Many reports have associated aging with deterioration in a number of cognitive functions. These reports have also demonstrated the beneficial effect of physical fitness on cognitive function, especially executive function. Here, studies related to cognitive-physical association in older adults are reviewed and I also report our recent studies for such association. In our study, we utilized task-based and resting-state functional magnetic resonance imaging techniques. The mechanism of the relationship between physical fitness and cognitive function could be further investigated by functional brain network.