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What is firefly™?

The firefly™ device is a simple, convenient and time efficient electronic device used to provide athletes with accelerated recovery after intense physical exertion. 

Powered by OnPulse™ neuromuscular electro-stimulation technology, the firefly™ device triggers the body's built in mechanisms to increase blood circulation to the lower limbs. The self-adhesive device is applied to the common peroneal nerve at the top of the fibula bone.

What does the firefly™ do?


The firefly™ device accelerates the removal of metabolic waste by increasing blood flow in the muscles of the lower leg. Worn immediately after high exertion exercise, the firefly™ device reduces delayed onset muscle soreness (DOMS) within 24 hours, accelerating lower limb muscle recovery.


The firefly™ relieves the discomfort of muscle soreness and helps the muscles to recover more quickly. Increasing the speed of recovery allows users to get back to training faster and more training means improved performance.



How does the firefly™ work?

Portable, with no leads or wires and worn behind the knee, the firefly™ device delivers painless electrical impulses to the common peroneal nerve to activate the muscle pumps of the lower leg that return blood towards the heart. Clinically proven, the firefly™ device, powered by OnPulse™ technology, is designed to increase blood circulation, and for the prevention and treatment of oedema and the prevention of venous thrombosis, for recovery when travelling.



How does the design affect the performance of the fireflyTM device?

Powered by a wrist-watch size battery with software controlled by a single button, the self-adhesive firefly™ device is encased in a flexible, moulded strap that shapes itself easily and comfortably to the leg, behind the knee.

A green flashing LED light indicates when the device is switched on and also defines which of seven possible stimulation levels has been set. On the underside of the strap, covered by a water-based conductive hydrogel for secure adhesion, two electrodes deliver painless neuromuscular electro-stimulation to the common peroneal nerve.


Who is the firefly™ for?

The firefly™ device is targeted at high level, elite and amateur sports people who undergo serious, high impact exercise in their training and in competitive events. These elite and competitive amateur athletes take their sport very seriously, committing time and money, they actively seek marginal gains and new ways to improve their performance.

Whilst not limited to a particular sport, the device is initially being introduced to competitive amateur triathletes. The sport requires a high level of focus and drive, making triathletes some of the most proactive new technology adopters in sport.  There is also an opportunity to promote the benefits of firefly™ to athletes training in just one of the three triathlon disciplines e.g.  swimmers, runners and cyclists.


Who has tested the firefly™ device?

A number of elite triathletes and Team GB athletes have used the firefly™ devices as part of their recovery strategies at the 2012 games, these include: GB Hockey, GB Swimming, GB Handball, GB Basketball and GB Synchronised Swimming.

Other users included premiership football clubs, premiership rugby clubs such Sale Sharks, London Irish and international rugby teams.

Used recently in the 777 project challenge. Mike Allsop ran 7 marathons, in 7 days, across 7 continents and used the firefly™ devices as part of his recovery in this gruelling challenge.  Mike said “Seven marathons is a challenge in itself but with the need to fly around the globe to complete this, recovery was vital to my success. The firefly™ devices were amazing as part my recovery protocol and they really helped to lighten my legs. This meant I could run again when I got off my flight”

Which locations on the body can I wear the firefly™ device?

The device is to be used on the lower limbs. Aligning the raised indicator line on the device (blue arrows) with the fibula head will stimulate the common peroneal nerve, which in turn increases the amount of blood pumped through the muscles and the overall venous return.

How long does the battery life last?

We publish the device is for 24 hour use – it has a battery life nominally up to 30 hours. After that the software switched the device off, permanently.



How long do I have to wear firefly™ device for?

Depending on your sport and how intense your session has been will determine how long you will need to wear the device for. Please refer to the website for sport specific guidelines/protocols.


Can I sleep with the firefly™ device on?

There is no detrimental effect to sleeping with the devices on. However we do see sleep as being the God of all recovery, so if you are finding the devices to be disruptive then either lower the settings or just turn them off completely.



How many times can I use a single firefly™ device?

According to its CE mark, the firefly™ is a single-use medical device. We are aware that firefly™ users share that they remove and re-apply the device, to maximize the battery life. This a personal choice made by the user.  


When is the best time to use the firefly™ device?

The best time to use fireflyTM is after intensive exercise where you would suffer from muscle soreness, the next day, following training sessions or races/competition. Typical use could be once a month, once a week or even once a day. We recommend using fireflyTM selectively, when you need that bit extra to aid your recovery. Ideally you should wear firefly™ immediately after exercise,  usually after you have showered and changed, so you are ready to relax.



How do I dispose of the firefly™ device once I have used it?

You would dispose of the firefly™ devices exactly the same way you dispose of your everyday house hold waste and batteries. Firstkind recommend recycling the firefly™ devices, as this is better for the environment. The contents inside a firefly™ battery is significantly less hazardous than in a normal AA battery, therefore more environmentally friendly when disposed of.



What is the benefit of the firefly™ knee strap?


