Intermuscular coherence
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Intermuscular Coherence is a measure to quantify correlations between the activity of two muscles, which is often assessed using electromyography. The correlations in muscle activity are quantified in frequency domain,[1] and therefore referred to as intermuscular coherence.[2]
History
The synchronisation of motor units of a single muscle in animals and humans are known for decades. The early studies that investigated the relationship of EMG activity used time-domain cross-correlation to quantify common input.[3][4] The explicit notion of presence of synchrony between motor units of two different muscles was reported at a later time.[5] In the 1990s, coherence analysis was introduced to examine in frequency content of common input.[2]
Physiology
Intermuscular coherence can be used to investigate the neural circuitry involved in motor control. Correlated muscle activity indicates common input to the motor unit pools of both muscles[6][7] and reflects shared neural pathways (including cortical, subcortical and spinal) that contribute to muscle activity and movement.[8] The strength of intermuscular coherence is dependent on the relationship between muscles and is generally stronger between muscle pairs that are anatomically and functionally closely related.[9][10] Intermuscular coherence can therefore be used to identify impairments in motor pathways.[11][12]
