There are many physical activity awareness systems available in today's market. These systems show physical activity information (e.g., step counts, energy expenditure, heart rate) which is sufficient for many self-knowledge needs, but information about the factors that affect physical activity may be needed for deeper self-reflection and increased self-knowledge. We explored the use of contextual information, such as events, places, and people, to support reflection on the factors that affect physical activity. We present three findings from our studies. First, users make associations between physical activity and contextual information that help them become aware of factors that affect their physical activity. Second, reflecting on physical activity and context can increase people's awareness of opportunities for physical activity. Lastly, automated tracking of physical activity and contextual information benefits long-term reflection, but may have detrimental effects on immediate awareness.