In this presentation, I introduce my work on human-factors in computer-aided system design to promote physical well-being and regular practice of physical exercie. Health problems associated with sedentary lifestyles are undeniably critical issues of our time. Computer-aided appraoches are promising instruments for resolving this crisis through theoretical and practical progress of sports and exercise science. Scholars consistently employ interdisciplinary informatics for training, coaching, testing, and educating individuals. However, common design principles often fail to address human factors and unique characteristics of physical exercise at the same time. In response, I utilize a human-computer interaction perspective and investigate fundamental cognitive elements of exercise psychology in computer-aided system design. I conduct three case studies to individually evaluate self-efficacy, outcome expectancy, and risk factors in physical exercise. During my first study, I introduce a role for age in exergame difficulty adjustments to promote self-efficacy and enhance motivation for regular physical exercise. Next, I focus on situated pedaling visualizations in an attempt to provide intuitive feedback and better satisfy outcome expectancies of cyclists. Finally, I study knee overuse injuries in cycling to address risk perception in exercise. Taken together, I consider these factors critical for solving problems associated with physical inactivity through computer-aided systems and substantially helpful for achieving a further increase in regular practice of physical exercise to bolster healthy lifestyles.