QUESTION: True or false: to improve your cardiovascular conditioning, get your heart rate as high as possible in aerobic exercise?
ANSWER: False. You improve your cardio condition by increasing cardiac output at lower heart rates. Here's the mathematical equation used by doctors and exercise physiologists:
Q = HR x SV
Your cardiac output, Q, is the product of your heart rate times your stroke volume - that's the amount of blood exiting the heart from the left ventricle every time it beats. A strong heart pumps more blood with every beat. At rest, Q is typically about 5-6 liters per minute. During exercise it can be 3-6 times as much.
Extra HorsepowerTo improve your cardiovascular conditioning, we focus on improving your Stroke Volume, conditioning the muscle fibers in the heart to pump more blood each time it beats. Think of it as adding horsepower to a pump.
We do this with a training program designed to increase your heart rate reserve --- the difference between your Resting Heart Rate and your Maximum Heart Rate. Your Maximum Heart Rate is most widely accepted at 220-age, it is a theoretical number that is the same for everyone.
We can’t change your Maximum Heart Rate, but we can lower your Resting Heart Rate. Typical Resting Heart Rate for adults is 60-80 beats per minute, if you’re already well conditioned it is probably lower.
The Frank-Starling LawFor over 100 years, doctors have relied upon the Frank-Starling law or mechanism for patients with heart arrhythmias and cardiac failure. It explains how the heart adapts to changes in heart rate and stroke volume, and applies equally to exercise.
If you train your heart to pump more blood what’s it going to do? Pump more blood. You will also see a lower resting heart rate and - as your heart rate reserve increases - an increase in potential cardiac output (Q in the formula discussed above).
If you train your heart to beat faster, what’s it going to do? Beat faster. You may not see improvement in cardiac output, in fact it may even decline. Frank-Starling explains that if the heart is literally beating so fast that the chambers don’t have time to fully fill with blood, the muscle contraction is not as strong. The muscle can actually weaken slightly over time. You burn more calories at a higher heart rate, but there's a good chance that you're burning muscle and not just fat. More about this in an upcoming article on Metabolic Training.
Your Cardio Training Heart Rate
- 60-80% of your Maximum Heart Rate, using the Karvonen formula, is targeted to increase stroke volume, therefore increasing cardiac output and lowering your resting heart rate. Gradually increase intensity of exercise that you are able to do while keeping your heart rate in this range.
- Above 80% of MHR not indicated for improving cardiac output. It provides other benefits such as improving lactic acid removal and strengthening fast twitch muscle fibers. So it is part of your program, but not the part that improves cardiac output.
THR = (220-Age-RHR) * Desired Intensity % + RHR
Ideally yes, but you can also use rate of perceived exertion. The Borg Scale is widely used, easy and scientifically validated, you rate your perceived level of exertion on a scale of 6-20, where 6 is no exertion and 20 is extremely difficult A rule of thumb is that you can then multiply by 10 to get an approximate heart rate.
Proceed with caution
Talk to a doctor and a fitness professional before beginning a new exercise program or substantially increasing the intensity. I'd be happy to meet with you to discuss your questions, goals and program options.