Effects of jump training on bone are preserved after detraining, regardless of estrogen secretion state in rats.
We investigated whether the effects of jump training on bone are preserved after a detraining period in female normal and estrogen-deficient rats. Forty-four 11-wk-old Wistar rats were divided into the following four groups: sham sedentary (n = 12), sham exercised (n = 11), ovariectomized sedentary (n = 10), and ovariectomized exercised (n = 11). An 8-wk exercise period was introduced in which the rats in the exercised groups were jumped 10 times/day, 5 days/wk. This was followed by 24 wk of detraining. At the end of the exercise period, the jump training significantly increased the bone mineral content of the tibia (P < 0.001), measured by dual-energy X-ray absorptiometry. After the detraining period, the bone mineral content (P < 0.01), strength (P < 0.001), and cross-sectional widths (P < 0.001) of the tibia in the exercised groups were still greater than in the sedentary groups, without significant surgery-exercise interactions, although bone stiffness in the fracture test (P < 0.05) and bone area in the center-proximal region, as measured by dual-energy X-ray absorptiometry (P < 0.05), showed significant surgery-exercise interactions. These findings suggest that the exercise effect on bone strength is preserved, accompanied by cross-sectional morphological changes, even under estrogen deficiency.
Umemura
Yoshihisa
Y
Laboratory for Exercise Physiology and Biomechanics, School of Health and Sport Sciences, Chukyo Univ., 101 Tokodachi, Kaizu-cho, Toyota 470-0393, Japan. yumemura@sass.chukyo-u.ac.jp
Nagasawa
Seigo
S
Sogo
Naota
N
Honda
Akiko
A
D015502:Absorptiometry, Photon; D000818:Animals; D001835:Body Weight / Q000502:physiology; D015519:Bone Density; D001842:Bone and Bones / Q000502:physiology*; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000378:metabolism; D009929:Organ Size / Q000502:physiology; D010052:Ovariectomy; D010805:Physical Conditioning, Animal / Q000379:methods / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology
D004967:Estrogens