Bigger muscles may look impressive, but their size might not tell the whole health story. New research suggests the quality of muscles around the chest and back could provide valuable clues about a person's future heart attack risk.

Researchers found that people with denser torso muscles had a lower risk of heart attack and death during long-term follow-up. Muscle quantity, by comparison, did not show the same meaningful connection with these outcomes. The findings put the focus on what muscle contains, rather than simply how much of it a person has.

The AI study appeared in the medical journal Radiology and examined routine heart CT scans from 1,722 adults. Participants had an average age of about 58, giving researchers a large collection of imaging data to study alongside later health outcomes. Artificial intelligence helped researchers analyze those scans in greater detail. Instead of looking only at the heart and coronary arteries, the system measured several parts of body composition visible in the images.

The findings could add another useful layer to cardiovascular risk assessment. Doctors already consider factors such as cholesterol, blood pressure, smoking, diabetes, and coronary artery calcium. Muscle quality could eventually provide extra information without requiring patients to undergo a separate imaging test.

Muscle Density Appears to Matter More Than Muscle Size

Alpha / Pexels / Muscle quality on a CT scan can be assessed using a measurement called ‘skeletal muscle attenuation.’

Denser muscle generally appears brighter on the scan and tends to contain less fat within the muscle tissue. Lower attenuation can signal greater fat infiltration and poorer muscle quality.

That distinction matters because two people can have similar amounts of muscle while having very different muscle composition. One person's muscles may contain less fat and show higher density, while another person's muscles may contain more fat. Measuring muscle size alone could miss that important difference.

The researchers found a striking association between muscle density and cardiovascular outcomes. Each 10-unit increase in muscle attenuation was linked with about a 31% lower risk of heart attack during the study period. That relationship remained notable after researchers considered several established risk factors.

Higher muscle density was also linked with a lower risk of death. Participants with better quality torso muscle had about a 39% lower risk of dying during the roughly 10-year follow-up period. These results suggest muscle composition could carry information about health that conventional measurements sometimes overlook.

Low muscle density was associated with about 1.58 times the risk of heart attack and 1.85 times the risk of death. Those figures describe statistical associations, so they do not mean low density directly caused those outcomes.

Researchers also adjusted their analysis for factors including age, sex, and coronary artery calcium. Muscle quality still showed an independent association with cardiovascular outcomes after those adjustments. Muscle quantity itself did not emerge as a significant predictor, making the difference between muscle quality and size especially interesting.

Why Healthier Muscle Could Be Connected to the Heart

Tima / Pexels / The researchers believe people with higher quality muscle may be more likely to exercise regularly and follow healthier lifestyles, which could partly explain their lower cardiovascular risk.

Regular physical activity affects much more than visible muscle definition. Exercise can improve blood pressure, insulin sensitivity, blood sugar control, and cholesterol levels. Those changes can reduce several established risk factors for cardiovascular disease at the same time.

Fat inside muscle tissue may also provide clues about metabolic health. Greater fat infiltration has been associated with aging, physical inactivity, obesity, and metabolic problems. Those same factors can overlap with conditions that raise a person's chance of developing cardiovascular disease.

Larger population research supports the broader connection between muscle quality and cardiovascular health. A UK Biobank study involving more than 350,000 adults found that a higher muscle quality index was associated with a lower risk of cardiovascular disease. That evidence strengthens interest in muscle quality as a useful health marker.

Muscle strength also appears to matter when viewed alongside overall cardiovascular health. Research has suggested that low muscle strength may carry greater cardiovascular risk when a person also scores poorly on measures such as the American Heart Association's Life's Essential 8.