The primary function of muscle in the body is to generate movement, but it also plays a major role in maintaining posture. To strengthen muscle it is necessary to apply the overload principle - this is a scientific principle that states you must work a muscle more than it is accustomed to in order for strength improvement to occur. There are a number of ways to overload your body's muscles for strength improvements. You can use your own body weight e.g. press ups, you can use machine weights, free weights, medicine balls and therabands. You can also use electrical muscle stimulation (EMS).
Electrical muscle stimulation operates in the same way as traditional strength training, you can use EMS to work your muscles so that you get a stronger, healthier body.
Electrical Muscle Stimulation (EMS) is a technique whereby a muscle is caused to contract by stimulating the nerve that supplies it. It is a well-established practice in physiotherapy, where it is used to exercise muscles in situations where it is difficult for the patients to perform normal voluntary exercises. Similarly in healthy subjects, EMS is used to exercise muscles that are difficult to exercise voluntarily, such as the abdominal muscles. In both cases, muscle function is improved because the muscle is stimulated to go through its normal physiological cycle of contraction and relaxation.
Exercise may be defined as bodily activity that develops or maintains health and fitness. Specific exercises are directed towards particular health and fitness outcomes, for example improving flexibility, increasing aerobic capacity, increasing strength, increasing endurance and/or improving speed of certain actions. An exercise which is designed towards a particular outcome may confer little benefit in another, for example, lifting weights improves muscle strength but does little or nothing for aerobic capacity. There is no single exercise which is optimal for all fitness objectives and therefore we need a mix of exercises for overall body improvement.
EMS is a form of exercise which focuses on strength improvement by repeatedly contracting and relaxing the target muscle. It works by sending a stream of electrical impulses to the nerve supplying the muscle. The muscle responds to each impulse by producing a contractile twitch, just as it would do during normal muscle function. If the impulses are sent at a sufficient rate (eg 50 pulses per second), the muscle contracts continuously (tetanically) and develops considerable force. When the pulse stream is turned off the muscle reverts to its relaxed state. EMS creates repeated contraction/relaxation cycles by controlling the stream of pulses to the motor nerve. Note that the electrical stimulus does not shock or convulse the muscle in any way, rather it sends it a message via its supply nerve so the muscle responds to the message by contracting in the normal way.
The muscle contraction created in this way is similar to a normal voluntary contraction. Research over many decades has shown that EMS, in addition to causing the muscle to generate force, reproduces the principal biochemical and physiological features of normal exercise. Furthermore, it has been consistently shown that repeated exercise with an EMS regime lasting several weeks has a training effect on the target muscle, leading to improved strength and endurance.
The fact that training with EMS leads to improved muscle performance is not in doubt. EMS is not a replacement for all exercise requirements, any more than any other specific exercise activity is nonetheless it does create physical activity in the muscle which develops or maintains health and fitness. Its principal benefits are improvements in strength and tone of the target muscle and there is evidence of improved muscular endurance equivalent to conventional resistance training exercises.
In relation to abdominal EMS with the Slendertone range of products, multiple studies have now been carried out which consistently show a strengthening effect. The most recent study, which was a double blind randomised controlled design, showed a 29% strength improvement after 6 weeks of usage. Strength gains of this magnitude are comparable to those achieved in similar regimes of voluntary exercises. Abdominal EMS targets the same abdominal muscles that are involved in doing crunch exercises. A typical 20 minute session activates these same muscles more than 120 times.