Cardiovascular fitness

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Cardiovascular fitness is a component of physical fitness, which refers to a person's ability to deliver oxygen to the working muscles, including the heart. Cardiovascular fitness is improved by sustained physical activity (see also Endurance Training) and is affected by many physiological parameters, including cardiac output (determined by heart rate multiplied by stroke volume), vascular patency, and maximal oxygen consumption (i.e. VO2 max). [1]

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Cardiovascular fitness measures how well the heart and blood vessels can transport oxygen to the muscles during exercise. It is an important component of overall fitness and has been linked to numerous health benefits, including a reduced risk of cardiovascular disease, improved cognitive function, and increased longevity. A study published in the American Journal of Epidemiology found that higher levels of cardiovascular fitness were associated with a lower risk of mortality from all causes, including cardiovascular disease and cancer. [2]

This article addresses cardiovascular health as well as fitness, because the two are dependent on each other. However, “cardiovascular health” often refers to the normal, non-diseased function of the heart as defined by medical professionals. While the definition of health is still controversial and debated, it is frequently used in contrast to disease, whereas “Cardiovascular fitness” further describes the performance of the heart and blood beyond normal functioning, or simply a non-diseased state. This article will focus on cardiovascular fitness, and reference health and disease to support this topic. For more information on cardiovascular health and disease, see cardiovascular disease.

Physiology of the Circulatory System

The cardiovascular system collectively refers to the heart and the blood vessels, which include arteries, capillaries, and veins. The heart and vessels function to distribute oxygenated blood to the body's organ systems where oxygen diffuses into cells to aid in the generation of ATP (a molecule used throughout the body to as a form of energy). Once the oxygen diffuses into cells, the blood is then "deoxygenated" and returns to the heart, where it is pumped into the lungs to receive more oxygen. The blood is then considered "oxygenated" and delivered from the lungs to the heart again, where it is pumped to the rest of the body. For more information, see Circulatory system.

Cardiovascular "fitness" is defined as the ability of the heart and blood vessels to oxygenated blood to the whole organism. Many diseases and conditions can reduce cardiovascular fitness by three main mechanisms:

  1. Obstructing the flow of blood from the heart through the vessels, e.g. coronary artery disease, peripheral artery disease, atherosclerotic disease, stenosis, aneurysms, etc.
  2. Inhibiting the flow of blood through the heart, e.g. valvular diseases (stenosis, sclerosis, ischemia to the papillae muscles), myocardial ischemia, constrictive pericarditis, etc.
  3. Reducing the return of blood to the heart, referred to as "preload," e.g. veinous insufficiency, orthostatic hypotension, pericardial effusion, etc.

These diseases are collectively referred to as "cardiovascular disease" (CVD). Ultimately, reduced cardiovascular fitness can lead to heart failure and ischemia, reducing the body's aerobic metabolism of energy to the degree that cells die and the organ can no longer perform its function. Therefore, treatment and prevention of these disease is key to maintaining and improving cardiovascular fitness to optimize the function of the whole body.

Assessing Cardiovascular Fitness

Cardiovascular fitness can be assessed through various methods, including maximal oxygen uptake (V̇O2max), which is the maximal amount of oxygen that can be used during exercise. Biomarkers, such as those used for assessing blood lipids, inflammation, glucose tolerance, and hemostasis, may be used to monitor progress during the development of cardiovascular fitness. [1]

The Role of Exercise in Cardiovascular Fitness

Regular physical activity is essential for improving cardiovascular fitness. [1] The American Heart Association recommends at least 150 minutes of moderate-intensity aerobic exercise or 75 minutes of vigorous-intensity aerobic exercise per week to improve cardiovascular fitness and reduce the risk of cardiovascular disease. [3]

Cardiovascular Changes Attributed to Aerobic Exercise

During aerobic exercise, cardiac output and oxygen consumption (VO2) increase, following the Fick equation: VO2 = Cardiac Output x Arteriovenous oxygen difference. Cardiac output results from stroke volume and heart rate (CO = HR x SV). Age-adjusted maximum heart rate is estimated with HRmax = 220 bpm - [subject's age]. Stroke volume rises due to enhanced preload and myocardial contractility, though excessively high heart rates may reduce cardiac output by shortening left ventricular filling time. [4]

