Cardiorespiratory Fitness in the Prevention and Management of Cardiovascular Disease

Abstract

Cardiovascular disease (CVD) is the leading cause of death among adults in the U.S. and elsewhere. Variation in the presence, severity, and control of major modifiable risk factors accounts for much of the variation in CVD rates worldwide. Cardiorespiratory fitness (CRF) reflects the integration of ventilation, circulation, and metabolism for the delivery and utilization of oxygen in support of dynamic aerobic physical activity. The gold standard measure of CRF is maximal oxygen uptake. Because the primary factor underlying differences in this measure between individuals is maximal cardiac output, it can serve as a clinical indicator of cardiac function. Higher CRF is associated with favorable levels of major CVD risk factors, lower prevalence and severity of subclinical atherosclerosis, and lower risks of developing both primary and secondary clinical CVD events. The beneficial associations between CRF and CVD are seen in women and men, older and younger adults, in those with multiple coexisting risk factors or prior diagnosis of CVD. Exercise training and regular physical activity of at least moderate intensities and volumes improves CRF in adults, and improvements in CRF are associated with lower risks of subsequent CVD and mortality. Routine assessment of CRF in primary care settings could enhance individual-level CVD risk assessment and thereby guide implementation of appropriate measures to prevent future clinical events.

Keywords: exercise; exercise prescription; heart disease; maximal oxygen uptake; physical activity; prognosis; risk assessment.

Fig. 1.

Ventilation $\mathrm{\to }$ Circulation $\mathrm{\to }$ Metabolism. $V_E$, minute ventilation; $V_F$, ventilatory frequency; $V_T$, tidal volume; ${\mathrm{CO}}_2$, carbon dioxide; $O_2$, oxygen; CO, cardiac output; SV, stroke volume; HR, heart rate; a-${\mathrm{vO}}_2$, arterial-venous oxygen difference.

Fig. 2.

Oxygen uptake according to various workloads and exercise testing modality. $O_2$, oxygen; mL, milliliters; kg, kilogram; min, minute; METs, metabolic equivalents; kpm, kilopond meters; mph, miles per hour; sec, second; GR, grade; USAFSAM, United States Airforce School of Aerospace Medicine; ACIP, Asymptomatic Cardiac Ischemia Pilot. Adapted from ACSM’s Guidelines for Exercise Testing and Prescription. 7th edn. Lippincott Williams & Wilkins: Philadelphia. 2006. [34].

Fig. 3.

Conceptual framework of CRF pathways to CVD prevention.

Fig. 4.

Cross-sectional associations between CRF and clinically relevant CVD risk factors in (A) Men and (B) Women. Odds ratios adjusted for age, percent body fat, smoking, and family history of CVD. BP, blood pressure; LDL-C, low-density lipoprotein cholesterol. Adapted from LaMonte MJ et al., Circulation. 2000; 102(14): 1623–1628. [56].

Fig. 5.

Prospective associations between CRF and incident metabolic syndrome according to number of components at baseline. Hazard ratios adjusted for age, exam year, BMI, smoking, alcohol, family history of CVD and diabetes. Adapted from LaMonte MJ et al., Circulation. 2005; 112(4): 505–512. [83].

Fig. 6.

Average walking speed over 8 feet according to coronary arterial calcification score. Adapted from Hamer M et al., Heart. 2010; 96(5): 380–384. [95].

Fig. 7.

Prospective association of measured maximal oxygen uptake and exercise test duration with CVD mortality in men. Relative risks adjusted for age and examination year. Adapted from Laukkanen JA, et al., Archives of Internal Medicine. 2001; 161: 825–831. [39].

Fig. 8.

Prospective association between CRF and CVD incidence according to number of major CVD risk factors present at baseline. Rates are adjusted for age and examination year. PY, person-years. Adapted from Sui X et al., American Journal of Epidemiology. 2007; 165: 1413–1423. [25].

Fig. 9.

Prospective association between CRF and CVD mortality according to age at baseline. Rates are adjusted for sex and examination year. PY, person-years. Adapted from Sui X et al., Journal of the American Geriatrics Society. 2007; 55: 1940–1947. [112].

Fig. 10.

Prospective association between CRF and all-cause mortality in men with and without CVD. Relative risks are adjusted for age. Adapted from Meyers J et al., New England Journal of Medicine. 2002; 346: 793–801. [42].

Fig. 11.

Meta-analysis results of observational studies on cardiorespiratory fitness (CRF) or physical activity (PA) exposures in relation to the relative risk of clinical CVD events. Exposure percentiles are ranked lowest (0) to highest (100) on the x-axis. Adapted from Williams PT. Medicine & Science in Sports & Exercise. 2001; 33: 754–761. [127].