Ch. 2 Cardio-respiratory exercise physiology

Introduction Physiology is the study of how the human body functions. Homeostasis…maintenance of a constant internal environment. Exercise presents a challenge to this! How does the transport of oxygen change during exercise? The ventilatory and cardiovascular systems work together in a highly coordinated manner to increase oxygen delivery during exercise. We must look at the rate at which oxygen is taken into the body and used…oxygen uptake, VO 2. Increases in gas exchange Figure 2.1

Ventilatory System Air will flow from and area of higher pressure to an area of lower pressure… For inhalation to occur the air pressure in the lungs needs to be lower than the atmosphere. Breathing in…At rest, the muscles of the diaphragm contract at the base of the chest cavity. The diaphragm pulls downward increasing the volume of the lungs. This increase in lung volume reduces the pressure in the lungs causing air to flow into the lung to balance the pressure gradient. Breathing out…at rest is a passive process, no energy required as the diaphragm relaxes and recoils to its original position. This recoil reduces the volume of the lungs, increasing the pressure causing air to flow back out again.

Ventilatory System During Exercise More oxygen is required More carbon dioxide is produced Air needs to be inhaled and exhaled at a faster rate So how does this happen… Additional muscles in the chest (external intercostal muscles), abdomen and even shoulder muscles can assist with increasing the lung volume during inhalation. Then contraction of these muscles during exhalation will also compress the lung faster and more forcefully than natural recoil. Since this requires additional muscles and is an active process it requires energy to fuel the muscles of the chest and abdomen.

Ventilatory System

Gas exchange Gas exchange in the lungs and other body tissue take place through the process of diffusion. Gas will move along a gradient of higher partial pressure to lower partial pressure. Partial pressure represents the pressure exerted by a single gas within a mixture.

Gas Exchange

Take a breath…

Ventilation during exercise V E : minute ventilation describes the amount of air being exhaled per minute V T : tidal volume is the volume of each breath B f : breathing frequency is breaths per minute V E (L/minute)= V T (L/breath) X B f (breaths/minute) Turn to page 35 and complete the TO DO box with a partner

Cardiovascular System During exercise the primary function of blood is transport to and from tissue…gases, nutrients, waste products, hormones or heat Total volume of blood is around 5 liters 55% of blood is plasma, assist transport of these… 1. Role of platelets (<1% of blood volume) is to assist the process of repair following an injury 2. Role of white blood cells (leucocytes) (<1% of blood volume)involved in immune function, to protect the body from infection 3. Red blood cells (erythrocytes) (make up 40-45%) primary function to transport oxygen to the body and remove carbon dioxide

Oxygen transport during exercise During exercise, oxygen temporarily attaches hemoglobin in the lungs, then detaches and diffuses from the blood into the active tissues. Deoxygenated blood cells then return to the lungs via the heart.

Oxygen and Exercise The hormone erythropoietin (EPO) is responsible for stimulating red blood cell production. EPO can increase hemoglobin concentration allowing more oxygen to be transported and aerobic exercise performance will improve. THE LEGAL WAY!! NOT synthetic EPO or blood doping, which are illegal!

Circulation Blood vessels 1. Arteries: transport blood Away from the heart, they become more narrow turning into arterioles. More muscular due to pressure 2. Capillaries: narrow vessels with thin walls, the site of exchange between blood and tissues. 3. Veins: capillaries link the venuoles and then larger veins, that take deoxygenated blood back to the heart. 4. The pump at the center, the heart is a sequence of chambers enclosed by walls of cardiac muscle fibers.

Circulation: the heart 2 loop for circulation 1. Pulmonary circulation: delivers deoxygenated blood from the right side of the heart to the lungs to pick up oxygen and then back to the left side of the heart. 2. Systemic Circulation: delivers oxygenated blood from the left side of the heart to the other tissues of the body where oxygen is used up and then delivers deoxygenated blood back to the right side of the heart

The cardiac cycle 4 chamber double pump system Right atria, right ventricle Left atria, left ventricle One way valves Tricuspid: between right atria and right ventricle Mitral/bicuspid: between left atria and left ventricle Pulmonic: between right ventricle and pulmonary artery Aortic: between left ventricle and aorta Muscular contractions Sinoatrial node (SA) Atrioventricular node (AV) Bundle of HIS Purkinje fibers

Electrical Conduction of the heart

Blood Pressure Systolic (top number): pressure on the arterial walls as the heart contracts Diastolic (bottom number): relaxation phase of pressure while the ventricle is filling. Resting blood pressure: 120/80 Prehypertensive: /80-89 Hypertensive: above 140/90

Blood Flow Distribution Involuntarily controlled by smooth muscles of the arteries and arterioles Blood vessels dilate to allow more blood to flow Blood flow is redirected to the working muscles from the organs Refer to figure 2.7

Acute Cardiovascular Response to Exercise Increase of blood flow out of the heart during exercise Cardiac output: amount of blood ejected from the left side of the heart in liters per minute Determined by how quickly the heart is beating (heart rate) and the amount of blood being ejected with each contraction (stroke volume) Cardiac output = (heart rate X stroke volume) / 1000

Cardiac output In order to achieve increases in cardiac output, the heart must beat faster (increased HR) and fill and empty more during each contraction (increased stroke volume) As maximum cardiac output is reached so too is exhaustion and exercise cannot continue at this intensity. At sub-maximal exercise, the cardiac output is maintained at the same level throughout as the demand stays constant with stroke volume and heart rate values higher than rest.

Functional Capacity Most common marker of individuals aerobic fitness is VO 2. Maximal oxygen uptake (VO 2 max) quantifies the maximum rate that an individual can take in and use oxygen. This is assessed by measuring the gas concentration and volume of air being expelled at progressively increasing intensities of exercise. As the oxygen demand increases so does the VO 2, until the person approaches their limit, VO 2 max aerobic capacity.

Fick Equation VO 2 max = maximum cardiac output X maximum A-V O 2 difference As well as larger cardiac output, blood shunting (redistribution) and increase in ratio of capillaries to muscle fibers allow for an increase in VO 2 VO 2 max values can be expressed in two formats: Absolute VO 2 max is L/min Relative VO 2 max is the same value but normalized according to body mass in ml/kg/min

Gender Regardless of training, gender has an effect Absolute VO2max values are lower in age-matched females, due to size differences 20 yr. old femaleVO 2 max levels Untrained, healthy female ml/kg/min Moderately trained40-50 ml/kg/min Professional team sports athlete ml/kg/min Endurance athlete55-60 ml/kg/min 20 yr. old maleVO 2 max levels Untrained, healthy male ml/kg/min Moderately trained45-55 ml/kg/min Professional team sports athlete ml/kg/min Endurance athlete>65 ml/kg/min

Age and VO2max Increases during childhood and adolescence due to growth and maturation Peaking in the early 20’s for males and mid-teens for females When normalized to body mass, male children and adolescents have very similar values to healthy adults. During adulthood, there is a decrease of about 1% each year on average

Type of Exercise and VO2max As more muscle mass is used, such as during running higher VO2max would be expected than compared to cycling. WHY?? Highest observe values is that of cross-country skiers. WHY??

How does training increase VO2max? Training-induced changes in the heart and cardiovascular system (central adaptations) Increase in stroke volume HR becomes lower at sub-max intensities, and the max in unchanged with training. The max heart rate just isn’t then reached until the person is working harder than before training. (capacity has improved) Changes in the muscle (peripheral adaptations) Muscles develop more capillaries. Increase in the amount of oxygen extracted from the blood