How can barriers affect physical fitness?

Hmm.

Explanation:

'Your barriers to physical activity fall into one or more of seven categories: lack of time, social influences, lack of energy, lack of willpower, fear of injury, lack of skill, and lack of resources. A score of 5 or above in any category shows that this is an important barrier for you to overcome'

So basically, barriers affect physical fitness by literally not allowing you to exercise.