The individual pulses combine to create the “pulse train” Which holds the muscle in a tetanic contraction. Pulse rates below 18 are likely to alow the muscles to differentiate and fire on and off, instead of being held in tetany throughout the contraction period. Otherwise go for comfort.
I personally own a Compex 400 Sport and the EMS 6500 (no involvement with both firms) and I can guarantee you that there is no comparison between the two (see the difference in price, too). The EMS 6500 has a too low maximum intensity for strength gains, but I found it useful for recovery using mild pulsing contractions.
The Compex 400 Sport is a wonderful expensive machine (I paid mine 800 € in Italy a pair of years ago) and I had very good results using it on different muscle (glutes, quads, tibialis, hams, abs, bis and tris, delts etc) and with different pre-programmed protocols (strength, strength endurance, explosive strength, plyometry etc) sometimes for training purposes, sometimes to experiment. I found it very useful, among the other things previously discussed by Charlie, also for activating “sleeping” muscles (for ex. the glutes and tris) that in a good number of athletes are not fully activated. After only one or two sessions I could “feel” the glutes and have an improved control on it. Hams are the only bodypart that create me a little too much discomfort even at low intensities, I don’t know if because I’m relatively weak compared to other muscle groups (for ex. quads) or because I have more FT fibres next to the skin.
Another thing I noticed, and sometimes I forget, is that the effect of EMS (improved strength, density etc.) is somewhat delayed (probably you need a few days for adaptations) and in this context I found particularly clever the periodization of EMS in Charlie’s approach. In my opinion EMS could be an important tool for intermediate and high-end athletes (I’m surprised elite powerlifters, for ex, Westsiders don’t use it).
I found this interesting document about EMS theory (and some “experiments” using the Compex 400 Sport).
http://www.iartonline.ca/articles/EMS.PDF
Good insights and some errors (both theoretical and practical), worth reading.
I found very interesting the part about the antagonist activation when the intensity rises too fast or when the body is not accostumed too such high intensities - Charlie?
Another interesting scientific study about EMS by Maffiuleti et al.(2000) about gaining in muscle strength and jumping ability in basketball players (14% improvement in squat jump after 4 weeks, very good results also in sprinting perspective considering the strong correlation between speed in the first 20 meters and the squat jump)
http://www.u-bourgogne.fr/EXPERTISE-PERFORMANCE/download.htm
I found some flaws in the experiment (way too many contractions for example and too many sessions, and, if I remember well, it is not clear if the athletes had previous experiences with strength work, which would be a strong discriminant factor), but in general it is a readable paper.
If you have a basic knowledge of French I suggest to get a look at the other documents on the same site by Gilles Cometti, a famous French sport scientist.
I gained a good hands-on experience with EMS use, in particular with Compex, and if you have any questions feel free to ask.
Simone Vincenzi
When judging intensities generated, it’s important to state how big and how lean you are. A few things to keep in mind
1: Fat is a insulator, raising the need for power.
2: Size influences power requirement
3: And possibly most influential, the higher the percentage of FT fibre- the lower the power requirement
4: Any study contrasting the use of EMS and no EMS must allow enough time for the consolidation of gains (in other words, the higher workload due to the addition of EMS)
My EMS 6500 finally arrived! What should the setting be for the Rate (Hz) and width(micro seconds).
sorry, what did you ask? just looking at the beauty above…
Charlie/ others in the know
You advocate 10 sets of 10 contractions, with 50 secs relaxation. How does this work? Is it a 10 second contraction, followed by a momentary relaxation then another contraction. How long does a typical hip complex session last?
That’s ten contractions of 10sec duration! not 10 sets of 10 contractions. 50sec rest is correect.
talk about a quick response. My legs and abilty to walk thank you.
Has anyone used this unit? Is it legit?
Thanks
VITAL STIM EMS 400:
Specs
Dual, Isolated channels
3 packages of 4 electrodes, lead wires and battery included
Asymmetrical Bi-phasic square pulse
Pulse Width (duration) 250 microseconds fixed each phase
Synchronous, Constant and Alternation setting available
Adjustable 0 - 100mA peak load each channel (500 ohm load)
Adjustable Frequency 2 - 120 Hz
Pulse Ramp: Adjustable 1-8 seconds
Contraction: Variable control (1-30 Sec.)
