We have aggregated all the important information about EMS and TENS gadgets. You will find a review of 8 muscle stimulators and will be able to choose the best one.

What is the best muscle stimulator? Don’t make a mistake — use only trusted brands when it comes to your health! It is important that the device has a varying intensity of the electrical stimulation and the optimal treatment time. Since you will use the unit regularly, rechargeable models have an advantage over battery-run ones. In our assessment, Compex Edge Muscle Stimulator Kit meets all the criteria and can be considered the most effective gadget in the market.

The product has become popular among many sportsmen. So Frederik Van Lierde, a Belgian professional triathlete and world champion, thanked the company for contributing to his success: “Compex helps me in every concept to improve. To recover faster and better so that I can train harder to get stronger.”

As to the wireless EMS machines, we think that iReliev® is the best trusted muscle stimulator for the money. For $189, you receive a wearable EMS and TENS therapy device with 7 pain relief, 1 arthritis, and 6 muscle conditioning modes.

Best Electric Muscle Stimulators

Gadgets acting on human muscles with the help of electricity have been existing on the market for dozens of years. Their reputation has undergone changes during this period. First portable muscle stimulators were insanely famous an immediately became TV shop hits as ads promised quick muscle growth without much effort. Disappointment in EMS followed soon enough once people realized that it’s impossible to become a jock without training and dieting.

However, EMS gadgets did not disappear over time as the consumers still managed to find use in them. Obviously, they won’t turn a skinny geek into Conan the Barbarian, but they will help during recovery or as pain therapy. Pro athletes use them during complicated training sessions or when rehabilitating after injuries. Add to that the fact that it is a drug-free method, and you will understand what a beneficial approach it is.

Electrical Muscle Stimulation has long been known to humanity. Scientists discovered electricity’s ability to cause motion in human muscles back in the 18th century. However, no useful application to the invention was found for the first century and a half. No scientist went further than weird experiments (oh look, a dead squirrel’s paw is jerking!) and fantasies about Frankenstein.

How USSR Wanted to Increase the Strength of Weightlifters by 40%

Soviet scientists realized that electrical muscle stimulation hides a load of potential in the 1970s. They began to study the possibilities of using electricity for the rehabilitation of paralyzed patients and for increasing athletes’ muscles.

NCBI has published an interesting article devoted to those experiments. Soviet researchers set amazing goals as they aimed to improve weightlifters’ strength by 40% with EMS. They believed that combining muscular stimulation with conventional training will lead to great achievements.

It is at that time that USSR became the world leader in all weightlifting sports. This could indirectly confirm the effectiveness of this new technology, but the results of the experiments were quite contradictory.

Soviet science concentrated on the medical application of EMS, and the idea abandoned by Soviets was revitalized in the USA where clever businessmen decided to make money on people’s desire to have a perfect body with minimum effort.

Does Electrical Muscle Stimulation Work?

First, portable muscle stimulators and wonder-belts promising to develop abs and pumped biceps with zero stress appeared in the 80s. Allegedly, you could watch TV and grow muscles. Soon, the authorities intervened in the market of EMS gadgets. None of them received a certificate of a weight-loss device. Ads promoting non-existing properties of these devices were also banned.

According to the FDA, EMS was certified as a means of treating muscular atrophy and spasms but not as a muscle growth stimulator.

Nowadays, EMSs are sold both for medical and athletic purposes. They are recommended for recovering and strengthening muscular tissue, for support during complex training, for improving blood flow, as well as for treatment of some musculoskeletal diseases. Some experts keep insisting that combining training with EMS results in synergic muscular growth. This hypothesis has neither been 100% proved nor refuted.

There is a number of studies that have proven the effectiveness of EMS in improving sportsmen's strength and jumping ability. Tests conducted with the participation of rugby players showed improvements not only in strength but also in power. A study on groups of tennis and soccer players has indicated a positive impact of EMS treatment on sportsmen's performance as well.

Our body is designed so that electricity contracts muscular fibers. EMS imitates our central nervous system so that the correct setting of the electric signal can help you bring such contractions closer to healthy training. Muscular movement guarantees to accelerate blood flow in the veins, can have an impact on the production of lactic acid and improve muscular elasticity.

It’s important to distinguish EMS (electrical muscle stimulation) and TENS (transcutaneous electrical nerve stimulation). EMS-marked gadgets act on muscles directly while the impulse of TENS devices is set to affect the nerves.

