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Muscle activation patterns in subjects with and without low back pain
Karen L Newcomer1, Timothy D Jacobson, David A Gabriel
1Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN 55905, USA.
Objective:
To analyze muscle activation patterns during various footplate perturbations, used as proprioceptive challenges in patients with low back pain (LBP) and in controls.
Design:
A prospective and controlled comparative study.
Setting:
Outpatient clinic.
Participants:
Twenty subjects with chronic LBP and 20 age- and sex-matched controls.
Interventions:
The subjects underwent 5 sets of footplate perturbations in 3 directions with 16 perturbations for each set.
Main Outcome Measures:
Latency, frequency, and asymmetry of muscle activation of the erector spinae, rectus abdominus, anterior tibialis, and gastrocnemius muscles were measured bilaterally with surface electromyography.
Results:
In the toes-up movements, subjects with LBP were significantly less likely to activate their rectus abdominus muscles (P=.02), and they were more likely to exhibit asymmetric muscle activation in the smaller forward movements (odds ratio=4.1, P=.03). The latter result appears to be driven by asymmetric contraction of the erector spinae and rectus abdominus.
Conclusions:
Significantly more subjects with LBP than control subjects exhibited absent firing of trunk muscles during 2 of the 5 footplate perturbations. These results suggest an abnormality of the neuromuscular loop and may represent altered proprioception.