Muscle stimulation involves the device sending an electrical impulse to the muscle, causing it to contract. The stimulation’s quality, strength and effect depend mainly on its frequency, duration and intensity (current). In this article, I will explain how muscle stimulation works, why it is effective and what is it used for.
Voluntary muscle contraction
You can make your striated muscles contract involuntarily. An electrical impulse from the motor centre of your brain triggers the process. It arrives at the muscle’s “motor point”, the point where the motor nerve reaches the muscle bundle.
The signal from the brain is just the “trigger”, or initiator of the process. However, muscle contraction itself is a complex biochemical process in which the molecules actin, myosin and titin in the muscle fibre move relative to each other and this causes the muscle to shorten and relax. This is an energy-intensive process, provided by adenosine triphosphate (ATP), which is produced in the cells either aerobically (in the presence of oxygen) or anaerobically (in the absence of oxygen). The raw materials for energy production are carbohydrates and fats, and ATP is produced when these are “burned”.
During an anaerobic or inert state, the body produces ATP through its own energy production processes.
Muscle contraction induced by an electric pulse
During muscle stimulation, the machine triggers muscle contraction by sending an electrical impulse to the muscle’s point of movement.
But for the muscle, it makes no difference whether the contraction is triggered by a signal from the brain or from an electrical device! Both produce exactly the same response in the muscle, the contraction takes place in exactly the same way, the same metabolic processes take place, they fatigue in exactly the same way.
It has been shown that repetitive muscle contractions trigger adaptation, i.e. regular muscle movement causes the body to build muscle and optimise muscle properties. Since the contractions produced by muscle stimulation are indistinguishable from natural contractions, their effects are exactly the same.
Regulation of muscle function
Your muscles are entirely under brain control. According to the principle described by Henneman, when a movement is performed, first the smaller muscles contract, then the larger muscles, and within the muscle bundle, first the slow (type I), then the intermediate (type IIa), and finally, if the amount of force required demands it, the superfast (type IIb) fibres.
By lifting a small amount of weight, you can only “poke” your I. fibres. However, these do not give you “mass”, only stamina. If you biceps with a five-kilo weight as an adult male, you can do this exercise a thousand times over, but the circumference of your arms will change by a few millimetres at most.
The muscle mass is mainly provided by the fast fibres, including the IIb (super-strength) fibres. However, they only come into play when you need to exert more than 80% of your maximum effort. If we go back to the previous example and assume you can lift 50kg in one repetition with your biceps (max strength), then to significantly increase your biceps mass you need to work with weights greater than 40kg.
You cannot exceed the muscle size limit at will. Brain regulation will not allow you to contract only your IIb fibers, for example. That’s why bodybuilders, for example, do sets with low reps but maximum weights to develop muscle.
You can stimulate the muscle stimulator directly at the motor point of the muscle, bypassing the brain “restriction.”
Motor neurons supply different fibers at different speeds. With a pulse of the right frequency range, you can therefore contract the IIb fibres without heavy weight! It can be a huge help if the strength and mass of a muscle is not developing at the desired rate. With the muscle stimulator, you can create a strong contraction that cannot be created voluntarily, precisely because of the regulatory system. This is not just me saying this, but also the athletes I have shown the “real” muscle stimulation.
Application of muscle stimulation
The muscle stimulator is a smart device that has a lot of uses.
The effect of the treatment depends on the settings of the treatment programme. It is not the same for relaxation and muscle gain. You can achieve both with muscle stimulation, but in a different way.
It’s just like cutlery. We have coffee forks, tea forks, soup forks, soup spoons, meat forks, dessert forks. Knives for roasts, steaks, fish, desserts. Special tools for cracking crab, mussels, snails. And there’s more. You can’t do with a spoon what you can’t do with a knife. And you can’t do with a knife what you can do with a fork! They’re all cutlery, but they’re all for different things.
A muscle stimulator is like that, a real “toolbox”. Depending on what you want to do, you will need to start a different tool, i.e. a different program.
