Introduction: The relationship between trunk muscles, low back pain, and exercise has been studied for many years. Subjects with low back pain have shown different responses to fatigue compared to healthy subjects, and this particular behaviour has been proposed as a predictor of low back pain. Several experimental studies have been conducted to identify valid and reliable biomarkers that explain the functioning of the trunk muscle complex. The aim of this study was to analyse the behaviour of the lumbar musculature in healthy subjects and a subject with a history of low back pain.

Methods: The participants underwent a squat protocol using a barbell loaded with 60% of their body weight. They performed as many repetitions as possible at controlled eccentric and maximal concentric speeds. The connectivity of the multifidus muscles was analysed using intermuscular coherence (IMC) during the concentric phase of the exercise.

Results and Discussion: The findings indicated that intermuscular coherence (IMC) decreased among control subjects by the end of the squat series, whereas the subject with a history of low back pain exhibited the opposite trend. These results contrast with the existing literature, though the study's limitations preclude definitive comparisons.

Conclusions: Despite the findings, IMC could potentially be a valuable tool for characterising fatigue and low back pain.