Studying the Complex Relationships Between Physical Activity and Infertility.

This article provides commentary on the accompanying review, "Modifiable Risk Factors and Infertility: What are the Connections?" by Rossi and colleagues. This commentary focuses specifically on the association between physical activity or exercise and infertility, given the equivocal evidence summarized in the Rossi et al. review paper. Several methodologic issues related to physical activity and infertility are discussed, including defining the components of physical activity that research studies assess in research studies (e.g., type, intensity, frequency, duration); considering the optimal way to measure physical activity; and investigating important effect modifiers, including age and body mass index. Researchers should also consider sedentary behavior as another potentially important, unexplored, modifiable behavior that may be associated with infertility. Given that unexplained infertility remains of widespread global concern, identifying modifiable risk factors and how much influence they have on infertility remains an important area for research.