Exercise of any type can help strengthen the heart. While there is no great evidence, it is widely assumed that exercises such as running, swimming and cycling are best for the cardiovascular system. This is because all of these exercises involve the use of a large amount of muscle mass and burn lots of calories. In addition, these types of exercises allow your heart rate to rise to a higher rate for a longer period of time than other types of exercises such as lifting weights.
The purpose behind exercising is burning calories, increasing demand on your heart, improving your health, and feeling good about yourself. It doesn't really matter whether you do it indoors or outdoors. In terms of where you start, well this depends on your personality. Some people need motivation and find it when they exercise in groups, or as a part of an organized plan. Others find it easier to exercise on their own. This is something you will have to answer for yourself.
I suggest that you schedule an appointment with your primary care physician
. The two of you can discuss the exercise plan you have in mind and your doctor
can give you tips on how to increase you chances of achieving your goals.