What is the ability of the body to function successfully and efficiently during physical activity

Physical fitness would be the answer. In order for you to walk, you have to be well enough to walk, For instance, you need to be in shape to walk. Some people are so overweight that that they need a wheel chair just to get around and are an extreme example of what it is not to be physically fit. Regular exercise should help you avoid this predicament.

Breastfeeding should last for 12 months.