Effects of free mobilization and low- to high-intensity treadmill running on the immobilization-induced bone loss in rats.
After an immobilization period of 3 weeks, the effects of free remobilization (8 weeks) as well as low- and high-intensity treadmill running on the bone mineral content (BMC) and density (BMD) of the hindlimbs of Sprague-Dawley rats (n = 70) were studied using a dual-energy x-ray absorptiometric scanner. In the low-intensity running program, the rats were allowed to move freely in the cage for 1 week, after which they started to run on a treadmill twice a day for 7 weeks. The speed of the treadmill was 20 cm/s, with an uphill inclination of 10 degrees. The running time was gradually increased from 20 minutes per session to 45 minutes per session. In the high-intensity group, the program was similar, with the exception that the speed of the treadmill was 30 cm/s, with an uphill inclination of 30 degrees. Immobilization for 3 weeks produced a significant BMC and BMD loss in the immobilized left femur and tibia (mean loss 9.6%, p < 0.001) but did not affect the right free limbs. Both low- and high-intensity running restored mineral content in the immobilized limb; however, an average 5% difference (p < 0.05) in mineral content of the right and left limb bones persisted. In the running groups, the values for the immobilized left limbs were at the same level or exceeded (range 3.8-11.6%, p < 0.05-0.01) and those of the free right limbs exclusively exceeded (range 5.3-15.9%, p < 0.05-0.01) the corresponding values of the age-matched control rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Kannus
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President Urho Kaleva Kekkonen Institute for Health Promotion Research, Tampere, Finland.
Sievänen
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Järvinen
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Järvinen
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Kvist
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Oja
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Vuori
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Jozsa
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D015502:Absorptiometry, Photon; D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology*; D004195:Disease Models, Animal; D005080:Exercise Test; D005269:Femur / Q000502:physiology; D006614:Hindlimb; D007103:Immobilization; D008297:Male; D009043:Motor Activity; D010024:Osteoporosis / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D010805:Physical Conditioning, Animal; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012420:Running; D013977:Tibia / Q000502:physiology