Reaching about 10 METs on a treadmill stress test is widely regarded as a strong result, associated with excellent cardiac prognosis regardless of age or sex. But “good” depends heavily on who you are. A 30-year-old man and a 70-year-old woman have very different expected capacities, so cardiologists increasingly judge performance not by a single cutoff but by how close you come to what’s predicted for your age and sex. The raw number matters, and so does the context around it.
What METs Actually Measure During a Stress Test
A MET, or metabolic equivalent of task, represents a multiple of your resting energy expenditure. Sitting quietly in a chair is roughly 1 MET. Walking at a comfortable pace is around 3 to 4 METs. During an exercise stress test, the treadmill gradually increases in speed and incline, and the workload you sustain at peak effort is expressed in METs. Most stress tests don’t measure your oxygen consumption directly; they estimate METs from the speed and grade of the treadmill at the moment you stop. On the standard Bruce protocol, the most commonly used treadmill test, average peak performance in a mixed clinical population falls around 9 to 10 METs, though this varies widely.
Beyond the raw number, your stress test generates several other data points your cardiologist reads alongside your METs score: how fast your heart rate climbed, whether your blood pressure responded normally, whether ST-segment changes appeared on the electrocardiogram, and how quickly your heart rate dropped after you stopped exercising. METs capacity is just one piece of that picture, but it’s arguably the most powerful single predictor of long-term survival to come out of the test.
The 10-MET Threshold and Why It Keeps Coming Up
If you’ve looked into this topic at all, you’ve probably encountered the idea that hitting 10 METs is the goal. That threshold isn’t arbitrary. In a study of patients referred for exercise stress testing with imaging, those who reached 10 METs or higher had an annualized cardiac death rate of just 0.1% and a combined rate of cardiac death and nonfatal heart attack of 0.4%.1PubMed Central. Prognosis in patients achieving ≥10 METS on exercise stress testing: Was SPECT imaging useful? That’s an exceptionally low risk, and it held up even without additional imaging data. The finding has been replicated in older adults specifically: patients 65 and over who achieved 10 METs or more had a cardiac death rate of about 0.6% per year over a median follow-up of seven years, with only about 3% showing significant ischemia on imaging.2Journal of Nuclear Cardiology. A high exercise workload of ≥ 10 METS predicts a low risk of significant ischemia and cardiac events in older adults
So 10 METs functions as a reassurance line: if you can get there, the chances of a serious cardiac event in the near future are very low. But that doesn’t mean falling below 10 is automatically bad. What matters more is where your score lands relative to what’s expected for someone your age and sex.
How Age and Sex Shape What’s Expected
Cardiorespiratory fitness declines with age, and men on average achieve higher peak METs than women. Researchers have developed prediction equations to account for this. One widely validated model for men estimates predicted METs as 18 minus 0.15 times age. For women, a well-performing model estimates predicted METs as 14.7 minus 0.13 times age.3PubMed. External prognostic validations and comparisons of age- and gender-adjusted exercise capacity predictions By these formulas, a 40-year-old man would be predicted to reach about 12 METs, while a 40-year-old woman would be predicted to reach roughly 9.5. A 70-year-old man would be expected to reach around 7.5 METs, and a 70-year-old woman about 5.6.
In clinical practice, reaching at least 85% of your age-and-sex predicted METs is generally considered adequate functional capacity, and achieving 100% or more is considered good to excellent. A study of patients with a heart condition called hypertrophic cardiomyopathy found that only 42% reached more than 85% of their predicted METs, illustrating how disease can drag performance well below expected levels.4European Heart Journal. Diastolic stress test echocardiography in patients with hypertrophy cardiomyopathy: association with exercise capacity For a healthy person, falling significantly short of that 85% mark often prompts further investigation.
