You may be pretty proud of your physical fitness. Perhaps you can run a couple of blocks to catch the bus or train without becoming short of breath. When you bound up flights of stairs, your heart hardly pounds. And perhaps you head to the gym several times a week for 30 solid minutes on the elliptical trainer or treadmill. But how do you really measure up in terms of fitness—that is, cardiovascular fitness?
What is cardiovascular fitness?
Your ability to use oxygen efficiently is what's meant by cardiovascular (CV) fitness, also often referred to as cardiorespiratory or aerobic fitness. Sounds simple, but myriad physiological changes occur in the body as fitness improves. The heart muscle becomes larger and stronger, boosting the amount of blood pumped with each beat. Blood vessels expand or dilate to deliver more blood to the working muscles, which are better able to extract oxygen from the blood. And the muscles' mitochondria (typically referred to as energy powerhouses) increase in number, something that dramatically and beneficially improves metabolism. In other words, to have good cardiovascular fitness, your heart, blood vessels, lungs, and muscles must all work efficiently.
Why care about your cardiovascular fitness?
Because it’s the most important component of fitness in terms of its relation to health and well-being. The link between cardiorespiratory fitness and both type 2 diabetes and cardiovascular disease is well known. According to a paper authored by Dr. Steven Blair, a researcher known for his work on aerobic exercise and health, low cardiorespiratory fitness was associated with some 16% of death among both men and women in one large study.Even among subjects considered at low risk for cardiovascular disease, a paper published in the Journal of the American Heart Association found that having high cardiorespiratory fitness reduced the risk even more.
The benefits of cardiovascular fitness are numerous. A study published in the Journal of Women's Health found that high cardiorespiratory fitness may reduce the stiffness of the aorta, the body’s major artery, in obese women with fat stored around their belly, a risk for all manner of chronic diseases, including heart disease and diabetes. Higher levels of cardiorespiratory fitness are also correlated with a lower risk of some cancers among men, according to a study reported in JAMA Oncology.
How to assess your cardiovascular fitness
The gold standard for evaluating your cardiovascular fitness is VO2 max or maximum aerobic capacity, which directly measures how much oxygen your body uses when you're running vigorously with increasing grade and speed on a treadmill (or bike ergometer).
VO2 max usually needs to be measured in a medical clinic, university lab, or specially equipped health club. There are a variety of other ways, called "field tests," that can roughly estimate VO2 max. Which test you choose depends on whether you're already fit and healthy, or sedentary and not necessarily well. Your age is also a factor to consider. Most non-athletes can try a walking, rather than a running, test. (The Rockport 1-Mile Walk Test in which you walk one mile as fast as you can was used in 60+ year olds in a 2014 pilot study published in Clinical Interventions in Aging.) There's also the 6-Minute Walk Test, which is often considered appropriate for older adults. For descriptions and instructions on the various fitness tests, visit the President's Challenge website, which allows you to plug in your results for an evaluation.
How to improve your cardiovascular fitness
According to the American College of Sports Medicine, you should engage in aerobic activities such as brisk walking, jogging, cycling, hiking, swimming, cross-country skiing, dancing, tennis, or soccer at a moderate to vigorous intensity several times a week. With moderate exercise, the duration should be at least 30 minutes—it can be in 10-minute bouts—for a weekly total of 2.5 hours to 5 hours.
But numerous studies have shown that there is a more efficient way to boost your CV fitness, called high intensity interval training. This sort of training means alternating short intense spurts with a more leisurely pace. For example, cycle as fast as you can for 30 seconds and then pedal for two minutes at a more relaxing pace. Then do another tough 30 seconds, and repeat. Of course, participating in continuous aerobic activity (such as jogging for 30 minutes) can also significantly boost your fitness. But it’s high-intensity interval training that provides greater gains and works well for young or old in a time crunch. Check with your doctor to make sure it's safe for you to engage in such vigorous exercise.
If you are largely sedentary, cardiovascular training can produce dramatic improvements. If you're already fit, the relative increase will be more modest. But with regular increases in your workout intensity, your cardiovascular fitness can be expected to continue to improve over 4 to 5 months, stabilizing thereafter.
Are you getting fitter?
You can gauge your progress simply by repeating the field test you originally chose. An even easier way is measure your heart rate recovery time: Check your heart rate immediately after you stop exercising, and then again two minutes later. The difference between the two numbers is your recovery heart rate. Keep a chart of this over time. As you become fitter, it'll take less time for your heart rate to recover (so the difference between the two numbers will get larger).