title: Five jumps per day increase bone mass and breaking force in rats.
abstract: The effects of jump training on bone morphological and mechanical properties were investigated in immature bones of female Fischer 344 rats. Five-week-old rats were divided into control or five jump-trained groups comprised of 5-, 10-, 20-, 40-, and 100-jump groups, representing the number of jumps per day. The rats were jump-trained 5 days/week for 8 weeks, and the height of jump was increased to 40 cm progressively. The femur and tibia in the 5-jump group had significantly greater fat-free dry weights per body weight and maximum loads at the fracture tests than those in the control group. The tibia in the 5-jump group also had significantly larger cortical area at the cross-sectional analysis. Although a slight tendency toward increase according to the number of jumps per day was observed, there were few differences in bone morphological and mechanical parameters among the 10-, 20-, and 40-jump groups. The present results indicate that a large number of strains per day is not necessary for bone hypertrophy to develop in rats.
authors.affiliation: Laboratory for Exercise Physiology and Biomechanics, School of Physical Education, Chukyo University, Toyota, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Umemura
authors.forename: T
authors.initials: T
authors.lastname: Ishiko
authors.forename: T
authors.initials: T
authors.lastname: Yamauchi
authors.forename: M
authors.initials: M
authors.lastname: Kurono
authors.forename: S
authors.initials: S
authors.lastname: Mashiko
mesh_terms: D000818:Animals; D015519:Bone Density; D005260:Female; D005269:Femur / Q000033:anatomy & histology; D015576:Hyperostosis / Q000209:etiology* / Q000473:pathology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D013314:Stress, Mechanical; D013977:Tibia / Q000033:anatomy & histology