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Completed

NCT Number: NCT07635979

Physiological Responses to Upper Limb NMES

The primary objective of this study is to explore the application of the Firefly® device for delivering NMES to anatomically defined regions of the upper limb and to observe associated physiological changes. Specifically, the study will assess alterations in arterial and venous blood flow, as well as local muscle oxygen saturation, as potential indicators of muscle perfusion during NMES.

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Key information

Conditions

Healthy Adult Participants

Age range

18 year–45 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Firstkind

High Wycombe, Buckinghamshire, HP11 1JX, United Kingdom

About this study

Participants will undergo NMES using the Firefly® device, applied to two predefined regions of the upper limb: one targeting the anterior arm nerve bundle (a collective term referring to motor and sensory nerves within the anterior and medial compartments of the upper arm, including the musculocutaneous and adjacent (median, medial cutaneous, ulnar and radial) nerves, and the other targeting the median nerve in the proximal forearm.

Vascular responses will be assessed at two sites, the brachial artery and axillary vein, using Doppler ultrasound. For each nerve-vascular site pairing, NMES will alternate between stimulation OFF and ON conditions (10 OFF and 10 ON cycles), comprising one stimulation block of approximately 20 minutes. Each participant will complete four stimulation blocks in total.

During both ON and OFF phases, blood flow volume and haemodynamic parameters, including peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI), will be recorded. Additionally, local muscle oxygen saturation (SmO₂) will be continuously monitored using functional near-infrared spectroscopy (fNIRS) to assess tissue-level physiological changes.

The total study participation time per individual is approximately 2 hours.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Aged 18 to 45 years (inclusive)
  • No known history of vascular or neurological conditions affecting the upper extremities
  • Able to read, understand, and communicate in English to ensure informed consent and safe participation in the study

Exclusion criteria

  • Presence of any condition that contraindicates the use of neuromuscular electrical stimulation (e.g., implanted pacemaker, epilepsy)
  • Current or recent injury to the upper limbs that may interfere with stimulation or measurement
  • Anatomical variations in the brachial artery or axillary vein, specifically vascular branching outside expected anatomical locations, as identified by ultrasound, which may impair accurate blood flow measurement or device placement
  • Currently participating in another interventional or physiological research study or having done so within the past 30 days.
  • Currently pregnant

Treatment and study plan

Firefly NMES device

Device

Firefly NMES device applied to the upper limb during a single-visit exploratory pysiological study

Primary outcomes

  1. Change in upper-limb blood flow volume during NMES (ON vs OFF)

    Time frame: During single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles

    Within-subject change in upper-limb blood flow volume (mL/min) measured using Doppler ultrasound during neuromuscular electrical stimulation (NMES) delivered via the Firefly device, comparing stimulation ON versus OFF conditions. Measurements will be collected across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.

  2. Change in upper-limb peak systolic velocity during NMES (ON vs OFF)

    Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.

    Within-subject change in upper-limb peak systolic velocity (PSV; cm/s) measured using Doppler ultrasound during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.

  3. Change in upper-limb end-diastolic velocity during NMES (ON vs OFF)

    Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.

    Within-subject change in upper-limb end-diastolic velocity (EDV; cm/s) measured using Doppler ultrasound during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.

  4. Change in upper-limb resistive index during NMES (ON vs OFF)

    Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.

    Within-subject change in upper-limb resistive index (RI; unitless ratio) derived from Doppler ultrasound measurements during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and vascular assessment sites.

  5. Change in upper-limb muscle oxygen saturation during NMES (ON vs OFF)

    Time frame: During a single study visit (approximately 2 hours), across repeated stimulation ON/OFF cycles.

    Within-subject change in upper-limb muscle oxygen saturation (SmO₂; %) measured continuously using functional near-infrared spectroscopy (fNIRS) during NMES delivered via the Firefly device, comparing stimulation ON versus OFF conditions across repeated stimulation cycles at predefined upper-limb stimulation zones and assessment sites.

Secondary outcomes

  1. Incidence of adverse events and device-related effects

    Time frame: During single study visit (approximately 2 hours)

    Number and type of adverse events (AEs), serious adverse events (SAEs), adverse device effects (ADEs), serious adverse device effects (SADEs), and device deficiencies observed during study participation.

Sponsors and collaborators

Lead sponsor

Kieron.Day

Industry

Registry information

Official study title

Exploring Local Physiological Changes in the Arm During NMES Using the Firefly® Device

Important dates

Study start
2025
Primary completion
2025
Study completion
2025
First posted
Jun 9, 2026
Registry last updated
Jun 9, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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