Objectives: Chronic low back pain (CLBP) is associated with an impaired control of transversus abdominis/internal oblique muscle (TrA/IO), volitionally and during anticipatory postural adjustment (delay) along with maladaptive reorganization of primary motor cortex (M1). Specific training of deep trunk muscles and repetitive peripheral magnetic stimulation (RPMS) improve motor control. We thus tested whether RPMS over TrA/IO combined with training could promote TrA/IO motor control and decrease pain beyond the gains already reached in CLBP.
Methods: Thirteen CLBP patients, randomly allocated to RPMS and sham groups and compared with 9 pain-free controls, were tested in 1 session before/after (stimulation alone) and after (stimulation+TrA/IO training) combination. TrA/IO motor patterns were recorded during ballistic shoulder flexion using surface electromyography. Transcranial magnetic stimulation tested M1 excitability and short-interval intracortical inhibition. A blinded physical therapist assessed pain, disability, and kinesiophobia.
Results: The missing short-interval intracortical inhibition in CLBP was restored by RPMS alone then reduced after combination of RPMS with training. This combination also normalized the (at-first delayed) anticipatory activation of iTrA/IO (ipsilateral to arm raised) and the (at-first shortened) TrA/IO coactivation duration. Sham did not influence. Pain was reduced in both groups but kinesiophobia was decreased only in RPMS 2 weeks later.
Conclusions: This study supports that peripheral neurostimulation (adjuvant to training) could improve TrA/IO motor learning and pain in CLBP associated with motor impairment. Testing of enlarged samples over several sessions should question the long-term influence of this new approach in CLBP.