CSCS CH. 6

Cardiovascular adpatations

Aerobic endurance results in increased maximal cardiac output, increased stroke volume, and reduced heart rate at during during submaximal exercise. Capillarization increases. Most significant change (6012 months) is increase in maximal cardiac output, resulting from improved stroke volume. Size of left ventricle and the strength of contractions are key to increasing stroke volume with submaximal as well as maximal exercise.

Study Key

Aerobic endurance training results in reduced body fat, maximal oxygen uptake, increased respiratory capacity, lower blood lactate concentrations, increased mitochondrial and capillary densities, and improved enzyme activity.

Respiratory Responses

Aerobic exercise provides for the greatest impact on both oxygen and carbon dioxide production, as compared to other types of exercise.

Blood transport of gases and metabolic By-products

Because oxygen is not readily soluble in fluids, only about 3 ml of oxygen can be carried per liter of plasma. Given the limited capacity of plasma to carry oxygen, the majority of oxygen in blood is carried by the hemoglobin. After carbon dioxide is formed in the cell, it is transported out of the cell by diffusion and subsequently transported to the lungs. ONly about 5% of that produced during metabolism is carried in the plasma; similar to oxygen, this limited amound helps contribute the partial pressure of carbon dioxide in the blood. Lactic acid is another important byproduct of exercise. If, at higher work intensities, aerobic metabolism is not sufficient to keep up with the formation of lactic acid, then the lactic acid level in the blood begins to rise.

Hyperoxic Breathing

Breathing oxygen-enriched gas mixtures. Done during rest periods or following exercise may positively affect some aspects of exercise performance. Suggested that it may increase the amount of oxygen caried by the blood and therefore increases the supply of oxygen to working muscles.

Ventilatory Equivalent

The ratio of minute ventilation to oxygen uptake. Ranges between 20 and 25 L of air per liter of oxygen consumed. In more intense exercise (45--65% untrained, 70-90% trained), ventilatory equivalent may increase to 35 or 40 L of air per liter of oxygen consumed with this high-intensity activity.

Total Peripheral Resistance

The resistance of the entire systemic circulation. As resistance is reduced, blood flow is increased; as resistance is increased, blood flow reduced. Resistance to blood flow is increased with increasing viscosity of the blood and the length of the vessel (these remain relatively constant under most circumstances). Vasoconstriction and vasodilation of blood vessels are the primary mechanisms for regulating regional blood flow.

Minute Ventilation

The volume of air breathed per minute.

End-diastolic volume

The volume of blood available to be pumped by the left ventricle at the end of the filling phase, or diastole.

Ejection Fraction

The fraction of the end-diastolic volume ejected from the heart.

Alveoli

The functional unit of the pulmonary system where gas exchange occurs. Air enters with inspiration.

Maximal Oxygen Uptake

The greatest amount of oxygen that can be used at the cellular level for the entire body.

Cardiovascular Responses

The primary function of the cardiovascular system during aerobic exercise is to deliver oxygen and other nutrients to the muscles.

Anatomical Dead Space

The nose, mouth, trachea, bronchi, and bronchioles. While air enters the alveoli during inspiration, it also enters above areas of the respiratory passages, which is not useful for gas exchange.

Neural adaptations

Athlete produces more efficient locomotion during the activity with lower energy expenditure. Improved performance may result in a rotation of neural activity among synergists and among motor untis within a muscle.

Heart Rate (Formula)

220- age in years= beats/min. Variance for this is + or - 10 to 12 beats/min. Increases linearly with increases in intensity during aerobic exercise.

Key Point

Acute aerobic exercise results in increased cardiac output, stroke volume, heart rate, oxygen uptake, systolic blood pressure, and blood flow to active muscles and a decrease in diastolic blood pressure.

Mean Arterial Pressure

Average blood pressure throughout the cardiac cycle. Usually less than the average of the systolic and diastolic pressures. Mean arterial blood pressure= [(Systolic blood pressure - Diastolic blood pressure)/3] + Diastolic blood pressure

Altitude

At elevations greater than 3900 feet, acute physiological adjustments begin to occur to compensate for the reduced partial pressure of oxygen in the atmosphere. First there is an increase in pulmonary ventilation (hyperventilation) at rest and during exercise. Second, in the early stages there is an increase in cardiac output at rest and during submaximal exercise, due primarily to increases in heart rate. However, despite these adjustments, arterial oxygen saturation decreases and results in maximal oxygen uptake and aerobic performance.

Key Point

During aerobic exercise, large amounts of oxygen diffuse into the tissues; increased levels of carbon dioxide move from the blood into the alveoli; and minute ventilation increases to maintain appropriate alveolar concentrations of these gases.