EMS (Electric Muscle Stimulator) causes relaxation, blood flow recovery and creates conditions for muscle growth, while TENS helps eliminate neck pain, arthritis, sciatica, and other forms of neuritis. These gadgets are suggested as good therapy for chronic pain.

EMS and TENS Action: photo

By the way, TENS is ancient technology. Ancient Romans made people with leg ache stand on electric fish, as historical sources testify. In the 19th century, doctors officially confirmed the effectiveness of electrical treatment.

The bottom line is, make sure you can tell EMS and TENS apart, even though certain gadgets combine these technologies with various levels of success.

Can Electric Muscle Stimulators Help Grow Muscles?

As we have mentioned above, several studies have proven that when used in combination with training, an EMS unit can help sportsmen become stronger and faster. So Kayvan Seyri from Still University of Health Sciences based in Missouri has revealed that the application of electrical current to the muscle results in involuntary contractions.

Moreover, he refers to other studies indicating that there are differential results depending on whether an EMS machine has been used for a short period of time (less than 3 weeks) or a longer period of time (about 12 weeks). This means that the technique has an accumulative effect or, put it otherwise, the more you use the device the better the result is.

Expensive and powerful medical equipment is capable of maintaining the muscles of paralyzed patients. Ultra-expensive sport EMS machines are used to train top athletes of the world. Perhaps these gadgets even tone their muscles. However, no mass-market product has yet proven its ability to really grow the buyers’ biceps and triceps.

Jerry Brainum, a nutritionist, draws our attention to one important detail: during regular exercise, our body first activates small and weak muscular fibers followed by larger ones, while EMS first involves the latter fibers (larger ones followed by weak ones). It seems that under such circumstances, the muscles are bound to grow, but the expert refers to scientific research and disappoints us by saying that this works in theory only.

Effective muscle growth is possible only if gadgets 60 times as powerful as the ones existing today are used (the impulses, though, will no longer be safe for human health).

Brainum also refers to an experiment involving students. One group trained in the gym for 45 days, while the other group worked with EMS gadgets for the same period. Unfortunately, the second team was far behind in all metrics. Moreover, all of the test subjects were bored during the electric workout and craved to go to the gym. C’est la vie!

personal trainer Pedro Bernardes: photoPedro Bernardes, an expert on fitness and sports equipment at Gadget Reviews, explains what factors contribute to developing strength.

“The main factor for strength development (almost 60% depends on this and it’s even greater than muscular factors like muscle size) are the neuromuscular factors like motor unit recruitment and stimulus. This is the process where it acts,” he said.

Now, how and where exactly does this technology work? The idea is quite simple: the EMS equipment is supposed to elicit muscle activity by means of electrical current.

Specialists from the University of Delaware note that this technology mimics the brain’s activity. The brain sends signals to the muscles which contract, responding to this stimulus. Something similar is happening when the EMS machine is applied, where the brain’s function is performed by electrodes placed on the body’s skin. These electrodes pass electrical current released by the machine and this is how your muscles are stimulated.

How does EMS differ from natural muscle contraction

Is there any difference between naturally contacting muscles and those stimulated by the machine? Yes, there are. When your muscles contract naturally, smaller motor units and slow-twitch, Type-I fibers are recruited first. And only then, the Type-II fibers are activated. While EMS works in reverse order, bypassing neurological coordination, something that makes the stimulation faster.

Another important distinction is that the brain activates the fibers gradually, one by one. This conserves energy and prevents our bodies from being exhausted too fast. The EMS stimulation is harsher at it affects all motor units at once, resulting in all the fibers contracting simultaneously.

What are the physiological changes?

Muscle stimulation leads to physiological changes, which happens because the affected muscles adapt to their intense use. Specialists from the University of California note that different muscles are sensitive to different electrical input. While skeletal muscles are activated at low frequencies, those with a high proportion of fast fibers tend to respond to high frequencies and in a discontinuous way only.

They have found that as a result of 24-hour muscle stimulation at a frequency of 10 Hz, there was “a well-defined progression of changes” whereby “the fast muscle first changes its metabolic and then its contractile properties to completely "transform" into a "slow" muscle”. So fast fibers turn into slow fibers, changing in appearance and obtaining a darker color. This means that the stimulated muscles can create a structure consistent with functional requirements.

