Changes in lumbar muscle activity because of induced muscle pain evaluated by muscle functional magnetic resonance imaging.
METHODS
Experimental study of changes in muscle recruitment during trunk extension exercise at 40% of the repetition maximum, because of induced muscle pain.


OBJECTIVE
To investigate the effect of lumbar muscle pain on muscle activity of the trunk muscles using muscle functional magnetic resonance imaging.


BACKGROUND
Changed muscle recruitment in patients has an important impact on the etiology and recurrence of low back pain. The mechanisms of these changes in muscle activity are still poorly understood. An experimental study investigating the cause-effect relationship of muscle pain on muscle recruitment patterns can help to clarify these mechanisms.


METHODS
In 15 healthy subjects, the muscle activity of the lumbar multifidus, lumbar erector spinae, and psoas muscles was investigated with muscle functional magnetic resonance imaging. Measurements at rest and after trunk extension exercise at 40% of repetition maximum were performed without and with induced pain.


RESULTS
The lumbar multifidus and lumbar erector spinae were significantly active during the trunk extension exercise, whereas the psoas showed no significant activity. The activity of the lumbar multifidus, lumbar erector spinae, and psoas muscles, was reduced bilaterally and multilevel during the exercise with unilateral low back muscle pain.


CONCLUSIONS
These data demonstrate that unilateral muscle pain can cause hypoactivity of muscles during trunk extension at 40% of the repetition maximum. The changes were not limited to the side and level of pain. Moreover, the inhibition was not limited to the multifidus muscle; also the lumbar erector spinae and psoas muscles showed decreased activity during the pain condition. Further research has to assess possible compensation mechanisms for this reduced activity in other muscles.
Dickx
Nele
N
Department of Rehabilitation Sciences and Physical Therapy, Faculty of Medicine, Ghent University, Gent, Belgium. nele.dickx@ugent.be
Cagnie
Barbara
B
Achten
Erik
E
Vandemaele
Pieter
P
Parlevliet
Thierry
T
Danneels
Lieven
L
D000328:Adult; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis* / Q000503:physiopathology*; D008161:Lumbosacral Region / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D055815:Young Adult