EMS stands for Electric Muscle Stimulation. Most sources call it Electrical Muscle Stimulation and I have heard Electronic Muscle Stimulation as well. However I’m in the habit of just using the word electric to save a syllable because I don’t play an electrical guitar. It all means the same thing though and is a type of electric stimulation designed to increase strength and/or endurance of muscle
TENS stands for Transcutaneous Electrical Nerve Stimulation, which is electric stimulation that goes through the skin “transcutaneous” activating underlying nerves, which may be sensory (meaning the impulses go up to the brain) or may be motor to the point where you get a muscle contraction either twitch or sustained. Technically all the electric stimulation I (and most therapists or athletes use) is TENS to include EMS because EMS works with via transcutaneous electrodes as well, however traditionally TENS refers to electrical stimulation used to control pain, while EMS is turned up to a higher intensity to recruit sufficient muscle to increase performance in strength, endurance or both. TENS is generally more continuous in nature, meaning it’s on for the entire treatment time though the rate and/or intensity of that stimulation might be programmed to vary with either frequency or amplitude modulation. EMS in contrast generally has on periods of perhaps 3-10 seconds and off periods of 10-50 seconds. The idea of the on and off period is to let muscles contract hard and then have a rest period so they can recuperate for another hard contraction, similar to lifting weights, where you lift hard for some number of reps then rest for a short period so you can do it again. The lines blur with some “aerobic TENS” settings typically done with a steady but low rate (typically 4-6 hz) impulses getting the muscle to twitch then rest instantly 4-6 times per second. One could also call this aerobic EMS and similar parameters and identical feelings can often be programmed into either the TENS or EMS settings on a machine, though this varies by brand. Also when purchasing a machine, most EMS machines are “combo” machines meaning they can do either EMS or TENS, while a number of TENS machines do not have EMS settings. Which is why all my machines are combo machines.
The Globus Genesy line of EMS/TENS units are the best I have ever seen or heard of. I haven’t put my hands on a Compex yet, but the Genesy beats it on paper with greater pulse width (450 uS vs 400 us), greater mA (120 mA vs 100 mA) and unlike the Compex units available in the United States, it’s fully programmable, meaning I can create my own programs. Knowing what I know now, I wouldn’t touch a unit that isn’t programmable. I love my Genesy 1100! It is strong, it allows for considerable experimentation and testing of hundreds of preset programs. Despite those useful features, I actually think the Genesy 300 is the sweet spot for function/price for an everyday use machine.The Genesy 300 is the least expensive, full power, four channel EMS unit that lets me write and save my own programs. That last feature is very important, being that I exclusively use programs I write for myself and my patients. The programs I use aren’t necessarily original, but what I want doesn’t come in any preset that I have seen anywhere..The Everyway Medical EV-906 that I picked to start with is also a really great unit, but with the lesser mA available (100 mA), lesser pulse width (300 uS), and biphasic asymmetric square wave current (vs the Globus symmetric square wave), it feels like it’s only about half the strength as the Globus. Even with half the strength of the Globus Genesy 300, the EV-906 is still stronger than most of my patients can take or need and it’s only a fraction of the cost. As of now, it is $150 for the EV-906 vs $650 for a Genesy 300, or $1200 for a Gensey 1100.
I like a 4-channel machine, as it lets me work enough muscle groups to actually be practical, which a 2-channel machine just doesn’t get you. If someone just has a small area they are working, perhaps for headaches or foot intrinsic muscles, a 2-channel machine will suffice, but I would say 85% of the time when I am doing EMS on myself or on a patient I am using all four channels. Four channels gives me more options and lets me strengthen more things
Well, the problem is that while there are some ES units available with additional channels, none of those machines give me the waveforms, intensity or programmability that I otherwise want. I did once have the idea of lining up two Globus machines and hoping to try three, 4-channel machines to use together but it's a logistical nightmare to get all the wires set up, keep them from tangling, and properly set the intensities on more than one machine