Effect of swimming exercise on three-dimensional trabecular bone microarchitecture in ovariectomized rats.
Swimming is generally considered ineffective for increasing bone mass in humans, at least compared with weight-bearing sports. However, swimming exercise has sometimes been shown to have a strong positive effect on bone mass in small animals. This study investigated the effects of swimming on bone mass, strength, and microarchitecture in ovariectomized (OVX) rats. OVX or sham operations were performed on 18-wk-old female Fisher 344 rats. Rats were randomly divided into four groups: sham sedentary (Sham-CON), sham swimming exercised (Sham-SWI), OVX sedentary (OVX-CON), and OVX swimming exercised (OVX-SWI). Rats in exercise groups performed swimming in a water bath for 60 min/day, 5 days/wk, for 12 wk. Bone mineral density (BMD) in right femurs was analyzed using dual-energy X-ray absorptiometry. Three-dimensional trabecular architecture at the distal femoral metaphysis was analyzed using microcomputed tomography (μCT). Geometrical properties of diaphyseal cortical bone were evaluated in the midfemoral region using μCT. The biomechanical properties of femurs were analyzed using three-point bending. Femoral BMD was significantly decreased following ovariectomy. This change was suppressed by swimming. Trabecular bone thickness, number, and connectivity were decreased by ovariectomy, whereas structure model index (i.e., ratio of rod-like to plate-like trabeculae) increased. These changes were also suppressed by swimming exercise. Femurs displayed greater cortical width and maximum load in SWI groups than in CON groups. Together, these results demonstrate that swimming exercise drastically alleviated both OVX-induced decreases in bone mass and mechanical strength and the deterioration of trabecular microarchitecture in rat models of osteoporosis.
Department of Health and Sports Sciences, Kawasaki University of Medical Welfare, Kurashiki, Okayama, Japan; jyi.k@mw.kawasaki-m.ac.jp.
Yong-In
YI
Ju
Department of Nuclear Medicine, Kawasaki Medical School, Kurashiki, Okayama, Japan;
Teruki
T
Sone
Department of Orthopedic Surgery, Kawasaki Medical School, Kurashiki, Okayama, Japan; and.
Kazuhiro
K
Ohnaru
Department of Nuclear Medicine, Kawasaki Medical School, Kurashiki, Okayama, Japan;
Kensuke
K
Tanaka
Kawasaki Medical School, Kurashiki, Okayama, Japan.
Masao
M
Fukunaga
D000818:Animals; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000517:prevention & control; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D005260:Female; D010052:Ovariectomy; D011897:Random Allocation; D011916:Rats, Inbred F344; D013550:Swimming / Q000502:physiology*; D055114:X-Ray Microtomography
microcomputed tomography; muscle contractile forces; non-weight-bearing exercise; trabecular architecture