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Dr khaled Abulfadle
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عدد المساهمات : 9680 تاريخ التسجيل : 06/08/2009
موضوع: Notes on: Exercise effects on CVS الإثنين مارس 28, 2011 7:20 pm
Strong tonic muscle contractions can cause rapid muscle fatigue Mechanism: tonic (maintained) contraction causes decrease in muscle blood flow as contracting skeletal muscle compresses the intramuscular blood vessels with susequent decrease in delivery of enough oxygen and other nuterients
The most strenous (severe) exercise causes up to 25 folds increase in muscle blood flow Mechanism: 1- increased muscle metabolism causes VD 2-increased ABP 2ry to exercise
In well trained athlets, the resting heart rate is decreased i.e. 50 beat/min Mechanism: high vagal tone
The marathoners can achieve maximal cardiac outputs about 40% greater than those achieved by untrained persons Mechanism: 1-the heart chambers of marathoners enlarge about 40% 2-the heart mass also increases 40% or more
Training and VO2 max : training increases maximal oxygen consumption (VO2 max). Mechanism: VO2 max is the product of maximal cardiac output and maximal oxygen extraction by the tissues and both increase with training.
Chronic isometric exercises do not lead to a change in resting heart rate or stroke volume Mechanism: chronic isometric exercise causes myocardial hypertrophy without chamber enlargement
CVS changes during isometric exercise (no work is done): include 1-increase heart rate by psychic stimuli on medulla increasing sympathetic activity 2-increase both systolic and diastolic blood pressures 3-decrease blood flow to steadily (tonically) contracting muscle 4-little change in stroke volume
CVS changes during isotonic exercises: include 1-marked increase in stroke volume 2-increase systolic blood pressure 2ry to sympathetic stimulation 3-decrease diastolic blood pressure 2ry to VD which decreases the total peripheral resistance
During exercise, blood flow to skin initially decreases and then increases Mechanism: initially sympathetic stimulation causes cutaneous VC but, later body temperature rises with susequent cutaneous VD and increase in skin blood flow
Effect of exercise on CVS by dr khaled A Abulfadle
الثلاثاء مارس 22, 2011 4:12 pm
