The AHA Recommends That Every Patient Have A Cardiorespiratory Fitness Evaluation

Reference (1), 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, reviews the importance of assessing cardiorespiratory fitness in every patient. What follows are some excerpts from the article:

Mounting evidence over the past 3 decades has firmly established that low levels of cardiorespiratory fitness (CRF) are associated with a high risk of cardiovascular disease (CVD) and all-cause mortality, as well as mortality rates attributable to various cancers, especially of the breast and colon/digestive tract.1–4 Importantly, improvements in CRF are associated with reduced mortality risk.5 Although CRF is now recognized as an important marker of cardiovascular health, it is currently the only major risk factor not routinely assessed in clinical practice

Conclusions and Recommendations: CRF as a Predictor of Health Outcomes

• CRF is as strong a predictor of mortality as established risk factors such as cigarette smoking, hypertension, high cholesterol, and T2DM.

• A CRF level <5 METs in adults is associated with high risk for mortality; CRF levels >8 to 10 METs are associated with increased survival.

• More than half the reduction in all-cause mortality occurs between the least fit (eg, CRF <5 METs) group and the next least fit group (eg, CRF 5–7 METs).

• The influence of race on the relationship between CRF and health outcomes requires further investigation.

• Small increases in CRF (eg, 1–2 METs) are associated with considerably (10% to 30%) lower adverse cardiovascular event rates.

• Efforts to improve CRF should become a standard part of clinical encounters (eg, an accepted “vital sign”).

Conclusions: CRF as a Predictor of Other CVD Outcomes

• CRF strongly predicts outcomes across a wide spectrum of CVD outcomes, including those related to stroke, HF, and surgery.

• Optimizing CRF prior to surgical interventions (termed “prehabilitation”) improves outcomes including surgical risk, mortality, and function in the postsurgical period.

Conclusions: Application of CRF to Risk
Prediction Models

• The addition of CRF to traditional risk factors significantly improves reclassification of risk for adverse
health outcomes.

• Traditional risk scores (such as Framingham risk score) are enhanced by adding CRF.

Conclusions: Serial Changes in CRF and Risk Prediction

• CRF is a variable that is responsive to therapy, and serial measures of CRF are valuable in risk stratification. Individuals whose CRF increases between examinations have a lower risk of adverse health and clinical outcomes than those whose CRF decreases, and this should be communicated to patients.

Conclusions: CRF and Its Association With Other Health Outcomes

• Higher levels of CRF are associated with a reduced risk of adverse health outcomes and chronic diseases in addition to CVD.

• A disproportionately high reduction in adverse health outcomes and cardiovascular risk factors occurs between the least fit and the next least fit cohorts.

• Physical activity interventions targeting the least fit individuals will likely have the largest health benefit.

Maximal Exercise Testing With CPX Measurements

CPX combines conventional exercise testing procedures with ventilatory expired gas analysis, which allows for the concomitant assessment of 3 prognostic/functional parameters: (1) V ⋅ o2; (2) carbon dioxide production (V ⋅ co2); and (3) minute ventilation (V ⋅ e). Detailed CPX methodology, which has several distinct advantages over other approaches to CRF assessment in terms of diagnosis, measurements, and procedures, is provided elsewhere. [See References (6) and (7) below in Resources]

Recently, the Fitness Registry and the Importance of Exercise National Database (FRIEND) published peak V ⋅ o2 reference standards for adult men and women (20– 79 years of age) obtained from CPX. [See Reference (5) below in Resources.]

Conclusions: Maximal Exercise Testing With CPX Measurements

• CPX, especially peak V ⋅ o2, represents the “gold standard” for assessing exercise capacity; other parameters, including the V ⋅ e/V ⋅ co2 slope, have become primary clinical measures in many patient subsets, including those with HF, pulmonary arterial hypertension, and lung disease;

• Although CPX involves higher levels of training and proficiency, as well as equipment and costs, for many patients the independent and additive information obtained justifies its use.

• The use of CPX for direct determination of CRF has become more feasible.

Conclusions: Maximal Exercise Testing Without CPX

• For many patients, CPX is not readily available,
and CRF can be estimated based on the attained
treadmill speed, grade, and duration or the cycle
ergometer workload, expressed as watts, from
standardized protocols.

