As the International Space Station moves us closer to the reality of space colonization, it becomes increasingly important to understand the effects of altered gravity on mammalian reproductive physiology and function. Based on the existing data, there is evidence for hypo- and hypergravity-induced changes in male and female reproductive processes. However, additional research is needed to fill in the gaps in our current knowledge.
Although spaceflight experiments are critical, ground-based studies are important for the correct interpretation of spaceflight findings because spaceflight studies are often encumbered by flight restrictions and effects of environmental factors unrelated to hypogravity (i.e., radiation, vibration, noise). Research incorporating ground-based models is yielding results quite similar to those obtained from spaceflight. These similarities confirm the appropriateness of HLS, bed rest, and centrifugation for studying reproductive physiological responses and adaptation to altered gravity. Together, these unique tools are yielding new insights into the gravitational biology of reproduction in mammals.