2. Hormonal Control Mechanism Adrenalin and noradrenalin are stress hormones that are released by the adrenal glands. Exercise causes a stress induced adrenalin response results in the following: Stimulation of the SA node (pacemaker) which results in an increase in both the speed and force of contraction. An increase in blood pressure due to the constricting of blood vessels. An increase in blood glucose levels which is used by the muscles for energy. What is Cardiovascular Drift? We used to think that while exercising at a steady level, the body reached a steady state where the heart rate remained the same. However, new research has shown that if you monitor heart rate more closely it does not remain the same but instead slowly climbs. This is cardiovascular drift. In more detail cardiovascular drift is characterised by a progressive decrease in stroke volume and arterial blood pressure, together with a progressive rise in heart rate. It occurs during prolonged exercise in a warm environment despite the intensity of the exercise remaining the same. Suggestions as to why this occurs are that when we sweat a portion of this lost fluid volume comes from the plasma volume. This decrease in plasma volume will reduce venous return and stroke volume. Heart rate again increases to compensate and maintain constant cardiac output. To minimise this cardiovascular drift it is important to maintain high fluid consumption before and during exercise. . Effects of Training on the Heart If you perform continuous, fartlek or aerobic interval training over a period of time, physiological adaptations take place that would make the initial training sessions appear very easy. This is because your VO2(max) has improved due to the changes your body has made. Some of these changes or adaptations effect the heart. It becomes much more efficient. The table below identifies the changes that have taken place in the heart. Key term: VO2(max) is the maximum amount of oxygen that can be taken in and used by the body in one minute
2. Hormonal Control Mechanism Adrenalin and noradrenalin are stress hormones that are released by the adrenal glands. Exercise causes a stress induced adrenalin response results in the following: Stimulation of the SA node (pacemaker) which results in an increase in both the speed and force of contraction. An increase in blood pressure due to the constricting of blood vessels. An increase in blood glucose levels which is used by the muscles for energy. What is Cardiovascular Drift? We used to think that while exercising at a steady level, the body reached a steady state where the heart rate remained the same. However, new research has shown that if you monitor heart rate more closely it does not remain the same but instead slowly climbs. This is cardiovascular drift. In more detail cardiovascular drift is characterised by a progressive decrease in stroke volume and arterial blood pressure, together with a progressive rise in heart rate. It occurs during prolonged exercise in a warm environment despite the intensity of the exercise remaining the same. Suggestions as to why this occurs are that when we sweat a portion of this lost fluid volume comes from the plasma volume. This decrease in plasma volume will reduce venous return and stroke volume. Heart rate again increases to compensate and maintain constant cardiac output. To minimise this cardiovascular drift it is important to maintain high fluid consumption before and during exercise. . Effects of Training on the Heart If you perform continuous, fartlek or aerobic interval training over a period of time, physiological adaptations take place that would make the initial training sessions appear very easy. This is because your VO2(max) has improved due to the changes your body has made. Some of these changes or adaptations effect the heart. It becomes much more efficient. The table below identifies the changes that have taken place in the heart. Key term: VO2(max) is the maximum amount of oxygen that can be taken in and used by the body in one minute
cardiac_function_and_the_vascular_system-sue_young_.docx