There are many different ways to improve the health of your heart through exercise. One method that has been around for centuries in endurance training and combat sports like boxing is long steady distance (LSD) or cardiac output training. In recent years this type of training has received criticism and people have shunned it in favour of higher intensity intervals, but this is a mistake when it comes to developing a healthy heart as cardiac output works in a way that other methods simply do not.
Cardiac output training works to increase stroke volume (the amount of blood pumped out with each beat) by increasing the size of the left ventricle of the heart (the chamber of the heart that pumps oxygenated blood around the body). By keeping your heart rate in a particular range (120-150 beats per minute) over an extended period of time (30 – 90 minutes) the chambers of your heart fill repeatedly with large volumes of blood. The walls of the left side of heart respond to this stimulus by stretching and you gradually end up with a larger left ventricular cavity. The result is a lower resting heart rate, lower exercising heart rates, and a healthier more efficient heart overall.
This is not to discount the importance of higher intensity methods for improving heart health but you can’t replace the cardiac output method with 10-20 minutes of intervals and expect to see the same results and benefits. The main reason for this is that once the heart rate goes above approximately 150 beats per minute (bpm) it’s beating too fast for the chambers to fill completely. This means the walls of the left ventricle do not get stretched and you don’t stimulate the same adaptation.
Cardiac output training is a great option for people who have a high resting heart rate (70bpm or above) as it will help to lower it to a healthier level (60bpm or below). It’s also perfect for those who are new to training or coming back to it after a long break. You can use any mode of low intensity exercise to complete a cardiac output session such as jogging, biking, swimming, and skipping or circuits as long as the heart rate stays in the correct range (120-150 beats per minute). This type of training can be used 1-3 times per week and each session should last 30 – 90 minutes. It’s best to increase duration gradually over a few weeks.
You can use this method to build a good base of fitness before you try some more intense methods or you can use it concurrently with higher intensity training on different days. Either way your heart will benefit from this type of training in a way that other methods simply do not provide.