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