People with fibromyalgia could experience physical and cognitive impairment as well as higher dual-task cost than healthy people when two tasks are performed simultaneously. Transcranial direct current stimulation is a promising non-pharmacological therapy. However, there is insufficient evidence about the intensities dose-response. Therefore, this protocol aims to 1) to compare the effectiveness and the impact of two tDCS intensities (1mA and 2mA) on cognitive, motor, brain functions, and cardiac autonomic modulation; 2) to study the impact of tDCS on the dual-task performance and creativity after applying tDCS in the dorsolateral prefrontal cortex. As hypotheses, a reduction of cognitive-motor interference in dual-task performance and also a modification in neurophysiological parameters, and an improvement in cardiac autonomic modulation are expected. Finally, no different effects are obtained depending on the intensity applied.

Fibromyalgia is characterized by widespread pain and other associated symptoms, including stiffness, fatigue, non-recovery sleep, anxiety, or depression. On a physical level, people with FM frequently suffer from a sedentary state which reduces cardiovascular fitness and leads to mobility, strength and balance impairments. On a cognitive level, people with FM have often impaired cognitive functions such as memory, attention, processing speed, and executive functions. As a result of all of these symptoms, people with FM have a decreased performance in activities of daily living that are commonly presented as a simultaneous execution of two or more task at the same time (dual-task; DT).

To the knowledge of the investigators, no studies have focused on the application of transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex (DLPFC) to reduce the interference in DT performance. Furthermore, there are no studies that have studied the effects of different intensities of tDCS on DLPFC in people with FM in DT performance. Similarly, there are no studies that have focused on describing how neurophysiological variables may be modified in people with FM during DT performance. Therefore, it seems interesting to know how tDCS can influence these types of variables in order to improve the quality of life of this population and to open new frontiers for research.

The hypotheses that are proposed for this study are as follows: a) the application of tDCS will improve physical performance in physical variables that will be measured through balance and strength tasks; b) the application of tDCS will improve performance on neurophysiological variables that will be measured through brain electrical activity and HRV; c) the application of tDCS will improve performance in DT conditions as well as in creativity tasks; d) tDCS will have different effects depending on the variability of fibromyalgia symptoms presented (pain, sleep problems and depression); e) no significant effects on the variables would be expected depending on the type of tDCS intensity applied.

At this point, the main objectives of this protocol are: 1) to compare the effectiveness and the impact of two tDCS intensities (1mA and 2mA) on neurophysiological variables, cognitive, and motor functions; 2) to study the impact of tDCS on the dual-task performance and creativity after applying tDCS in dorsolateral prefrontal cortex.

Inclusion Criteria:

• Be able to communicate with the research staff
• Have read, understood, and signed the informed consent form

Exclusion Criteria:

• Physiatric or neurological disorders
• Pharmacological treatment for anxiety or depression
• Substance abuse or dependence
• Contraindication for physical effort
• Difficulty in maintaining balance
• Leg injury that interferes with flexion and extension of the knee
• Being pregnant

Healthy and fibromyalgia women living in Caceres (Spain) and the surrounding area

Data sharing will be evaluated upon reasonable request by the research group.