A stress test helps medical professionals understand how well your heart functions under physical exertion. A key measure during these tests is the Metabolic Equivalent of Task (METs), which offers insight into your physical fitness. Understanding your METs score, especially relative to your age, provides valuable perspective on your cardiovascular health and helps interpret test results.
Understanding Metabolic Equivalents (METs)
A Metabolic Equivalent of Task (MET) quantifies the energy expenditure of physical activities. It compares the energy cost of an activity to the energy your body uses while at rest. One MET represents the energy expended when sitting quietly, which is approximately 3.5 milliliters of oxygen consumed per kilogram of body weight per minute. Higher MET values indicate more demanding activities that require greater energy and oxygen consumption.
METs Measurement During a Stress Test
During a cardiac stress test, equipment like a treadmill or stationary cycle gradually increases exercise intensity. As the workload progressively rises through set stages, your heart rate, blood pressure, and oxygen consumption are closely monitored. The METs value is calculated based on the workload achieved at each stage, reflecting the oxygen your body consumes. The highest METs score you reach during the test, known as your peak METs, represents your maximum oxygen consumption and indicates your overall exercise capacity. Common protocols like the Bruce protocol have specific METs values assigned to each stage.
General METs Score Guidelines by Age
METs scores provide general benchmarks for cardiovascular fitness, though individual results vary by gender and training status. For an average non-trained person, a good maximum METs score is around 8 for women and 10 for men. More active individuals achieve higher scores, such as trained 30-year-olds who might reach 14 METs for women and 15 METs for men. Elite athletes can demonstrate exceptional fitness, with scores potentially reaching up to 22 METs for women and 25 METs for men.
Age also influences METs capacities. For instance, a healthy 20-year-old man might aim for 13.5 METs, while a woman of the same age could target 12.1 METs. These values decrease with age, with healthy 50-year-old men having a capacity of at least 9.2 METs and women 8.2 METs or higher. For individuals over 75, average METs achieved during a Bruce protocol stress test were 6.5 for women and 7.7 for men. A score of 10 METs or more is considered good and is associated with a favorable prognosis.
What Your METs Score Indicates
Your METs score provides valuable insights into your cardiovascular fitness and overall health. A higher METs score indicates good cardiorespiratory fitness, which is associated with a lower risk of certain heart conditions. For example, achieving 10 METs on a stress test suggests effective blood pumping by the heart and efficient oxygen use during physical activity, linking to a lower risk of cardiovascular disease. Conversely, a lower METs score might suggest reduced exercise capacity or potential underlying health considerations. For instance, a score below 5 METs may indicate health concerns, and below 7 METs can be a cause for attention.
A METs score is just one component of a comprehensive health assessment. Healthcare professionals interpret this score within the context of your complete medical history, any symptoms you experience, and other test results. While higher METs are linked to lower mortality, the exact prognostic value can vary depending on the specific stress test protocol used. Therefore, your doctor will consider all these factors to gain a full understanding of your health status.