Muscle physiology is included in the core curriculum in the biomedical, health, and exercise science fields. It is always challenging to understand the dynamic nature of motor unit (MU) functioning, neuromuscular activity or muscle contractions. Different teaching instruments can be used during a didactic lecture to make it more engaging for the students, including the use of electromyography and dynamometry techniques. Electromyography (EMG) serves as a clinical and educational tool to evaluate skeletal muscle activity, enhancing the understanding of muscle physiology. This activity aims to describe several sessions where EMG is used as a tool to teach muscle physiology. EMG demonstrates muscle activation and MU recruitment, bridging theory and practice in physiology education. Surface EMG measures electrical activity in muscles, providing real-time data during rest, contraction, and fatigue. At rest, muscles exhibit minimal electrical activity. During contraction, increasing MU recruitment raises the amplitude and frequency of EMG signals. Fatigue is shown by altered patterns, reflecting declining muscle force and changes in MU activation. These principles highlight Henneman’s size principle, where smaller motor units are activated first, followed by larger, stronger ones as contraction strength increases. Clinically, EMG distinguishes between neuropathies and myopathies. Neuropathies show delayed or reduced MU activation, spontaneous discharges, and impaired nerve-muscle communication. Myopathies display low-amplitude signals and rapid MU recruitment due to intrinsic muscle weakness. EMG also tracks denervation and reinnervation, revealing fibrillations or polyphasic MU potentials during nerve recovery. Integrating EMG with nerve conduction studies enhances diagnostics, clarifying whether issues stem from nerve or muscle pathology.
Cristina M. Sena (Fri,) studied this question.