walking during the stance phase of gait cycle. The differences between the
mean NRMS amplitudes were statistically significant (p<.05) among the three fibers of
EO. Also, there was a significant difference between 10 muscle site and the anterior and
posterior fibers of the EO. The CLBP group had higher variability for all investigated
muscles except anterior fibers of the EO compared to controls. High muscular
coordination was found based on correlational analysis between GM and posterior fibers
of the EO in both groups. Also, a reciprocal relationship was found between sides for GM
muscles during heel strikes in both groups. Discussion and Conclusion: The muscle
activation amplitudes of abdominal oblique and GM during stance phase of gait cycle
were similar during walking at a self-selected walking speed between groups. CLBP
group had higher variability in EMG waveforms compared to the CON group for all
muscles except the anterior fibers of EO. Correlation analysis showed that CON group
had muscular coordination between bilateral E01,E02 and 10 whereas only 10 showed
between side coordination in the CLBP group. Both groups had high muscular
coordination among E03-GM muscle pair with ipsi-lateral heel strike. These results
suggest that self selected walking does not result in a higher burden on the abdominal
muscles, but that muscle synergies are different between the two groups.