Chapter 6 Adaptations to Aerobic Endurance Training Programs

Muscular adaptations to aerobic exercise at the cellular level

-increase in the size and number of mitochondria (organelles in cells that make ATP) -increased myoglobin content (protein that transports oxygen within the cell

During aerobic exercise

large amounts of oxygen diffuse from the capillaries 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

CO2 removal

- CO2 is a waste product, it produces H+ which gives it a toxicity - H+ in large amounts changes pH Forms of transport: 1. 5% dissolves in plasma 2. limited amount carried by hemoglobin 3. 70% is converted to HCO3-, where we get the Hydrogen ions that alter pH levels -combination of CO2 with water in red blood cells to form carbonic acids catalyzed by enzyme carbonic anhydrase. -carbonic acid breaks down to Hydrogen ions and bicarbonate ions. -hydrogen ions combine with hemoglobin which helps maintain the pH of the blood. -bicarbonate ions diffuse from the red blood cells to the plasma while chloride ions diffuse into the blood cells to replace them.

Heart rate acute responses to aerobic training

-HR increase in anticipation to exercise -HR increases linearly with increases in intensity

Respiratory Response to Exercise

-Increased O2 consumption. -Increased CO2 production. -Increased Ventilation rate. -UNCHANGED PaO2, PaCO2, pH [moderate exercise, strenuous exercise can lower pH via lactic acidosis] -Increased Venous PCO2 (increased CO2 prdxn) -Increased CO. HR+SV! Increased pulmonary blood flow, perfusing more capillaries, increasing gas exchange & decrease physiologic dead space.

aerobic metabolism plays a vital role in human performance, if no other reason than for recovery

-Krebs cycle and electron transport chain are main pathways in aerobic energy production -aerobic metabolism produces far more ATP than anaerobic -uses fats, carbs and protein as fuel for making ATP -many sports have constant movement thus the need for aerobic conditioning

Blood transport of gases and metabolic by-products

-O2 is carried in blood by hemoglobin -O2 is not readily soluble in fluids (only 3ml of O2 can be carried per liter of plasma -this limited amount of O2 transported contributes to the partial pressure of O2 in blood and other bodily fluids, thus playing a role in the mechanisms that regulate breathing and in diffusion of O2 into alveolar blood and cells of body tissues

A minimum of _____ is needed to adapt to moderate altitude

3-6 weeks **reduced performance is expected than at sea regardless of the period of acclimatization

Inspiration

-air enters the ALVEOLI (functional unit of the pulmonary system where gas exchange occurs) -air also occupies areas of the respiratory passage (nose, mouth, trachea, bronchi and bronchioles) not function for gas exchange called ANATOMICAL DEAD SPACE [normal volume of this air space is ~ 150 ml in young adults and increases with age. **dead space increases as tidal volume increases **increase in tidal volume with deep breathing is proportionately greater than any increase in anatomical dead space. **increasing tidal volume provides for more efficient ventilation than increasing frequency of breathing alone

potential markers of aerobic overtraining

-decreased performance -decreased percentage of body fat -decreased maximal oxygen uptake -altered blood pressure -increased muscle soreness -decreased muscle glycogen -altered resting HR and decreased HR variability -increased submaximal exercise HR -decreased lactate -increased creatine kinase -altered cortisol concentration -decreased total testosterone concentration -decreased ratio of total testosterone to cortisol -decreased ratio of free testosterone to cortisol -decreased ratio of total testoertone to sex hormone-binding globulin -decreased sympathetic tone (decreased nocturnal and resting catecholamines) -increased in sympathetic stress response -change in mood states -decreased performance in psychomotor speed tests

Capillary circulation

-delivers oxygen, nutrients and hormones -removes heat and metabolic by-products -aerobic exercise increases capillary density - decreasing the diffusion distance for oxygen and metabolic substrates.

Lactic acid is another important metabolic by-product of exercise.

-during low to moderate exercise sufficient oxygen is available to the working muscles and lactic acid does not accumulate because removal rate is greater than or equal to the production rate. -called Cori cycle. muscle-derived lactate is transported via the blood to the liver, where it undergoes gluconeogenesis. -high intensity exercise if aerobic metabolism is not sufficient to keep up with formation of lactic acid, then lactic acid level in the blood begins to rise. The aerobic exercise level at which lactic acid (called blood lactate at this point) begins to show an increase is termed the ONSET OF BLOOD LACTATE ACCUMULATION or OBLA.

