Free mobilization and low- to high-intensity exercise in immobilization-induced muscle atrophy.
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.
Kannus
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P
Accident and Trauma Research Center and Research Center of Sports Medicine, The President Urho Kekkonen Institute for Health Promotion Research, FIN-33500 Tampere, Finland. klpeka@uta.fi
Jozsa
L
L
Järvinen
T L
TL
Kvist
M
M
Vieno
T
T
Järvinen
T A
TA
Natri
A
A
Järvinen
M
M
D000818:Animals; D001284:Atrophy; D002196:Capillaries / Q000473:pathology; D003238:Connective Tissue / Q000473:pathology; D006651:Histocytochemistry; D007103:Immobilization; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000473:pathology / Q000502:physiology*; D010805:Physical Conditioning, Animal; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley