CARDIAC OUTPUT TRAINING: WHY LESS IS SOMETIMES MORE
It is pretty well established that “cardio” is a great activity to participate in to improve overall health outcomes. Most people begin their journey into aerobic fitness by running. After all, the barrier to entry is extremely low.
So we lace up our shoes, do a couple of stretches on the front porch, and begin pounding the pavement with a goal to run a predetermined amount of miles in a particular time frame. We go hot out of the gate and the excitement continues to build until the wall hits, usually much sooner than we anticipated, and we’re left struggling to crawl past the finish line.
This article is not about pushing yourself to the brink and destroying yourself with an incredibly hard effort - it is about replenishing your physiological bank account. We want to discuss an aspect of aerobic training that can have a significant impact on your ability to train, recover, and adapt positively to stress.
Cardiac Output Training
Improvement in aerobic fitness has everything to do with the efficiency of your heart’s ability to pump oxygenated blood to the tissues that make up your body. Your resting heart rate gives a lot of useful information about your overall aerobic fitness. A lower resting heart rate indicates more efficient oxygen delivery. Cardiac output is the volume of blood your heart pumps in a given amount of time.
Cardiac Output = Heart Rate x Stroke Volume
Stroke volume is the amount of blood per pump of the heart and your heart rate is the number of times your heart is beating per minute. So, if we want to decrease resting heart rate and improve cardiac output we need to increase the amount of blood we are pumping per heart beat. Coach Erik Jernstrom of EForce Sports often uses the analogy of blowing up a balloon. Blowing up a balloon requires an even effort that will stretch the walls of the balloon to fill it with air. However, if you hyperventilate into the balloon, the short, fast, floundering breaths will not do much to stretch and fill the balloon despite the high amount of effort it requires.
The magic of cardiac output training lies in the filling of the heart with a longer, smoother effort that stretches the walls of the heart to take in more blood. So despite the best of intentions, going too hot out of the gate in your aerobic training is akin to hyperventilating into the balloon in an effort to fill it with air. Coach Erik has a quote that I often repeat: “beneficial work isn’t always hard, hard work isn’t always beneficial”. The majority of people embarking on aerobic training after some significant time away would do well to take some time investing in improving cardiac output, lowering their resting heart rate, and improving their aerobic window.
Cardiac output training involves a sustained effort, typically at a Rate of Perceived Exertion of 3 out of 10, for 20-60 minutes. This level of effort typically means you should be able to hold a conversation of short sentences while training. Over time this training approach increases your heart’s oxygenated blood output per beat and lowers the amount of beats per minute required.
Cardiac output and recovery
Time spent on cardiac output training is also beneficial for recovery. Low and slow cardio tends to be restorative in nature. It downshifts individuals from a stress (sympathetic dominant) state to a more adaptable (parasympathetic dominant) state. Low intensity, sustained cardio is a great way to actively facilitate recovery. This can even lead to an improved ability to get to sleep, stay asleep, and achieve higher quality sleep during the night.
In closing, there is more to “cardio” than just running yourself into the ground. Remember, anyone can go out and get tired. However, having a specific purpose in mind (ie lowering resting heart rate) will allow you to have confidence that the training you are doing is addressing a specific, desirable adaptation. The frequency with which you implement specific types of training should be determined by individual needs and goals.
Please do not hesitate if you have questions about how to apply these principles to your goals!