Evaluation of Three Neuromuscular Electrical Stimulation Foot Pad Programmes on Lower Limb Haemodynamics in Healthy Adults (TRI-HEX)

The TRI-HEX study is a single-centre, randomised, double-blind, crossover clinical investigation evaluating the haemodynamic performance of three neuromuscular electrical stimulation (NMES) foot pad programs delivered through an investigational version of the Revitive device platform. The study will recruit 24 healthy adult participants in the United Kingdom.

Revitive is a non-invasive NMES device designed to improve blood circulation in the lower limbs during use. The investigational device (14065AT) is derived from the commercially available Revitive Medic Coach device and incorporates firmware modifications that enable delivery of additional predefined stimulation programmes for research purposes. The modification does not alter the device's intended purpose, mode of action, hardware, materials, or electrical output limits.

The study will evaluate three NMES programmes:

Medic - the currently marketed Revitive NMES foot pad programme. Programme 1 (P1) - a newly developed stimulation program designed to minimise muscle adaptation during use.

Personalised Medic v7 (PM7) - a stimulation programme that incorporates a personalised modulation function intended to optimise haemodynamic response.

The primary objective is to compare the effect of P1 and PM7 against the Medic programme on lower limb blood volume flow during a single 30-minute NMES session. Blood volume flow will be measured at the superficial femoral artery using Doppler ultrasound.

Secondary objectives are to compare:

User discomfort during stimulation using a visual analogue scale (VAS). Changes in muscle oxygen saturation (SmO2) measured by near-infrared spectroscopy (NIRS).

Exploratory objectives include assessment of:

Time averaged mean velocity (TAMV) at the superficial femoral artery. Changes in superficial femoral artery diameter. Post-stimulation recovery of muscle oxygenation. Relationships between haemodynamic outcomes and device-recorded accelerometry data.

Relationships between haemodynamic outcomes and skin hydration measurements.

The study uses a double-blinded crossover design, where each participant receives all three interventions in a randomised sequence and both participants and the Chief Investigator remain blinded to intervention allocation. Randomisation is performed using a predefined crossover allocation schedule, and an independent unblinded assessor is responsible for treatment sequence management.

Participants will attend four visits:

Visit 1: eligibility confirmation, informed consent, device familiarisation, collection of baseline demographic and lifestyle information, and a motion analysis baseline assessment.

Visits 2-4: completion of one 30-minute NMES session per visit using one of the three study programmes, with a washout period of 12 hours to 7 days between sessions.

During each testing visit, participants will undergo a 10-minute baseline measurement period, followed by a 30-minute NMES session and 8-minute post-stimulation monitoring. Doppler ultrasound and NIRS measurements will be collected throughout the assessment period. Participants will also complete questionnaires regarding discomfort and device experience.

The study is designed as an exploratory clinical investigation to generate haemodynamic performance data on newly developed NMES stimulation programmes under controlled conditions. Results will be used to assess differences in haemodynamic performance between the investigational programmes and to support future product development and evidence generation activities.