Genetic potential with aerobic exercise

-every system has a predetermined upper limit and as you get closer to that limit smaller and smaller gains are observed.

Neural adaptations to aerobic exercise

-important in the early stages of aerobic training. Efficiency is increased and fatigue of muscle is delayed. -improved activation/deactivation versus maintaining a constant state of activation in syngergistic muscles. More efficient locomotion during the activity with lower energy expenditure

Resting oxygen uptake is estimated at

3.5 ml of O2 per kg of body weight per min (ml*kg-1*min-1) Also defined as 1 metabolic equivalent (MET)

adaptations to aerobic endurance training

-increased VO2 -increased cardiac output -increase aerobic power -after 6-12 months further changes in aerobic endurance performance consist of increases in running efficiency and increased lactate threshold. -Metabolic changes include - increased respiratory capacity, - lowerblood lactate concentrations at a given submax exercise intensity, -increased mitochondrial density - increased capillary density **possible that experienced runners don't see further improvements in VO2 max, rather their performance improves due to enhanced running economy.

age and sex effect on aerobic exercise

-increased age causes -reduced muscle mass and strength -increased fat mass women -higher percentage of body fat -lower hemoglobin values men -larger heart size and blood volume

smoking affects on aerobic exercise

-increased airway resistance due to nicotine-related bronchiole constriction or increased fluid secretion and swelling in the bronchial tree due to the irritation of smoke -paralysis of the cilia on the surfaces of the respiratory tract by nicotine, which limits the ability to remove excess fluids and foreign particles, causing debris to accumulate in the respiratory passageways and adding to the difficulty of breathing. -carbon monoxide is a component of cig smoke and has a higher affinity for hemoglobin than oxygen. Results in carboxyhemoglobin and reduces amount of oxygen that can be carried by hemoglobin --> reduces O2 provided to working muscles -may reduce max exercise capacity -The increased catecholamine release increases HR and BP

Acute aerobic exercise results in

-increased cardiac output (Q) -increased stroke volume (SV) -increased HR -increased oxygen uptake (VO2) -increased SBP -increased blood flow to active muscles -decrease in DBP

Chronic physiological and metabolic adjustments that occur during a prolonged altitude exposure include

-increased formation of hemoglobin (generally 5-15% increase) and red blood cells (30-50% increase) -increased diffusing capacity of oxygen through the pulmonary membranes -maintenance of the acid-base balance of body fluids by renal excretion of HCO3- and through hyperventilation -increased capillarization

Chronic cardiovascular adaptations to aerobic exercise

-increased maximal cardiac output -increased stroke volume -reduced heart rate at rest and during submaximal exercise -muscle fiber capillary density increases resulting in increased delivery of O2 and removal of CO2 -increased maximal oxygen uptake caused by -increased cardiac output -slower discharge rate at SA node (HR) due to increase in parasympathetic tone -increased stroke volume means more blood being pumped each time = fewer times heart needs to pump to meet same cardiac output. -highly conditioned aerobic athletes resting HR can range from 40-60. BRADYCARDIA (slower HR) more efficient pumping = less times it has to pump

During aerobic exercise

-large amounts of oxygen diffuse from the capillaries into the tissues -increased levels of CO2 move from blood to alveoli -minute ventilation increases to maintain appropriate alveolar concentrations of these gases

strategies for prevention of overtraining syndrome

-make sure athletes are getting good nutritional guidelines, sufficient sleep and recovery time -coaches should track an athlete's training program-cath markers for OTS -the program should provide variety in intensity and volume -athletes should have a multidisciplinary health team (coach, physician, nutritionist, psychologist)

Given the limited capacity of plasma to carry O2, the majority of O2 in blood is carried by hemoglobin.

-men have about 15-16 g of hemoglobin per 100 ml of blood -women have about 14 g of hemoglobin per 100 ml of blood **1 g of hemoglobin can carry 1.34 ml of O2 **therefore O2 carrying capacity of 100 ml of blood is about 20 ml of O2 in men and a little less in women.

