Benefits of progressive resistance training on motor performance and muscular hypertrophy in rats with Parkinson’s disease

ABSTRACT Parkinson’s disease (PD) is a progressive neurodegenerative condition defined by the presence of primary debilitating motor symptoms. This study aims to investigate the benefits of high-intensity progressive resistance training on muscle tissue and motor performance before and after the induction of PD in rats. A total of 80 male Wistar rats (Rattus norvegicus, var. albinus) aged 40 days and weighing between 250 and 450g were used. A total of 40 animals were subjected to PD surgery to induce electrolytic injury and were randomly assigned to the following subgroups: animals trained before PD induction (PA-Exa); animals trained after PD induction (PA-Exd); animals trained before and after PD induction (PA-Exad); and sedentary animals with PD induction (PA-Sed). The other 40 animals (control) were subjected to surgical access but not to PD electrolytic injury (Sham) and distributed in the same subgroups described above. For the PD induction surgery, electrolytic stimulation was used at the following coordinates: anteroposterior (AP) −4.9, mid-lateral (ML) 1.7,and dorsoventral (DV) 8.1. High-intensity progressive resistance training was performed on a vertical ladder five days/week from 30 to 45 minutes for four weeks. For our functional evaluation, the parallel bars and the misstep tests were used at the beginning (after surgery) and at the end of the experiment. After euthanasia, the forelimb biceps and hindlimb flexor hallucis longus muscles were removed. Processing, coloration, and histomorphometry analysis of muscle tissue were performed for all groups. To analyze the data, GraphPad Prism 9.4 was used with one-way analysis of variance (ANOVA) and a p<0.05. Data on muscle fiber count and area in forelimb biceps showed no significant differences, with a 0.853 and 0.4122 p-value, respectively. Flexor hallucis longus muscle fiber count showed a significant difference (p=0.0356), and PA-Exa and PA-Exd averaged the highest means. Hindlimb flexor hallucis longus muscle fiber area also evinced a significant difference (p=0.0306), in which PA-Exd, PA-Exad, and Sham-Exad showed the largest areas. Analysis of hindlegs in the parallel bars test showed that PA-Exad evinced the best functional performance. In the misstep test, we observed an increase in the number of errors animals made for almost all the groups, evincing a significant difference in the number of errors before and after the test only for PA-Exa, PA-Exd, and PA-Sed. We concluded that the animals that underwent high-intensity progressive training showed better performance in their hindlegs than in their fore ones and that animals that exercised before and after surgery benefited more from training.