Every MET Counts for Survival
The relationship between exercise capacity and mortality is not just about clearing a threshold. It’s a gradient. One of the landmark studies on this topic, published in the New England Journal of Medicine, found that each 1-MET increase in exercise capacity corresponded to roughly a 12% improvement in survival among men referred for stress testing.5PubMed. Exercise capacity and mortality among men referred for exercise testing That’s a strikingly consistent benefit per unit of fitness.
Larger, more recent data confirms this. The Henry Ford Exercise Testing Project, which included both men and women, found that each additional MET of fitness was associated with about a 16-17% lower risk of death, and this held true across the entire fitness spectrum without flattening out at high levels.6PubMed Central. Sex Differences in Cardiorespiratory Fitness and All-Cause Mortality: The Henry Ford Exercise Testing (FIT) Project In other words, going from 4 to 5 METs is roughly as beneficial, proportionally, as going from 10 to 11. There’s no point of diminishing returns. A meta-analysis of patients with existing cardiovascular disease found a similar pattern: each 1-MET increase was associated with about a 19% lower risk of dying from any cause.7PubMed Central. Cardiorespiratory fitness measured with cardiopulmonary exercise testing and mortality in patients with cardiovascular disease: A systematic review and meta-analysis
A large Cleveland Clinic study with over 120,000 patients put the magnitude in perspective. People with the lowest fitness had a five-fold higher risk of death compared to elite performers, and the mortality risk associated with low fitness was comparable to or greater than the risk from smoking, diabetes, or coronary artery disease.8JAMA Network Open. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing That comparison tends to surprise people: being unfit carries a mortality risk on par with lighting up a pack a day.
Your METs Score Alongside Other Stress Test Markers
Cardiologists don’t look at METs in isolation. Your heart rate response during exercise and recovery provides additional prognostic information. Failing to reach 85% of your age-predicted maximum heart rate during the test is an independent predictor of death, roughly doubling the risk in one well-known study.9JAMA. Impaired Chronotropic Response to Exercise Stress Testing as a Predictor of Mortality How quickly your heart rate drops in the first minute after exercise, called heart rate recovery, is another powerful indicator. A slow recovery (typically defined as 12 beats per minute or fewer in the first minute) suggests problems with the autonomic nervous system’s ability to shift gears.
When researchers combined low exercise capacity (below 6 METs), reduced heart rate recovery, and an elevated marker of electrical instability in the heart, the hazard ratio for cardiovascular death reached a striking 16.5, meaning that combination of poor results was associated with more than sixteen times the mortality risk.10PubMed. Prognostic capacity of a clinically indicated exercise test for cardiovascular mortality is enhanced by combined analysis of exercise capacity, heart rate recovery and T-wave alternans The takeaway is that a strong METs score with a healthy heart rate profile is much more reassuring than a strong METs score alone, and a weak METs score with poor recovery signals a need for closer attention.
Researchers have even developed a concept called “estimated age” from stress testing, which combines exercise capacity, heart rate dynamics, and other variables to produce a physiological age that can differ substantially from your calendar age. A higher estimated physiological age was independently associated with higher mortality, even after adjusting for traditional risk factors.11European Journal of Preventive Cardiology. Estimated age based on exercise stress testing performance outperforms chronological age in predicting mortality In practical terms, your stress test can tell your doctor whether your cardiovascular system is aging faster or slower than your birth certificate would suggest.
Why the Treadmill Protocol Affects Your Number
Not all stress tests are created equal, and this is an underappreciated wrinkle. The Bruce protocol, which most people encounter, uses aggressive jumps in speed and grade every three minutes. Other protocols, like the modified Bruce, Naughton, or Cornell protocols, use gentler ramps designed for less fit or older patients. The same person can achieve different METs on different protocols, and importantly, the prognostic meaning of a given METs value shifts depending on which test was used.