Chronic aerobic exercise improves cardiovascular function through adaptations like increased left and right ventricular function, raising cardiac output and maximum oxygen consumption. Vascular changes, such as reduced arterial stiffness and better endothelium-dependent vasodilation (from nitric oxide), also occur. These adaptations help mitigate age-related declines in cardiac performance. While people with cardiovascular disease (CVD) see lesser structural adaptations, exercise remains beneficial, underscoring its role in cardiac rehabilitation. [4]

Physical activity reduces CVD mortality, with high fitness levels linked to fewer CVD risk factors, including obesity and hypertension. For instance, Barry et al. found that individuals with low cardiorespiratory fitness had double the mortality risk of fit individuals, regardless of BMI, while individuals with high cardiorespiratory fitness had similar survival rates (again, regardless of BMI). [4] [5]

Prescribing Exercise: Type, Dosing, and Adverse Effects

Moderate-intensity continuous exercise is standard for CVD patients, though high-intensity interval training (HIIT) may offer superior cardiorespiratory and cardiac improvements. The Physical Activity Federal Guidelines suggest 150 minutes of moderate or 75 minutes of vigorous weekly aerobic activity, yet over half of adults fall short of these targets. Studies show even low doses of activity (e.g., <6 miles of running per week) can significantly reduce all-cause and CVD mortality risks. [4]

Resistance training complements aerobic exercise by enhancing muscular fitness, which reduces cardiovascular risk factors, improves insulin sensitivity, and decreases atherosclerosis. It's recommended to incorporate resistance exercise twice weekly for at least 15–20 minutes, particularly in older adults and those with heart failure. [4]

Excessive endurance training can negatively impact cardiac function, causing myocardial injury markers, chamber dilation, and reduced right ventricular function. Long-term, this training may result in adverse remodeling, fibrosis, and increased arrhythmia risk, notably atrial fibrillation. Optimal exercise volumes are under 30 miles of running or 46 miles of walking per week, as higher volumes may reduce cardiovascular benefits. [4]

Despite the risks of excessive exercise, the primary public health concern remains insufficient physical activity. [4]

Related Research Articles

<span class="mw-page-title-main">Coronary artery disease</span> Reduction of blood flow to the heart

Coronary artery disease (CAD), also called coronary heart disease (CHD), or ischemic heart disease (IHD), is a type of heart disease involving the reduction of blood flow to the cardiac muscle due to build-up of atherosclerotic plaque in the arteries of the heart. It is the most common of the cardiovascular diseases. CAD can cause stable angina, unstable angina, myocardial ischemia, and myocardial infarction.

<span class="mw-page-title-main">Angina</span> Chest discomfort due to disorder of the heart muscles

Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease.

<span class="mw-page-title-main">Exercise</span> Physical activity that improves health

Exercise is physical activity that enhances or maintains fitness and overall health. It is performed for various reasons, including weight loss or maintenance, to aid growth and improve strength, develop muscles and the cardiovascular system, prevent injuries, hone athletic skills, improve health, or simply for enjoyment. Many people choose to exercise outdoors where they can congregate in groups, socialize, and improve well-being as well as mental health.

<span class="mw-page-title-main">Heart rate</span> Speed of the heartbeat, measured in beats per minute

Heart rate is the frequency of the heartbeat measured by the number of contractions of the heart per minute. The heart rate varies according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. It is also modulated by numerous factors, including genetics, physical fitness, stress or psychological status, diet, drugs, hormonal status, environment, and disease/illness, as well as the interaction between these factors. It is usually equal or close to the pulse rate measured at any peripheral point.

<span class="mw-page-title-main">Aerobic exercise</span> Low to high intensity physical exercise

Aerobic exercise, also known as cardio, is physical exercise of low to high intensity that depends primarily on the aerobic energy-generating process. "Aerobic" is defined as "relating to, involving, or requiring oxygen", and refers to the use of oxygen to meet energy demands during exercise via aerobic metabolism adequately. Aerobic exercise is performed by repeating sequences of light-to-moderate intensity activities for extended periods of time. According to the World Health Organization, over 31% of adults and 80% of adolescents fail to maintain the recommended levels of physical activity. Examples of cardiovascular or aerobic exercise are medium- to long-distance running or jogging, swimming, cycling, stair climbing and walking.

