O ne-third of adults worldwide are physically inactive (16). The period of transition from high school to college is frequently accompanied by increased inactivity leading to weight gain, with most studies showing a gain of about 4 lb in the first year of college, which may mark the beginning of a trend (15). In 2014, 51% of women attending college in the United States did not meet the physical activity guidelines set by the American College of Sports Medicine (ACSM), and 31% were estimated to be overweight or obese (1). Among the multitude of established ramifications of low fitness, suboptimal cognitive performance secondary to low fitness may jeopardize learning and academic success in college-attending women (19).The bidirectional association between physical and mental health has been acknowledged for millennia (46). Within research relating fitness to brain and behavior, a focus on life stage extremes-periods during which rapid brain changes occur-has predominated, and little is known about this association during young adulthood. It is now widely recognized that lifelong brain remodeling occurs (14), which has generated interest in how to optimize brain function in young adults. Evidence for an association between fitness and cognition has been identified at the neural level in studies using electroencephalography to examine event-related potentials, suggesting that fitness promotes neural plasticity (34). However, limited evidence at the behavioral level prevents forming implications for real-life scenarios. The lack of data to support behavioral effects also makes it difficult to distinguish whether fitness benefits the whole brain or only certain systems underlying certain behaviors, that is, whether the effects of fitness are general or specific. Furthermore, previous investigations in young adults have involved methodological constraints such as small sample size, assessment of fitness using self-reported or indirect measures, or aggregation of data across different age groups or sexes (18,21,45). Given the changes in fitness and high dependence on optimal cognition in university settings, we sought to better understand relations between cardiorespiratory fitness (CRF) level and executive function in young adult women. Our purpose was to test whether and older adults. Women attending college live in a cognitively demanding setting where optimal cognition matters but often experience declines in CRF. Our aim was to test whether CRF is associated with executive function in young adult women. Methods: Participants in this cross-sectional study included 120 healthy women age 18-35 yr in a university setting. Each woman completed a maximal treadmill-based exercise test to determine peak oxygen uptake (V O 2peak ), computerized tests of executive function, and questionnaires to assess motivation and other factors with potential to influence physical and cognitive performance. Results: Overall CRF was excellent, with a sample mean V O 2peak of 44.6 mL·min -1 ·kg -1 . After adjusting for covariates, higher V...