Central mechanisms during fatiguing muscle exercise in muscular dystrophy and fibromyalgia syndrome: a study with transcranial magnetic stimulation.

INTRODUCTION

The aim of this study was to apply paired-pulse transcranial magnetic stimulation (TMS) to assess intracortical inhibition (ICI) during fatiguing muscle exercise in healthy humans and patients with muscular dystrophy (MD) and fibromyalgia syndrome (FMS) to obtain insight into differential central mechanisms.

METHODS

We studied 23 patients with MD, 16 patients with FMS, and 23 healthy controls. All participants performed a fatiguing motor task. TMS recordings were taken pre-exercise, immediately post-exercise, and 40 minutes post-exercise.

RESULTS

ICI was already reduced pre-exercise in MD and FMS, whereas ICI decreased significantly during fatiguing muscle exercise only in healthy subjects.

DISCUSSION

Reduced baseline ICI in patients might prevent further utilization of this presumably compensatory mechanism during fatiguing muscle exercise. Although reduced baseline to be ICI in MD can be explained as compensatory due to peripheral weakness, in FMS reduced ICI must be considered an indicator of primary central disinhibition.