Research suggests that exercise can help improve brain health and decrease the risk of dementia, but there is variation in the benefit of different exercise interventions. Cindy Barha, Ph.D. and colleagues hypothesize that male and female brains may respond in different ways to different types of exercise such as aerobic training versus resistance-strength training. Both types of exercise benefit cognitive function in older adults, but they do so using different biological factors. Dr. Barha and colleagues will conduct an exercise study of 210 male and female participants with mild cognitive impairment (MCI), a condition of subtle memory loss that may precede Alzheimer’s disease. The participants will do aerobic training or resistance-strength training three times a week for 6 months and the researchers will measure changes in their memory function and brain structure. They will also measure the participants’ levels of estrogen, testosterone, cortisol and BDNF before and after the exercise intervention. The results of this study may provide new information on how exercise affects the brains of men and women differently. A better understanding of these mechanisms could help scientists develop sex-specific, personalized exercise interventions that more effectively slow or prevent memory decline in people with mild cognitive impairment.