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From the Athletic Training Program, Department of Human Performance and Health Education (MGM, GT), and the College of Education and Human Development (CCC), Western Michigan University, Kalamazoo, Michigan; Twin Cities Orthopedics, Robbinsdale, Minnesota (HC); and the Athletic Training Program, School of Human Performance and Recreation, University of Southern Mississippi, Hattiesburg, Mississippi (WRH).
The authors have no financial or proprietary interest in the materials presented herein.
Electrical stimulation is sometimes used therapeutically to address decreased muscle function, localized pain, and increased edema. 1 It has been suggested that muscle contractions, both voluntary and electrically induced, 2 can promote tissue healing through the action of a muscle pump. 3 The muscle pump results from the compressive forces that act on the muscle vascularity to reduce blood flow during a contraction, but are suddenly removed once a muscle relaxes. This relaxation reduces pressure and allows for vascular refilling and increased blood flow, if adequate time between contractions is provided. 3
Research has shown that static contractions produced by electrical stimulation currents can cause increases in blood flow 4,5 and that electrical stimulation of muscles can also help decrease venous pooling. However, the percentage of maximal voluntary isometric contraction (MVIC) needed to generate hemodynamic changes is still somewhat speculative. 3,6-9 Subsequently, the ideal parameters of electrical stimulation (ie, type of electrical current, pulse rate, duty cycle, and length of treatment) necessary to generate muscle contractions that optimize blood flow has also not been established. Constant twin peak high volt modulation over a short period of time (5 minutes) has shown minimal changes in blood flow at various MVIC intensities. 8 Intermittent square biphasic and sinusoidal waveforms were also found to increase blood flow during a 10-minute treatment, but there were no significant differences between each type of waveform. 7 One study with intermittent bidirectional symmetric rectangular impulses applied for 4, 8, and 12 minutes found significant increases in blood flow with 8- and 12-minute treatments, but not with 4-minute treatments. 10 Another study found that constant asymmetrical biphasic balanced square impulses with a 15-minute treatment resulted in increases in blood flow with motor level stimulation but not with sensory level stimulation.
None of the aforementioned studies used a medium polyphasic frequency current over multiple contractions to determine changes in...