*2.1.1. Smooth muscle*

Smooth muscle is found in the digestive tract, surrounds the blood vessels, airways and respiratory systems. Smooth muscle is innervated by the autonomic nervous system such as cardiac muscle and therefore we do not have voluntary control over its contractions [20,17].

## *2.1.2. Cardiac muscle*

Cardiac muscular system is located in the heart tissue and has striped appearance under light microscopy. The same striations are also found in skeletal muscle and indicate the presence of different proteins required for muscle contraction [21,17].

#### *2.1.3. Skeletal muscle*

Skeletal muscular system has the only muscle type that can be voluntarily contracted and skeletal muscle has active elements forming the movement. The human body consists of more than 600 muscles [21,17]. The functions of the muscular system are movement of blood and food within the body, the ability to stop the body moving, to store oxygen and nutrients such as glycogen for energy production and, through the energy production reactions, to produce heat to help maintain body temperature [17]. Skeletal muscle converts chemical energy to mechanical and heat energy. Skeletal muscle uses adenosine triphosphate (ATP) as fuel during electrical, mechanical and chemical events. This process, called action potential begins with an electrical impulse from the brain [22,23]. This initiates a chain of biochemical reactions that ends in the burning of adenosine triphosphate, the fuel for muscle contraction. Its use results in the forces that move the limbs and generate heat. Electrodes attached to a muscle group record the electrical activity accompanying contraction; the name of this recording process is electromyography (EMG) [23].
