Generalizability of trunk muscle EMG and spinal forces

The use of surface electromyography (EMG) has been a great tool for understanding various aspects of muscle physiology and pathology in the areas of basic and clinical science. Although the properties of the surface EMG signal obtained during isometric conditions have been well defined in the exhaustive body of research, there is much to learn about the nature of EMG recorded during variable-length muscle exertions. Several papers have explored the analysis of surface EMG obtained during fatiguing exertions using recently developed methods of signal processing, including wavelet and time-frequency analysis. In addition to utilizing surface EMG as an indicator of fatigue, researchers are using the measurement of surface EMG to predict muscle and joint forces. The objective of this article is to examine the reproducibility of trunk muscle surface EMG and estimated L3/L4 disc forces obtained during isokinetic trunk extension.Identifying sources of variability during dynamic trunk extension that affect measurement of EMG and disk forces.