<span class="mw-page-title-main">Physical fitness</span> State of health and well-being

Physical fitness is a state of health and well-being and, more specifically, the ability to perform aspects of sports, occupations, and daily activities. Physical fitness is generally achieved through proper nutrition, moderate-vigorous physical exercise, and sufficient rest along with a formal recovery plan.

<span class="mw-page-title-main">Cardiac stress test</span> Measures the hearts ability to respond to external stress in a controlled clinical environment

A cardiac stress test is a cardiological examination that evaluates the cardiovascular system's response to external stress within a controlled clinical setting. This stress response can be induced through physical exercise or intravenous pharmacological stimulation of heart rate.

V̇O2 max (also maximal oxygen consumption, maximal oxygen uptake or maximal aerobic capacity) is the maximum rate of oxygen consumption attainable during physical exertion. The name is derived from three abbreviations: "V̇" for volume (the dot over the V indicates "per unit of time" in Newton's notation), "O2" for oxygen, and "max" for maximum and usually normalized per kilogram of body mass. A similar measure is V̇O2 peak (peak oxygen consumption), which is the measurable value from a session of physical exercise, be it incremental or otherwise. It could match or underestimate the actual V̇O2 max. Confusion between the values in older and popular fitness literature is common. The capacity of the lung to exchange oxygen and carbon dioxide is constrained by the rate of blood oxygen transport to active tissue.

<span class="mw-page-title-main">Exercise intensity</span>

Exercise intensity refers to how much energy is expended when exercising. Perceived intensity varies with each person. It has been found that intensity has an effect on what fuel the body uses and what kind of adaptations the body makes after exercise. Intensity is the amount of physical power that the body uses when performing an activity. For example, exercise intensity defines how hard the body has to work to walk a mile in 20 minutes.

<span class="mw-page-title-main">High-intensity interval training</span> Exercise strategy

High-intensity interval training (HIIT) is a training protocol alternating short periods of intense or explosive anaerobic exercise with brief recovery periods until the point of exhaustion. HIIT involves exercises performed in repeated quick bursts at maximum or near maximal effort with periods of rest or low activity between bouts. The very high level of intensity, the interval duration, and number of bouts distinguish it from aerobic (cardiovascular) activity, because the body significantly recruits anaerobic energy systems. The method thereby relies on "the anaerobic energy releasing system almost maximally".

Aerobic conditioning is the use of continuous, rhythmic movement of large muscle groups to strengthen the heart and lungs, as well as changes to the skeletal muscles. Improvement in aerobic conditioning occurs when athletes expose themselves to an increase in oxygen uptake and metabolism, but to keep this level of aerobic conditioning, the athletes must keep or progressively increase their training to increase their aerobic conditioning.

Cardiorespiratory fitness (CRF) refers to the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during sustained physical activity. Scientists and researchers use CRF to assess the functional capacity of the respiratory and cardiovascular systems. These functions include ventilation, perfusion, gas exchange, vasodilation, and delivery of oxygen to the body's tissues. As these body's functions are vital to an individual's health, CRF allows observers to quantify an individual's morbidity and mortality risk as a function of cardiorespiratory health.

Interval training is a type of training exercise that involves a series of high-intensity workouts interspersed with rest or break periods. The high-intensity periods are typically at or close to anaerobic exercise, while the recovery periods involve activity of lower intensity. Varying the intensity of effort exercises the heart muscle, providing a cardiovascular workout, improving aerobic capacity and permitting the person to exercise for longer and/or at more intense levels.

<span class="mw-page-title-main">Coronary ischemia</span> Medical condition

Coronary ischemia, myocardial ischemia, or cardiac ischemia, is a medical term for abnormally reduced blood flow in the coronary circulation through the coronary arteries. Coronary ischemia is linked to heart disease, and heart attacks. Coronary arteries deliver oxygen-rich blood to the heart muscle. Reduced blood flow to the heart associated with coronary ischemia can result in inadequate oxygen supply to the heart muscle. When oxygen supply to the heart is unable to keep up with oxygen demand from the muscle, the result is the characteristic symptoms of coronary ischemia, the most common of which is chest pain. Chest pain due to coronary ischemia commonly radiates to the arm or neck. Certain individuals such as women, diabetics, and the elderly may present with more varied symptoms. If blood flow through the coronary arteries is stopped completely, cardiac muscle cells may die, known as a myocardial infarction, or heart attack.

