Anyone who exerts themselves sufficiently, (including perfectly healthy people) can become breathless.
It is a normal response to physical activity. It varies dependant on how strenuous or for how long the activity is sustained. Obviously, those with a lung disease or older people will have a lower threshold at which breathlessness occurs.
Breathlessness (or dyspnoea) is common in people with lung or heart conditions as well as in people who are overweight or unfit.
People who are overweight or unfit will have to work harder during everyday activities and, as a result, will fatigue more quickly while people who are too slim may also fatigue quickly as they have no reserve energy.
As people get older, their lung function declines due to changes in their lungs, their chest wall, and the strength of their breathing muscles. These changes contribute to older people becoming more breathless when performing activities.
Those with lung diseases like COPD will experience breathlessness as the disease affects the breathing tubes or airways and the lungs. The feelings of breathlessness may increase as the disease progresses.