Bone mechanical properties after exercise training in young and old rats.

Area of Science:

• Gerontology
• Exercise Physiology
• Biomechanical Engineering

Background:

• Bone mechanical properties decline with age, impacting skeletal health.
• Exercise is a known modulator of bone health, but its efficacy in aged populations requires further investigation.

Purpose of the Study:

• To investigate the effects of a 10-week training regimen on the mechanical properties of the femur and humerus in young and old Fischer 344 female rats.
• To determine if age limits the positive effects of exercise on bone health.

Main Methods:

• Rats (2.5- and 25-mo-old) underwent treadmill training for 10 weeks, gradually increasing duration, grade, and speed.
• Excised femurs and humeri were subjected to a 3-point flexure test to assess mechanical properties (force, stress, strain).
• Fat-free dry weight (FFW) and moment of inertia were measured to evaluate bone mass and structural properties.

Main Results:

• Aging led to similar increases in FFW, moment of inertia, and force in both femur and humerus.
• Senescent femurs showed reduced ultimate stress and elevated strain; a similar trend was noted in the humerus.
• Training increased FFW and breaking force in both young and old rats' femurs and humeri, with similar training-induced differences in bone mass and force across age groups.
• In old trained rats, femur ultimate stress increased to levels comparable to young rats.

Conclusions:

• Treadmill training enhances bone mechanical properties in both young and old rats.
• The positive effects of exercise on bone health are not limited by age.
• Exercise interventions can be effective in improving skeletal integrity in aged individuals.