Transcranial Stimulation for Physiotherapy Optimisation - Chronic Low Back Pain (STOP-CLBP)

The main objective of this study is to investigate the effects of non-invasive brain stimulation (the so-called transcranial direct current stimulation ; tDCS) combined with an active physiotherapy program on the multidimensional impact of pain in patients with Chronic Low Back Pain (CLBP). The secondary objectives are to compare the effects of these interventions on fear of movement, psycho-emotional state, function, functional connectivity of the left dorsolaterla prefrontal cortex (DLPFC) and erector spinae activity. Participants will perform: * 2 sessions including clinical assessments including questionnaires, brain activity assessment (with EEG), and back muscle activity assessment (with EMG) * 9 interventional sessions of active physiotherapy combined with active or sham tDCS during 3 weeks (3 per week). Investigators will compare active tDCS with sham tDCS (non active) to evaluate if active tDCS is more effective than sham tDCS.