Developing normal number of small segments-activity clouds of the electromyography interference pattern.

Background: Number of small segments (NSS) and activity analysis is a mature method for electromyographic automatic interference pattern analysis (IPA), but there are few reports on the application of this technique. Our objective was to establish normal reference values of NSS-activity clouds.

Methods: The NSS and activity data of the sternocleidomastoid, deltoid, biceps brachii (long head), extensor digitorum communis, abductor digiti minimi, vastus medialis, tibialis anterior, and gastrocnemius (lateral head) muscles were obtained from 34 men and 25 women, aged 15-80 years, using concentric needle electrodes. A linear regression of log(NSS) vs log(activity) was performed and the slope, intercept and standard deviation were calculated for each muscle. These variables were transformed back to the original parameters to yield clouds.

Results: Normal NSS-activity clouds for the above eight muscles were obtained.

Conclusions: Normal reference values of NSS-activity may facilitate detection of early and mild neurogenic and myogenic abnormalities.