Relaxation: Variable control (1-30 Sec.)
Power Source: 9V alkaline battery
Hard Plastic Case
Size: 27 x 62 x 95 mm
Weight: 140 grams (including battery)
I think I have used that unit. It is quite inexpensive, right?
The biggest problem with it is that the rest intervals only go up to 30sec (you can unplug the leads for every other interval to get the 60s rests.) Other than that, it works pretty well and the price is right.
It works a little to well. I thought it was weak so I put it up all the way CHRIST… That little thing made me jump. To top it off I was talking to people at work when it went on then I tried to take it off and it turned on while I had the pads stuck to my fingers But my calve does feel worked out though LOL Such a rookie…
The EMS 6500 isn a very good unit. It’s rest time goes to 50. the rate goes all the way up to 120. I needed all of that to feel a strong contraction. I’m a little unsure about pad placement (any charts on the web?), should I have them near the insertion or near the belly of the muscle? Also is there a way to work the VMO muscle.
Hi elars,
Are you using all 4 pads on say your right quad or less? This is the only bad thing I have to say about this EMS so far. I am limited to doing one group at a time. Quads for instance take (2) 10 minute sessions, one for the right and one for the left.
I just looked at my EMS-6500 and the rest time actually goes up to 99 seconds. Still not an eternity but being that Charlie’s 10/50 guidelines are the only ones I have to follow, it’d do for me right now.
Being a rookie to EMS, I don’t really know about other machines quality, but let’s just say I have at least a few 12-15 session cycles to go through before I’ll feel I need a higher intensity unit.
I’m just finished session #10 of the 15 I plan to do this time. It took some getting used to, but it definitely feels like a much stronger isometric contraction than I can produce voluntarily.
Here are my notes from last night for example:
Dec 1
shower
(all sets are 10 minutes 10 sec on, 1 sec ramp, 50 sec rest)
L quad - 120 Hz, 300 width, intensity = 5
R quad - 120 Hz, 300 width, intensity = 5
L ham - 120 Hz, 300 width, intensity = 4
R ham - 120 Hz, 300 width, intensity = start at 4, changed to 5 upper/4 lower , having trouble getting tetanic (sp?) contraction, messed around with intensity and placement
lower back - 120 Hz, 300 width, intensity = 3.5
Feet - 80 Hz, 200 width, intensity = 4
Glutes - 120 Hz, 300 width, intensity = started at 5, up to 5.5, then up to 6
For pad placement, Charlie has some diagrams in one of his books. Usually closer to the insertions I believe.
I just move the pads a little if I’m not getting a good contraction. I’ve been having trouble with my right ham the last 2 sessions.
Best,
Erik
P.S. This may just be a poor boy rationalizing his $50 ems unit because he knows he can’t afford a compex right now 
For a description and diagrams, you can look in the CFTS manual
I undertand the Hz, contraction time, rest time, ramp, but don’t understand width and intensity (is this how intense it felt, cause I don’t see that on the display?) what does the width do?
Is the ems 6500 that week? Is this the reason why somebody shouldn’t buy this product?
Pulse Amplitude Constant current 0 ~ 80 mA peak into 500 ohm load each channel; adjustable
Pulse Frequency 2 - 120 Hz
Pulse Width 50 - 300 micro-second adjustable pulse width.
Without being redundant, would you recomend this product Charlie (I know you haven’t looked at it upclose) with the features mentioned above.
Trust me it’s not weak. Especially if you press down on the pads. It’s very minimal (i.e. only 4 pads) but definitely gets the job done.
Stims are highly individual to the user. Basicaly, the leaner you are and the more FT fibre you have, the less current it takes to blow your socks off- and, believe me, thats the kind of intensity we’re talking about here.
Thanks for the fastest reply I’ve ever seen. 
Any idea when the new SPP video will be coming out?
Dec 21, just in time for christmas. LOL
Its too bad Derek was feeling a little under the weather, I was waiting to be strapped up. LOL