The article was written by Simon Billeau, a professional triathlete from France, for Tri-Max Magazine: Issue 206, June 2021, and has been translated for Firefly Recovery.

Simon Lessing, a legendary figure of our beautiful sport, said, “If I win triathlons, it's not because I train more than my competitors, but because I recover more than them.” Recovery is often overlooked or even forgotten due to lack of time, and is a fundamental part of training.  Like it or not, we are not machines and physiological, psychological, biomechanical and mental adaptations can only be achieved if recovery between sessions has been optimized. Recovery is something people might think they understand. However, the mechanisms of recovery are much more complex than they appear and the processes for improving performance are multifactorial.

Do you know that it takes 72 hours for our body to recover completely from an exhaustive session at VO2max? At this rate, if we did not apply any recovery rules, we could not even do one “hard” session of exercise per week (in triathlon...). Fortunately, everyone makes more or less effort to reduce the negative consequences of training.  

Methods used to speed up recovery include active recovery, sleep, physiotherapy, nutrition and rehydration. Many companies have developed their own technologies. However, their products are sometimes expensive: electrostimulator, pneumatic compression device, cryotherapy... Others are easier and “free”, such as stretching and ice baths. However, all these methods have advantages and disadvantages. Recently, I discovered a device of a new kind used in the medical world successfully for post-surgical patients to reduce edema. It’s called Firefly.


What is Firefly?

Firefly is a recovery device which is small (7.3in x 1.2in x 0.4in), light (⅓ oz) so very easy to carry, and versatile. How does it work? Firefly is placed on both legs just below the knees. The Firefly should be placed on the fibular head. Finding this bony part is quite easy. It is the protrusion below the knee on the outer side. It’s the proximal part of the fibula bone, which forms the leg together with the tibia. Firefly recommends placing a finger on the outside of the ankle and following the fibula up the leg, until you feel the protuberance that is the fibular head. Firefly is a neuromuscular stimulation device. It is therefore different from an electrostimulator which directly stimulates the muscles. This is because the electrodes directly stimulate the peroneal nerve. This nerve is important for sensation and participates in the motor functions of many calf muscles. So, just place the electrodes on the fibular head and apply an adequate level of stimulation to activate the calf muscles. And voila. The human body is wonderfully well structured, with circulation systems like the bloodstream. Its main purpose is to transport and distribute essential substances (energy, oxygen, etc.) to tissues (muscles, organs, etc.) and to remove their metabolites. These two aspects are fundamental for the purpose of recovery after strenuous exercise. Blood circulation also plays a crucial role in thermoregulation, humoral communication (immunity ...).


Muscle Contraction, an Ally of Recovery

As most people know, the cardiovascular system is made up of a pump (the heart), a series of arteries and veins, and an extensive series of small veins called arterioles, which allow very rapid exchanges between tissues. In general, a healthy adult has a blood volume of about 5 to 6 liters. The venous system usually contains about 70% of the blood volume. Due to our standing position and gravity, a large part of this percentage is contained in the calves. Conceptually, cardiac output is the volume of blood ejected by the heart every minute. Venous return is the volume returning to the heart during the same period of time. The two are closely related and feedback loops regulate the cardiovascular system. Other factors like muscle contractions affect venous return. Due to the specific orientation of the valves within the veins, venous return can be stimulated either by muscle contraction, but also by external electrical stimulation. Muscular contraction of the muscles in our lower limbs lowers blood pressure and assists venous return as an auxiliary pump. Finally, muscle contractions decrease capillary hydrostatic pressure (also called transmural pressure) and increase local blood circulation. The effect on transmural pressure causes water to pass from the interstitial medium to the blood medium. All of this contributes to increasing venous return. So there is no doubt that muscle contractions are good for helping with recovery. However, muscle contraction goes hand in hand with heart fatigue. However, we do not want to increase the workload of the heart pump. What's more, our schedules are often busy. So active recovery is not ideal either.

Other techniques have shown results in reducing recovery times. Dynamic air pumps (or pneumatic, depending on the name) offer an alternative to voluntary muscle contractions. However, the devices are expensive (well over $600), relatively large and heavy if you want to transport them with you to a competition venue, especially if you are traveling by plane with therefore a weight limitation. But also and most importantly, they have been proven to be much less effective than electrostimulators. A study by Shayan Bahadori et al - Published in Elsevier in 2017 without any funding - showed that electrostimulators increase microcirculation by 399%, while the IPC (intermittent pneumatic device) increases it by 117%. Note that Firefly's neuromuscular electrostimulation increases calf blood circulation by up to 60%, which corresponds to an effort such as walking, without having to move a single toe! 


What are the Differences between Firefly and an Electrostimulator?

While an electrostimulator stimulates muscles directly, Firefly innervates the peroneal nerve. This would apparently reduce muscle fatigue and therefore it would be possible to use the Firefly for extended periods of time. When, for example, the recovery session of an electrostimulator is about 25 ’, Firefly can be used for 24 hours. I would add that with an electrostimulator, it is possible but difficult to perform another task while with Firefly, you can indulge in other activities such as preparing a meal, traveling without carrying a box, etc. Fireflies are very affordable, and getting a high quality, clinically tested device for $20 is a steal. Not to mention the practical side, just place the point on the fibular head. You press the plus (+) to start the device. There are 7 levels of stimulation. The intensity is increased by pressing the most until you get a visible vibration of the ankle. Rest assured, the aforementioned study also showed that if the intensity was not high enough to see oscillations, there was still a 150% increase in microcirculation. To decrease the intensity, simply press the minus (-). And to turn it off, press the minus for a few seconds. Unfortunately, Firefly is a device that only works for 30 hours. You will therefore need to dispose of it when the battery is discharged. But since the price of the Firefly is no higher than electrodes from any brand of electrostimulator, it is still very inexpensive.

More information at

June 01, 2021