Prolonged immobility is a major risk factor for developing deep vein thrombosis, particularly in the lower extremities (Samama, 2000), and venous and arterial insufficiency related disorders such as ulceration and lipodermatosclerosis. Induced (involuntary) muscle contractions may minimize venous pooling in the lower leg by reducing venous stasis, and increasing venous return, lymph flow, and interstitial hydrostatic pressure, which would reduce capillary filtration and assist fluid reabsorption (Man et al., 2003). Thus, we investigated whether involuntary muscle contractions of the foot and calf after protracted sitting can affect leg blood flow and tissue oxygenation in a similar manner to voluntary foot and calf exercise. Sixteen (11♂) healthy volunteers (30±8yrs; 75±19kg) gave informed consent to participate in the study that received local ethics committee approval. Leg arterial blood flow (Doppler Ultrasound) was reduced (ns; p>0.05) with 40 min seated immobility (Immob). The effects of 20 min foot exercise (Ex) – either involuntary via non-painful electrical stimulation of the plantar surface (ES; 2x motor threshold; Revitive CX, Actegy, Ascot, UK), or voluntary heel-raises (VOL; contraction frequency 10/min), on femoral arterial flow, tissue oxygenation status (Near-Infrared Spectroscopy) and cutaneous perfusion (Laser Doppler Flowmetry) were compared. All data (mean± SEM) were analysed with a 2-way repeated measures ANOVA. Arterial blood flow declined following VOL whilst an increase occurred after ES; however differences were not significant across time or interventions (0.98±0.31 to 1.01±0.35 vs. 0.97±0.35 to 0.86±0.28; Post Immob to Post Ex; ES vs. VOL; p>0.05). Muscle oxygenation status was significantly increased with both interventions in the foot (1.2±0.2 vs. 1.1±0.1, p=0.044 time effect; Ex relative to baseline; ES vs. VOL) and calf (1.02±0.009 vs. 1.08±0.01, p<0.0001 time effect; Ex relative to baseline; ES vs. VOL) but calf tissue oxygenation was greater with VOL (p=0.001 interaction effect). Cutaneous perfusion was also significantly enhanced in the foot (11.5±3.1 vs. 6.3±1.1, p<0.0001 time effect; Ex relative to baseline; ES vs. VOL) and calf (3.7±0.3 vs. 3.3±0.4, p<0.0001 time effect; Ex relative to baseline; ES vs. VOL) with both interventions but was not significantly different between VOL and ES. We conclude that ES delivered through the plantar surface is effective for increasing lower limb blood flow and tissue oxygenation. The greater calf tissue oxygenation seen with VOL may be due to voluntary calf muscle contraction to induce rotation about the ankle joint during heel raises. Painless plantar surface ES is simple and safe to use and may be valuable for clinical groups who experience venous insufficiency as part of their disease progression.