I borrowed one from someone and thought it would yield little to no results. I am pretty sceptical about that kind of thing. Sceptical enough that I was determined to prove it wrong. After a long ride I used the device on one leg only, quads and calves.
In short, after the session the treated leg felt great, the other was the same as it was after the ride. BUT ... having had a massage type stimulation you would expect the leg to feel 'nicer' anyway so I came to the conclusion that it was a placebo type "I've paid a lot of money so it must work" type scenario for most people.
The next day I was sold. I had pretty much forgotten / ignored the fact that I had used Compex the night prior and did my ride the next day. The leg I had treated was noticeably better than the other, both at rest and when on the bike. I purchased one shortly after that.
I only use it for recovery, mainly quads and calves. I also used it on a chronic ant tib issue that I had on and off for a couple of years. It fixed in one session and never came back. Might be coincidence but I'll take it.
Don't expect miracles ... if you go for a long hard ride then your legs are going to feel tired but they should, and in my case do, feel a decent amount better after a Compex session and I don't get that initial super fatigued leg feeling when I workout out the next day.
I use it mainly after hard / long sessions and racing. I have the Compex Wireless.
The difference between qualities (uneducated response here!) is probably the way the current works. When I use the machine at my physio (some uber device on wheels) the current / contraction is bigger, hard to explain but the whole muscle contracts with a smoother more solid squeeze. The small Compex style machines are less of a contraction. They still contract, with force - more than you will be able to handle, but it is less all encompassing. Hard to explain unless you feel it.
I imagine the cheaper you go the more that feeling is likely to diminish. On another note, we had ours about a year using the same pads, they got 'unsticky' but we lubed them with some ultrasound gel (cheap) and they sprang back to life.
Hope that helps.
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