Blood Flow Changes in the Trapezius Muscle and Overlying Skin Following Transcutaneous Electrical Nerve Stimulation

Various researchers have studied the effects of transcutaneous electrical nerve stim-ulation (TENS) on hemodynamics. The purpose of this study was to examine the effects of TENS on local blood flow in the trapezius muscle and overlying skin. Subjects Thirty-three women who were healthy, aged 25 to 55 years, were randomly assigned to receive 1 of 3 different modes of TENS. Methods Skin and muscle blood flow were monitored noninvasively using a new application of photoplethysmography for 15 minutes of TENS applied at high frequency (80 Hz) and sensory-level intensity and at low frequency (2 Hz) and motor-level intensity and for 15 minutes after stimulation. Subliminal 80-Hz TENS was used as a control. Blood flow was monitored simultaneously on stimulated and nonstimulated shoulders. Results Blood flow in the trapezius muscle, but not skin blood flow, increased significantly with motor-level 2-Hz TENS, whereas no increase occurred with sensory-level 80-Hz TENS or subliminal 80-Hz TENS. Discussion and Conclusion Muscle contractions induced by motor-level 2-Hz TENS appear to be a prerequisite for increasing blood flow in the trapezius muscle. However, high stimulation intensity may prevent increased blood flow in the overlying skin. ML Sandberg, PT, PhD, is Re-searcher and Lecturer, Depart