If you have to choose between a long stroll versus a shorter power walk, which is better for heart health? According to a study published in the British Medical Journal (2012,doi:10.1136/bmjopen-2012-001711) the less leisure time and the more active time you have, significantly reduces the risk of developing metabolic syndrome and heart disease. So, more is better, in terms of overall time spent on physical activity, when trying to improve your heart health.
Specifically, the researchers also found that the intensity of your activity efforts is most important. So if you have a finite amount of time daily to walk, then the walk needs to be vigorous; if your fitness level allows, then a run is better than a jog. If you have two or three small windows of opportunity for exercise, then each opportunity should be challenging enough to raise your heart rate. The point is to move as much as possible and to make those activity moments vigorous enough to increase your heart rate.