Changes in the Intermuscular Coherence of the Multifidus and Its Relationship with Fatigue and Low Back Pain: A Case Series

Subjects with low back pain (LBP) have shown different responses to fatigue compared to healthy individuals. The aim of this study was to analyze and compare the connectivity of the multifidus muscles using intermuscular coherence (IMC) in a squat protocol between healthy subjects and a subject with a history of low back pain. The protocol consisted of three sets of squats, with the final set performed with as many repetitions as possible to induce muscular fatigue. The findings indicated that IMC decreased among healthy subjects during the last repetitions of the squat series, with percentage changes in connectivity (CC) ranging from approximately 43.3% to 67.3% when comparing the first and last 10 repetitions. In contrast, the subject with a history of low back pain (LBP) exhibited an opposite trend, showing a 41.8% increase in IMC. These results suggest a different response of IMC to fatigue related to LBP. This also establishes IMC as a potentially useful tool for characterizing fatigue and LBP during physical exercise.