This Fitness Metric May Be The Most Overlooked Predictor Of Heart Disease

Most people track their weight, blood pressure, maybe cholesterol. But there's another number that researchers say may tell you even more about your heart health, and most of us have never thought to check it.

Cardiorespiratory fitness (CRF) is a measure of how well your heart, lungs, and muscles work together when you're moving, and VO₂ max, the maximum amount of oxygen your body can use during exercise, is the most common way to measure it.

Higher CRF has long been linked to better heart health. The American Heart Association has even recommended it be treated as a standard clinical measurement, like blood pressure or cholesterol.

But researchers wanted to know something more specific: can CRF actually be used to detect heart disease in someone who already has it, or predict who's likely to develop a serious cardiac event down the line?

To find out, they pulled together findings from six large research reviews covering more than 31,000 people. Most of the reviews looked at heart health outcomes across different populations.

The results varied depending on who was being studied, but the overall picture was consistent: fitness level is a meaningful signal for heart health.

In people with heart failure, CRF was a strong predictor of serious cardiac events, things like sudden cardiac death or needing a heart transplant. In women being evaluated for blocked arteries, CRF showed high accuracy as a diagnostic tool.

For people with type 2 diabetes, the accuracy was lower, likely because heart disease in that group is more complex and harder to detect with a single measure.

CRF also showed the ability to flag cardiovascular risk in otherwise healthy kids and teens, a notable finding, since fitness is rarely discussed as a health marker in children.

The standout result: CRF was highly accurate at detecting mitochondrial disorders (conditions where cells can't produce energy properly) in adults. This was the only finding in the entire review rated with high certainty.

One important caveat: the quality of the underlying research was rated low across the board, and the confidence in results varied widely by outcome.

The findings are most reliable for people who already have a health condition. For healthy adults, the picture is less clear.

You don't need a lab test to start paying attention to your cardiorespiratory fitness. Many fitness trackers and smartwatches now estimate VO₂ max using heart rate data during exercise, and some offer a resting estimate based on age and basic health metrics.

These aren't perfectly precise, but they're useful for tracking trends over time.

Consider tracking your CRF alongside other standard health markers like blood pressure and cholesterol.

Cardiorespiratory fitness has long been framed as a performance goal, but a growing body of evidence increasingly positions it as a meaningful clinical signal, one that may reveal cardiovascular risk before other standard markers do.