• Importantly, when CRF is estimated using a treadmill
protocol, tests should be performed without allowing
patients to hold the handrails; resting hands on
the handrails without gripping may be acceptable.

• Care should be taken to select a protocol that optimally
matches a person’s exercise or functional capacity.

Conclusions: Submaximal Exercise Testing Without CPX Measurements

• Other performance tests, including submaximal
exercise test protocols and the 6MWT, can provide
valuable information in clinical practice and should
be considered when resources are limited. However,
these assessments are not as precise as peak or
symptom-limited exercise testing in quantitating CRF.

Conclusions and Recommendations: Nonexercise
Prediction Equations for Estimating CRF

• While avoiding the costs and and modest risk associated
with exercise testing, nonexercise algorithms using readily available clinical variables may provide reasonably accurate estimates of CRF.

• Nonexercise estimated CRF should not be viewed
as an alternative for objective assessment of CRF,
especially in some at-risk patient populations.

Conclusions and Recommendations: Nonexercise CRF and CVD

• Nonexercise estimates of CRF may be useful to provide an initial estimate of one’s CRF, particularly to identify those at increased risk of CVD because of low CRF.

• In most clinical patient subsets, nonexercise estimated CRF should not be viewed as a replacement for objective assessment of CRF.

Conclusions: Assigning CRF Values According to Age and Sex

• Age and sex significantly impact average CRF levels and should be considered when using CRF in clinical situations.

• Multiyear studies need to be conducted to better delineate the changes in the biological mechanisms by which sedentary behavior and exercise alter CRF.

Conclusions: Biological Changes Produced by Exercise That Contribute to the Increase in CRF

• Habitual endurance-type exercise produces a variety of biological adaptations that lead to an increase in peak/maximal CRF, primarily because of an increase in stroke volume and a decrease in venous oxygen content resulting from an increase in o2 extraction in the trained muscle.

• CRF can be increased in most people by regularly performing rhythmic contractions of large muscle groups continuously for an extended period of time at a moderate or vigorous intensity or with recovery breaks at lower intensity if the exercise approaches maximal effort.

Conclusions: Research Establishing the Dose of Exercise Required to Increase CRF

• When performed frequently over weeks or months, a wide variety of endurance-type physical activity regimens produce clinically significant increases in CRF (ie, ≥1 MET) in most adults.

• In general, the greater the activity amount or intensity, the greater the increase in CRF. Increases in CRF appear more responsive to increases in intensity than increases in session duration or frequency.

• The higher the baseline CRF, the more vigorous the intensity needed to produce a clinically significant increase in CRF. For example, in adults with a CRF <10 METs, a training intensity of ≈50% HR reserve or  V ⋅ o2R is adequate; at a CRF level of 10 to 14 METs, training intensities in the range of 65% to 85% of HR reserve or V ⋅ o2R are likely more effective, and among those with a capacity >14 METs, a training intensity >85% HR or V ⋅ o2R may be needed for most participants to obtain a significant increase in CRF.

Conclusions: High-Intensity Training and CRF

• Both HIT and MICT regimens can be effective for increasing CRF in healthy adults and patients with CVD. When total work performed during training is held constant, HIT is likely to elicit greater increases in CRF than MICT. Results across studies are inconsistent in comparisons of the effects of HIT and MICT on increasing CRF. Reasons for these differences may include population-specific response differences, training protocol variations (intensity, session duration, training duration), and differences in testing protocols.

• The role of HIT regimens in the reduction of cardiovascular clinical events remains unclear, and the added risk of musculoskeletal and cardiac complications in selected patients needs additional evaluation. Most studies on the clinical benefits of HIT in cardiac rehabilitation have used MICT for comparative purposes, and long-term validation in patient populations is needed.

• Although HIT may be as safe as MICT for patients with CVD, more data are needed.


