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Sculpt, Firm, and Tone Your Muscles Quickly and Easily
“Sculpt, firm and tone your muscles with the quick, inexpensive solution,” the Ab Sonic!! (http://www.achievecn.com) There are several exercise devices out there that advertise losing weight, 6-pack abs, and hard bodies with the use of a simple belt. Products include Ab Sonic, Ab Tronic, Ab Gymnic, Ab Energizer, Fast Abs, Alpha-Wave Healthtronic, Ultratone Futura Plus, and the list goes on. As we have all seen on TV, the ads state that by using the fitness belt it is possible to burn fat and build muscle without the hassle of gym memberships and without even breaking a sweat. Use it “while you’re walking you dog, washing the dishes, reading a book or watching TV; at anytime, anywhere” and you can even hide it under your clothes (http://wonderfulbuys.com). But how does it work?
The Ab Sonic and others are called electrical muscle stimulators (EMS) or iontophoresis devices. They use electrical shock to stimulate the nerves causing contractions in muscle several times per minute. With a 10 minute “workout” 5 days a week, you can have hard sexy abs without breaking a sweat. Most products have up to ten different intensity levels and multiple training modes. “You will know its working, because you will feel a tingling sensation in your muscles” (http://abenergizer4less.com). Ads claim that by electrically stimulating the muscles, calories are burned and muscle is built thus reducing the waist line and body fat. Some come with multiple cuffs so that the electrical pads can be placed anywhere on the body. The electrical signal is transmitted through the skin into the body. To avoid burns a water based gel is applied to the electrode to avoid a current hotspot and prevent electrical burns.
A few of the advertisers do remark that “with consistent use and a balanced diet you will start seeing results in 4 weeks” (http://www.achievecn.com). Disclaimers also state that no cardiac benefits are seen by the Ab Sonic. The Ab Energizer even has a warning to use it according to the directions, start off light at a low intensity and use it only 5 days a week otherwise, it can be harmful to your body. The ab energizer also comes with a 30 day full refund guarantee (http://abenergizer4less.com).
A muscle cell, called a muscle fiber, is composed of many tubular structures called myofibrils. Several muscle fibers are grouped together and wrapped in a layer of connective tissue, and several of these bundles make up a muscle. Within each myofibril are the contractile units of the cell. Protein filaments are arranged in a spatial pattern to maximize overlap of the fibers. There are two kinds of fibers: thick filaments called myosin that perform the actual pulling, and thin filaments called actin that is pulled. The organization of these contractile units gives the muscle a striped or striated appearance.
The key to muscle contraction is in the interaction between these thin and thick filaments. When the muscle is excited, Ca2+ rushes into the sarcomere, where the filaments are arranged, from the sarcoplasmic reticulum, a storage area for Ca2+. The intracellular Ca2+ causes a conformational change in the thin filament by moving a band called tropomyosin. This exposes binding sites on the actin to which the thick filament attaches. The thick filament goes through a conformational change that pulls on the thin filament. This action is called a power stroke and requires ATP for energy to release the thin filament. More ATP is used to pump the Ca2+ back into the sarcoplasmic reticulum to stop contraction (Sherwood, 2004). This happens several hundred times all along a single muscle fiber for contraction of the cell.
A muscle cell is excited by a nerve fiber at a neuromuscular junction. There are normally several neuromuscular junctions along the muscle fiber so that contraction can occur simultaneously along the cell. A single action potential is a wave of charges moving down the axon of the nerve fiber. When the action potential reaches the end of the axon at the neuromuscular junction, the chemical acetylcholine is released into the synaptic cleft. This causes receptor proteins on the surface of the muscle to start an action potential which eventually travels down into the cell via T-tubules and stimulates the release of Ca2+ which causes a contraction. The nerve can be artificially excited by causing ion currents to flow around the cell and triggering the voltage-gated channels on the axon's membrane. This is how it is possible to use an electrode on the skin to contract a muscle. A voltage is put across the electrodes of the EMS unit. The current produced is transferred into the patient through a conducting gel or water. The current causes a change in extracellular potential that stimulates an action potential. The same process as the natural phenomena of propagation and muscle excitation then occurs at all of that nerve's muscular junctions.
