This is a draft of my Project 2 R Notebook. My scientific question is: "How does an active cycle of breathing techniques and aerobic exercise training affect the physical fitness, as measured by muscle endurance and speed, of young children between the ages of 5-13 with cystic fibrosis?" My scientific hypothesis is "if clinically stable pediatric cystic fibrosis patients undergo an active cycle of breathing techniques in addition to aerobic exercise training, then their thoracic mobility and physical fitness parameters such as muscle endurance and speed will increase."