Efeito agudo da estimulação transespinhal por corrente contínua na força e resistência muscular ventilatória em jovens e em pessoas idosas: um estudo controlado randomizado

Abstract

Objective: To evaluate the effect of Transspinal Direct Current Stimulation in the C3-C5 segments on inspiratory muscle strength and ventilatory muscle endurance in healthy young and elderly women. Methods: Experimental, double-blind, randomized study. Approved by the Ethics Committee of the Federal University of Amazonas, registered under CEP No. 66350622.0.0000.5020, and by the Brazilian Clinical Trials Registry (REBEC) under RBR-5nwn9xf. The sample size was calculated based on dynamic inspiratory muscle strength, measured by the strength index (S-index). The target population was young women aged 18 to 25 years and elderly women aged 60 years or older. Participants were recruited through a public call on the Federal University of Amazonas bulletin boards, social media, and other media outlets. Participant assessments were conducted on two separate days. On the first visit, clinical data and anthropometric measurements such as weight, height, body mass index (BMI), age, and health history were collected using a semi-structured questionnaire, in addition to lung function assessment. After the first assessment, volunteers were randomized, and on the second day, dynamic inspiratory strength and ventilatory muscle endurance were assessed before and after transmedullary direct current stimulation (TDCS) or placebo. Participants were randomized in a 1:1 ratio. Double-blinding was used to control bias. Statistical analysis: The nature of the distribution of variables was assessed using the Shapiro-Wilk test. The homogeneity of the variables was assessed by Levene's test. For the ET, partial η² values were used, accepting small values of 0.01 ≤ partial η² < 0.06, medium 0.06 partial η² < 0.14, and large partial η² ≥ 0.14. The significance level accepted was p < 0.05. Results: No significant impact of electrical stimulation on the phrenic nerve was observed in young participants for any variable. Contrary to what was observed in young individuals, ETECC had a significant impact on the inspiratory muscles of elderly women. Conclusion: Elderly women had greater benefit from ETECC in increasing inspiratory muscle strength and inspiratory flow, when compared to young women, who did not obtain any significant difference in all the variables analyzed. These findings suggest that future research explore the applicability of ETECC on the ventilatory muscles in different age groups, clinical conditions, and with more days of electrical stimulation.