Cardiac output responses to acute aerobic exercise

-progression from rest to steady-state aerobic exercise Q (cardiac output) increases rapidly, then more gradually until it reaches a plateau. -maximal exercise Q may increase to 4x resting level ***resting level of Q is about 5 L/min to max of 20-22 L/min

Altitude affects

-pulmonary -acid-base -cardiovascular -hematologic -local tissue

Intensity of training is most important factors in improving and maintaining aerobic power

-short, high-intensity bouts of interval sprints can improve VO2 max if interim rest period is also short -longer training sessions with higher amounts of rest periods result in less improvement

Stroke volume increases due to

-the increased size of the left ventricle both chamber volume and wall thickness increase strength of contractions

Oxygen demand of working muscles increases during an acute bout of aerobic exercise and is directly related to

-the mass of exercising muscle -metabolic efficiency -exercise intensity

Bone and connective tissue adaptations to aerobic exercise

-to stimulate bone growth activity must be significantly more intense than daily activities and be at a cyclical strain to exceed the minimum and strain frequency for bone growth. Intensity must systematically increase. High intensity interval training is an example of affecting bone growth and aerobic exercise -aerobic exercise can strengthen ligaments, tendons and cartilage. Strenuous running overtime can cause cartilage thinning, but moderate running (1 hr per day, 5 days/wk for 15 wks) have increased cartilage thickness and bone remodeling

Estimate max heart rate

220-age

Maximal oxygen uptake values in normal healthy individuals are

25 to 80 ml*kg-1*min-1 or 7.1 to 22.9 METS

Endocrine Adaptations

Aerobic exercise leads to increases in hormonal circulation and changes at the receptor level. High-intensity aerobic endurance training augments the absolute secretion rates of many hormones in response to maximal exercise. Trained athletes have blunted responses to submaximal exercise. -Testosterone, insulin, insulin-like growth factor (IGF-I) -increases in hormonal circulation and changes at the receptor level (both number and turnover rate)

Control of local circulation with aerobic exercise

During aerobic exercise, blood flow to active muscles increase because of dilation of local arterioles but blood flow to other organ systems reduced by constriction of arterioles (vasoconstriction and vasodilation) -At rest 15-20% cardiac output goes to skeletal muscle -vigorous exercise could be up to 90% of cardiac output

Oxygen uptake (VO2) can be calculated with the

FICK EQUATION (expresses the relationship of cardiac output, oxygen uptake and arteriovenous oxygen difference: VO2 = Q x a-vO2 difference (Q=HRxSV) -Q is cardiac output in ml*min-1 -a-vO2 diff is the ARTERIOVENOUS OXYGEN DIFFERENCE (the difference in the oxygen content between arterial and venous blood) in ml O2/100 ml blood -divide answer by body wt in kg to get into ml*kg-1*min-1

Muscular adaptations to aerobic exercise

Increased Type I and IIa hypertrophy. Mitochondria increase in size and number. Myoglobin levels increase. Increase in enzyme activity and increase in muscle glycogen stores. The net effect is a greater ability to produce energy aerobically (increase in aerobic threshold). -increased aerobic capacity of the trained musculature. (athlete can do more intense exercise with greater ease. Due to increased glycogen sparing and a switch to more fat utilization within the muscle. Resulting in OBLA occurring at a higher percentage of athlete's aerobic capacity. -may be due to reduce the production of lactic acid, changes in hormone release (particularly catecholamine release at high-intensity exercise), and more rapid rate of lactic acid removal. -training affects muscle fibers -Type I has a higher aerobic capacity than type II. But Type IIx fibers -Type I can have some hypertrophy but not as great as type II. -Type II can't change into Type I but can have a gradual conversion from Type IIx to Type IIa. Type IIa fibers possess greater oxidative capacity and have more functional characteristics similar to Type I fibers. Resulting in more muscle fibers that can contribute to aerobic endurance performance.

