Fell running, particularly steeply uphill puts a great deal of stress on the lower leg muscles.
I frequently suffer from sore or tight calves, especially after racing and often need a couple of days recovery before I can run again comfortably. Anything legal that can help speed recovery is worth investigating and so I was very interested to hear of the Firefly device. It’s a small battery powered device that you strap to your leg which delivers a light electric shock.
Firefly device
How does it work?
By neuromuscular electrostimulation! Basically a small battery delivers an electric shock to a nerve which causes your lower leg muscles to contract, thus increasing blood flow. This helps clear metabolic waste and reduces the dreaded DOMS – the delayed onset muscle soreness that we get the day after a hard run.
There is scientific evidence that the device actually works and several case studies attest to this.
The device is intended to be used immediately after exercise and has a peel off strip which allows you to stick it to your leg just below the knee. You can also get a velcro strap that further holds the device in place. Once fitted you can go about your normal routine including walking and driving.
Firefly attached to lower leg
What does it feel like?
Weird! It’s a little bit like the shock you’d get from a gentle electric fence. The device has 7 levels which allows you to alter the intensity of the stimulation which is delivered about once every second. I played around with the settings and found that the effect ranged from a mild localised twitch to quite a pronounced twitch in the lower leg and foot.
The effect isn’t at all painful and not even unpleasant. At first I was fascinated by the involuntary twitch and found that if I adopted different positions: legs bent, legs extended etc. I could vary the amount of twitch it produced. After the first 20 minutes or so you forget the device is there and I even slept with it on overnight without it affecting my sleep.
Is it expensive?
The device costs £29 for a pack of two (the velcro straps cost more but it can be used without them). It is designed as a disposable product although with a battery life of around 24 hours I actually used one 3 times. So although it isn’t cheap if you plan on using it weekly it might be something that you occasionally use. It works out cheaper than a sports massage and might be something that you use instead of.
device with velcro strap
So the big question: Did it work?
I used the device on a number of occasions and only on one leg so that I could compare the results between a leg that had received the neuromuscular electrostimulation and one that hadn’t. The first time was after an undulating 40 minute run. I wore the device for around 5 hours immediately afterwards whilst I was mainly sitting on the settee. The next day I couldn’t feel any noticeable difference whilst walking but if I pressed my calves one did seem to be a bit less tender than the other, however this wasn’t enough evidence to convince me!
The second trial was after a mammoth eight and a half hours in the Welsh mountains. Again I wore the Firefly on only my left leg and this time kept it on overnight giving a good eight hours of stimulation. The next day I was surprised that I didn’t have muscle soreness in either calf so again it was difficult to say if the device had worked. However what I did notice was that when I ran again a couple of days later the stimulated leg’s calf muscles were less tight than those on the non stimulated leg. Self massaging my calves afterwards it did feel like one was less tight than the other. I was keen to get a second opinion and so I had someone else have a feel to compare the calf muscles on each leg and they confirmed that one was noticeably tighter.
My verdict
The Firefly is a very convenient way of recovering. It takes seconds to put on and you can then carry on as normal for example driving home from a run or race. I am still experimenting with the device, intending to use it after races to confirm if it really does reduce tightness in my calf muscles. If it does I will be happy to purchase it again as I have had problems with calf and achilles injuries in the past which have been very hard to shift.
I have tried out several remedies such as compression socks and foam roller and there’s one thing I can confirm without doubt: It might be electric shock treatment but it’s a lot less painful than a sports massage!