Bone mineral content in laboratory rats following swim and run training

• Main Author: Zierath, Juleen R.
• Other Authors: Snyder, Ann C.
• Format: Others
• Published: 2011
• Subjects: Exercise > Physiological aspects.; Bones > Growth.; Rats > Physiology.
• Online Access: http://cardinalscholar.bsu.edu/handle/handle/183191; http://liblink.bsu.edu/uhtbin/catkey/472942

Increased bone density has been observed following physical training. However, it is not known whether the mechanical forces of muscular contraction, gravitational pull, or a combination of these forces are required to cause this adaptation. Therefore, the purpose of this study was to determine which mechanical force, muscular contraction or gravitational pull, offered the greatest contribution to increased bone mineral content observed following either swim or run training. METHODS: Female Wistar rats were randomly assigned to one of three groups: 1) Sedentary Control (SC; n = 12), 2) Run Trained (RT; 27.7 m/m, 8% incline, 2 hrs/day; n = 20), and 3) Swim Trained (ST; 2 hrs/day, 2Y/ body weight; n = 14). The animals were sacrificed after 9 weeks of training and the humeri and femurs were removed for analysis.RESULTS: Femur weight, length, diameter, and ponderal index (a measure of robustness), and bone mineral content (BMC) were not different between the three treatment groups. However, femur cortical thickness was significantly (p < 0.01) smaller in the RT when compared to ST and SC rats. The ST humeri were significantly (p < 0.05) heavier, wider, and had a greater BMC when compared with those of the RT and SC rats, while cross sectional area was unaffected by physical training. CONCLUSION: The results of this study indicate that the mechanical forces applied by the swim training protocol produced marked bone adaptation in the ST animals following 9 weeks of physical training. Whereas, the combined mechanical and gravitational forces applied during running by the RT rats produced minimal adaptation of bone following 9 weeks of physical training.