Aerobic endurance training results in

Increased: • maximal oxygen uptake, • respiratory capacity • mitochondrial and capillary densities • improved enzyme activity. Decreased: • reduced body fat, • Lower blood lactate concentrations

Diffusion

Movement of gas from an area of higher concentration to an area of lower concentration.

blood doping

Practice of artificially increasing red blood cell mass as a means to improve athletic performance -infusion of one's own red blood cells or from someone else or taking erythropoietin (EPO) which stimulates red blood cell production Risks -increase risks forembolic events like stroke, myocardial infarction, deep vein thrombosis, or pulmonary embolism -increased arterial blood pressure -flu-like symptoms -increased plasma potassium levels -risk with infusion or transfusion

Respiratory adaptations to aerobic exercise

Respiratory muscles get stronger. Lung volume increases. Number and size of alveoli increases. The net effect is an increase in VO2 max. -ventilation generally doesn't limit aerobic exercise and unaffected by or only moderately affected by training. Ventilatory adaptations result from local, neural or chemical adaptations in the specific muscles trained through exercise -increased tidal volume and breathing frequency with maximal exercise -submaximal exercise: breathing frequency is reduced and tidal volume is increased

Tidal Volume (TV)

amount of air inhaled and exhaled with each breath. resting .4 to 1 L exercise up to 3 L

Blood pressure responses to acute aerobic exercise

Systolic BP is estimate of pressure against arterial wall during SYSTOLE (ventricular contraction)

Stroke volume acute response to aerobic exercise

Two physiological mechanisms are responsible for the regulation of stroke volume 1. END-DIASTOLIC VOLUME - volume of blood available to be pumped by the left ventricle at the end of the filling phase or diastole. 2. action of catecholamines including epinephrine and norepinephrine - hormones of sympathetic nervous system that produce a more forceful ventricular contraction and greater systolic emptying of the heart. VENOUS RETURN - amount of blood returning to the heart With aerobic exercise -venous return increases because of *venoconstriction induced via increased sympathetic nervous system activation *skeletal muscle pump (1-way valves and muscle contraction *respiratory pump These all increase pressure on heart chambers and thoracic vena cava to increase venous return = end-diastolic volume increases. -increased end-diastolic vol increases stretch on the myocardial fiber --> more forceful contraction (FRANK-STARLING MECHANISM) EJECTION FRACTION - (cardiac emptying) is increased. Even the thought of exercise increases sympathetic stimulation --> increases myocardial contractility --> increases stroke volume

4. The mean arterial pressure is defined as the a. average blood pressure throughout the cardiac cycle. b. average of the systolic and diastolic blood pressures. c. average systolic blood pressure during exercise. d. average of blood pressure and heart rate.

a. average BP throughout the cardiac cycle

1. A 17-year-old high school cross-country runner has been training aerobically for six months in preparation for the upcoming season. Which of the following adaptations will occur in the muscles during that time? a. increased concentration of glycolytic enzymes b. hyperplasia of Type II fibers c. transformation from Type I to Type II fibers d. hypertrophy of Type I fibers

a. increased concentration of glycolytic enzymes

______ are most sensitive to periods of inactivity because of their enzymatic basis

aerobic endurance adaptations -reduction in VO2max is primarily a result of -decreased blood volume -decreased stroke volume -decreased maximal cardiac ouput -increased submaximal heart rate

physiological dead space

alveoli in which gas exchange is less than normal pic distribution of TV at rest. TV is about 350 ml of room air that mixes with alveolar air, about 150 ml of anatomical dead space, and smaller portion of physiological dead space (poorly ventilated alveoli)

Mean Arterial Pressure (MAP)

average BP over the cardiac cycle. (120 mmHg at systole in aorta to 0 mmHg at vena cava) Mean arterial BP = [(SBP - DBP) / 3] + DBP

5. Primary training adaptations of elite aerobically-trained athletes include which of the following? I. increased maximal oxygen uptake II. decreased blood lactate concentration III. increased running economy IV. decreased capillary density a. I and III only b. II and IV only c. I, II, and III only d. II, III, and IV only

c. I, II, and III only

Markers for aerobic overtraining

criteria for a reliable marker -the marker should be sensitive to the training load -it should not be affected by other factors -changes in the marker should precede development of overtraining syndrome -marker should be easy to measure accurately -measurement should not be profoundly invasive -marker should not be expensive to use or measure

3. Which of the following does NOT normally increase during an aerobic exercise session? a. end-diastolic volume b. cardiac contractility c. cardiac output d. diastolic blood pressure

d. diastolic blood pressure

2. The amount of blood ejected from the left ventricle during each beat is the a. cardiac output. b. a-v-O2 difference. c. heart rate. d. stroke volume.

d. stroke volume

Rate-pressure product (RPP) or double product

estimate of the work of the heart (myocardial oxygen consumption) RPP = HR x SBP (systolic blood pressure)

Detraining

gradual deterioration of training adaptations due to termination of training or inactivity tapering-planned reduction of volume of training (usually in duration and frequency but not intensity) that occurs before an athletic competition or a planned recovery microcycle. **this is designed to enhance athletic performance and adaptations.

