In addition to traditional testing measures, a timed walking test (6- or 12-minute walk test) can be used to estimate maximal aerobic power and assess the risk for cardiopulmonary morbidity and mortality in various patient populations (8,15). These tests possess administration benefits over maximal exercise tests, are well tolerated in many clinical populations, and have demonstrated significant correlation with maximal oxygen consumption tests (11,14). Although both methods provide advantages in safety and ease of use, the potential for error in estimating functional capacity should be recognized in a clinical setting.
When evaluating maximal aerobic power, protocol selection is very important to ensure accurate outcomes are achieved. In the United States, testing is typically completed using a motorized treadmill or cycle ergometer, although treadmill is the preferred mode because of greater familiarity. Arm ergometer testing is typically avoided as a testing modality because of an inability to achieve and maintain high work rates as a result of a smaller muscle mass being used. Avoidance of protocols that involve large work rate increments is recommended, instead focusing on protocols that allow for smaller MET increments per stage (i.e., Balke and Ware (1) or Naughton et al. (20) protocols). Regardless of the protocol selected, the test should be tailored to each patient to yield fatigue-limited exercise duration of approximately 10 minutes (19).
Decreased maximal aerobic power, as a measure of cardiorespiratory fitness, is associated with increased cardiovascular disease and all-cause mortality (7). Low cardiorespiratory fitness increases the relative risk of death to a similar level as tobacco abuse, hypertension, and/or diabetes (2,16). Maximal aerobic power also has significant prognostic capabilities in patients with known or suspected cardiovascular disease. In particular, when using the standard Bruce protocol during graded exercise testing, a maximal aerobic power exceeding 14 METs was associated with a reduced probability for severe coronary artery disease and an improved 4-year survival rate when compared with those with less than a 5 MET maximal aerobic power (18). Additionally, in coronary artery disease patients undergoing preoperative evaluations before noncardiac surgery, the ability to achieve a high exercise workload was consistent with a low postoperative cardiac risk, regardless of associated symptoms or ST-segment changes (6). In patients entering cardiac rehabilitation, maximal aerobic power measurements provide the necessary information for developing an appropriate exercise prescription and for evaluating the results of an exercise training regimen.
In patients with chronic heart failure, estimates of maximal aerobic power are less reliable than the direct measurement of gas exchange (3). Thus, in this patient population, cardiopulmonary gas exchange measurements have become standard for the assessment of maximal aerobic power. In particular, measurements of peak VO2 and VT are highly reproducible and recommended for this patient population (4). Markedly impaired exercise tolerance places the heart failure patient in a high-risk category for a poor outcome. For instance, a peak VO2 of less than 10 to 12 mL O2/kg body weight per minute identifies a poor 1-year prognosis, whereas a peak VO2 of greater than 14 mL O2/kg body weight per minute demonstrate a more favorable outcome (17).
Data support the use of maximal aerobic power in clinical populations, particularly in those with cardiovascular disease, to help guide treatment and evaluate interventions. Exercise professionals, particularly those with clinical backgrounds, are uniquely qualified to assist with research and testing in this area. These individuals can play a significant role in the coordination of oxygen consumption testing to ensure protocol optimization and data collection. Although directly measured VO2 is primarily used in patients with cardiovascular disease and in athletes, the use of estimated V˙O2max is a regular part of fitness evaluations. Thus, clinical exercise professionals who are adept at exercise testing, including in the measurement of VO2, can play an important role in the use and interpretation of these important clinical measures.
1. Balke B, Ware RW. An experimental study of physical fitness of Air Force personnel. US Armed Forces Med J
2. Blair SN, Kohl HW 3rd, Barlow CE, et al.
Changes in physical fitness and all-cause mortality: a prospective study of healthy and unhealthy men. JAMA.
3. Cohen-Solal A, Chabernaud JM, Gourgon R. Comparison of oxygen uptake during bicycle exercise in patients with chronic heart failure and in normal subjects. J Am Coll Cardiol
4. Cohen-Solal A, Zannad F, Kayanakis JG, et al
. Multicentre study of the determination of peak oxygen uptake and ventilatory threshold during bicycle exercise in chronic heart failure: comparison of graphical methods, interobserver variability and influence of the exercise protocol: the VO2 French Study Group. Eur Heart J
5. Davis JA, Vodak P, Wilmore JH, et al
. Anaerobic threshold and maximal aerobic power for three modes of exercise. J Appl Physiol
6. Eagle KA, Brundage BH, Chaitman BR, et al
. Guidelines for perioperative cardiovascular evaluation for noncardiac surgery: report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Perioperative Cardiovascular Evalutation for Noncardiac Surgery). J Am Coll Cardiol
7. Ekelund LG, Haskell WL, Johnson JL, et al.
Physical fitness as a predictor of cardiovascular mortality in asymptomatic North American men. N Engl J Med.
8. Enright P. The six-minute walk test. Respir Care.
9. Fleg JL, Lakatta EG. Role of muscle loss in the age-associated reduction in V˙O2
max. J Appl Physiol
10. Fleg JL, Pina IL, Balady GJ, et al
. Assessment of functional capacity in clinical and research applications: An Advisory from the Committee on Exercise, Rehabilitation, and Prevention, Council on Clinical Cardiology, American Heart Association. Circulation
11. Gayda M, Temfemo A, Choquet D, Ahmaidi S. Cardiorespiratory requirements and reproducibility of the six-minute walk test in elderly patients with coronary artery disease. Arch Phys Med Rehabil
12. Gibbons RJ, Balady GJ, Beasley JW, et al
. ACC/AHA guidelines for exercise testing: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on Exercise Testing). J Am Coll Cardiol
13. Jones AM, Carter H. The effect of endurance training on parameters of aerobic fitness. Sports Med
14. Kervio G, Carre F, Ville N. Reliability and intensity of the six-minute walk test in healthy elderly subjects. Med Sci Sports Exerc
15. Lankin JL, Bundy S, Marron H, et al
. Using a treadmill for the 6-minute walk test. J Cardiopulm Rehabil Prev
16. Laukkanen JA, Lakka TA, Rauramaa R, et al.
Cardiovascular fitness as a predictor of mortality in men. Arch Intern Med.
17. Mancini DM, Eisen H, Kussmaul W, et al
. Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure. Circulation
18. McNeer JF, Margolis JR, Lee KI, et al
. The role of the exercise test in the evaluation of patients for ischemic heart disease. Circulation
19. Myers J, Buchanan N, Walsh D, et al
. Comparison of the ramp versus standard exercise protocols. J Am Coll Cardiol
20. Naughton J, Balke B, Nagle F. Refinements in method of evaluation and physical conditioning before and after myocardial infarction. Am J Cardiol
21. Wasserman K, Beaver WL, Whipp BJ. Gas exchange theory and the lactic acidosis (anaerobic) threshold. Circulation