EoneandMineml, : i 1989) 91-105 Elsevier BAM W218 91 Effect of swimming on bone growth and development in young rats Aaron Swissa-%a@, Ariel Simkin235, Isaac Leichter’33, Abraham Nyska4, Meir Nyska5, Marian Statters, Arye Bivas’, Jacob Mencze1135 and Shlomo Samueloft ‘Jn&,n o~,~~porosir Cenrer, zCorell Cenrer of Physical Educarinz, ‘Jelerwolem C&g of Technology. ‘Life Science Research, Ness-Ziona, 5Hadassnk Zkupitol md ‘Deparlmmt of Physiology, Hebrew University, Hodmoh .kdicalSchool, Jerwdm, Israel (Received 31 October 1988) (Accepted 21 April 1989) Summary The effect of chronic swimming on bone modelling was studied. Forty female Sabra rats (5 weeks aid) were randomly assigwd to the following experimental groups: 30 rats were trained to swim (water bath 35 i 1 -C. one h daily. five timesaweek) for20 reeks-2Oofthem loaded with leadweights (1% body weigbr) while the rest (IO animals) swam load free. Ten sedentary rats matched for age and weight served as controls. At the end ofthe twenty-week swimming period, all ratswere sacrificed, both humeri bones were dissected and prepared for the following examinations: morpbomerrie. bone density (BD), bone mineral content (BMC). compression tests and cross-seclional geometrical parameters, hisoxnor- phometry and biochemical analysis of minerals (Ca, Pi, Mg, Zn). AS measured parameters were found to be significantly higher(P< 0.05) in theswimmingralsirrespectiveolload, ascompared with thecon- trols. Bone weight was higher by 198, bone volume by 11%. bone length by 2.8%, cortical area by 161, 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 signihcanlly dif- ferent. Maximal and minimal moment of inertia at the distal diapbysis were 33.4 and 40% higher. re- spectively, for rhe swimming groups th.m the co~:~rols. Ca, Pi. Mg and Zn levels per total humeral bone were significantly higher in the exercising rats. The histomorphometry and cross.seclionaI data empha- size longitudinal and transversal growth. These data indicate that swimming exercise exerts a positive ef- fect on bone growth and development in young rats. Key wordo: Swimmingexercise; Bone mcdelling; Bone growth; Bone density; Bane mineral Correspondence to: Dr Aaron Swissa-Sian, Department of Physiology, Hebrew Universby-Hodassah Medical School, P.O. Box 1172,Jerusakm, 1srae191010. 0169-6009/89i$03.50~ 1989 Elsevier Science Publishers B.V. (Biomedical Division)