ABSTRACT
Electromyography is a technique used for recording changes in the electrical potential of muscle fibres that are associated with their contraction. The fundamental unit of the neuromuscular system is the motor unit, which consists of the cell body and dendrites of a motor neuron, the multiple branches of its axon, and the muscle fibres that it innervates. The number of muscle fibres belonging to a motor unit, known as the innervation ratio, ranges from about 1:6 (e.g. extraocular muscles) to 1:1900 (Enoka, 2002). Detailed descriptions of the generation of an action potential by a motor neuron, its propagation along a muscle fibre and the processes that convert it into force within the fibre are beyond the scope of these guidelines and are more than adequately covered elsewhere (e.g. Enoka, 2002, and Luttman, 1996). Knowledge of these processes is, however, paramount as the biomechanist needs to understand the nature of the detected signal. In addition, and in agreement with Clarys and Cabri, 1993, a detailed knowledge of musculo-skeletal anatomy is also essential to ensure that electrodes are placed over the correct muscles.
