1. Introduction
Fibromyalgia is a chronic disorder characterized by widespread musculoskeletal pain and associated fatigue, sleep disturbances, and other cognitive and somatic symptoms [
1], with a prevalence of 1.3–8% in the general population. The main cause of this disease is yet to be established. However, brain imaging studies and other research have uncovered evidence of altered signaling in neural pathways that transmit and receive pain in people with fibromyalgia, contributing to many of the problems that people with this disorder experience [
2]. Further, fibromyalgia is a heterogeneous condition that is more common in females and is often associated with specific diseases such as infections, psychiatric or neurological disorders, diabetes, and rheumatic pathologies [
3]. Along this line, current pharmacological treatments for patients suffering from this condition are mainly directed toward palliating symptoms, and relevant benefits are only achieved by a minority of patients, with a 50% pain reduction being achieved only by 10 to 25% of individuals [
4]. Therefore, a multidisciplinary approach including pharmacological therapies, along with behavioral therapy, exercise, nutrition, patient education, and pain management, could be a solution for the treatment of this disease [
5,
6,
7].
Further, the use of electrical stimulation with surface electrodes is a non-invasive therapeutic method used in patients’ central nervous system injuries, improving voluntary motor control and range of motion and reducing pain and spasticity [
8]. Moreover, Scaturro et al. (2019) described the beneficial effects of a physical rehabilitation program composed by group exercise, laser, and the use of transcutaneous electrical nerve stimulation (TENS) treatment on fibromyalgia patients’ pain perception, fatigue, and overall life quality. Along this line, TENS is a safe intervention that delivers an electrical current through electrodes attached to the skin for pain control [
9], activating central inhibitory pathways [
10,
11,
12,
13] and decreasing central excitability [
11,
14,
15,
16], with already proven effects in fibromyalgia patients for pain, fatigue, and hyperalgesia [
17]. Furthermore, the EXOPULSE Mollii
® method (EXONEURAL NETWORK AB, Danderyd, Sweden) could be considered an evolution of the TENS system, as it is an innovative approach for non-invasive and self-administered electrical stimulation with multiple electrodes incorporated in a full-body suit [
18]. This method is based on the concept of reciprocal inhibition elicited by stimulating the antagonist of a spastic muscle at low frequencies and low intensities by stimulating afferent nerve fibers of the antagonist muscle, which activates inhibitory Ia interneurons in the spinal cord and reduces the excitability of the agonist’s motor neuron [
19,
20]. Additionally, other mechanisms of action of the EXOPULSE Mollii suit may include neuroplastic changes in brain or spinal cord circuitries [
21]. Further, the EXOPULSE Mollii suit has already proven beneficial in its use in children with cerebral palsy [
22], spasticity [
18], and chronic stroke patients [
23]. Therefore, the present study aims to evaluate the acute effects that a 60 min session with the EXOPULSE Mollii suit has on a female fibromyalgia patient.
3. Results
Table 1 presents spirometry values before and after the intervention. FEV1 and FEV1/FEV6 values were higher prior to the intervention (pre:3.26 l, 0.84; post:3.11 l, 0.79), while FEV6 behaved the opposite way, with a higher value after the intervention (pre:3.86 l post:3.92 l). There were no differences in chest perimeter difference values before and after the intervention.
Muscle oxygen values are present in
Table 2, with a clear increase in SmO
2 and O
2Hb after the intervention (pre: 41.8% ± 8.13, 4.79 ± 0.9; post: 52.2 ± 28.79, 5.97 ± 0.06), while HHb decreased after the intervention (pre: 6.68 ± 1.01; post: 5.47 ± 0.02), and there was no change in THb (pre: 11.47 ± 0.11; post: 11.44 ± 0.04).
Table 3 presents NRS values with a two-point decrease in pain after the intervention (pre: 7; post: 5), while PPT increased when measured in the epicondyle and decreased when measured in the knee (pre:1.4, 1.5; post: 1.7, 1.2).