<span class="mw-page-title-main">Myocardial infarction</span> Interruption of cardiac blood supply

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction to the heart muscle. The most common symptom is retrosternal chest pain or discomfort that classically radiates to the left shoulder, arm, or jaw. The pain may occasionally feel like heartburn.

In kinesiology, the ventilatory threshold (VT1) refers to the point during exercise at which the volume of air breathed out (expiratory ventilation) starts to increase at an exponentially greater rate than VO2 (breath-by-breath volume of oxygen (O2)). VT1 is thought to reflect a person's anaerobic threshold — the point at which the oxygen supplied to the muscles no longer meets its oxygen requirements at a given work rate — and therefore lactate threshold — the point at which lactate begins to accumulate in the blood, because with ongoing dependence on anaerobic glycolysis, increasing amounts of CO2 need to be exhaled to accommodate its production during the conversion of lactic acid to lactate.

<span class="mw-page-title-main">Cardiovascular disease in Australia</span>

Cardiovascular disease, including heart disease, is a major cause of death in Australia. Heart disease is an overall term used for any type of Cardiovascular disease that affects the heart reducing blood supply to the heart. It is also often referred as Cardiac disease and Coronary heart disease. It is generally a lifelong condition where damage to the artery and blood vessel cannot be cured.

Training masks are facial masks worn to limit the intake of air during breathing. Their ostensible purpose is to strengthen the respiratory musculature by making it work harder. There is some evidence that they may improve endurance capacity (VO2 max) and power output, but research into their benefits has so far generally proven inconclusive.

The benefits of physical activity range widely. Most types of physical activity improve health and well-being.

Cardiovascular disease in women is an integral area of research in the ongoing studies of women's health. Cardiovascular disease (CVD) is an umbrella term for a wide range of diseases affecting the heart and blood vessels, including but not limited to, coronary artery disease, stroke, cardiomyopathy, myocardial infarctions, and aortic aneurysms.

References

  1. 1 2 3 Lin X, Zhang X, Guo J, Roberts CK, McKenzie S, Wu WC, Liu S, Song Y (June 2015). "Effects of Exercise Training on Cardiorespiratory Fitness and Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials". Journal of the American Heart Association. 4 (7). doi:10.1161/JAHA.115.002014. PMC   4608087 . PMID   26116691.
  2. Kodama, Satoru (2009-05-20). "Cardiorespiratory Fitness as a Quantitative Predictor of All-Cause Mortality and Cardiovascular Events in Healthy Men and Women". JAMA. 301 (19): 2024–2035. doi:10.1001/jama.2009.681. ISSN   0098-7484. PMID   19454641.
  3. Wang, Cuihua; Liu, Gang; Xing, Jun; Wang, Yahui; Zhao, Baoli; Zheng, Mingqi (2022). "The effects of high-intensity interval training vs. moderate-intensity continuous training on exercise tolerance and prognosis in heart failure and coronary artery disease: a systematic review and meta-analysis". Cardiovascular Therapeutics. doi: 10.37766/inplasy2020.8.0112 . PMC   9203221 . PMID   35801132. S2CID   225297610.
  4. 1 2 3 4 5 6 7 Lavie, Carl J.; Arena, Ross; Swift, Damon L.; Johannsen, Neil M.; Sui, Xuemei; Lee, Duck-Chul; Earnest, Conrad P.; Church, Timothy S.; O'Keefe, James H.; Milani, Richard V.; Blair, Steven N. (2015-07-03). "Exercise and the cardiovascular system: clinical science and cardiovascular outcomes". Circulation Research. 117 (2): 207–219. doi:10.1161/CIRCRESAHA.117.305205. ISSN   1524-4571. PMC   4493772 . PMID   26139859.
  5. Barry, Vaughn W.; Baruth, Meghan; Beets, Michael W.; Durstine, J. Larry; Liu, Jihong; Blair, Steven N. (2014). "Fitness vs. fatness on all-cause mortality: a meta-analysis". Progress in Cardiovascular Diseases. 56 (4): 382–390. doi:10.1016/j.pcad.2013.09.002. ISSN   1873-1740. PMID   24438729.