What about weight loss? The amount of calories burned during electric workouts is considered marginally low by Nicola A. Maffiuletti in his publication devoted to electric stimulation. Other scientists confirm this and emphasize the fact that only physical exercise involving various muscle groups simultaneously leads to weight loss.

Of course, EMS is not surrounded by negative feedback only. The latest research proves the positive effect of electricity on the adaptation and learning of muscular fibers, improving their stamina and stress-resistance, which is crucial to a systemic training approach.

Gadgets not only vary by the type of technology used (EMS or TENS). Other differences exist, such as in devices’ modes, in the power of the electric impulse, mobility or dimensions of a gadget.

EMS abs belts are most popular. Certain sensors are designed to train legs and arms. However, nowadays the market is flooded with universal devices connecting various sensors to the control section. They are convenient as they can be attached to various body parts to activate different muscle groups simultaneously.

An FDA certificate is crucial for products distributed in the USA. It is only legal to sell certified devices; the consumers will bear all the risks at their own expense if they buy uncertified units. We recommend that you check the FDA database before buying a certain device, especially since the blacklist is constantly updated.

  1. First of all, EMS trainers have a large list of contraindications. Using these devices is contraindicated to pregnant women, heart disease patients, those who have cardio stimulators, patients with renal insufficiency or chronic diseases of the digestive tract. Oncology or blood flow problems are also a reason for an EMS or TENS ban.
  2. Experts recommend consulting a physician before using any gadget, especially if you have recently been ill with flu, cold, broke a bone, ruptured a ligament or damaged a muscle. Be careful with electricity!
  3. As for increasing the effectiveness of EMS, most manufacturers give the following recommendations. Instead of training your back, abs and ankles simultaneously, focus on each area in turn. Even wiring both limbs disperses the current.
  4. Start the gadget when the muscles are relaxed, do not stimulate flexors and extensors at the same time. Be careful about fixing the sensor on a muscle as improper fixation can give zero results.

Best Electric Muscle Stimulators

Best EMS Machine

1. Compex Edge Muscle Stimulator Kit for Pain Treatment, Back Pain, Rehabilitation, Muscle Growth & Strength — Best Professional


Compex Edge Muscle Stimulator Kit: photo

This is the most expensive gadget of our review; its price is 6-7 times higher than that of the main competitors.

First, we deal with a large Swiss brand. Compex is a manufacturer of medical and sports electronics, and many of its products are respected both by the mass audience and pro athletes. By no means is Compex a no-name brand, so your claims will surely be handled, should any arise.

This is the only device in this rating that promises to grow muscles without stressing heart and lungs. The gadget’s main aim is still pain relief and improvement of blood circulation. The manufacturers promise to strengthen capillaries and improve muscle flexibility. Compex can allegedly increase blood flow up to 600 percent faster and reduce lactic acid production in 4-6 minutes.

The product description contains an important disclaimer: Compex Edge is recommended for professional use so that athletes stay in shape. The brand is known to collaborate with pro athletes, so it can be trusted. The stimulator has four wires with two sensors each. Electrode sensors are made with the brand’s own technology, and two sucker sizes are available. In the comments, the customers praise the gadget’s durability and long autonomous performance. Read all customer reviews

There are only three modes instead of dozens: muscle recovery, training, and intensive training. Each mode has been designed using medical expertise, and you can read all the details regarding lactic acid distillation and various muscle fiber exercises.

Compex Wireless & Sport Stimulator: photo

By the way, this is not a single product; there is a whole range of Compex stimulators. For instance, you can find a wireless stimulator and Sport Elite stimulator.

Compex Edge Muscle Stimulator Kit: Check the current price

2. iReliev® Wireless TENS + EMS Machine — Best for the Money

Wireless Therapeutic Wearable TENS EMS System: photo

Why do I trust iReliev? This brand belongs to ExcelHealth, a company that develops FDA-cleared devices for electrical therapy, offering a wide range of products including muscle stimulators. By the way, the company's CEO Mike Williams was announced a finalist for the Entrepreneur Of The Year 2019 Award. The award was established by Ernst & Young LLP, one of the world's largest professional services companies, and is among the most prestigious awards in the U.S. 

