title: Tissue Doppler imaging for detecting onset of muscle activity.
abstract: Tissue Doppler imaging (TDI) is typically used to image and quantify tissue motion. We investigated whether this method would serve as a viable alternative to surface electromyography (EMG) in providing a reliable and valid measure of the onset of muscle activity. Ten healthy subjects performed maximal knee extension exercises at 0 degrees /s (isometric), 60 degrees /s, 120 degrees /s, 180 degrees /s, and 240 degrees /s (5 times each, on each side), using an isokinetic dynamometer. Simultaneous EMG and TDI velocity (superimposed on motion-mode ultrasound cine-loops) recordings were made from vastus lateralis. All tests were repeated 1 week later. There was a good correlation between the onset times determined with TDI velocity and EMG: r = 0.78 (day 1), and r = 0.80 (day 2) (each P < 0.001). The mean difference (and SD) in muscle onset time between the two methods (TDI minus EMG) was -20.3 +/- 31.0 ms (day 1) and -17.4 +/- 27.2 ms (day 2). TDI represents a reliable and valid measure of detecting onset of muscle activity. The mean difference between EMG and TDI onset times (approximately 20 ms) is likely explained by electromechanical delay. TDI represents a viable method for measuring the onset of muscle activity; it may offer a non-invasive alternative to fine-wire EMG for use with small or deep muscles.
authors.affiliation: Department of Rheumatology and Institute of Physical Medicine, University Hospital Zürich, Zürich, Switzerland. natascha.pulkovski@medcontrol.ch
authors.forename: Natascha
authors.initials: N
authors.lastname: Pulkovski
authors.forename: Peter
authors.initials: P
authors.lastname: Schenk
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
authors.forename: Anne F
authors.initials: AF
authors.lastname: Mannion
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D018618:Echocardiography, Doppler, Color / Q000379:methods*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D016059:Range of Motion, Articular; D015203:Reproducibility of Results