 Cardiovascular Response to Exercise  Exercise Pressor Response  Cardiac Effects  Peripheral Effects ▪ Net Reduction in Total Peripheral Resistance ▪ Increased Cardiac Output ▪ Increase in Systolic Blood Pressure  Respiratory Response to Exercise

 The SNS stimulation response includes  generalized peripheral vaso-constriction in non exercising muscles and  Increased myocardial contractility,  an increased heart rate,  an increased systolic blood pressure..

 Cardiac Effects  Increased Cardiac Output because of the:  increase in SNS stimulation.  decrease in vagal stimuli  Increase in heart rate  Increase in myocardial contractility, with a resultant  increase in stroke volume  Increase in the blood flow through the working muscle

 Net Reduction in Total Peripheral Resistance  Generalized vasoconstriction occurs that allows blood to be shunted from the nonworking muscles, kidneys, liver,spleen, and splanchnic area to the working muscles.  locally mediated reduction in resistance in the working muscle arterial vascular bed is produced by metabolites such as Mg2, Ca2, ADP, and PCO2.  The veins of the working and nonworking muscles remain constricted.  Exercise increases blood pressure as a result of the augmented cardiac output

 Gas exchange (O2, CO2) increases across the alveolar- capillary membrane.  Increased muscle metabolism during exercise results in  more O2 extracted from arterial blood resulting in an increase in venous PCO2 and H  Increase body tmp., inc. epinephrine  These factor stimulate respiratory system.  Minute ventilation increases  Respiratory frequency increases  Tidal volume increase.  Alveolar ventilation, increases 10- to 20-fold during heavy exercise to supply the additional oxygen needed and excrete the excess CO2 produced.

 Increased Blood Flow  Increased Oxygen Extraction  Oxygen Consumption

A. Increased Blood Flow The increased blood flow to the working muscle previously discussed provides additional oxygen. B. Increased Oxygen Extraction There is also extraction of more oxygen from each liter of blood. There are several changes that allow for this. 1. As the PO2 decreases, the unloading of oxygen from hemoglobin is facilitated. 2. The production of more CO2 causes the tissue to become acidotic (the hydrogen ion concentration increases) and the temperature of the tissue to increase. Both situations increase the amount of oxygen released from hemoglobin at any given partial pressure. 3. The increase of red blood cell 2,3-diphosphoglycerate (DPG) produced by glycolysis during exercise also contributes to the enhanced release of oxygen.

 Oxygen Consumption  Factors determining how much of the oxygen is consumed are:  Vascularity of the muscles.  Fiber distribution.  Number of mitochondria.  Oxidative mitochondrial enzymes present in the fibers.

 (1) Intensity  (2) Duration  (3) Frequency  Reversibility Principle

 A conditioning response occurs generally at 60% to 90% maximum heart rate (50% to 85% VO2 max) depending on the individual and the initial level of fitness. For healthy young individuals:  70% maximum HR ( minimal-level stimulus) for eliciting a conditioning response.  Sedentary or (deconditioned)individuals: 40% to 50% of VO2 max.  Cardiopulmonary disease: 40% to 60% of their symptom-limited HR  The exercise does not have to be exhaustive to achieve a training response.

 The optimal duration of exercise for cardiac rehab. is dependent on the i. Exercise intensity ii. Frequency, iii. Fitness level  Generally speaking, the greater the intensity of the exercise, the shorter the duration needed for adaptation; and the lower the intensity of exercise, the longer the duration needed.  A 20- to 30-minute session is generally optimal at 60% to 70% maximum HR.  When the intensity is below the heart rate threshold, a 45-minute continuous exercise period may provide the appropriate overload.  With high-intensity exercise, 10- to 15-minute exercise periods are adequate  three 5-minute daily periods are effective in some deconditioned patients.

 Frequency varies, dependent on the health and age of the individual.  Optimal frequency of training is generally three to four times a week.  If training is at low intensity, greater frequency may be beneficial.  A frequency of two times a week does not generally evoke cardiovascular changes, although older individuals may benefit from a program of that frequency. Recommendations.  The American Heart Association recommends 30 minutes of moderate intensity aerobic exercise on most if not all days of the week.  The Centers for Disease Control (CDC) supports these recommendations,  The American College of Sports Medicine recommends aerobic exercise 3 to 5 days/ week at 65% to 90% maximum heart rate for 20 to 60 continuous or intermittent minutes. They further recommend that if the activity is lower intensity it should have a longer duration

 Effects of exercise training are transient and reversible.  Detraining occurs rapidly when a person stops exercising.  After only 2 weeks of detraining, significant reductions in work capacity can be measured, and improvements can be lost within several months.  A similar phenomenon occurs with individuals who are confined to bed with illness or disability:

 Three components of the exercise program: (1) a warm up period, (2) the aerobic exercise period, (3) a cool down

 The purpose is to enhance the numerous adjustments that must take place before physical activity. Physiological Responses  An increase in muscle temperature. The higher temperature increases the efficiency of muscular contraction and increasing the rate of nerve conduction.  Extraction from hemoglobin is greater at higher muscle temperatures, facilitating the oxidative processes at work.  Dilatation of the previously constricted capillaries with increases in the circulation, augmenting oxygen delivery to the active muscles  An increase in venous return. This occurs as blood flow is shifted centrally from the periphery.

 Guidelines :  The warm-up should be gradual and sufficient to increase muscle and core temperature without causing fatigue or reducing energy stores.  Characteristics of the period include:  A 10-minute period of total body movement exercises, walking slowly.

 Submaximum, rhythmic, repetitive, dynamic exercise of large muscle groups is emphasized.  be great enough to stimulate an increase in stroke volume and cardiac output and to enhance local circulation and aerobic metabolism in the appropriate muscle groups.  The exercise period must be within the person’s tolerance, above the threshold level for adaptation to occur, and below the level of exercise that evokes clinical symptoms. Methods of training that challenge the aerobic system :  Continuous,  Interval (work relief),  Circuit

 The most effective way in the healthy individual, to improve endurance.  A sub-maximum activity, sustained throughout the training period.  Once the steady state is achieved, the muscle obtains energy by means of aerobic metabolism. Stress is placed primarily on the slow-twitch fibers.  The activity can be prolonged for 20 to 60 minutes  The work rate is increased progressively as training improvements are achieved. Overload can be accomplished by increasing the exercise duration.

 Exercise followed by a properly prescribed rest interval.  In the healthy individual, interval training tends to improve strength and power more than endurance.  The relief interval (a few seconds to several minutes) is either a; i. Rest relief (passive recovery) ii. Work relief (active recovery) continuing the exercise but at a reduced level.  Muscular stores of ATP and the oxygen associated with myoglobin that were depleted are replenished  The total amount of work completed with intermittent work is greater than that done with continuous training.

 A series of exercise activities.  At the end of the last activity, the individual starts from the beginning and again moves through the series. The series of activities is repeated several times.  A mix of static or dynamic effort.  Can improve strength and endurance by stressing both the small and large muscle groups.

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 Follow the exercise period.  Purpose:  Prevent pooling of the blood in the extremities by continuing to use the muscles to maintain venous return.  Prevent fainting by increasing the return of blood to the heart and brain as cardiac output and venous return decreases.  Enhance the recovery period with the oxidation of metabolic waste and replacement of the energy stores.  Prevent myocardial ischemia, arrhythmias, or other cardiovascular complications.  Guidelines :  Similar to those of the warm-up period.  Total-body exercises such as static stretching are appropriate.  The period should last 5 to 10 minutes.