Cardio Respiratory Fitness

11 April 2018

Importance of Assessing Cardio-respiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement from the  American Heart Association

Reference: online version:

  • There’s growing evidence showing that CRF could potentially be a stronger predictor of mortality than other known risk factors such as smoking, hypertension, high cholesterol and type 2 diabetes mellitus and by adding CRF to these risk factors significantly improves the reclassification of risk for unfavorable outcomes.
  • It’s concluded that CRF < 5 METs in adults is associated with a high risk of mortality, while a CRF of > 8-10 METs are associated decreased mortality.
  • CRF can be a strong predictor on the outcome of CVD conditions such as stroke, heart failure and surgery
  • By using exercise intervention to improve CRF as part of pre-surgery rehabilitation improves the outcome of the surgical risk, mortality as well as post-op rehabilitation.
  • An increase in CRF is associated with a lower risk of unfavorable health outcomes and chronic diseases in addition to CVD.
  • Higher levels of CRF are linked to a reduced risk of dementia and Alzheimer disease development, as well as lower levels of anxiety and depression
  • Multiple studies have shown that there’s an inverse relationship between CRF and the risk of developing prediabetes, metabolic syndrome and Type 2 Diabetes Mellitus
  • It’s been reported that that there’s a 20% – 45% lower risk of all-cause cancer mortality in moderate and highly active and fit individuals.
  • Low CRF levels have been associated with a higher risk of disability in when getting older.
  • Estimation of CRF can be done by performing standardized protocols on a treadmill speed, grade or duration test or a cycle ergometer workload test (in watts) using established predictive equations. Submaximal exercise tests can be valuable in a clinical practice and should be considered when resources are limited, however they are not as accurate as maximal exercise tests in determining CRF.
  • Exercise prescription to improve CRF should include regular rhythmic contractions of the larger muscle groups for an extended duration at a moderate to vigorous intensity with lower intensity recovery periods in between if effort is reaching the maximum.
  • See tables in the statement for recommended exercise dose to improve CRF. The higher the intensity, the higher the increase in CRF will be and is more sensitive to exercise intensity than duration or frequency. If the individual has a higher starting CRF, he needs to engage in more vigorous intensity exercise to significantly increase CRF.


  • CRF <10 METs: training intensity of 50%HRR or VO₂R required
  • CRF 10 – 14 METs: training intensity of 65% – 85% of HRR or VO₂R required
  • CRF > 14 METs: training intensity of > 85% HRR or VO₂R required

General recommendation regarding CRF measurements in your practice:

  1. All adults should have their CRF tested at least once a year
  2. Individuals with CVD risk profiles or a chronic disease should have more frequent CRF tests done

Cardio-respiratory Fitness is related to the risk of sudden cardiac death.

Reference: Laukkanen JA, Makikallio TH, Rauramaa R et al.: Journal of the American College of Cardiology 2010; 56: 0735 – 1097

  • The Journal of The American College of Cardiology published a population-based follow-up study that stretched over 17 years looking at how CRF is related to Sudden Cardiac Death (SCD) risk.
  • They’ve concluded that CRF in addition to other risk factors can be seen as a predictor of sudden cardiac death (SCD). Other risk factors includes ischemic  ST – segment depression during exercise testing, smoking, systolic blood pressure, prevalent coronary heart disease, family history of coronary heart disease and type 2 diabetes mellitus.
  • The study showed that an increase in VO₂ max  of 1 MET (3.5 ml/kg/min) in cardiorespiratory fitness was related to a decrease in 22% in the risk of sudden cardiac death  for healthy men and 25% risk reduction in men with previously diagnosed disease.
  • They’ve also found an association between CRF and physical activity and the occurrence of coronary heart disease (CHD). Higher physical activity levels and CRF reduce the risk of early death under individuals with an unfavorable risk profile.

Featured News

What is Health Sciences?

1 year ago