Abstract

The effect of chronic swimming on bone modelling was studied. 40 female Sabra rats (5 wks) were randomly assigned to the following experimental groups: 30 rats were trained to swim (water: 35+/-1 deg C, 1 h/d, 5 times/wk) for 20 wks - 20 of them loaded with lead weights (1 BW) while the rest (10 animals) swam load free. 10 sedentary rats matched for age and weight served as controls. At the end of the 20-wk swimming period, all rats were sacrificed, both humeri bones were dissected and prepared for the following examinations: morphometric, bone density (BD), bone mineral content (BMC), compression tests and cross-sectional geometrical parameters, histomorphometry and biochemical analysis of minerals (Ca, Pi, Mg, Zn). All measured parameters were found to be significantly higher in the swimming rats irrespective of load, as compared with the controls. Bone weight was higher by 19, bone volume by 11, bone length by 2.8, cortical area by 16, BD by 7 and BMC by 15. The compression breaking force at the distal shaft of the humerus was higher by 24 in the trained group, while the ultimate compressive stress was not significantly different. Maximal and minimal moment of inertia at the distal diaphysis were 33.4 and 40 higher, respectively, for the swimming groups than the controls. Ca, Pi, Mg and Zn levels per total humeral bone were significantly higher in the exercising rats. The histomorphometry and cross-sectional data emphasize longitudinal and transversal growth. Verf.-Referat (gekuerzt)