A large study from the Henry Ford cohort found that after adjusting for clinical risk factors and exercise capacity, simply being tested on a less demanding protocol like the modified Naughton was independently associated with higher mortality compared to the Bruce protocol. Achieving a given METs level on a gentler test carried a worse prognosis than hitting the same number on the Bruce.12PubMed Central. Prognostic Value of Functional Capacity in Different Exercise Protocols The likely explanation is selection bias: patients placed on easier protocols tend to be sicker or more limited to begin with, so a “10 METs on modified Naughton” doesn’t mean the same thing as “10 METs on the Bruce.” Still, across all protocols, higher METs consistently predicted lower mortality.
Another study found that using a ramped version of the Bruce protocol, where the speed and incline increase continuously rather than in abrupt stages, patients lasted longer and achieved higher peak METs (about 11.4 versus 9.6 on the standard Bruce).13American Heart Journal. Exercise testing: Improving performance with a ramped Bruce protocol The smooth ramp may better reflect true exercise capacity by eliminating the sudden jumps that sometimes cause patients to stop prematurely. If your test used a ramp protocol, your METs number might be somewhat higher than what you’d achieve on the traditional stepwise Bruce.
Estimated METs Can Overstate Your Actual Fitness
Standard treadmill stress tests don’t directly measure how much oxygen your body is consuming. They estimate it based on the treadmill’s speed and incline using long-established equations. This works reasonably well on average, but it can overestimate actual peak oxygen consumption by a meaningful margin in certain individuals. A study comparing estimated METs to directly measured oxygen uptake during treadmill exercise found that the standard prediction equations overestimated true capacity by about 21%.14PubMed Central. How Accurate Is the Prediction of Maximal Oxygen Uptake with Treadmill Testing? That’s a substantial gap. A person whose stress test report reads “10 METs” might actually be performing at closer to 8 METs of true oxygen consumption.
This overestimation tends to be larger in people who are less fit, obese, or taking certain medications. The conventional definition of 1 MET as 3.5 milliliters of oxygen per kilogram per minute is itself an approximation based on a reference person. Actual resting metabolic rate varies, and in populations like those with coronary disease, significant obesity, or people taking beta-blockers, the standard 3.5 figure overestimates resting metabolism, which inflates the MET calculation across the board. For most clinical purposes, the estimated METs from your stress test report still predicts outcomes reliably because the same estimation method was used in the studies that established the prognostic thresholds. But if you’re comparing your stress test METs to values from a test where oxygen was measured directly (a cardiopulmonary exercise test), the numbers won’t line up perfectly.
How Medications Change the Picture
Beta-blockers are probably the most important medication to consider. These drugs slow your heart rate and lower blood pressure, which is their therapeutic purpose, but they also limit how high your heart rate can climb during exercise. In the Henry Ford study, patients on beta-blockers achieved about 8% less of their age-predicted maximum heart rate compared to those not on the medication.15PubMed Central. Effect of Beta-Blocker Therapy, Maximal Heart Rate, and Exercise Capacity During Stress Testing on Long-Term Survival The prognostic value of reaching a certain heart rate target was also blunted by beta-blocker use, meaning the usual benchmarks for adequate heart rate response don’t apply as neatly when you’re on these drugs.
Interestingly, in patients with heart failure, beta-blocker therapy can actually improve exercise capacity over time. One study found that after three months of beta-blocker treatment, heart failure patients increased their METs from about 6.7 to 8.0 on average, alongside improvements in heart function and energy metabolism in the heart muscle.16PubMed. Beneficial effects of beta-blockers on left ventricular function and cellular energy reserve in patients with heart failure So the short-term effect of beta-blockers during a test (limiting peak heart rate) is different from their long-term effect on the heart’s capacity, which can be beneficial. If you’re on a beta-blocker when you take your stress test, your doctor will factor that in when interpreting the results.