Let’s start with the Wireless Therapeutic Wearable TENS and EMS System. It will cost you $189 and is significantly more affordable than Compex. That said, the device uses medical-grade technologies and shows high performance. The company apparently bets on simplicity and convenience of its products, which is why it is so user-friendly. You will be able to move around the house while getting treatment and, from my experience, this encourages to apply it more frequently, enhancing the effect.

With a weight of just two pounds, the device is rechargeable, which makes it more cost-efficient. As a rule, it takes about an hour and a half to charge the receiver and over two hours to charge the remote. The unit comes with a 1.22-inch LCD display that is backlit for your convenience.

Add to that the unit’s portability and quick setup, and you have a truly indispensable machine that you will want to have always at hand. For better results, you may add extra pods, which will allow you to cover a larger area of your body at a time.

While being easy-to-use, the electric muscle stimulator is very powerful, effectively helping you to manage pain and recover the muscles. The device includes 14 programs, eight of which are intended to mitigate pain. The timing can be set in five-minute increments for up to one hour per session. The product comes with a two-year warranty, which speaks to the manufacturer’s willingness to stand behind the product. But, if anything, you may return the stimulator within 45 days.

What do buyers say?

Customers seem to be fully satisfied with iReliev products and some of them have even purchased more units for their family members. Check out this video by Rick, an American pilot working for the government, who has been told that he needed shoulder replacement surgery. He was undergoing physical therapy and his doctor suggested that he got a machine to do that at home. So he purchased one of the iReliev machines on Amazon.

Rick says that since he started using the unit, he has got as good relief as he did at the therapist office. Now he has a greater range of motion and less pain in his right shoulder and left foot. Rick set the machine on the program five and an intensity level of 12 which is actually very intense. Of course, you may not need that level of intensity and can choose other settings if you like.

Wireless iReliev®: Check the current price

3. PlayMakar PRO Electrical Muscle Stimulator | Best for Athletes

PlayMakar PRO Electrical Muscle Stimulator: photo

The PlayMakar® unit stands out among other new, young, and innovative brands that are engaged in the production of medical-grade athletic training muscle stimulators for professional athletes. What makes it different from others is that the company’s team includes professional sportsmen. And, as you might be aware, these guys know the stuff better than anyone else.

This muscle stimulator features 14 different programs and 25 intensity levels. Also, the product comes with 4 pods and a durable battery that lasts for up to 10 hours. A nice set of features, isn’t it? In this video, you can see in what ways this muscle stimulator can be helpful. This is a great tool to recover faster, train stronger, warm up safer, and manage pain easier.

So what do athletes say about the PlayMakar PRO? Philadelphia 76ers’ basketball player Trey Burke is one of the athletes who has chosen this muscle stimulator. He takes the unit with him to warm up before a game and recover from workouts. Preparatory exercise is critical in such a demanding sport as basketball, which is why Trey has incorporated PlayMakar PRO into his warm-up.

Professional bodybuilder J Warren has been playing sports all his life. Today, PlayMakar PRO has become a critical tool for his preparations for competitions. “I’m speeding up my recovery so I can perform for me and my clients by using PlayMakar,” he says.

PlayMakar: Check the current price

4. iReliev ET-7070 Wired Muscle Stimulator | Best Cheap

iReliev Combination Unit Muscle Stimulator: photo

You may buy even less expensive model — iReliev ET-7070 TENS EMS Muscle Stimulator. Unlike the previous product, this one is wired and, therefore, less convenient. But keep in mind that you get it for half the cost. That said, this model has become very popular among customers and is widely available on the market. This machine comes with the same number of programs and has 25 intensity levels. The therapy timer is adjustable and can be set for up to one hour of continuous use.

Compared with the wireless option, this model has a larger LCD display (1.4 inches) but is smaller in size and is two times lighter. So if these features are important for you, ET-7070 may be exactly what you need. Based on customer reviews, I have concluded that this machine is especially popular with people who suffer arthritis. One of the purchasers recommends the product for those who have to travel a lot because it is lightweight, easy-to-use but comes in a sturdy case.

