Detection and Conditioning of EMG

Background

Movement in the living milieu is essential for many organisms in maintaining life. The musculoskeletal system is responsible not only in achieving the movements including locomotion but also in the maintenance of the posture and in the establishment of the gestures and speech by means of the actuators referred as skeletal muscles (Pozzo, Farina, & Merletti 2004; Moritani, Stegeman & Merletti 2004). In human beings, skeletal muscle has four functions which can be explained as follows.

• 1.

  Production of body movement: In order to enable the organism to adapt rapidly to environmental changes, skeletal muscles have responsibilities for all locomotion including not only the movements playing role in displacement but also gestures and speech.

• 2.

  Maintenance of Posture: In the presence of gravity, equilibrium of the body is ensured by means of some skeletal muscles.

• 3.

  Stabilization of Joints: The joints such as shoulder and knee without complementary surface and hence with poor reinforcement can be stabilized with the help of the skeletal muscles

• 4.

  Generation of Heat: The skeletal muscles constituting 40% of body mass produce heat during their contractions which has a vital importance in maintaining normal body temperature (Marieb, 1995; Tortora, 2009; Tortora, 2010).

These functions are controlled by electrical signals transmitted from the nervous system to muscle fibers that bring about skeletal muscle contraction. (Henneberg, 2000, 2006). During the contractions the conversion of the chemical energy and electrical energy into mechanical energy takes place by the cleavage of ATP molecules in order to establish the motor activity (Guyton, 2002). Hence mechanical force is generated as the output of the motor system (Cotterill, 2002). The process of contribution of additional motor units to produce force at a certain level is referred as motor unit recruitment and it occurs in an orderly sequence based on the size of the motor units (Preston & Shapiro, 2005). According to the Henneman’s Size Principles, as the contraction increases the small motor units are recruited first and then larger ones participate to this process (Loeb & Ghez, 2000).