Cardiorespiratory fitness: the vital sign doctors rarely measure
Physical ActivityKey points
- AHA: fitness should be assessed as a vital sign.
- Low fitness carried a mortality risk comparable to smoking and diabetes.
- The highest fitness had the lowest risk; no upper limit was found.
- Fitness improves at any age.
What the research shows
Treadmill tests. At the Cleveland Clinic, researchers followed more than 122,000 patients who completed treadmill exercise tests. Lower fitness was linked to higher mortality, and the risk associated with low fitness was comparable to or greater than that of smoking, diabetes and coronary artery disease. People with “elite” fitness had the lowest risk, and there was no upper limit to the benefit (Mandsager et al., 2018).
AHA statement. In 2016, the American Heart Association issued a scientific statement arguing that cardiorespiratory fitness should be routinely assessed in clinical practice as a vital sign, because it predicts mortality as strongly as traditional risk factors (Ross et al., 2016).
How to improve it. Interval training improved fitness almost twice as much as moderate continuous training in people with cardiometabolic disease (Weston et al., 2014).
In practice
- Aerobic activity most days: brisk walking, cycling, swimming.
- Once or twice a week, add intervals where you push hard for 1 to 4 minutes.
- Progress gradually; consistency matters most.
Frequently asked questions
How can I estimate my fitness?
A treadmill stress test is most accurate. A rough guide: how far you can walk or run in 12 minutes, or how quickly your heart rate recovers after climbing stairs.
How fast can fitness improve?
Measurable gains often appear within 6 to 12 weeks of regular aerobic exercise, especially with intervals.
Sources
- Mandsager et al. (2018). Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open 1(6):e183605. doi:10.1001/jamanetworkopen.2018.3605
- Ross et al. (2016). Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement From the American Heart Association. Circulation 134(24). doi:10.1161/CIR.0000000000000461
- Weston et al. (2014). High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis. British Journal of Sports Medicine 48(16):1227-1234. doi:10.1136/bjsports-2013-092576
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