I’d like to draw your attention to the fact that iReliev products are recommended by healthcare professionals. For example, Joe Noel, Physical Therapist in Florida, recommends the iReliev unit for treating pain and stimulating the muscles at home. Moreover, he has been using this device in his clinical practice for many years, which is the clearest evidence of the product’s efficiency.

iReliev TENS + EMS Wired: Check the current price

5. Compex Mini Wireless Electric Muscle Stimulator | Smartphone Compatible

Compex Mini Wireless Electric Muscle Stimulator: photo

If you want something more portable, try this option. The unit connects to your smartphone and is Bluetooth-controlled from both Android and iOS devices. With a weight of 0.32 ounces, this mini electric muscle stimulator is very convenient in use. Since it is wireless, you will not be dependent on a power outlet. With this device, you will get your therapy anytime and anywhere you need it! The battery is rechargeable and lasts for up to 7 hours on a charge. The stimulator comes with 6 programs for different goals — enhancing blood flow, relieving muscle soreness, loosening stiff muscles, and pain relief.

Compex Mini: Check the current price

6. TENS 7000 2nd Edition Digital TENS Unit for neck pain, carpal tunnel relief, arthritis, shoulder, knee, elbow, leg and foot pain

Edition Digital TENS Unit with accessories: photo

This is a very popular product with nearly 6000 customer reviews. This gadget looks more respectable as it resembles pro medical equipment. A large screen is replaced with a small technical one with two sections, and the streamlined plastic case is replaced with rubber and metal elements. All four control buttons are covered by the protective lid on the rear side.

The wires connecting the sensors are more solid and thick than those of the competitors (they are made of lead). However, it has the least amount of sensors in our review: only four. A firm case can be used to transport the gadget.  

This is a very powerful and affordable stimulator. Note that incorrect settings can turn it into an electric shocker, so the first try of TENS 7000 can be painful if you ignore the manual and don’t adjust the settings. This unit stores up to 60 sets of operation records, with the total recorded time amounting to 999 hours.

There are five consumer modes available, which is less than in other products. However, each mode combines a predefined set of speed, intensity and power, so you don’t have to adjust them manually. The powerful 9A battery is supposed to provide 48 hours of continuous performance.

Roscoe Medical 7000: Check the current price

7. FDA cleared OTC HealthmateForever YK15AB

HealthmateForever Electronic Pulse Massager: photo

Judging by the amount of feedback, this must be the most popular product for pain TENS therapy. The gadget uses 8 suckers and has 15 modes. Its design resembles a TV or an AC remote control. It has a small screen but also a bunch of backlit buttons. Each button is labeled and turns on a particular mode, e.g. “Shoulder”, “Back”, “Elbow” or “Ankle”. Such control is more user-friendly for many customers than having a single button for everything. A rear strap allows attaching the gadget to jeans or a shirt pocket. Many competitors haven’t implemented this convenient option in their devices.

A control, four sets of wires (with a sensor at each end), eight sucker sensors, a holder and 3 AAA batteries are supplied. A manual and body atlas are also available.

The manufacturer deserves extra credit for consumer responsibility as the contraindications (which are often not even mentioned by competitors. Familiarize yourself with the list before you buy this product!

star Excerpts from buyers’ reviews star

«I had a 400lbs patient fall on me 3 years ago, blowing out 2 disks in my lower back, and I've been a mess ever since. But one night with this machine and I already feel much better. On my first night, I already have it on the 4th intensity setting for my low back and 3rd for my mid».

«I'm recovering from whiplash soft tissue neck injury from being rear-ended. The first 2 days I was in even more pain, but now I am doing much better. The seller emailed to make sure the product was not only received but to make sure it was as excepted. I think that is an awesome service. Thank you».

Healthmate: Check the current price

8. FDA Cleared Muscle Pain Tens Unit, Ohuhu

Rechargeable Electric Muscle Stimulator Machine: photo

It has 16 modes and 12 electric sensors (six of them can be attached simultaneously) to be fixed on the muscles. Ohuhu’s advantage is definitely its large informative display.

Everyone has faced a situation when a gadget claims to have plenty of possibilities and modes that are very difficult to handle as a small screen and unknown icons confuse you. Here, the screen is divided into sectors providing information about performance (from head massage to acupuncture). Moreover, time, intensity and power of the session as well as the battery charge data are output on the screen.

The manufacturers recommend buying this gadget to relieve muscular pain, normalize blood flow, sleep, and even stomach processes. They honestly warn that Ohuhu won’t inflate your muscles and will only relieve pain. A session can be set to last from 10 to 60 minutes with 20 stages of massage intensity.