A single nerve activates more than a single muscle fiber. Each nerve controls a group of muscle fibers that are normally spaced throughout the muscle tissue. A motor unit is a single neuron and all the muscle fibers it controls (Campbell, 2005). A single action potential from the motor neuron excites all the muscle cells as a group. This is how the body controls the force output by the muscle. Muscles with fine precision such as the ones in our hands and the ones used for posture contain fewer muscle fibers per neuron than the larger muscles of, for example, the legs. The force produced by the muscle can be varied by the number of motor units working at one time, the amount of overlap in between the thin filaments and thick filaments and the frequency at which the motorneurons are firing. The action potential of nerves lasts only about 1-2 milliseconds, but the action potential of the muscle lasts much longer, approximately 100 milliseconds, because the contraction lasts as long as Ca2+ is still floating around. Each action potential induces what is called a twitch. When a muscle is excited repeatedly by the neuron, the muscle may not completely relax before the next excitation comes along. This is called twitch summation and if it continues to occur then a state referred to as tetanus occurs. Tetanus is when the muscle has no time to relax so the muscles stay completely contracted (Campbell).
Some EMS devices excite the nerves at a slow enough rate that the single twitch has enough time to relax completely before the next one occurs, but others rely on the rapid rate of excitation to reach a tetanic contraction in hopes of increasing strength. In tetanus, the muscles exert a strong force and the patient would feel discomfort and uncontrolled movement. Many of the EMS devices instead come with adjustable power settings that allow the user to adjust the amount of current entering their body. This in effect changes the number of muscle fibers contracting by increasing or decreasing the number of nerves stimulated by each pulse.
The claims that the EMS devices burn fat stems from the fact that muscles use ATP. Single twitches are hardly strong enough to feel so by exciting the muscle to perform single twitches, energy in the form of calories are burned. Muscles get their energy in several ways depending on the type of muscle cell. The first muscle source of energy is from creatine phosphate. A reversible reaction occurs by kicking off a phosphate group from the creatine and adding it to ADP to form ATP. This ATP can then be used by the muscle. Creatine phosphate is only a temporary store of energy and is both used and regenerated quickly. When oxygen is present in the blood, mitochondria within the muscles cells can utilize the electron transport chain to take the energy stored within O2 and glucose, and transfer it into ATP producing CO2. This is the ideal method for energy production of the muscle. Glucose is also used in this process. Glucose is the sugar found in the body that is easiest to use. Sugars that are consumed by the body are converted into glucose for fast, easy energy. When the glucose level in the blood falls, glucose is added to the blood from stores within the body. The body can use proteins and fat to produce more glucose and therefore supply the muscle with energy. The claim that EMS devices can burn fat seems logical and is definitely possible given that the EMS can stimulate the nerve effectively. The other method for muscle energy in the absence of O2 is anaerobic. This method is not relevant to the slow twitches caused by EMS.
It is also possible that through electrical stimulation muscles can gain efficiency or strength. In normal aerobic muscle exercise, the muscle uses large amounts of oxygen and this induces vascularization of the muscle tissue leading to better blood flow and better efficiency for aerobic metabolism. This increase in blood flow may cause a noticeable change in muscle size within only a few weeks, but no increase in strength. An increase in endurance can also occur by using muscles aerobically. Muscle cells may produce more mitochondria to help handle the load of ATP production within the cell. Finally, the strength of muscle is normally increased by the production of more filaments within the cell, not more cells. The use of muscles may cause this result, however this is usually the case for anaerobic exercise in which a fast, strong pull is needed with more muscle fibers. Once again, since the EMS devices do not directly control muscle actions, so it is plausible that the stimulation through the nerve can cause the same effects as natural exercise stimulated from the brain.
First of all, EMS devices have been around since before 1970 to help with therapy for muscle atrophy (Porcari, 2002). The EMS devices grew in popularity over the 1990s and were used in weight training. There is no doubt in the medical community that it is possible to transcutaneously, that is, through the skin, stimulate nerves. A variation of EMS is transcutaneous electrical nerve stimulation (TENS). TENS is a pain management system that uses less intense shocks to block pain signals. EMS can also be used on strained muscle to stretch it out and relax the muscle. The question about EMS is can it really burn enough calories to reduce a waistline, decrease body fat, and strengthen muscles?
Although it is not a scientific article, one EMS device from www.bodyshapers.com has more modest claims. They advertise that the EMS has been "proven to exercise muscles fast, efficiently, and effectively through a series of stimulated contraction and relaxation phases". Body Shapers also says that a forty-five minute treatment can be equivalent to 300 sit-ups, but on the other hand they say, "EMS does not 'burn calories'…. To burn calories you must expend energy, as EMS is 'passive exercise' this is not possible". Although the Body Shapers is a website with the objective to sell you a product, their claims are a little bit more modest than the others that claim inches off your waist.
