This is a very good article found on Ezine.com by a writer who was attempting to explain what, and how, does muscle stimulation work. 

   I've reprinted it below so you can have another perspective on understanding what happens when electricity enters the body to fire motor nerves in conjunction with volitional exercising. 

  Red fibers are type 1 fibers or,  slow twitch fibers,  white are type 2 fast twitch fibers.

 

 

  • Individual Sessions - Preparation


   EMS works best as the last training element of the day, separated from other work by at least two hours. This is usually done at night before bed, as it can be done at home and the supra-maximal stimulus it provides is

excellent for promoting the release of growth hormone during sleep.  Use a hot shower as warm up preparation, being careful to remove any oils or creams from the areas to be treated to ensure proper conductivity (oils left on

the skin can cause the current to jump around the skin surface causing considerable discomfort). The increased blood flow in the muscles after the shower heats the muscle motor neurons, lowers electrical resistance, and makes

them more receptive to EMS.

  Start the EMS session with a gentle pulsing mode for three to five minutes to complete the warm-up before starting the maximal contractions. Warm down using the same pulsing method.

 

  • Contractions - Timing


   Each muscle group is stimulated maximally for ten reps of ten seconds duration with a fifty second rest period between contractions. It's critical to maintain the rest periods as prescribed as this is the absolute minimum

recovery time needed to maintain a maximal contraction on the next rep. A shortened rest period may, in fact, change the nature of the exercise so that it enhances the wrong fiber type.

  Sprinters use the full ten second contraction time, though shot putters and linemen find that six seconds is about the longest they can maintain a maximal contraction. In either case, the same fifty second rest period must
be maintained.

  • Procedure


   Though modern stim equipment allows for a number of muscle groups to be stimulated simultaneously, never work more than two muscle groups at a time. The athlete must be able to determine where the stimulus is coming from.

Keep the limbs straight and unsecured. Never stimulate antagonists at the same time for safety reasons. This also allows the athlete to concentrate on the contraction in isolation for learning reasons.

When stimulating the soles of the feet, have the athlete stand on the pads to prevent cramping. The athlete must always control the intensity of the contraction as the amount of current necessary for a maximal contraction

varies widely between individuals depending on fiber type, fat distribution (fat is an insulator), muscle size, and injury history.   As a rule, sprinters require much less current to achieve a maximal contraction because

their higher percentage of white fiber provides less resistance. The better the sprinter, the more this is so. EMS units have a "rise-time" feature (the time it takes to ramp up the contraction from zero to max) that is

either preset or adjustable. Where it's adjustable, choose the shortest time the athlete can tolerate, usually half to three-fourths of a second.

  • Crank It Up


    Most users never come near the level of contraction they need for best results, especially in clinical settings. To understand the intensity the athlete needs to experience, have him contract the quads as hard as he

possibly can voluntarily, and then have him imagine a goal 30% higher than that! The contraction is massive, and it feels that way! Don't worry about "burning" the muscle though, as it takes only five-millionths of an amp to

maximally contract the quad.

   To give you an example of what I mean by cranking it up, my athletes would often have to bite down on a piece of leather or a stick while being "stimmed". Is it really that painful? Well, it should feel like riding up a very steep and long hill on a

bike. That's the type of "burn" you should feel.
 

  • Electrode Pad Placements


    Most EMS (Electronic Muscle Stimulators) come with a series of electrode pads secured by Velcro straps. This is a very cumbersome and time-consuming arrangement that can be greatly improved with the purchase of self adhesive pads. Choose pads that are two inches and be sure to replace them when they lose their stickiness.

    When choosing pad placements, a lot of experimentation will be needed to find the most comfortable and effective setup, though four pads per large muscle group usually helps. Since the EMS contraction is always strongest

around the negative pole, you should place the negative pad over the largest bulk of the muscle to keep the contraction even throughout the muscle.  When treating the quad muscles, keep the pads towards the outside part of

the upper quads to keep the current from jumping over into the groin area unexpectedly. In a four pad setup, crossing the pairs of leads in an "X" pattern may help ensure a tolerable, but complete contraction.

  • Recovery with EMS: The Fallacy


    The search for ever greater specificity, compounded by a basic misunderstanding of exercise itself, has driven athletes away from low intensity work, much to their detriment. For decades, exercise programs have been based

on the false premise that exercise doesn't count unless it's carried out at 70% of maximum voluntary contractile force or lasts at least twenty minutes, the threshold for protealysis (the breakdown of proteins in the muscle).

Once considered to be the precursor of muscular development, it's now known to be a side effect to be avoided if possible. In fact, steroids eliminate proteolysis and no one would suggest that steroids limit muscular growth!

  • Twofold Effect


   Low intensity exercise has a positive effect not only on recovery from high intensity work but on the high intensity work itself. While high intensity exercise is anti- circulatory as it pumps up the muscles (restricting

blood flow), low intensity exercise promotes circulation, which aids in nutrient transfer and hastens recovery.

    Exercise of a low enough intensity will not lead to detrimental fiber type changes! In fact, the enhanced capillary density it creates leads to precisely the opposite effect! The enhanced capillary density raises the

temperature around the motor neurons, lowering electrical resistance, allowing more fiber to take on the characteristics of fast twitch fiber in response to high intensity work.
 

