Swim-trained rats have greater bone mass, density, strength, and dynamics

Weight-bearing exercise is traditionally recommended for improving bone hea lth in postmenopausal women. Effects of swim exercise were studied as an al ternative to weight-bearing exercise in ovariectomized rats. Rats in a swim group (Sw, n = 8) swam for 12 wk, 5 days/wk for 60 min per session. A cont rol group (Con, n = 9) engaged in no structured exercise. Femurs were analy zed for bone mineral density and for bone mineral content by dual energy X- ray absorptiometry, biomechanical properties by three-point bending (Instro n), and bone structure and formation by histomorphometry. Food intake did n ot differ among groups. Final body weights were significantly lower in Sw c ompared with Con (P < 0.05). Swimmers had significantly greater femoral sha ft bone mineral density and content (P < 0.05) compared with Con. Femurs of the Sw group had greater mechanical properties (P < 0.05) compared with Co n. Histomorphometric data were significantly better in the Sw group compare d with Con after the 12-wk intervention (P < 0.05). In conclusion, data fro m this study demonstrate some beneficial effects of swim exercise on bone s tructure, turnover, and strength.