What are other advantages of this device? Suckers do not require any gel as they are sticky (up to 6 large and 6 small two-foot wired sensors can be connected). The battery lives for up to 10 hours and is charged via USB. The device itself is rather small: its dimensions are 8.7x6.5x2.3 inches. Twelve suckers, a manual, a body atlas, a USB cable and a charger are supplied. The quality of translation of the manual from Chinese to English leaves much to be desired, though.

star Excerpts from buyers’ reviews star

«I was diagnosed with Frozen Shoulder. I go to the chiropractor every 2 weeks and they use the TENS on my back and shoulders. I've been using it in the morning for about 20 minutes and have not had to take medication during the day time for pain. I've also decided to use it for other areas of pain, my right knee, left forearm and my right foot (plantar fasciitis)».

«I have rheumatoid arthritis and my shoulders were killing me, so I purchased this. It came with 12 gel pads, 6 large and 6 small, a charger, charging cord, a diagram of where to place the pads for the relief you want, 2 sets of connector cables and a charging cord. I love that it not only has adjustments for the intensity and duration, but I found it also gives you additional adjustment options within each mode setting».

Ohuhu: Check the current price

Electric Muscle Stimulators Comparative Chart

Product Features

Compex Edge Silver

Type: EMS

3 modes

Trusted Swiss brand

The treatment lasts 4-6 min

Rechargeable battery

4 electrode wires of two different sizes

iReliev TENS + EMS

iReliev Combination Unit Muscle Stimulator min: photo

Type: TENS + EMS/Electric Muscle Stimulator

Trusted U.S.-based brand

14 modes

Small size and portable

4 electrode sensors

The treatment lasts 5-60 min

Roscoe Medical 7000

Type: TENS

Trusted brand

5 modes

4 control buttons

Stores up to 60 sets of records

Comes with a protective lid

Run on 9A battery

Compex Wireless EMS

Type: EMS

9 modes

Trusted Swiss brand

16 snap electrodes

The treatment lasts 4-6 min

Rechargeable battery

Wireless PODs


Compex Sport Elite

Type: EMS

9 modes

Trusted Swiss brand

The treatment lasts 4-6 min

Rechargeable battery

4 electrode wires of two different sizes


Type: TENS

16 modes

12 electric sensors

Rechargeable battery

The treatment lasts 10-60 min

HealthmateForever YK15AB


15 modes

Backlit buttons

Comes with a rear strap

Runs on 3AAA batteries


What is the best muscle stimulator?

Compex is definitely the most trusted brand in the market and is a device that is really used by many professional sportsmen, including champions. This is a great stimulator as over the course of a 6-minute treatment your blood will flow 600 percent faster!

The best wireless for the money is iReliev TENS+EMS machine.

Read a detailed insight into trusted electric muscle stimulators in our Buyer's Guide - Best Electric Muscle Stimulator Reviews.

Apart from Compex Edge Silver, a standard option, there are other models of this brand: Wireless EMS and Sport Elite models. These devices have three times more modes and as many as 16 snap electrodes. So if you are dreaming about great sports achievements, these ones are likely to significantly contribute to your success.

How long does TENS treatment last?

It depends. Pain relief may last only as long as the device is operating or for a longer period of time — up to one day. In some cases, even though the pain returns after the treatment, it is not as intense as it was before the stimulation. Read more...

According to Ailsa Wright, a clinical nurse specialist at Sandwell and West Birmingham Hospitals Trust, the more often you apply TNS therapy, the longer the effect is. In other words, it tends to accumulate.

On the other hand, the repeated TENS treatment may result in increased tolerance to it. Therefore, there is no uniform rule on how long the therapy should last, with its recommended duration varying from 20 minutes to several hours.

Is TENS treatment safe?

Generally, this is a safe method of pain relief that does not involve any side effects. And yet, there is a number of contradictions for using these devices. Read more...

The website of the UK Department of Health and Social Care mentions the following ones. First, those people who have metal implants in their bodies should consult a doctor before applying this therapy. Secondly, it is not recommended for pregnant women and thirdly, this gadget should not be used by those who suffer epilepsy or heart issues. Apart from that, the TENS pads may cause allergy symptoms in some people. This is why some manufacturers offer special pads for people with allergies.

How many modes should the unit have: 3 or 15?

It depends on whether the unit combines both EMS and TENS treatments or focuses on a single method. However, keep in mind that the rule "The more the better" should not be applied here as it is the technologies used that make the device effective.