Physical Exercise After Immobilization of Skeletal Muscle of Adult and Aged Rats

Abstract

Introduction: Immobilization is a treatment technique often used to reduce pain and prevent worsening of the injury. However, it promotes harmful effects on musculoskeletal tissue, resulting in a marked loss of muscle function, which may be aggravated in the elderly. Physical exercise is an important intervention to mitigate these harmful effects. Objective: To analyze possible morphometric changes in the gastrocnemius muscle of rats after immobilization and remobilization with physical exercise. Methods: Fifty-six rats were divided into adult (A) and aged (E) groups and subdivided into adult and aged control (AC and EC), immobilized (AI and EI), free remobilized (AIF and EIF), and remobilized through physical exercise (AIE and EIE). The hind limbs were immobilized with the gastrocnemius muscle in a shortened position for a period of seven days, except for the control group. The exercise protocol consisted of five swimming sessions, once per day (25 minutes/session). The animals were euthanized by administration of an overdose of ketamine hydrochloride plus xylazine hydrochloride, followed by sample collection and preparation of hematoxylin and eosin slides. Measurements of the smallest diameter of 120 muscle fibers of each animal were taken with software NIS-Elements D3.0 - SP7 - Nikon® instruments Inc., NY, USA. Results: There was a significant reduction in the mean fiber diameter in the AI (38.43 µm ± 4.20; p=0.01) and AIF (36.97 µm ± 3.41; p<0.01) groups compared to AC (45.39 µm ± 3.41) and in the EI (42.26 µm ± 4.39; p<0.01), EIF (36.00 µm ± 4.15; p<0.01), and EIE (41.86 µm ± 4.95; p<0.01) groups compared to the EC (51.37 µm ± 3.86) group. The data showed that exercise was able to restore muscle trophism in the adult groups; however, none of the protocols has succeeded in aged rats. Conclusion: Immobilization in the shortened position induced muscle atrophy and physical exercise was effective in restoring muscular trophism only in adult animals. Level of Evidence I; Therapeutic studies - Investigating the Results of Treatment.

Morphological effects of whole‐body vibration on remobilization of the tibialis anterior muscle of Wistar rats

“…Musculoskeletal disorders resulting from injuries affect individuals in all age groups and are often treated with partial or total immobilization of the limb involved, leading to some degree of functional disability (Cornachione et al, 2013;Koike et al, 2018). This inactivity, caused by immobilization, causes harmful effects on muscle tissue, with the main changes being a reduction in size and mass and loss of muscle function after periods of immobilization (Kunz et al, 2014).…”

“…In this sense, the most diverse therapeutic means are used to accelerate remobilization, and among them are physical exercises. Physical exercises have many benefits in the restoration of morphological and functional muscle parameters such as mass gain and consequently the ability to generate strength (Brandão et al, 2017;Koike et al, 2018;Lovison et al, 2018;Peretti et al, 2017).…”

Effect of high-intensity interval training on the skeletal muscle of spontaneously hypertensive rats

“…Forty-eight hours after the end of the experiment, the animals were euthanized with an overdose of anesthetics (ketamine hydrochloride and xylazine hydrochloride), administered intraperitoneally 28 . Next, the Medial Gastrocnemius muscle was extracted and immersed in 10% formaldehyde solution 18,28 .…”

“…After this procedure, the skeletal muscle was processed, embedded in paraffin, and histological sections of 5 μm thickness were made. The slices were produced transversely, in the ventral portion of the muscle, in a rotating microtome, and stained with hematoxylin-eosin (HE) 22,28,29 .…”