Aside from the various physical and psychological benefits of physical activity engagement, recent findings suggest levels of habitual physical and sedentary activity can predict patterns of lateralized frontal cortical activity at rest measured by electroencephalography (EEG). These lateralized brain activity patterns are linked to motivational systems proposed by Reinforcement Sensitivity Theory (RST) thought to govern behavioral approach, fight-flight-freeze, and motivational control responses. Research to date has primarily focused on the link between these patterns of frontal asymmetry at rest and self-reported habitual physical activity levels. However, past research has yet to examine whether these physical activity levels are linked to activation of specific motivational systems during situational frontal asymmetry patterns, neuro-correlates of motivation systems proposed by RST. The current study measured resting frontal asymmetry in addition to using a novel task to elicit situational frontal asymmetry to extend prior work on frontal asymmetric patterns of activity as a marker of habitual physical and sedentary activity. Results revealed a link between habitual sedentary activity and greater left frontal asymmetry, supporting recent frameworks of energy minimization that could mark more sedentary lifestyles. Situational frontal asymmetry results were in line with recent evidence suggesting strong situational manipulations may diminish the link between individual differences in physical and sedentary behaviors to motivation in a decision-making task. Potential limitations and further explanations are discussed.