title: Short-term exercise-induced improvements in bone properties are for the most part not maintained during aging in hamsters.
abstract: Physical exercise during growth affects composition, structure and mechanical properties of bone. In this study we investigated whether the beneficial effects of exercise during the early growth phase have long-lasting effects or not. Female Syrian golden hamsters (total n=152) were used in this study. Half of the hamsters had access to running wheels during their rapid growth phase (from 1 to 3months of age). The hamsters were sacrificed at the ages of 1, 3, 12, and 15months. The diaphysis of the mineralized humerus was analyzed with microCT and subjected to three-point-bending mechanical testing. The trabecular bone in the tibial metaphysis was also analyzed with microCT. The collagen matrix of the humerus bone was studied by tensile testing after decalcification. The weight of the hamsters as well as the length of the bone and the volumetric bone mineral density (BMDvol) of the humerus was higher in the running group at the early age (3months). Moreover, the mineralized bone showed improved mechanical properties in humerus and had greater trabecular thickness in the subchondral bone of tibia in the runners. However, by the age of 12 and 15months, these differences were equalized with the sedentary group. The tensile strength and Young's modulus of decalcified humerus were higher in the runners at early stage, indicating a stronger collagen network. In tibial metaphysis, trabecular thickness was significantly higher for the runners in the old age groups (12 and 15months). Our study demonstrates that physical exercise during growth improves either directly or indirectly through weight gain bone properties of the hamsters. However, the beneficial effects were for the most part not maintained during aging.
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; SIB Labs, University of Eastern Finland, Kuopio, Finland. Electronic address: arto.koistinen@uef.fi.
authors.forename: Arto P
authors.initials: AP
authors.lastname: Koistinen
authors.affiliation: Department of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Esa P
authors.initials: EP
authors.lastname: Halmesmäki
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Jarkko T
authors.initials: JT
authors.lastname: Iivarinen
authors.affiliation: Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, Kuopio, Finland; Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland.
authors.forename: Jari P A
authors.initials: JP
authors.lastname: Arokoski
authors.affiliation: Veterinary Clinical Sciences, School of Veterinary Medicine, University College Dublin, Ireland.
authors.forename: Pieter A J
authors.initials: PA
authors.lastname: Brama
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: Jukka S
authors.initials: JS
authors.lastname: Jurvelin
authors.affiliation: Department of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
authors.forename: Heikki J
authors.initials: HJ
authors.lastname: Helminen
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Division of Solid Mechanics, Lund University, Lund, Sweden; Department of Orthopedics, Lund University, Lund, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Isaksson
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D050281:Bones of Lower Extremity / Q000502:physiology*; D001133:Bones of Upper Extremity / Q000502:physiology*; D003094:Collagen / Q000502:physiology; D006224:Cricetinae; D005260:Female; D010805:Physical Conditioning, Animal / Q000502:physiology*; D012420:Running / Q000502:physiology; D013718:Tensile Strength / Q000502:physiology
chemical_list: D003094:Collagen
keywords: Aging; Bone; Exercise; Growth; Hamster; Maturation; Mechanical properties