Rate Pressure Product, or Double Product

Estimate of the work of the heart: Rate-pressure product= Heart rate x Systolic blood pressure

Systolic Blood Pressure

Estimates the pressure exerted against the arterial walls as blood is forcefully ejected during ventricular contraction (systole) and, when combined with heart rate, can be used to describe the work of the heart.

Diffusion

The movement of oxygen and carbon dioxide across a cell membrane and is a function of the concentration of each gas and the resulting partial pressure exerted by the molecular motion of each gas. Results from the movement from high concentration to low concentration. Diffusing capacities of oxygen and, in particular, carbon dioxide increase dramatically with exercise, which facilitates their exchange.

Muscular adaptations

Glycogen sparing and increased fat utilization within the muscle prolongs performance and allows an athlete to perform at a greater intensity of a now higher maximal aerobic power. Type 1 fibers possess a greater oxidative capacity than that of Type II fibers both before and after training. Selective hypertrophy of Type 1 muscle fibers occurs due to their increased recruitment during aerobic activities. There may be a gradual conversion within the two major Type II fiber subgroups- of Type IIx fibers to Type IIa fibers. Type IIa have greater oxidative capacity than Type IIx and thus contribute more to oxidative efforts. Cellular- Increase in size and number of mitochondria and increased myoglobin content.

Cardiac Output

The amount of blood pumped by the heart in liters per minute and is determined by the quantity of blood ejected with each beat (Stroke volume) and the heart's rate of pumping (Heart rate), where Q is the cardiac output. Q= stroke volume x Heart rate blood/beat x beat/minutes= blood/minutes In the progression from steady-state aerobic exercise, cardiac output initially increases rapidly, then more gradually, and subsequently reaches a plateau.

Heart Rate

Heart's rate of pumping.

Mitochondria

Organelles in cells that are responsible for aerobically producing adenosine triphosphate (ATP) via oxidation of glycogen.

Fick equation

Oxygen uptake (VO2) calculated using this equation. VO2= Q x a-vO2 difference Q is the cardiac output in millimeters per minute and a-vO2 difference is the arteriovenous oxygen difference millimeters per 100ml of blood.

Myoglobin

Protein that transports oxygen within the cell.

Stroke Volume

Quantity of blood ejected with each beat. Regulated by two physiological mechanisms: First: End-diastolic volume- The volume of blood available to be pumped by the left ventricle at the end of the filling phase, or diastole. Second: Action of catecholamines, including epinephrine and norepinephrine.

Physiological Dead Space

Refers to Alveoli in which poor flow, poor ventilation, or other problems with the alveolar surface impair gas exchange.

Frank Starling Mechanism

Related to the concept that the force of contraction is a function of the length of the fibers of the muscle wall.

Oxygen Uptake

The amount of oxygen consumed by the body's tissues. Oxygen demand of working muscles directly related to the mass of exercising muscle; thus, larger muscles require more oxygen.

Designing Aerobic enduracnce programs for optimizing adaptations

Requires proper progression, variation, specificity, and overload. Aerobic training plays a vital role if for no reason than recovery. Krebs cycle and electron transport chain are the main pathways in energy production. Aerobic production produces far more ATP energy than anaerobic metabolism and uses fats, carbohydrates, and proteins. Metabolic changes include increased respiratory capacity, lower blood lactate concentrations at a given submaximal exercise intensity, increased mitochondria and capillary densities, and improved enzyme activity. The intesnity of training is one of the most important factors in improving and maintaining aerobic power.

Metabolic Equivalent Of Tasks (EMT)

Resting oxygen uptake is estimated at 3.5 ml of oxygen per kilogram of body weight per minute (ml x kg-1 x min-).

Tidal Volume (TV)

The amount of air inhaled with each breath. During low- to moderate-intensity aerobic exercise, there is an increase in ventilation directly associated with both increased oxygen uptake and carbon dioxide production, primarily due to increased tidal volume.

Venous Return

The amount of blood available to the heart. Increased with aerobic exercise, and thus end diastolic volume drastically increased.

Arteriovenous Oxygen Difference

The difference in the oxygen content between arterial and venous blood.

Diastolic blood pressure

Used to estimate the pressure exerted against the arterial walls when no blood is being forcefully ejected through the vessels (diastole).

Respiratory adaptations

Ventilatory adaptations appear to be highly specific, i.e. lower body affects lower body and not upper. Maximal- Increased tidal volume and breathing frequency Submaximal- breathing frequency reduced and tidal volume increased.