Effect of passive stretching on the immobilized soleus muscle fiber morphology

Abstract

The aim of the present study was to determine the effect of stretching applied every 3 days to the soleus muscle immobilized in the shortened position on muscle fiber morphology. Eighteen 16-week-old Wistar rats were used and divided into three groups of 6 animals each: a) the left soleus muscle was immobilized in the shortened position for 3 weeks; b) during immobilization, the soleus was stretched for 40 min every 3 days; c) the non-immobilized soleus was only stretched. Left and right soleus muscles were examined. One portion of the soleus was frozen for histology and muscle fiber area evaluation, while the other portion was used to identify the number and length of serial sarcomeres. Immobilized muscles (group A) showed a significant decrease in weight (44 ± 6%), length (19 ± 7%), serial sarcomere number (23 ± 15%), and fiber area (37 ± 31%) compared to the contralateral muscles (P < 0.05, paired Student t-test). The immobilized and stretched soleus (group B) showed a similar reduction but milder muscle fiber atrophy compared to the only immobilized group (22 ± 40 vs 37 ± 31%, respectively; P < 0.001, ANOVA test). Muscles submitted only to stretching (group C) significantly increased the length (5 ± 2%), serial sarcomere number (4 ± 4%), and fiber area (16 ± 44%) compared to the contralateral muscles (P < 0.05, paired Student t-test). In conclusion, stretching applied every 3 days to immobilized muscles did not prevent the muscle shortening, but reduced muscle atrophy. Stretching sessions induced hypertrophic effects in the control muscles. These results support the use of muscle stretching in sports and rehabilitation.

Effects of GaAs laser and stretching on muscle contusion in rats

“…However, Amaral et al 31 found no statistical difference in the body weight of animals subjected to muscle injury and myotoxin treated by laser. Coutinho et al 27 reported increased body weight in animals subjected to stretching in rat soleus muscle.…”

“…The muscle fibers were isolated and fixed as described by Coutinho et al 27 In each muscle fiber, the serial sarcomere number was identified over 300 µm in a light microscope (Nikon, Tokyo, Japan) at 100x immersion objective. The quantification was performed on a video monitor (14") with video-image system (Adler CCTV) coupled to the microscope (Nikon, Tokyo, Japan) with the help of a counter (Veeder -Root, Washington, USA).…”

“…The photomicrographs of the histological slices were performed under a light microscope (Axyophot, Carl Zeiss, Oberkochen, Germany) and captured on a video-image system (Applied Spectral We measured the cross-sectional area of 100 muscle fibers of each muscle, chosen randomly from the area of the muscle belly of the histological section 27 .…”

Exercício excêntrico e alongamento para músculos flexores plantares aplicados durante 21 dias após imobilização não modificam o tecido não contrátil

“…After four weeks of immobilization and application of stretching in daily sessions or 3 times a week (10 stretches held by 1 minute with 30-second interval), we concluded that the protocols were effective in recovering the cross-sectional fiber area of the soleus muscle, compared with the contralateral muscle and with the control group 7 . Stretching is an important technique capable of reducing the disorganization and aggregation of collagen bundles and preventing the loss of sarcomeres in series of immobilized muscles 1,7 , being recommended to prevent injuries 8 .…”

“…Stretching is an important technique capable of reducing the disorganization and aggregation of collagen bundles and preventing the loss of sarcomeres in series of immobilized muscles 1,7 , being recommended to prevent injuries 8 . Stretching programs used by several researchers, after segmental immobilization, are effective in restoring the range of motion to the normality patterns of the joints 6,8,9 .…”