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3. Effects of Exercise on the CVS


What changes occur during exercise? Why do they occur? Increased heart rate as: • Muscles need more oxygen and glucose • More waste to be disposed of • This means an increased blood flow is needed => Increased heart rate


• Increased systolic blood pressure only • Increase is due to the ventricles pumping harder to keep up with demand from muscles • Systolic pressure can increase from 120-200mmHg • SV also increases due to ventricles working harder • If SV and HR increase, so too does the CO • Recovery time is the time taken for the body to return to normal after exercise • A shorter recovery time indicates a fitter individual


Distribution of Blood • During exercise – heart, muscle and skin have an increased demand for oxygen • To meet the demand, they have an increased blood flow during exercise by blood vessels dilating (widening) • Abdominal organs do not have as high a need for oxygen during exercise, so blood flow is reduced by blood vessels constricting (narrowing)


The ‘Athletic’ Heart • Athletes experience the same benefits previously mentioned • Due to increased workload from training, the heart gets bigger • Known as cardiac hypertrophy • Occurs due to increased protein synthesis in muscle fibres of the heart => Increases muscle size • Increase in myocardium enables ventricles to contract with a greater force, increasing the SV • Bigger heart muscle lowers resting heart rate


Exercise Testing


• Used to test a person’s aerobic fitness • Also used to monitor fitness and recovery after MI • Aerobic capacity – ability to use oxygen • Depends on efficiency of cardiovascular and respiratory systems 2 types of test: 1.Maximal testing 2.Sub-maximal testing


1.Maximal Testing •. Measures the maximum rate at which the body can take up and use oxygen => VO2max •. Measured in cm3 (ml-1) kg-1 min-1 •. Individual exercises to exhaustion whilst breathing a measured air supply •. More O2 is taken in as exercise intensity is increased •. VO2max is when oxygen intake no longer changes


• Greater VO2max, fitter the individual • Difficult to measure as need sophisticated equipment and medical back-up • Only suitable for trained athletes as it requires being exercised to exhaustion


2. Sub-maximal Testing • Subjects do not exercise to exhaustion • Lower intensity of exercise and data extrapolated to estimate VO2max Test assumes that: 1.There is a linear correlation between VO2max, heart rate, and exercise 2.Maximum heart rate = 220 - age


• Pulse rate and oxygen uptake are measured at various levels of activity • Graph is constructed of pulse rate against oxygen uptake. • Maximum heart rate is calculated (220-age) • This number is then used to predict VO2max from the graph • Step tests, beep tests and shuttle runs are examples of sub-maximal exercise tests (see monograph and scholar booklet)


Sub-maximal testing is inaccurate as: • Other factors can increase heart rate (e.g., temperature and anxiety levels) • Predicted heart rate may not be accurate


Stress Testing and Cardiac Rehabilitation • CHD patients sometimes show normal ECG readings at rest, but show abnormalities during exercise • Stress (exercise ECG) test shows traces before, during and after exercise • Low intensity of exercise to start, and it is gradually increased until patient is too tired, or breathlessness or chest pain is experienced • Results establish exercise limits, and a rehabilitation fitness programme can be drawn up


• In 1970s, after heart surgery, 6 weeks bed rest was recommended for recovery • Now – medically supervised exercise is thought to lead to a better recovery and survival rate • Programmes are tailored to each individual • Aerobic exercise gradually increases as patient becomes fitter • Stress test is repeated to monitor progress

3 Effects of exercise on the CVS  
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