  • The Treatment


    EMS used in a pulsing mode for ten to twenty minutes at very low intensity assists with recovery by stimulating circulation and the exercise it provides promotes capillary density. The effects can be enhanced if the legs


are slightly elevated during treatment. These sessions can be carried out at the end of the day, before bed, at least two hours after your last workout.
 

  • Rehabilitation
  •  

    EMS can play a role in the rehab of a variety of injuries and is used extensively in clinics to treat the VMO with knee cases. But its value in the rehab of hamstring injuries is poorly understood and under appreciated.

The selection of isokinetic machines over EMS contributes to a lengthening of injury downtime as the fluid resistance on which these machines rely hits the muscle all at once, causing muscle shortening and irritation. Often,

effective treatment including EMS can have the athlete back in action within ten days.

  • Injury Assessment


    Immediately after the injury, with the leg in its normal straight position, run your hand along the hamstring to feel for a depression in the muscle to determine if there's been actual fiber separation (a third degree tear).

  In all but severe cases this won't have happened, meaning it's a first or second degree strain where a quick recovery can be expected.   This must be checked before swelling sets in and fills up any depression and
afterwards the muscle should be wrapped, iced, and elevated in the usual fashion. Do not test or stretch the muscle, as further damage could occur and, regardless of the findings, the initial treatment remains the same.

  Surprisingly, it usually takes only 72 hours for the injury to heal, but extension injuries can occur above and below the original site and adhesions can form if the tissue isn't mobilized sufficiently.

   During the initial 72 hours, the athlete should stay off his feet as much as possible and an EMS pulsing mode can be applied above (not on) the injury site three to four times per day to reduce swelling and promote the

transfer of nutrients to the site. After 72 hours, very gentle EMS pulsing can be applied to the injury site once per day while retaining the pulsing routine four times per day above the site.

    From the third day on, high intensity EMS can be applied to all other muscles to maintain fitness during the recovery period. Additional therapy should include Active Release Technique (ART) if possible, to further reduce

the prospect of adhesions.

  • Bodybuilding Applications


    Most of what I've covered has dealt with non-strength athletes and rehab settings, but what about bodybuilding? Yes, EMS does have its cosmetic uses. Much like high intensity weight training, EMS increases muscular
density or "hardness". Think of Ben Johnson. If you slapped him on the back you'd think you were hitting a brick wall. Although he had a great physique, he wasn't "puffy" like Arnold; he was as hard as a rock. So the thing to
think about with EMS is density, not size. Think of it as maximal strength training and not hypertrophy training.

   Also keep in mind that EMS is for large muscle groups only. Although an expert might be able to pull it off, the average user will not be able to use it on small muscle groups like the biceps, triceps and calves. These

muscles will "roll up" on you, plus even if you could do it (like by placing your foot in a ski boot for calves) it would be excruciating.

    Bodybuilders could also use EMS to help them break through a barrier. For example, if a guy's upper body is weak as compared to his legs, he could use EMS to maintain his legs for a few weeks while focusing on upper body

training. Basically, he'd be allowing all his body's recovery mechanisms and central nervous system to focus on his upper body. He wouldn't lose any size in his legs and may even see some improvement in density during this

time of upper body specialization.

   Here's another trick that may help competitive bodybuilders. EMS can be used to temporarily "burn off" a layer of fat in small areas. What happens is that about two millimeters of subcutaneous fat is mobilized in the area

directly under the pads. You can compare this to the effect seen when shooting growth hormone, i.e., there's local mobilization of the fat at the point of injection.

    Now, since that layer of fat is a protective mechanism, this isn't permanent. In fact, the effect doesn't last long at all. Once the area under the pad starts to cool, the fat starts storing again. So if you're already
very lean and are competing in a bodybuilding show, you'd have to use the machine (possibly even backstage) and then cover up and keep warm until you hit the stage.
 

  • Selecting a Machine


    Are the machines in the muscle magazine ads powerful enough? Most are. This is because they're designed for fat, non-athletes. It takes power to get through all that fat, after all. For an athlete who has a lot of white fiber (which conducts better) and very little fat, most machines are fine in terms of power. The machines we used with athletes were converted Slender Tone machines that were originally designed for fat women!

   When looking for a machine there are a few things to keep in mind. First, I've seen good ones for as little as $280 as well as over a thousand. Some of them only allow you to use two seconds on/two seconds off pulses and

rest periods. You don't want that (although that's fine for abs since abs should be trained as endurance fibers for ten to fifteen minutes at a time). Instead, look for a machine that allows you to control the rest periods.

You'll want to be able to get ten second contractions with fifty second rest periods.

   The price may also affect the comfort level of the machine, though this isn't always the case. More expensive machines may be more comfortable to use. A machine with higher hertz is usually more comfortable and better for

sprinters, but the battery life will be very short. A low hertz machine has better battery life. Lastly, look for quality in the leads and pads.
 

  • Conclusion


  No, EMS will not give you Arnold's biceps while sitting on the couch, but as you can see, it does have many uses in athletics, rehabilitation, and even for bodybuilding. Just remember, crank it up!

The views & opinions in this article are those of Charlie Francis of Medword.