Cardiovascular endurance

General endurance of the body as a whole is traditionally considered cardiovascular endurance, or aerobic capacity. Cardiovascular endurance is most frequently viewed in terms ofVo2max- This chapter considers only endurance of neuromuscular systems. Although many central and peripheral anatomic sites and physiologic processes contribute to a loss of endurance, endurance of neuromuscular functional units is also referred to as muscular endurance. 

Well-rounded physical fitness includes four basic elements that can be improved with regular exercise cardiovascular endurance, muscular strength, muscular endurance, and flexibility. To be tmly fit, each element should be developed, but the most vital is cardiovascular endurance. Physiologically, cardiovascular endurance is the sustained ability of the heart, blood vessels, and blood to carry oxygen to the cells, coupled with the ability of the cells to use oxygen, and the ability of the blood to carry away waste products. Since every cell in the body requires oxygen to function, there is no more basic element of fitness than this—to see that the heart, lungs, and circulatory system function properly. 

Cardiovascular endurance is improved through exercises that require the body s systems to deliver even larger amounts of oxygen to working muscles. To achieve this, the exercise should utilize the large muscle groups (such as those in the legs), but. 

At low levels of COHb (0.5-2.0%) the body burden is measurable, but research has not shown any substantive effects at these low levels. When COHb increases to higher levels the body burden of CO is elevated, producing adverse effects on the cardiovascular system and reducing physical endurance. 

Butyl rubber - This material generally had the least endurance in fatigue tests, but it may be adequate for some cardiovascular applications. Advantages include less sensitivity to stress concentrators than Pellethane, a very low permeability to fluids, a moderate creep resistance and widespread availability at low cost. Disadvantages include a relatively low fatigue resistance compared to the elastomers specifically designed for these applications. The rubber tested was not designed for medical applications and had standard rubber additives and modifiers that were cytotoxic unless the material was extracted after manufacture. 

Chewing the leaves of Catha edulis (khat, qat) results in subjective mental stimulation, increased physical endurance, and increased self-esteem and social interaction. Until recently, this habit was confined to Arabian and East African countries, because only fresh leaves are active, but because of increased air transportation, khat is now also chewed in other parts of the world. Although cathine (norpseudoephedrine) is quantitatively the main alkaloid, the amphetamine-hke euphorigenic and sympathomimetic cardiovascular effects of khat are primarily attributed to cathinone (1). In Yemen chewers of khat produced in fields where chemical pesticides are used regularly have more sjmptoms than chewers of khat produced in fields where chemical pesticides are rarely or never used (2). 

Achieve physical fimess by including cardiovascular conditioning, stretching exercises for flexibility, and resistance exercises or calisthenics for muscle strength and endurance. 

Biostable PUs are considered the materials of choice for the manufacturing of cardiovascular devices that need high flexural endurance, fatigue resistance, and good blood compatibility. 

Atherosclerotic cardiovascular disease is the major cause of morbidity and mortality, producing localized reduction in the quality of arteries (stenosis), which ultimately leads to occlusion. It reduces or even stops the blood flow through affected blood vessels. Clinically, prosthetic heart-valves often fall in a very short period of time compared to mechanical valves due to mineralization and inability to endure a difficult environment, including cyclic bending stresses and high pressure transients across the valve, for long periods of time [231]. These problems have attracted a great amoimt of attention towards the development of biobased scaffolds with better mechanical performances. 

Cardiovascular tissue engineering aims to create functional tissue scaffolds that can re-establish the structure and function of injured sites of the cardiovascular system. A considerable amount of cardiovascular therapeutics, particularly for major and serious disorders, involves the use of devices. Some of these may be implanted by surgery, whereas others are inserted via minimally invasive procedures involving catheterization. Although different synthetic materials have been used for the development of cardiovascular devices, PUs have several advantages over the others. Besides their biocompatibility and their mechanical flexibility [100-103], PUs have very high flexural endurance compared to most elastomers, making them prime candidates for cardiovascular implants. 

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