The following is from Reference (3), Top Ten Things to Know [about the] Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign, which briefly summarizes the points made in Reference (1):

1. Cardiorespiratory fitness (CRF) is a reflection of overall physiological health and function, especially the cardiovascular system. Many factors can contribute to CRF including gender, age, race or ethnicity, and genetics. Regular physical activity is a behavior that can contribute to improved CRF.1
2. CRF is an independent marker of risk for cardiovascular (CV) and all-cause mortality. It is a stronger predictor of
mortality than established risk factors such as cigarette smoking, hypertension, high cholesterol, and type 2 diabetes.
3. CRF can be expressed in several ways, including metabolic equivalents (METs). Lower CRF in adults (<5 METs) is
associated with higher risk for CV mortality; whereas CRF levels >8 to 10 METs are associated with increased survival. More than half of the reduction in all-cause mortality occurs between the least fit group (CRF <5 METs) and the next least fit (CRF 5-7 METs), suggesting that individuals don’t have to become elite athletes to benefit from increased CRF. Small increases in CRF are associated with considerably (10-30%) lower adverse CV event rates.
4. This Scientific Statement reviews the currently available data linking cardiorespiratory fitness to cardiovascular and overall health and establishes the foundation to incorporate cardiorespiratory fitness measurements in standard clinical practice.
5. In addition to the improved cardiovascular outcomes, higher levels of CRF are associated with improved outcomes for certain forms of cancer, surgical risk, dementia and Alzheimer’s disease, depression, type 2 diabetes, and metabolic syndrome.
6. The potential mechanisms for the independent inverse association are not yet fully understood, however the
benefits of improving CRF are greatest for those at the lowest CRF suggesting that some physical activity is better than none – especially for habitually sedentary individuals.
7. Increasing CRF by even 1 MET is associated with a 10% – 20% decrease in mortality rates. To decrease CV risk, physical activity regimens should be implemented with an initial target of increasing CRF ≥10%.
8. While both high intensity interval training (HIT) and moderate intensity continuous training (MICT) can be effective
for increasing CRF, results across studies are inconsistent when comparing the effects of HIT and MICT on increasing CRF. Although HIT may be as safe as MICT for patients with CVD, more data are needed.
9. Cardiopulmonary exercise testing (CPX) is considered the gold standard for assessing exercise capacity, however
other methods are available to estimate CRF including submaximal exercise test protocols, the 6-minute walking
test (6MWT), and non-exercise prediction equations. These alternative methods have less precision than CPX testing, but may be more readily-available in certain clinical situations. Care should always be taken to select a protocol that matches an individual’s exercise and functional capacity.
10. Adding CRF metrics to risk classification presents health professionals with unique opportunities to improve patient management and to encourage lifestyle-based strategies designed to reduce cardiovascular risk. These opportunities will help optimize the prevention and treatment of CVD and hence, meet the AHA 2020 goals.

The following is from Reference (4), 2016 Focused Update: Clinical Recommendations for Cardiopulmonary Exercise Testing Data Assessment in Specific Patient Populations:

CPX in Apparently Healthy Individuals

Aerobic capacity is one of the strongest predictors of the risk for future adverse events in apparently healthy individuals.3,5,45,58,59 In 2013, the AHA published a policy statement calling for the development of a national aerobic capacity registry in apparently healthy individuals,60illustrating the recognized importance of accurately quantifying aerobic capacity in assessing an individual’s overall health and risk for the development of future noncommunicable diseases and adverse events. This policy statement resulted in the establishment of the Fitness Registry and the Importance of Exercise National Database Registry, which recently published normative aerobic capacity values for the United States.6 Moreover, assessing the physiological response to aerobic exertion provides a wealth of information on potential underlying abnormalities that, if detected, would ideally be addressed before the subject is diagnosed with a noncommunicable disease or suffers an initial adverse event. It should be noted that an apparently healthy designation indicates the absence of a medical diagnosis as opposed to good health and high cardiorespiratory fitness. In fact, the majority of individuals in the United States who are defined as apparently healthy present with less-than-ideal cardiovascular health as a result of unhealthy lifestyle characteristics (ie, physical inactivity, poor diet, excess body weight, smoking) and poor health metrics (ie, dyslipidemia, hypertension, hyperglycemia).61

