Exercise physiology

the study of the exercise effects on the functions of the body as it pertains to health & performance.

Archibald V. Hill

-Nobel Prize winner in 1922-Studied heat production and muscle contraction

August Krogh

Nobel Prize winner in 1920Studied capillary blood flow in skeletal muscle

Otto F. Meyerhof

Nobel Prize winner in 1920Studied metabolism, glycolysis, and lactate

C.G. Douglas

studied the role of O2 and lactic acid in control of breathing during exerciseDouglas bags

Christian Bohr

Studied O2 off-loading on hemoglobinBohr effect oxyhemoglobin-dissociation curve named after him

D.B. Dill

Director of Harvard Fatigue Laboratory from 1927-1947

Dr. Dudley Sargent

Hired by Harvard in 1879Set up training programs for individualized exercise prescriptions

A major cause for rejecting military recruits is

obesity "Too fat to fight

During the civil war, WWI, and WWII many draftees failed induction exams due to

Low body weight and/or low fitness levels "Too weak to fight

Autopsies of young children in Korean War showed

coronary artery disease being developed at a early age

Physical inactivity was recognized as a major health factor in the

early 1980's

Physical activity was shown to:

↓ risk of dying prematurely and from heart disease↓ risk of getting diabetes & high blood pressureMaintains healthy bones, muscles, and joints↓ blood pressure in those with high blood pressureHelps achieve & maintain a healthy body weight

Surgeon General's Report (1996)

Inactivity killing adults - 60% not getting enough physical activity, 25% not active at all (sedentary)

Physical activity/inactivity linked to diseases of

Behavioral factors; poor diet, lack of exercise, and habits (smoking)

Government and societies tried

Educating the public

Programs of study include courses in:

BiomechanicsExercise PhysiologyFitness assessment Exercise Testing/prescription 1/2 Clinical exercise physiologyDevelopment & Implementation of Fitness programs HOPE - Dr. Brady

Current research in exercise physiology uses an integrated approach for research questions

Systemic physiology and applied physiology Molecular and cell biology (cell signaling) Molecular levelGenomics- genetics- Does exercise influence gene activation? YESProteins- proteomics how proteins are made, modified, etc. YESMetabolomics- study of metabolites within organism/blood or tissueCell signaling processes- 1970s to now- pathways

American College of Sports Medicine (ACSM)

United physicians, physical educators, and physiologists science and certifications

National Strength and Conditioning Association (NSCA)

Educational aspect and certification in resistance and conditioning

Examples of Research Journals

International Journal of Sports MedicineMedicine and Science in Sports and Exercise

Requirements for Careers for Exercise Science and Kinesiology

Rigorous science-based courseworkInternship - gain experience - recommendationsGraduate study for some careersCertification exam-American College of Sports Medicine: Ties Medicine to Scholars-National Athletic Training Association: Injuries and prevention-National Strength and Conditioning Association: Personal trainer

Graphs typically have....

a shape and a direction

Independent variable

what you manipulatex-axis

Dependent variable

outcome measurey-axis

Homeostasis

Maintenance of a constant and "normal" internal environment

Steady State

Physiological variable is unchanging, but not necessarily "normalmay not result in steady outcome in your variable EX) Body Temp and Blood Glucose

Simple Biological Control Systems

Interconnected components that maintain a physical and/or chemical parameter at or near constant value Components are:1) Stimulus2) Sensor or receptor3) Control center4) Effector

Sensor or Receptor

Detects changes in variable

Control center

assesses input and initiates response

Effector

Tries to change internal environment back to normal

Negative Feedback

Response reverses initial disturbance in homeostasisMost control systems work this way

Positive Feedback

Response increases original stimulusCa2+ feed forward mechanism - muscle contractionSodium feed forward mechanisms - depolarizationInflammation feed forward mechanisms

Appropriate Gain

more capable of maintaining homeostasis than system with low gainToo High= heat problemsToo Low= too much energy used

Adaptation

Change in structure or function of cell or organ systemimproves ability to maintain homeostasis

Acclimation or Acclimatization

adaptation to environmental stresses improved function of existing homeostasis systemAcclimation = short termAcclimatization = long term

Cell Signaling

communication between or within cells using chemical messengersimportant for maintaining homeostasis

Intracrine Signaling

Chemical messenger inside the cell triggers response

Juxtacrine signaling

Chemical messenger passed between 2 connected cellsone is signaling to the other

Autocrine signaling

Chemical messenger acts on the same cell (self)goes out of the cell then goes to receptor

Paracrine Signaling

chemical messengers act on nearby cellsnot connected

Endocrine Signaling

Chemical messengers released into bloodaffects cells with specific receptors to the hormone

