Radiographic evidence for acceleration of skeletal growth in adult hamsters by exercise

Voluntary exercise permanently elevates body weight in adult hamsters (Borer, K.T. Physiol. Behav. 12:589, 1974). Possible effects of such exercise on skeletal growth were examined in female hamsters in the asymptotic phase of growth, 14 of which had a 34-day access to horizontal disc exercisers, while 14 others remained sedentary. Skeletal measurements were taken from radiographs obtained at the start and at the end of exercise and on day 29 of retirement. Exercise was associated with more pronounced growth of axial than appendicular skeleton. Vertebral column, skull, humerous and femur of excercising hamsters grew 5.61 +/- 0.75 (p less than .001), 1.26 +/- 0.49 (p less than .05), 1.96 +/- 0.81 (p less than .02) and 2.80+/-1.34 (p less than .05) percent more, respectively, than the corresponding bones of sedentary hamsters. Appendicular skeleton continued to grow during retirement. Humerus and femur grew 1.96+/-0.65 (p less than .02) and 1.67+/-0.59 (p less than .02)% more, respectively, during retirement in exercised than in sedentary hamsters. Significantly greater weight gain was seen in active than in sedentary hamsters during both exercise (25.62 + 2.68%, p less than .001) and retirement (6.43 + 2.23, p less than .02). These data indicate that disc exercise accelerates skeletal and ponderal growth in adult hamsters and that axial and appendicular skeleton respond to this stimulus differently.