Muscle synergy patterns as altered coordination strategies in individuals with chronic low back pain: a cross-sectional study.
Hiroki Saito, Hikaru Yokoyama, Atsushi Sasaki and 1 others
PMID 37259142WHAT IT FOUND
Across 15 people with chronic low back pain and 15 matched controls, trunk muscle synergy patterns were similar; the pain group showed more consistent patterns in some back-muscle synergies and more variable patterns in one trunk-stability synergy.
Key findings
01When five synergies were extracted, the reconstructed EMG accounted for 90.85% ± 1.86 in non-CLBP and 91.62% ± 1.96 in CLBP, with no significant difference (p = 0.260).
02For the matched synergy components W1 to W5 and C1 to C5, there were no significant differences in individual muscle weightings or temporal activation levels between groups (p > 0.05).
03Intra-cluster similarity differed between groups: W2 and W3 were higher in chronic low back pain (p = 0.00006, d = 0.89; p = 0.0012, d = 0.53), W4 was lower (p = 0.0021, d = 0.57), and C2, C3, and C5 were higher (p = 0.000009, d = 1.07; p = 0.0000006, d = 0.70; p = 0.047, d = 0.30).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only 15 participants in each group, so the results are group-level patterns from a small sample. The chronic low back pain group was young and had low current pain (3.1 ± 1.0 or 3.2 ± 1.0 on the numerical rating scale) and low disability (Roland-Morris 3.6 ± 2.6), which the paper notes may make it hard to generalize to the entire chronic low back pain population. Only superficial trunk muscles were recorded; deeper trunk muscles such as multifidus and transversus abdominis were not measured. No kinematic data were collected, so task complexity, clinical impairment, and movement output could not be linked. The design was cross-sectional, so it cannot determine whether the variability differences are adaptive or maladaptive. The main synergy structure comparisons were null, and the significant findings were about inter-participant similarity, not treatment response.
Declared interests
The work was funded by the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (C), the Joint Project (A) from Tokyo University of Technology, the Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research (A), and the Japan Science and Technology Agency MOONSHOT program.
The easy way to misread this
Do not conclude that altered trunk muscle synergy variability is a diagnostic marker or treatment target for chronic low back pain. The study compared EMG coordination patterns at one time point in a small sample, and the main synergy structure comparisons were not significant.