Venous hemodynamics of the lower extremities in response to electrical stimulation

Objective: To evaluate the calf muscle pump function using an air plethysmograph (APG) applied to the lower leg of subjects during three different tiptoe exercises. Design: A controlled trial design was selected to compare the hemodynamic effects of three exercise conditions on a group of able-bodied, healthy patients. Setting: Testing was performed in an outpatient clinic at a rehabilitation hospital. Subjects: Patient groups were selected from a convenience sample of 10 healthy volunteers with normal venous capacitance and no reflux, determined through impedance pleythysmography before the study. Interventions: Three exercise conditions undertaken by each subject consisted of loaded and unloaded lower leg muscle contractions produced by (1) voluntary contraction (VOL), (2) electrical stimulation of the gastocnemius-soleus and tibialis anterior muscles (ES), and (3) combined ES and VOL (ES/ VOL). Main Outcome Measure: Hemodynamic measurements of venous filling index upon standing from the supine (VFI), ejection fraction (EF), ejection volume (EV), residual volume (RV), and residual volume fraction (RVF) were recorded after each protocol. These results were used to compare the lower leg hemodynamic effects of the treatments. Results: Combined ES/VOL single tiptoe exercise produced the highest EV (97.8mL), followed by VOL (80.6mL) and ES (51.7mL) (p < .0008). The EF was also highest for combined ES/VOL (73.1%), followed by VOL (64.5%) and ES (37.8%) (p < .0001). Ten tiptoe ES exercises produced the highest RV (96.2mL), followed by ES/VOL (44.7mL) and VOL (28.2mL) (p <,0001). RVF was also highest in the ES group (71%), followed by ES/VOL (33.4%) and VOL (22.8%) (p <.0001), Conclusion: Periodic single ES-induced calf muscle contractions produced significant muscle pump function and could be used to improve venous blood flow and reduce stasis in the lower leg. Continuous ES-induced contractions, on the other hand, could improve lower leg peripheral perfusion while eliciting the physiologic venous muscle pump. Higher RV and RVF after 10 ES-induced contractions in this sample of healthy subjects with normal VFI may be caused by an increase in arterial blood perfusion after repeated ES-induced contractions. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.