The effect may vary depending on the stimulation pulse settings. To understand why, you need to know a few things about the fibres and motor nerves that make up your muscles.
Types of muscle fibres
Your striated muscles are composed of three types of muscle fibers, and their ratios are determined by genetics. As per current knowledge, you cannot transform these fibers into one another, and it is from this inherent set of fibers that you must maximize the benefits of your training and stimulation. If you have a predominance of slow fibers, you are better suited for endurance sports, while if fast fibers dominate, you are better suited for short-duration, high-impact activities.
Type I fibre
- These fibers are known as “slow-contracting” or simply slow fibers. The motor nerve (motoneuron) that runs to these fibers has a low conduction velocity, and you can stimulate them with a low-frequency pulse, typically between 1-50Hz.
- Slow fibres are surrounded by an abundant capillary network, which gives them their red colour. They are capable of sustained, continuous, moderate exertion while producing their own energy to function (oxidative metabolism)
- Fibre I fatigue is extremely low.
- If you stimulate this type of fiber, you can improve endurance. You’ll need it for running, cycling, swimming, cross-country skiing, etc.
Fibre type IIa
- Also called type IIb fast fibre or intermediate fibre.
- They have properties intermediate between type I and type IIb fibres. Their motoneuron speed is faster than that of slow fibers, and you can stimulate them with a pulse in the medium frequency range (50-70Hz).
- They can produce energy aerobically as well as anaerobically (both oxidative and glycolytic). With appropriate stimulation, their capabilities can be “shifted” in one direction (slow or superfast)
- Fibers II are capable of rapid and sustained contraction (lasting several minutes) at low energy input.
- Stimulation of this type of fibre can increase strength and endurance, which you need in sports requiring a few minutes of near-maximal effort. For example, martial arts, kayaking, rowing, crossfit, etc.
Type IIb fibre
- Superfast and strong fibre IIb is stimulated by a phasic motoneuron, which is high speed, so it can be stimulated with extremely fast pulses (80-120Hz)
- The fibres are white, due to their high glycogen and glycolytic enzyme content.
- Their contraction is fast and strong, but lasts up to 1 minute, although they are capable of an extraordinary effort.
- The fibres are extremely fatigue-resistant due to the almost complete absence of mitochondria. They cannot produce energy when they are working, so they can only function for as long as their “stores” are sufficient.
- If you stimulate these fibres, you will benefit from them in sports requiring maximum strength and explosiveness. Such as weightlifting, running less than 400m, throwing, jumping, etc.
What does the effect of muscle stimulation depend on?
There are three main characteristics of the muscle stimulation pulse. You can get the best results by adjusting these correctly.
Specifies the number of pulses per second.
The effect of stimulation depends on the frequency
As mentioned above, the excitation of different muscle fibre types is provided by motoneurons with different speeds. Knowing this, you can precisely set the frequency to develop slow fibres or fast fibres.
Low frequencies improve endurance, medium frequencies improve endurance, and high frequencies improve explosiveness and muscle mass. Likewise, you have the right frequency range to improve muscle blood flow or reduce muscle stiffness, etc.
- 1 – 50 Hz – capillarisation, improve blood circulation, relieve muscle stiffness (relaxation), improve endurance strength, stimulate collagen production (beauty treatment)
- 50 – 70 Hz – endurance strenght
- 80 – 100 Hz – strength increase, maximum strength
- 100 – 120 Hz – speed, explosiveness, hypertrophy (mass increase)
Low frequencies create distinct “twitches” in the muscle, while at high frequencies these twitches “fuse” into a single powerful contraction (a bit like what you feel when you have a muscle spasm)
It may be obvious from this, for example, that if your muscles are spasming, you are not using a high frequency (because that will further increase the ability to spasm), but a low frequency, which will have a relaxing effect.
The unit of measurement for pulse duration is the microsecond (millionth of a second). In stimulation terminology, pulse duration is often referred to as amplitude, although technically, amplitude pertains to the height of the wave, and in this context, it is referred to as temporal extent.
