Altered trunk muscle recruitment in people with low back pain with upper limb movement at different speeds

Objective: To compare trunk muscle coordination in people with and without low back pain with varying speeds of limb movement. Study Design: Abdominal and back extensor muscle activity in association wi th upper limb movement was compared among three speeds of movement and betw een people with and without low back pain. Participants: Fourteen subjects with a history of recurrent low back pain a nd a group of age- and sex-matched control subjects. Measures: The onsets of electromyographic activity of the trunk and limb mu scles, frequency of trunk muscle responses, and angular velocity of arm mov ements. Results: Early activation of transversus abdominis (TrA) and obliquus inter nus abdominis (OI) occurred in the majority of trials, with movement at bot h the fast and intermediate speeds for the control group. In contrast, subj ects with low back pain failed to recruit TrA or OI in advance of limb move ment with fast movement, and no activity of the abdominal muscles was recor ded in the majority of intermediate speed trials. There was no difference b etween groups for slow movement. Conclusion: The results indicate that the mechanism of preparatory spinal c ontrol is altered in people with lower back pain for movement at a variety of speeds. (C) 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.