Effects on Acid-base from altitude hypoxia

immediate -body fluids become more alkaline due to reduction in CO2 with hyperventilation long term adjustments -excretion of HCO3 by kidneys with concomitant reduction in alkaline reserve

cardiovascular adjustments to altitude hypoxia

immediate adjustments -cardiac output increases at rest and durming submaximal exercise -submaximal HR increases -stroke volume remains the same or is slightly lowered -maximal HR remains the same or is slightly lowered -maximal cardiac output remains the same or is slightly lowered long-term adjustments -continued elevation in submaximal HR -decreased stroke volume at rest and with submaximal and maximal exercise -lowered maximal cardiac output

Altitude affects pulmonary

immediate adjustments -hyperventilation longer-term adjustments -increase in ventilation rate stabilizers

Cardiovascular responses to acute aerobic exercise

include -cardiac output (Q=stroke volume x HR) is the amount of blood pumped by the heart in L/min -stroke volume - quantity of blood ejected with each beat (mL of blood/beat) -HR

Normal resting BP 110 - 139 mmHg systolic 60-89 mmHg diastolic

maximal aerobic exercise SBP 220 - 260 mmHg DBP 60 - 80 mmHg DBP stays the same or decreases a little.

Low to mod exercise increase in ventilation is do to increase in tidal volume.

more intense exercise (45-65% of max oxygen uptake in untrained and 70-90% in trained) breathing frequency takes on a greater role. **at these levels minute ventilation rises disproportionately to increase in Ox uptake and begins to parallel the abrupt rise in blood lactate. -at this point ventilatory equivalent may increase to 35-40 L of air per liter of ox consumed

local tissue adjustments to altitude hypoxia

no immediate adjustments long-term adjustments -increased capillary density of skeletal muscle -increased number of mitochondria -increased use of free fatty acids, sparing muscle glycogen

hematologic adjustments to altitude hypoxia

no immediate adjustments long-term adjustments -increased red cell production (polycythemia) -increased viscosity -increased hematocrit -decreased plasma volume

At rest the partial pressure of O2 in the interstitial fluid (fluid immediately outside a muscle cell) drops from 100 mmHG in the arterial blood to as low as 40 mmHg, while

partial pressure of CO2 is elevated above that of arterial blood to about 46 mmHg. **during high intensity exercise O2 is 3 mmHg and CO2 is 90 mmHg. These pressure gradients cause the movement of gases across cell membranes. **with exercise the gradients are greater especially with CO2 facilitating their exchange At rest alveoli: PO2 = 105, PCO2 = 40 systemic arteries: PO2 = 100, PCO2 = 40 exchange in muscle cell systemic veins: PO2 = 40, PCO2 - 46

Pressure gradients for gas transfer in the body at rest.

pressures of O2 (PO2) and carbon dioxide (PCO2) in alveolar air, venous and arterial blood, and muscle tissue are shown.

What protects against serious detraining effects

proper -exercise variation -intensity -maintenance programs -active recovery periods

Oxygen Uptake (VO2)

the amount of oxygen transported to, taken up by and used by the body for energy production

maximal oxygen uptake

the greatest amount of oxygen that can be used at the cellular level for the entire body The capacity of max oxygen uptake is affected by -ability of heart and circulatory system to transport oxygen -ability of body to use it

Most significant change in cardiovascular function with long-term (6-12 months) aerobic endurance training is

the increase in cardiac output resulting primarily from improved stroke volume.

diastolic blood pressure

the pressure remaining in the arteries when the left ventricle of the heart is relaxed (DIASTOLE) and refilling **indicates peripheral resistance **can decrease with exercise due to vasodilation

Ventilatory equivalent for oxygen

the ratio between the volume of air ventilated and the amount of oxygen consumed; indicates breathing economy ranges from 20-25 L of air per liter of Oxygen consumed

minute ventilation

total volume of air inhaled and exhaled each minute *increase during exercise due to increase in depth of breathing, frequency of breathing or both. Strenuous exercise increases from 12 to 15 breaths per min at rest to 35 to 45 breaths per min. Minute ventilation = tidal volume x respiratory rate