A strong heart has many benefits. Increased circulation of blood results in more fuel and oxygen being delivered to muscles and other organs. This improves endurance for activities as well as enhancing cognitive function. A brain with good blood flow does perform better.
How do we make the heart more fit? Raising the heart rate and then keeping it elevated returns more blood to the heart, which in turn causes the muscle of the heart to become stronger and more efficient. Lifting weights does induce changes in the heart muscle, but this has more to do with how quickly blood is ejected from the heart. To make the heart more efficient, endurance training is the best.
Endurance training has several forms. Typically, we think of long duration, low intensity endurance first. This is accomplished by doing any activity – such as hiking, running, paddling, swimming, or biking – at a steady pace for 12 minutes or longer, where longer could be potentially many hours.
There is also high intensity interval training (HIIT). This involves performing exercise for a given time interval and then resting afterwards. Intervals can be done for various lengths and with various levels of intensity. The key here is that the exercise is performed at a higher intensity during the work interval than if you were doing the activity for a longer duration. Also, the rest period is a real rest, not another activity performed at a similar intensity. If the activity is maintained at a steady state without periods of intensity and rest, this is not HIIT. Realistically this is done for just 3-12 sets depending on how long the work intervals are.
To have a fit heart, do endurance training. Include some long slow distance and some interval training. If you are doing only one or the other, mix it up and try the other category. If you do only long intervals, try some shorter ones. If you do only short bursts, try to go long.