In a 2005 AHA scientific statement, Lauer et al5 elucidated a compelling case for exercise testing without ventilatory expired gas in the asymptomatic population, given the value of data obtained. However, the use of exercise testing procedures, including CPX, is still not common in apparently healthy individuals receiving health care (eg, as part of an annual checkup with a primary care physician). Clearly, research is needed to determine the clinical value of exercise testing in general, and CPX specifically, in apparently healthy populations before concrete recommendations can be made. Moreover, in the United States, both standard exercise testing and CPX are not reimbursable by government or private health insurers in this population. Nonetheless, apparently healthy individuals may undergo CPX services through gym memberships, hospital- or university-based health and wellness centers, private companies that provide CPX services for self-pay, and executive health assessments. In addition, normative aerobic capacity values, derived from large cohorts in the United States6 and Europe,62 have recently been published, demonstrating an increased recognition of the performance of this assessment in apparently healthy individuals. Given that there are avenues for apparently healthy individuals to undergo CPX and recent publications,6,62 the writing group felt that an evidence-based algorithm is warranted at this time. Even so, we acknowledge CPX is currently not standard practice in apparently healthy individuals. We also strongly encourage additional research that assesses the value of exercise testing in apparently healthy individuals, as proposed in the 2005 AHA scientific statement by Lauer et al.5

Appendix 6 illustrates the CPX algorithm for apparently healthy individuals. This population will present with a wide range of peak Embedded ImageO2 values, therefore warranting assessment of a percent-predicted value. Assessment of ventilatory efficiency provides insight into cardiopulmonary coupling and function and, when abnormal, is related to lower levels of aerobic capacity62 and may indicate subclinical pathophysiology that warrants further investigation.63 For example, in a series of 510 subjects with differing levels of cardiovascular risk but no previous cardiovascular event enrolled in the EURO-EX trial, exercise oscillatory ventilation was observed in 17% of cases. Subjects with exercise oscillatory ventilation had a comparatively poorer CPX performance and gas exchange phenotype.63 Quantifying heart rate recovery provides another dimension that improves prognostic resolution to the CPX assessment in apparently healthy individuals.3,5 Abnormal hemodynamic and ECG responses, as well as angina or dyspnea as primary reported symptoms for test termination, when present, should be investigated further.3,45,64 For example, individuals with a normal resting BP who have a hypertensive response to exercise are at increased risk for resting hypertension in the future.64 It is important to note that heart rate recovery, hemodynamics, and electrocardiographic and subjective symptoms are accessible through standard exercise testing procedures without the use of ventilatory expired gas analysis (ie, standard exercise test). Thus, when ventilatory expired gas is not available, analysis of these variables in conjunction with estimated aerobic capacity via metabolic equivalents has value and should be considered. In these instances, portions of the algorithm presented in Appendix 6 that do not require ventilatory expired gas analysis should be considered for test interpretation.


(1) 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 [PubMed Abstract] [Link to Download Full Text PDF]. Circulation. 2016 Nov 21. pii: CIR.0000000000000461. [Epub ahead of print]

(2) Assessing Cardiorespiratory Fitness to Improve Risk Prediction and Get More People Moving: a Late but Welcome Guest to the Party Monday, Nov. 21, 2016. Stephen W. Farrell, PhD, FACSM. The Cooper Institute, Dallas Texas.

(3) Top Ten Things to Know – Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign. [Full Text PDF]

(4)  2016 Focused Update: Clinical Recommendations for Cardiopulmonary Exercise Testing Data Assessment in Specific Patient Populations [PubMed Abstract] [Full Text HTML with link to PDF download].  Circulation. 2016 Jun 14;133(24):e694-711. doi: 10.1161/CIR.0000000000000406. Epub 2016 May 2.

(5) Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the Fitness Registry and the Importance of Exercise National Database. [PubMed Abstract] [Full Text HTML] [Full Text PDF] Mayo Clin Proc. 2015;90:1515–1523. doi: 10.1016/j.mayocp.2015.07.026.

(6) Clinician’s Guide to cardiopulmonary exercise
testing in adults: a scientific statement from the American Heart
Association. [PubMed Abstract] [Full Text HTML with a link to download the Full Text PDF] Circulation. 2010;122:191–225. doi: 10.1161/CIR.0b013e3181e52e69.

(7)  EACPR/AHA scientific statement: clinical recommendations for cardiopulmonary
exercise testing data assessment in specific patient populations. [PubMed Abstract] [Full Text HTML] [Full Text PDF]. Circulation. 2012;126:2261–2274. doi: 10.1161/

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