Risk Factors Modifiable – can be changed Non-modifiable – cannot be changed

Modifiable Non- Modifiable Diet Smoking Activity Obesity Age Gender Heredity Race

Exercise decreases the modifiable risk factors by: Improving cholesterol levels – increases HDL, lowers LDL Decreasing heart rate Lowering arterial blood pressure Reducing percentage body fat Decreasing the chance of developing atheroma Improving the efficiency of the heart Controlling stress

Oxygen delivery improves during moderate exercise During exercise the CVS must increase O2 to the muscles, by the following ways Cardiac output increases Redistribution of blood round the body

Cardiac output is increased by increasing both the heart rate and stroke volume, both which increase in proportion to the intensity of exercise. In an untrained person HR may increase from beats/min, SV from ml/beat, CO from 5-20 L/min

These changes are caused by: An increased output of sympathetic nerves to the heart which increases the Heart Rate Increased release of adrenaline into the blood increases the Stroke Volume An increase in blood volume returning to the heart, increases the rate of filling the heart chambers. This stretches the ventricular walls which respond by contracting more forcibly so that more blood is ejected with each contraction. In other words… the stroke volume is increased.

Redistribution of blood flow during exercise During exercise there is an increased blood flow to the muscles to supply them with oxygen and a decreased blood flow to parts of the body not active during exercise (e.g.. gut + kidneys) Achieved by vasodilation of arterioles supplying active muscles Vasoconstriction of arterioles supplying gut + kidneys

The athlete’s heart Exercise has long term benefits for the CVS which answer the question below. “Why do endurance athletes have lower heart rates both at rest and at any given level of exercise?”

a) Skeletal muscle is strengthened by training and do more forceful contractions b) Heart increases in size – cardiac hypertrophy c) Heart contractions increase in strength due to :- An increase in protein synthesis leading to thickening of individual muscle fibres An increase in the contractile elements within each fibre d) Increased Stroke Volume e) The increase is temporary, and the heart returns to its pre-training size if intensity of training decreases

Comparison of Maximal CO in Trained and Untrained Individuals When comparing the Cardiac Output during maximal exercise in trained and untrained individuals, it can be seen that the endurance athlete achieves a larger CO mainly because of a relatively greater increase in stroke volume. HR (per min)SV (ml)CO (l/min) Untrained Trained

These changes to the heart structure account for the facts that athletes have:- Lower resting Heart Rates Shorter recovery times after exercise