What are some personal or common barriers that prevent a person from being physically active

Some common barriers that might prevent a person from being physically active could be, their health, no accessibility, or laziness, plus many more. A person might have certain health concerns that cause them to exercise in moderation or not at all. It just depends on what that person is dealing with healthwise, because sometimes you need to exercise even more with a medical condition. Accessibility might also be a problem because a person may live far away from a gym or may not be able to afford a gym membership or home equipment; but, remember, you can always find ways to work out without equipment. A person might also just be lazy and might not want to exercise in a certain state of mind which causes them to not be very physically active.  

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.