What is a myogram?

Definition:

A myogram is a graphic record of the changes in muscular tension or contractions that occur in a muscle during its excitation and contraction. It displays the temporal sequence and magnitude of the electrical and mechanical events related to muscle activity, providing insights into the dynamics and physiological properties of the muscle. Myograms are typically obtained through various techniques, including electromyography (EMG) and mechanomyography (MMG).

Here's a more detailed explanation:

1. Electromyography (EMG): EMG records the electrical activity associated with muscle contractions. Electrodes are placed on the skin over the muscle or inserted directly into the muscle, capturing the electrical potential generated by the muscle fibers during their excitation. The resulting EMG signals show the timing, duration, and intensity of muscle activation.

- Motor Unit Action Potential (MUAP): MUAP represents the electrical activity of a single motor unit, which consists of a group of muscle fibers innervated by a single motor neuron. MUAPs are small, discrete waveforms seen in EMG recordings.

- Compound Muscle Action Potential (CMAP): When a group of motor units is stimulated simultaneously, the summated electrical activity is observed as a CMAP in EMG. The amplitude and shape of the CMAP provide insights into the number of activated motor units and their synchronization.

2. Mechanomyography (MMG): MMG records the mechanical changes associated with muscle contractions. Sensors or transducers are placed on the skin or attached to the muscle to measure the displacement, force, or vibration produced during muscle contractions. MMG signals reflect the mechanical properties and behavior of the muscle during contraction and relaxation phases.

- Muscle Displacement: MMG can measure the changes in muscle length or displacement during contraction and relaxation. This information helps evaluate muscle function, spasticity, and muscle fatigue.

- Muscle Force: MMG can also quantify the force generated by the muscle during contractions. This is particularly useful in assessing muscle strength, neuromuscular disorders, and rehabilitation outcomes.

Myograms are valuable tools in various fields, including physiology, sports science, rehabilitation, and medicine. They help researchers, clinicians, and healthcare professionals understand muscle function, diagnose muscle disorders, evaluate treatment interventions, and enhance human performance.