Lecture 2

CVS in exercise - CVS serves 5 import func during ex; 1) Delivers O 2 to working muscles 2) Oxygenates blood by returning it to the lungs 3) Transports heat from the core to the skin 4) Delivers nutrients and fuel to active tissues 5) Transports hormones - Due to ex the following changes take place; * ↑ demand on the CVS * ↑ O 2 demand by the muscles * Speed up metabolic processes * ↑ waste production * More nutrients are used * ↑ BT To perform as efficiently as possible the CVS must regulate the changes and meet the body’s increasing demands.

- Training sig improve the CV performance. Trained athletes have bigger hearts and larger SV than do non athletes and these are important functional differences (see the table). At rest, 15-20% of blood goes to skeletal muscle; during exercise, this amount increases to 80-85% of Q. - Due to the delivery of O2 to the working muscles, the muscle BF can ↑ approx 25-fold during strenuous ex. 2 reasons for the ↑ in flow; 1- intramuscular vasodilation caused by the direct effect of ↑ muscle metabolism. 2- multiple factors, such as ↑ in arterial BP that occurs in ex, usually about a 30% ↑. 2 major adjustments to BF must occur to meet the metab demands of skeletal muscle during ex. 1) Q from the H must ↑. 2) BF from inactive organs and tissues must be redistributed to active skeletal muscle.

Normal BP at rest varies mmHg (systolic BP) and mmHg (diastolic BP). During ex, systolic pres may ↑ to mmHg while diastolic pres remains relatively unchanged regardless of ex intensity. An ↑ of more than 15 mmHg may indicate a CHD. - The ↑ in pres → forces more blood through the BV, stretches the walls of the arterioles and reduces the vascular resistance. A linear relation of work output, VO 2 & Q occurred → VO 2 in turn dilates the muscle BV → ↑ venous return and Q.

Fig 84-9

- Normal Q at rest is approx 5-6 L/min, and may ↑ to L/min during heavy ex (table 21-2). This ↑ is achieved by ↑ of both SV & HR. Q = SV X HR Q is the amount of blood pumped by the H in 1 min measured in L/min. SV is amount of blood ejected/b from left ventricle & measured in ml/beat. - Fig shows the approx changes in SV & HR as the Q ↑ from its resting level to a marathon runner. The SV ↑ from 105 to 162 ml, whereas HR ↑ from 50 to 185 bpm. Therefore, the HR accounts by far for a greater proportion of the ↑ in Q than does the ↑ in SV during strenuous ex.

Table 21-2

Fig 84-10

- - CVS is normally much more limiting on VO 2 max than is the RS, because O 2 utilization by the body can never be more than the rate at which the CVS can transport O 2 to the tissues. VO 2 max is the rate of O 2 under max aerobic metabolism.

Exercise and CV disease - Regular ex has several beneficial effects. Even moderate ex routine can lower total blood choles levels. - A high choles level of the major risk factors for atherosclerosis, which leads to CV disease and stroke. - A regular ex, a healthy lifestyle, a balanced diet, weight control and not smoking → reduces stress, lowers BP and slows the formation of plaque. - A regular mod ex may cut the incidence of HA 50%. - Ex is also beneficial in accelerating one’s recovery after a HA. - Regular light to mod ex coupled with a low fat diet and a low stress lifestyle, not only reduces symptoms of CAD (e.g. angina) but also improves one’s mood and overall quality of life.

Exercise & immune system - Mod ex has a beneficial effect on overall health and may reduce the incidence of minor infectious disease. However, exhaustive ex does not promote disease resistance and may even reduce immune response. - Intensive ex has been found to reduce both the levels of antibody secretion by B lymphocytes and the effectiveness of T lymphocytes. - Recent research indicates that fit people tend to have higher No. of NK cells in their circulation. NK cells are an important part of our immune defence mechanisms against viral infect and some bacterial infect. NK cells are able to destroy the cells of our body that become infected with these disease-causing micro-organisms. There is some evidence that in the elderly a mod degree of physical activity (e.g. regular walking) confers some protection against picking up infections of the upper respiratory tract compared with a sedentary lifestyle.

Warning signs If you experience any of the following symptoms, stop exercising and seek medical help: Extreme breathlessness Breathing problems such as wheezing or coughing Chest pain or pressure Extreme perspiration Dizziness, fainting Severe muscle pain or cramps Nausea Severe pain in any muscles or joints Extreme and long-lasting fatigue after exercising.