Free mobilization and low- to high-intensity exercise in immobilization-induced muscle atrophy

Abstract

After 3 wk of immobilization, the effects of free cage activity and low- and high-intensity treadmill running (8 wk) on the morphology and histochemistry of the soleus and gastrocnemius muscles in male Sprague-Dawley rats were investigated. In both muscles, immobilization produced a significant (P < 0.001) increase in the mean percent area of intramuscular connective tissue (soleus: 18.9% in immobilized left hindlimb vs. 3.6% in nonimmobilized right hindlimb) and in the relative number of muscle fibers with pathological alterations (soleus: 66% in immobilized hindlimb vs. 6% in control), with a simultaneous significant (P < 0.001) decrease in the intramuscular capillary density (soleus: mean capillary density in the immobilized hindlimb only 63% of that in the nonimmobilized hindlimb) and muscle fiber size (soleus type I fibers: mean fiber size in the immobilized hindlimb only 69% of that in the nonimmobilized hindlimb). Many of these changes could not be corrected by free remobilization, whereas low- and high-intensity treadmill running clearly restored the changes toward control levels, the effect being most complete in the high-intensity running group. Collectively, these findings indicate that immobilization-induced pathological structural and histochemical alterations in rat calf muscles are, to a great extent, reversible phenomena if remobilization is intensified by physical training. In this respect, high-intensity exercise seems more beneficial than low-intensity exercise.

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

“…After periods of immobilization in shortened position, important adaptations occur, such as muscle atrophy and changes in the intramuscular connective tissue 1,3 . Only few studies investigated the response of the intramuscular connective tissue regarding the interventions of disuse and rehabilitation [1][2][3][4] .…”

“…Only few studies investigated the response of the intramuscular connective tissue regarding the interventions of disuse and rehabilitation [1][2][3][4] . Coutinho et al 14 noted that after four weeks of immobilization, there was disorganization and reduction of the aggregation state of collagen bundles for the soleus muscle.…”

“…The immobilization procedure determines unfavorable changes in the muscle, such as muscle atrophy and increase of the intramuscular connective tissue, leading to loss of extensibility and limitation of movements [1][2][3][4] .…”

Efeitos da estimulação elétrica neuromuscular sobre o membro posterior imobilizado de ratos durante 15 dias: análises metabólicas e morfométricas

“…Gomes et al 3 , observaram redução de 43% da área da fibra do músculo sóleo imobilizado durante 3 semanas. Kannus et al 2 relataram redução de 69% da área das fibras desse músculo imobilizado por meio de aparelho gessado durante 3 semanas.…”

“…Desse modo, o desuso muscular promove redução na área das fibras musculares, bem como na densidade dos capilares 2,3 . Simultaneamente, ocorre proliferação do tecido conjuntivo intramuscular tanto no perimísio quanto no endomísio, além de aumento do "turnover" do colágeno no tecido 4,5,6 .…”