The firefly™ knee strap secures the firefly™ device to the leg to provide greater adhesion and a more consistent level of stimulation. On some shaped legs the head of the device can sometimes not stick down fully to the front of the knee. The knee strap provides a solution to combat this issue and ensures the device doesn’t catch on any clothing.


Can I wear the firefly™ device whilst I am training?

The firefly™ device is designed as a recovery device to be worn after high exertion training to increase blood flow when you are at rest. However, it will not do any harm if worn whilst training and exercising. If you are mobile you will naturally have an increased blood circulation and this will override the firefly™ device.



Can I wear the firefly™ device in the shower?

The firefly™ device is not designed to be used in the shower as it not waterproof. The adhesive gel is water based, therefore slight dampening of the gel will help remove device from the leg.



Is the fireflyTM device painful to use?

No, there is no sensation of pain. Instead there is the feeling of the muscles in the lower leg contracting every second. This may take a few moments to adjust to but once accustomed to the sensation the muscles contracting are soon ignored by the consciousness.



How does it differ from other electrical stimulation devices?


The firefly™ device is unique in that it delivers neuromuscular electrostimulation via the common peroneal nerve to activate the muscle pumps of the lower leg, as opposed to other electro-stimulation devices that deliver stimulation direct to the muscle and might be less well tolerated in terms of comfort.



Can I use the fireflyTM device for to treat injury conditions?

The fireflyTM is a medical device that is CE Marked for recovery after exercise. Its intended use is:

  • to increase blood circulation
  • for the prevention and treatment of oedema (firefly™ can be used to treat an oedema following an injury, to return an athlete to fitness, when no longer injured)
  • for the prevention of venous thrombosis – for recovery during travel


What published evidence do you have to support the firefly™ recovery claims?

We have a range of published research posted on the Studies section on the firefly™ website.


Are there any contraindications for using the fireflyTM device?


There are just two contraindications:

  • Do not use on individuals with cardiac demand pacemakers
  • Do not use following a recently diagnosed DVT



What is considered the correct level of stimulation?


When fitted you look for a discernible movement of the muscles in the lower leg and visible outwards movement of the foot. It is not sufficient to see only a slight movement in the muscles of the lower leg alone. The movement in both the lower leg and foot should be discernible.



How do I fit the firefly™ device?


Follow the fitting instructions enclosed in the foil pouch, or simply click this link to see our fitting video on the firefly website.


1. First find the location where the device is to be secured. It can be found on the outside of the leg, just below the level of the knee, at the centre of the fibula head. The fibula head can be felt as a round protrusion at the very top of the fibula bone.

2. Using the grey abrasive pad, gently exfoliate the area of skin that will make contact with the electrodes (once a week should be sufficient for this process). Do not over exfoliate, especially if the skin is fragile or may be damaged through abrasion, and then wipe thoroughly with the electrode preparation wipe. For best results, remove any excess hair and moisturiser if present.

3. After 30 seconds, peel-off the protective film and secure the device to a straight leg so that the raised indicator line on the device (marked with arrows) is positioned at the centre of the fibula head. The head of the device should be positioned towards the front of the leg – with the tail of the device wrapped around and to the rear of the leg below the crease of the knee.

4. For additional adhesion, apply on of the supplied adhesive strips over the device.

5. Use a short press/click of the button (0.5 seconds) to activate the device (the device will start once the button is released) and further short clicks to set the appropriate level – reached when there is discernible movement of the muscles in the lower leg and visible outwards movement of the foot. To accommodate any variation in stimulus due to leg position changes, simply turn the setting up or down. There are 7 levels (indicated by the flashing light); in most cases levels 3 or 4 are ideal. To reduce the levels, one-by-one, use a longer click (1 to 2 seconds) and to turn off the device completely, hold the button down until the light stops flashing.


I am allergic to sticking plasters. Is the firefly™ device likely to cause skin irritation?

Skin reactions, such as rashes, are a recognised minor complication associated with electro-stimulation. Some skin reactions with the firefly™ device have been reported to us, but we do not yet have enough data to say whether the incidences reported are in line with other electro-stimulation devices. We do warn users of the potential for skin reactions in our Instructions for Use: ‘In some cases skin inflammation or irritation can develop in the contact area: either remove the device or re-attach in the alternative fitting location. Details on the alternative fitting locations are explained in the Instructions for Use.

We are not aware of any instances where the skin reactions represent a serious risk to the health of the patient.


Who is Firstkind?

FirstKind Ltd is a wholly owned subsidiary of Sky Medical Technology Ltd, a privately held UK company based in High Wycombe and Daresbury. Firstkind manufacture medical devices utilising OnPulseTM, Sky Medical’s proprietary neuromuscular electro-stimulation technology designed to enhances the body’s own circulation to increase lower limb blood circulation.

The OnPulse™ technology has been developed, manufactured and brought to market by Firstkind Ltd following a three year programme of applied research with St. Bartholomew's Hospital and Queen Mary, University of London. The OnPulseTM technology leverages a deep understanding of the anatomy and physiology of the human body, biomedical engineering and isometric neuromuscular stimulation.