Further on the
Table 4, cortical arousal values before and after the intervention are very similar (pre: 36.1; post: 35.8), whereas saliva flux increased after the intervention (pre: 0.18; post: 0.42), and salivary proteins decreased after the intervention (pre: 5.587 ± 1.295; post: 3.73 ± 0.564).
Functional test results are present in
Table 5, with the patient performing better in all tests after the intervention except for the monopodial balance with the left leg.
In
Table 6, we can see temperature values of the hands and fingers of the patient measured with the thermographic camera, showing an overall decrease after the intervention in the temperature of all points measured.
4. Discussion
The present study is a novel case report study in the use of the EXOPULSE Mollii suit in a fibromyalgia patient procedure that has never been carried out in a scientific setting. As such, there is no previous research on this actual topic to compare our results with. Along this line, the main findings of our study are the drastic change in muscle oxygenation, with a 10.4% increase in SmO
2, and the changes in HHb and O
2Hb distribution, with both values being more equal than before the intervention. These findings are in line with previous research on muscle oxygenation in fibromyalgia patients, which states that fibromyalgia patients have lower SmO
2 and O
2Hb and higher HHb compared to healthy controls [
47]. Authors hypothesize that fibromyalgia patients have a mitochondrial dysfunction, making energy production insufficient due to an abnormal synthesis of adenosine-triphosphate (ATP) [
48]. However, the introduction of a 60 min session with the EXOPULSE Mollii suit somewhat corrected this condition, increasing the basal value of SmO
2 from 41.8% to 52.2% after the intervention, although it did not reach healthy population normal values of around 70–75% [
49]. Further, NRS as a means for subjective pain perception decreased by two points after the intervention, changing from seven to five points. These findings could also be related with mitochondrial disfunction, as pain has already been related to this alteration [
50], and as this mitochondrial dysfunction is corrected by the intervention as shown by an increase in muscle oxygenation. ATP production may be corrected, and thus, muscle oxygen demands decrease, decreasing the patient’s pain perception, and increasing the patient’s performance in functional tests as shown by our results.
Along this line, the patient performed better in all tests after the intervention, which could be attributed to this increase in muscle oxygenation, or to a better ATP production and the reduction in pain allowing the patient to better exert herself in the tests. Further, we should highlight the increase in balance with the right leg, where the subject went from holding only for 3 s to being able to maintain balance for 30 s before having to stop. As previously stated, this increase in performance could be attributed to the reduction of pain, or to the better oxygen usage acquired after the intervention. However, further research should be conducted on the duration of these effects, and whether these effects could be made chronic with successive sessions.
Furthermore, it has been demonstrated that fibromyalgia patients have a higher sympathetic nervous system activation in basal conditions than healthy individuals, which is consistent with a decrease in salivary flow [
51,
52]. Along this line, after the intervention, an increase in salivary flow is observed, without a significant change in protein concentration, contrary to the decrease in flow produced by a fatigue protocol implemented by Costa et al. 2022 [
52], which was correlated with an increase in sympathetic nervous system activation. This increase in flow after the intervention with the suit suggests an increase in parasympathetic tonus. The decrease of temperature observed in the hands of the patient could also be related to a higher parasympathetic nervous system activation, as there, blood flow reduction occurs with parasympathetic activation [
53]. Further, a reduction in sympathetic activation could also be consistent with the reduction in the patient pain perception.
To summarize, in this study, we have found significant changes in muscle oxygenation, functional test performance, and subjective pain perception measured through the NRS, saliva flux, and hand temperature, which in turn suggest a better mitochondrial function and an increase in parasympathetic tone. Along this line, now that a successful case report has been produced, it would be of great interest to implement this same procedure with a wider sample. Moreover, the duration of these acute effects on this fibromyalgia patient should be studied, and the effects of successive sessions should also be studied.