Anyone who has CF should most definitly try to be an active person. Swimming, tennis, football, soccor, hockey, basketball, netball, running, high jump, long jump, walking, sprinting, jogging... it's all good. Just as long as it makes you breathless, they it's good for you. When a physical activity makes you breathless, it means that it is working your lungs to an extent that they are breathing even deeper then usual, which means getting air into the spaces that your lungs hardly use. This prevents collapse in your lungs and it's all around great for your health.