At ozonic current intensities, the longer the pulse duration, the more muscle fibres contract.
Each muscle has an optimal pulse duration. The upper limbs require 150-250 ms, the lower limbs 350-450 ms, and the trunk 250-350 ms.
The more fibres in a muscle, the longer the pulse duration required for a complete contraction. If the amplitude is too short, only a small number of muscle fibres will contract, or only under high current intensity, which is painful.
The correct ratio of intensity to pulse duration (amplitude) helps to achieve optimal contraction and at the same time painlessness.
Pulse intensity is actually the current intensity of the pulse. Most devices allow you to adjust it from 1 to 120 mA.
You can induce a contraction with a short, high-intensity pulse alone. The higher intensity will cause more muscle fibres to contract, but at the same time the high current can cause severe pain.
High-quality stimulators use the right combination of current intensity and pulse duration to ensure that as many fibres as possible contract at lower current intensities.
The intensity required for stimulation varies from individual to individual and from treatment to treatment. It also depends on the position of the electrodes, the thickness of the fatty tissue, sweating, the hair on the treated surface and other characteristics.
The same current intensity can produce different sensations from day to day. Even within a treatment, the intensity should be constantly controlled to maintain the same level of contraction.
Do not go above the pain threshold during warm-up, endurance, capillarization, or regeneration (usually low-frequency) treatments! Medium, well-tolerated, visible twitch-inducing pulses are appropriate.
In contrast, when developing strength, muscle mass, and explosiveness, it is worth constantly adjusting the intensity of the impulse to the pain threshold. This will give much more efficient and faster results.
Positioning the electrodes
Accuracy of positioning
The placement of electrodes is essential for effective muscle stimulation. You may feel clueless when you first try a muscle stimulator. But fear not, despite the complete lack of accuracy, the treatment still works! However, understanding a few basic principles of placement will be an important aid to using stimulation correctly. However, if perfection is your goal, buy a motor point pencil. This will help you to map the exact point where the muscle-motor nerve meets. Once you have that, there’s nothing to stop you from getting the perfect treatment.
Where to place the electrodes on the muscle
Place one of the electrodes on the part of the muscle that bulges the most. It is also known as the active electrode because it aligns with the motor point where the motor nerve enters the muscle.
Place the “inactive” electrode at the muscle’s end. Both electrodes should stay on the fleshy part of the muscle! From where the muscle continues into the tendon, there are no nerve endings. Tighten the muscle you want to treat and feel all the way through. Determine how far it is “soft” and where it goes into a tendon. Place the electrodes only on the muscle.
High-quality devices come with diagrams showing electrode placement. If you “copy” the below, you shouldn’t have too much trouble. But feel free to experiment! Move one electrode left and right, up and down a few mm and observe the effect. You’ll soon find out which is the most effective point.
The imaginary line connecting the pair of electrodes should follow the direction of the muscle fibres. This is usually parallel to the direction of pull of the muscle. If you place the electrodes crosswise instead of this way, the muscle will twitch and you may feel cramping pain. This is because the current exiting the electrodes forms a closed circuit on the muscle and hits several nerves at once.
Locate in the direction of the muscle fibres. Properly closing the circuit reduces the resistance encountered by the electric current. This is important to maintain a strong contraction and also improves your sense of comfort.
The intensity of the stimulators
Professional muscle stimulator users usually raise the current to the limit of tolerance, well below their pain threshold. Tension passing through the skin triggers the pain.
Run a warm-up program first, because you can then treat with higher current (more intensity). Warming up stimulates blood flow to the muscles, and more blood (fluid) reduces resistance. With lower resistance, a lower current is sufficient for the effect. If the voltage is low, you will feel little to no “pain”. In simpler terms, warming up allows you to withstand higher intensity due to decreased tissue resistance, improving the effectiveness of muscle stimulation.
You can achieve the following with some of these devices:
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