Innervation zones in the biceps brachii measured with a surface grid electrode

A back analysis system has been used to assess the occurrence of low back pain by evaluating the fatigue characteristics of back muscle during a sustained, constant-force trunk extension. A study was made to compare the median frequency values simultaneously obtained from six back muscles of patients (in remission, but having a history of chronic back pain) and normal control subjects. The median frequency was obtained while the subjects extended their trunks isometrically. Statistically significant (p<0.05) differences were found in the slope of the median frequency from the erector spinal (L5) level and iliocostalis (L2) level at 80% MVC, with the back patients fatiguing faster. The initial value of the median frequency was found to be lower in patients than in control subjects in the erector spinal (L1 level) at 40%, 60%, and 80% MVC. Another study was performed on 23 members of the men´s varsity crew team of Boston University. The tests correctly identified those subjects with a known chronic back pain history solely on the basis of the median frequency measurements. Initial tests indicate that the back analysis system is a potentially useful assessment tool for revealing the presence or absence of back pain.<>