The purpose of this study was to simultaneously assess 5 surface electromyography (SEMG) ratios commonly used to quantify the flexion relaxation phenomenon in chronic low back pain patients relative to clinical and musculoskeletal abnormalities.
Seventy-six persons with low back pain (LBP) were assessed through SEMG in standing, flexion, maximum voluntary flexion, and extension. Additionally, participants were assessed for clinical status (pain intensity, perceived disability, and pain-related fear) and musculoskeletal abnormalities (supine straight leg raise, Faber test, and lumbar restrictions).
Flexion-relaxation assessed as the ratio of maximum SEMG during flexion to average SEMG during maximum voluntary flexion, and maximum SEMG during extension to average SEMG during maximum voluntary flexion, demonstrated that highest associations with clinical and musculoskeletal status. Ratio of maximum SEMG during flexion to average SEMG during maximum voluntary flexion was significantly associated with 2 measures of perceived disability (both rs=−0.31, P<0.01), pain-related fear (r=−0.45, P<0.001), as well as range of motion during flexion (r=0.51, P<0.001), and elicitation of pain during straight leg raise (r=0.30, P<0.05). Ratio of maximum SEMG during extension to average SEMG during maximum voluntary flexion was also significantly associated with these same measures, at a slightly higher magnitude, in addition to a measure of clinical pain (r=−0.29, P<0.05).
These data suggest that measures of flexion-relaxation that contrast SEMG during flexion or extension to MVF are more highly associated with clinical status compared with measures that contrast SEMG during flexion and extension, SEMG whereas standing to MVF, or SEMG during MVF alone.
*Department of Psychology, Eastern Michigan University, Ypsilanti
†University of Michigan Health System, Department of Physical Medicine and Rehabilitation, The Spine Program, Ann Arbor, MI
‡Productive Rehabilitation Institute of Dallas for Ergonomics, Dallas, TX
Reprints: Michael E. Geisser, PhD, University of Michigan Health System, Department of Physical Medicine and Rehabilitation, The Spine Program, 325 E. Eisenhower Parkway, Suite 300, Ann Arbor, MI 48108 (e-mail: firstname.lastname@example.org).
Received for publication January 19, 2009; revised May 7, 2009; accepted May 16, 2009