Load-carrying effects on the adult beagle tibia.

The response of the skeleton to carrying extra weight while exercising was studied in 30 young adult male beagles. Following 34 wk of a caged control period, 18 dogs carried lead-weighted jackets for 1 h and 15 min, 5 d/wk for 2 yr, on a carousel-type treadmill at 3.3 kph. During the next 23 wk, the load carried was gradually increased to 130% of the animal's body weight, and then maintained for 48 wk. The other 12 dogs served as controls. The dogs remained healthy and responded to exercise showing decreased skinfolds and body weight. All dogs showed increases in both tibial mineral content and width with time; but, the exercise group increased significantly more in mineral content than the controls. It is concluded that the gradual increase in bone mineral and width of the tibia is normal in the epiphyseal-closed skeleton of a young adult beagle. Also important is the fact that the intervention of exercise with added weight will increase tibial mineral content above these normal levels.