Application of neuromuscular electrical stimulation to the calf muscles of the patient in order to elicit contraction of the calf muscle pump and thus, eject venous blood proximally.

Applied using a custom built, medically approved stimulator called the Duo-STIM. NMES to be applied to the calf muscles to elicit a muscular contraction to eject blood through the venous system.

Duplex Doppler ultrasound will be used as the outcome measure. Both legs will be measured for hemodynamic performance in the popliteal vein by placing the probe at the popliteal fossa.

Measurements of peak venous velocity (cm/s), popliteal vein diameter (cm), time averaged mean velocity (TAMEAN, cm/s) and volume flow (ml/min) will be recorded.

Doppler measurements will be taken initially at rest, before the application of NMES and once again when the NMES session had commenced.

Measurements will be taken at 3 time points (before application of NMES, after application of NMES had begun and at the end of the protocol).

The measurement consists of asking patients to mark their level of comfort using a 100mm, non-hatched visual-analogue-scale (VAS).

A VAS of 30 mm or less will be categorised as mild pain, between 31 and 69mm as moderate pain and scores of 70mm or greater as severe pain.