A full research study was conducted at the University of Wisconsin and published in 2002 by Porcari et al. The study was to test the claims of EMS manufactures on there marketing of "rock-hard abs" and other weight loss claims. They took 29 college aged students that had not been in a formal exercise program within the past 6 months and assigned them to either a treatment EMS group or a control group that was given faulty EMS equipment. The subjects body weight, body fat percentage, girths, and isometric and isokinetic strength of key muscle groups and a self- perception survey were all taken. The groups were shown how to use the equipment and came in to use it 3 times per week for 8 weeks. 16 treatment and 11 control subjects completed the 24 stimulation sessions. Over the course of the eight weeks, the intensity of the electrical pulses was increased along with decreasing the resting time between pulses. The subjects used the device made by body shapers on five muscle groups: bilateral biceps, triceps, quadriceps, hamstrings, and abdominal muscles. The results showed no significant changes in weight, percent body fat, girth or strength of the treatment areas. The EMS device did not work for any of the claims. There were a few significant changes, but both groups experienced the same changes which makes it negligible. The proposed mechanism for muscle growth is that the muscle must be stimulated beyond a certain threshold of the maximum voluntary contraction in order for there to be a response of building more muscle. The EMS device caused burns most likely due to a thin area of water conducting a significant amount of charge causing the skin to burn. The conclusion of the study was that over the counter EMS devices fall well short of the expectations and should not be used by apparently healthy people.
The FDA responded to the claims of these manufacturers and put out a report on the validity of the claims. Several of the makers are overseas and do all business by mail order to get around the US regulations. The devices are not in compliance with 21 CFR which is the FDA codes on food, drugs and medical devices. The report from the FDA IA #89-01 was published in 2006. The report states, "These electrical devices are prescription devices and are misbranded when labeled for lay use. In addition, the muscle stimulators are misbranded when inappropriate claims, such as weight reduction, are made." Several manufacturers are named including many of the devices listed in this report. The muscle stimulators are "misbranded when any of the following claims are made: girth reduction, loss of inches, weight reduction, cellulite removal, bust development, body shaping and contouring, and spot reducing." The FDA recognizes the use of these devices for relaxation of muscle spasms, prevention of atrophy, muscle reeducation, increasing blood circulation, to prevent venous thrombosis by stimulating the calf muscles, and maintaining or increasing range of motion.
Is EMS safe?
Answer: There is no known harm to muscles or nerves from electrical stimulation, but the method of applying the current can cause burns on the skin. Most EMS devices come with a gel or a sponge to disperse the energy across a wider area of skin and reduce the risk of burn.
Can electronic muscle stimulators cause contraction of muscle tissue?
Answer: Yes, EMS devices can stimulate muscle contraction by exciting the innervating nerve fiber through a pulse of current.
Can EMS devices burn calories?
Answer: Yes and No. EMS can burn calories because "burning calories" is the process of using consumed energy and using its chemical properties for energy. This does occur in muscle stimulated by EMS; however, the amount of calories burned is hardly enough to affect blood sugar. An EMS unit would have to be worn for a very long time to cause enough energy to make a noticeable difference.
Can EMS target a specific region of fat?
Answer: No, the few calories that are burned from the body's stores come from all throughout the body. As the body breaks down molecules for the production of glucose, the fat stores are used all throughout the body. It is not possible to burn fat in just one area.
Can EMS target a specific muscle group?
Answer: Yes, EMS has been used to prevent muscle from atrophy by stimulating the muscles in a specific area. There is varying evidence on whether or not muscle can be built from EMS stimulation. On most healthy people, the effects of EMS on muscle growth will be nearly negligible.
Campbell, Neil, and Reece, Jane. Biology. San Francisco: Pearson Education Inc., 2005.
Marieb, Elaine, and Hoehn, Katja. Human Anatomy and Physiology. San Francisco: Pearson Education Inc., 2007.
Porcari, John et al. Effects of Electrical Muscle Stimulation on the Body Composition, Muscle Strength, and Physical Appearance. Journal of Strength and Conditioning Research. 2002. 16(2). Pg 165-172. http://www.hawaii.edu/hivandaids/Effects%20of%20Electrical%20Muscle%20Stimulation%20on%20Body%20Composition,%20Muscle%20Strength.pdf
Sherwood, Lauralee. Human Physiology: from Cells to Systems. Belmont, CA: Thomson Learning, Inc., 2004.
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