Effects of running on the torsional strength, morphometry, and bone mass of the rat skeleton.
Intensity and duration effects of weight-bearing exercise on the rat skeleton were investigated. Eighty-four 3-month-old female Sprague-Dawley rats were assigned to control and nine exercise groups. Exercised rats were run on a treadmill for either 30, 60, or 90 min.d-1 at low (Vo2max approximately 55%), medium (VO2max approximately 65%), or high (VO2max approximately 75%) intensity 4 d.wk-1 for 10 wk. Rat femurs, tibias, and vertebrae were harvested for torsional mechanical tests, bone density assessment, and morphometry. Our results indicate exercise has a significant effect (P < 0.05) on the femoral mechanical response (energy absorbed and twist angle), tibial morphometry (cortical bone area and thickness), and tibial and vertebral bone density measurements but had no effect (P > 0.05) on bone strength when compared with control values. Higher intensity exercise decreased tibial and femoral torque (P < 0.05). Long duration exercise increased tibial and femoral stiffness and decreased twist angle and energy absorbed (P < 0.05). These results indicate bone adapts to its loading environment by increasing bone mineral density, increasing cortical bone area, increasing stiffness, decreasing energy absorbed, and decreasing twist angle. High-intensity exercise decreased the maximum force the bone could withstand, whereas long duration exercise made the bone more brittle.
Wheeler
D L
DL
Division of Orthopaedics, School of Medicine, Oregon Health Sciences University, Portland, USA.
Graves
J E
JE
Miller
G J
GJ
Vander Griend
R E
RE
Wronski
T J
TJ
Powers
S K
SK
Park
H M
HM
D015502:Absorptiometry, Photon; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001842:Bone and Bones / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley