ABSTRACT

As in human populations, physical activity can represent a range of behaviors in animal models. Consequently, context matters when discussing the genetic regulation of physical activity. For example, assessing exercise endurance in rodents typically utilizes forced running on a motorized treadmill equipped with a shock grid for a negative stimulus (48). Alternatively, assessing daily movement distance may involve measuring the number of revolutions an animal voluntarily turns a running wheel in a given amount of time (16). These two types (forced vs. voluntary) of physical activity are a result of, and result in, at least some variation in physiological and molecular responses. And, most relevant to this chapter, these exercise types may be regulated by different genetic architectures or genomic mechanisms. I emphasize this early in the text because results (e.g., genetic mapping, transcriptomic, and proteomic) across animal models and between studies may appear inconsistent, and, in part, this lack of replication may simply be a reflection of measuring different phenotypes, however subtle. This is especially pronounced within the broad category of voluntary physical activity, where subtypes are numerous (e.g., wheel running, home-cage activity, open-field activity, spontaneous physical activity, and nonexercise activity thermogenesis). So, context certainly matters when comparing results obtained from a variety of measures, but may not be as important if we are broadly looking for genetic regulation of physical activity that transcends specific activity types (i.e., a set of master activity regulators). Thus, in this chapter, I will attempt to provide examples in the context of specific measurements.