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Age does not influence the bone response to treadmill exercise in female rats
Kim L Bennell1, Karim M Khan, Stuart Warmington
1Centre for Sports Medicine Research and Education, School of Physiotherapy, University of Melbourne, 200 Berkeley St., Carlton, 3052, Victoria, Australia. k.bennell@unimelb.edu.au
Medicine and Science in Sports and Exercise
|December 10, 2002
Summary
Treadmill running improved bone geometry and strength in both immature and mature rats. Bone gains resulted from geometric changes, not material property improvements, indicating age-related sensitivity to exercise loading.
Area of Science:
- Exercise physiology
- Bone biology
- Comparative physiology
Background:
- Bone responds to mechanical loading, but age-related differences in response are not fully understood.
- Exercise interventions are crucial for bone health across the lifespan.
Purpose of the Study:
- To compare bone responses to a 12-week treadmill running program in immature versus mature female rats.
- To investigate age-specific effects of mechanical loading on bone adaptation.
Main Methods:
- Immature (5-week-old) and mature (17-week-old) rats underwent 12 weeks of treadmill running or served as controls.
- Dual-energy x-ray absorptiometry (DXA) assessed bone mineral and soft tissue composition.
- Histomorphometry and three-point bending tests evaluated tibial bone properties.
Main Results:
- Running increased tibial geometric properties (subperiosteal area, cortical area, moment of inertia) and strength (peak load, stiffness) in both age groups.
- Periosteal bone formation rates were higher in trained rats, with no differences in trabecular bone.
- Lumbar spine and total body bone mineral content showed gains, with greater increases in immature rats for total body measures.
Conclusions:
- Both immature and mature rats exhibit sensitivity to mechanical loading from exercise.
- Bone strength adaptations were primarily driven by changes in bone geometry rather than material properties.
- These findings highlight the importance of exercise for bone development and maintenance across different life stages.