Exercise reduces gonadal atrophy caused by short photoperiod or blinding of hamsters.

The effect of voluntary exercise upon several reproductive parameters was assessed in male Syrian hamsters. Forty-two animals were caged in five groups and then blinded: Ten housed five per plastic cage; eight housed individually in plastic cages; six housed individually in plastic cages with 15 cm exercise wheels in the cage; eight housed in Wahmann steel activity cages with 36 cm wheels locked to prevent rotation; ten housed in functional Wahmann running wheel cages. At 16 weeks after blinding, animals with access to functional running wheels had significantly larger testes (3.7 +/- 1.0 g) than those with no wheels or locked wheels (1.86 +/- 0.6 g; mean +/- SD; p less than 0.001). These results suggested that voluntary exercise reduces testicular atrophy caused by blinding. A second experiment was run in which the animals were subjected to a short photoperiod (LD 6:18) for 12 weeks instead of blinding. Similar results were obtained except that access to the small exercise wheels did not affect testicular atrophy: Mean testicular mass of animals in individual cages = 0.79 +/- 0.3 g, small wheels = 0.74 +/- 0.4 g, functional Wahmann wheels, 2.56 +/- 1.0 g, locked Wahmann wheels 0.52 +/- 0.1 g (p less than 0.01).