VO2 max has moved from sports labs into everyday conversation, helped by fitness watches that estimate it. The term refers to the most oxygen your body can use during hard exercise. It is the best-known measure of cardiorespiratory fitness: how well your heart, lungs, blood vessels and muscles work together.

There is good reason for the interest. In large studies, fitness predicts how long people live about as well as, or better than, many of the risk factors doctors track routinely.

What the research shows

In 2016 the American Heart Association published a scientific statement arguing that cardiorespiratory fitness should be treated as a clinical vital sign. It noted that low fitness is linked to higher risk of cardiovascular disease, death from any cause, and death from several cancers, and that fitness may be a stronger predictor of mortality than smoking, high blood pressure, high cholesterol or type 2 diabetes.

A 2009 analysis of 33 studies in JAMA found that each step up in fitness, measured in metabolic equivalents or METs, was linked to a 13 percent lower risk of death from any cause and a 15 percent lower risk of heart disease events.

A 2018 Cleveland Clinic study followed more than 122,000 adults who had treadmill tests. Those in the lowest fitness group had a risk of death about five times higher than the fittest group, and the gap between below-average and above-average fitness was comparable to the effect of smoking or diabetes. The benefit continued at the highest fitness levels, including in people 70 and older.

These are observational findings. People who are fit may also differ in other ways. But the association is strong and consistent, and unlike age or family history, fitness can change.

What the numbers mean

Fitness is often expressed in METs, short for metabolic equivalents. One MET is roughly the energy you use sitting quietly, so an activity rated at 8 METs takes about eight times as much. The JAMA analysis grouped people as low fitness below 7.9 METs, intermediate from 7.9 to 10.8, and high at 10.9 or more.

You do not need to know your number to benefit. The practical message from these studies is that moving from the least fit group into the next one brings the largest gain, which is good news for anyone starting from a low base.

How fitness is measured

A true VO2 max is measured during a cardiopulmonary exercise test, usually on a treadmill or bicycle while you breathe through a mouthpiece that analyzes your breath. It is done in exercise physiology labs and some cardiology and sports medicine settings. Standard treadmill stress tests estimate fitness from how long and how hard you can exercise, which is how the studies above measured it.

Smartwatch estimates are convenient but approximate. They are most useful for watching your own trend over months, not for comparing yourself with a chart. If you are curious about formal testing, ask Dr. Shtern whether it makes sense for you.

How to improve cardiorespiratory fitness

Fitness responds to training at any age. The federal guidelines for adults 65 and older call for at least 150 minutes a week of moderate aerobic activity, or 75 minutes of vigorous activity, along with strength and balance work. The National Heart, Lung, and Blood Institute describes how physical activity benefits the heart and how to build up safely.

  • Build a base first. Brisk walking, cycling, swimming and rowing all count. Most of your weekly time can be at a pace where you can talk but not sing.
  • Add some harder intervals once you are ready. Short stretches of faster effort, followed by easy recovery, are an efficient way to raise fitness.
  • Be consistent. Fitness fades when training stops. A schedule you can keep through a Florida summer matters more than an ambitious one.
  • Pair it with strength work. Stronger legs make every aerobic activity easier. See strength training after 50.

When to check with your doctor first

Talk with your doctor before stepping up intensity if you have heart disease, chest pain or pressure with exertion, unexplained shortness of breath, fainting, or several risk factors that have not been evaluated. Stop and seek care for chest discomfort, unusual breathlessness or lightheadedness during exercise.

Heat is also a factor here. Exercising outdoors in South Florida means planning around the hottest hours and drinking enough fluid. Our article on heat, hydration and your kidneys has practical tips, and the benefits of exercising covers the basics.

An ECG is done in the office at Legacy Medical, and the annual executive physical includes one, which gives Dr. Shtern a baseline before you train harder. To meet her and talk about your goals, book a complimentary meet and greet.

This article is general information, not advice for your situation. Members can call the office with questions about their own care.