When You Can’t Exercise Enough for the Test to Be Useful
A stress test provides the most diagnostic and prognostic information when you push close to your maximum capacity. If you stop early because of joint pain, poor balance, or deconditioning rather than because of cardiac symptoms, the test may be “submaximal,” and the METs value it produces won’t carry the same meaning. Many patients who can’t exercise adequately on a treadmill end up being referred for pharmacologic stress testing instead, where a drug like dobutamine or a vasodilator simulates the cardiac stress of exercise while you lie still.17PubMed. Functional capacity and cardiovascular assessment: submaximal exercise testing and hidden candidates for pharmacologic stress
In preoperative cardiac evaluation, the ability to achieve at least 4 METs (roughly the effort of climbing a flight of stairs or walking briskly) is used as a key decision point. Patients with poor or unknown functional capacity below that level who face elevated surgical risk may be sent for additional pharmacologic stress testing, and the results can change the surgical plan or medication management.18Mayo Clinic Proceedings. Perioperative Cardiovascular Evaluation and Management for Noncardiac Surgery: A Clinical Review The 4-MET threshold isn’t a “good” score by any definition, but for a surgeon deciding whether you can safely tolerate an operation, it’s the minimum functional marker that provides some comfort.
For patients who can’t use a treadmill at all, arm ergometry (cycling with your arms) is another option. Exercise capacity measured during arm testing, expressed in METs, still predicts mortality, though the absolute numbers tend to be lower than treadmill testing because arm exercise uses smaller muscle groups.19BMJ Open. A prognostic scoring system for arm exercise stress testing For elderly patients who can’t exercise at all, dobutamine stress echocardiography has been shown to be safe and prognostically useful.20PubMed. Dobutamine-atropine stress echocardiography in elderly patients unable to perform an exercise test
How Much of Your METs Score Is Genetic
If you’re wondering why some people seem to breeze through stress tests while others struggle despite regular exercise, genetics plays a bigger role than most people realize. A twin study combined with a meta-analysis of existing research estimated that genetic factors account for roughly 59% of the variation in maximal oxygen consumption (the gold standard for cardiorespiratory fitness) when measured in absolute terms, and up to 72% when adjusted for body weight.21PubMed Central. Twin-sibling study and meta-analysis on the heritability of maximal oxygen consumption A separate meta-analysis of endurance-related traits found heritability estimates ranging from 44% to 68% depending on how the measurement was adjusted.22PubMed. Heritability estimates of endurance-related phenotypes: A systematic review and meta-analysis
This doesn’t mean training is futile. It means that two people who follow the same exercise program may end up with meaningfully different METs scores, and that’s normal biology, not a failure of effort. Genetics sets a wide range; training determines where within that range you land. For previously inactive adults, even moderate physical activity (around 3 METs intensity or above) can improve MET capacity over time and reduce the risk of future cardiac events. Given that each additional MET carries a survival benefit, even modest improvements in exercise capacity are clinically meaningful, regardless of where you started.
METs in Heart Failure and Cardiac Rehabilitation
For people with heart failure, METs scores carry special weight. Exercise capacity was the single strongest predictor of survival in a study of heart failure patients, outranking age, body mass index, and whether the heart failure was caused by blocked arteries. Researchers used a scoring system based on peak METs, BMI, age, and cause of heart failure to sort patients into low-risk (about 2% annual mortality), medium-risk (about 5%), and high-risk groups (about 7%).23Journal of Cardiac Failure. Prognostic Value of Body Mass Index and Exercise Capacity in Patients With Heart Failure In this population, what counts as a “good” METs score is much lower than in the general population. A heart failure patient achieving 6 or 7 METs may be doing quite well relative to their peers.
Cardiac rehabilitation programs, which combine supervised exercise with education and risk-factor management, consistently improve METs capacity. Because the survival benefit of each additional MET appears to operate without a ceiling, even small gains in a cardiac rehab setting translate into measurably lower mortality risk. For someone recovering from a heart attack or living with heart failure, the stress test serves a dual purpose: it measures current risk and tracks whether rehabilitation is working. A follow-up stress test that shows even 1 or 2 METs of improvement represents a meaningful shift in prognosis.