Stress proteins

Heat Shock Proteins"protects and repairs damaged proteinsare synthesized when homeostasis is disrupted

Exercise-induced protein synthesis improves...

the ability of cells to maintain homeostasis

Metabolism

sum of all chemical reactions in the bodyAnabolic reactions= Synthesis of molecules (Building up)Catabolic reactions= Breakdown of molecules

Bioenergetics

process of converting foodstuffs into usable energy for cell workfoodstuffs= (fats, proteins, carbs)

Nucleus

Control center of the cellcontains genes (DNA)regulates protein sythesis

Cytoplasm

fluid portion of cellH2O, Ions, Sugars, glycogen, proteins, lipids

Mitochondria

Powerhouse" of the cellmost ATP is made here (oxidative phosphorylation)

Endoplasmic Reticulum

stores Ca+ in cell

Endergonic Reactions

Requires energy (ATP) to reactants

Exergonic Reactions

release energy (energy exits)Energy released = ATP + Heat

Coupled Reactions

Liberation of energy in a exergonic reaction can drive an endergonic reaction(energy given off by the exergonic reaction powers the endergonic reaction)

Oxidation

removing a electron and Hydrogen ionEX) NADH to NAD+

Reduction

Addition of an electron and Hydrogen ionEX) NAD+ to NADH

Oxidation-Reduction Reactions

a reaction that involves the transfer of H+ between reactantscoupled reactionsmolecule loses both a H+ and a electron then sends it to another molecule to be reduced

Enzymes

Catalysts that regulate reaction speedLower the energy of activationInteract with specific substrates

Kinase

Adds a Phospahte group

Phosphatase

Removes a Phosphate group

Dehydrogenase

removes a H+ ion

DeCarboxylase

removes a carboxyl group

Factors that Alter Enzyme Acitivity

Temperature- Small increase in body temp increases enzyme activitypH- change in pH alters enzyme activitySubstrate- if there are no substrates there will be no reactionProduct- inhibits reaction rateCo-factors- enhance or inhibit reaction

Carbs

Fuels Brain, Red Blood cells, and musclesMonosaccharides (1), Disaccharides (2), Polysaccharides (3 or more)

Glycogen

carb storage form in cells in liver and skeletal musclesythesized by enzyme glycogen synthase

Glycogenolysis

enzyme phosphroylase breaks down glycogen

Fats

fuel primary at restFatty acids, Triglycerides, Phospholipids, and Steroids

Fatty Acids

have a even # of carbons the primary type of fat used by skeletal muscle for energyAerobic metabolism= Acetyl-CoA via B-oxidation

Triglycerides (TG)

the storage form of Fats in muscle and adipose tissueAdipose tissue = TGare broken down to glycerol + fatty acids (3) via lipolysis

Protein

not a primary energy source during exercise < 2% is proper nutrition~ 20 amino acidsare altered to carbs when CHO needed (glucconeogenesis)Are altered to fat if there is too much protein

Adenosine Triphosphate (ATP)

the bodies universal energy sourceConsists of adenine, ribose, and 3 linked phosphates

Anerobic Formation of ATP

(no O2 involved)1) Phosphocreatine2) Adenylate Kinase reaction3) Degradation of glycogen and blood glucose4) Glycogenolysis

Glycolysis

breakdown of glucose 1) Phosphorylase2) Hexokinase3) PhosphofructokinaseEnergy Investment phase= requires 2 ATPEnergy Generation phase= Produces 4 ATP, 2 NADH, and 2 Pyruvate or 2 Lactate (2 ATPs formed for each 3 carbon)has a net gain of 2 ATP

lactic acid

rapidly disassociates to lactate and H+ in solution

Hydrogen and Electron Carrier Molecules (NAD+ and FAD2+)

Transport hydrogens and associated electrons to mitochondria for ATP generation (aerobic)To convert pyruvic acid to lactic acid (anaerobic)

Lactate

is formed by the addition of two H+ to pyruvate from NADH + solution reforms NADcatalyzed by Lactate Deydrogenase

Aerobic formation of ATP

requires O2Krebs cycle1) Oxidative Phosphorylation 2) Uses glycogen, glucose, and then fatty acids

Krebs Cycle (Citric Acid Cycle)

1) pyruvic acid is converted to acetyl-CoA2) Acetyl CoA binds to oxaloacetate to form Citrate and releases CoA3) Citrate is metabolised to OAA2 CO2 molecules are given offProduces 3 NADH, 1 FADH, 1 GTP(ATP) (Per Turn)Total 10 ATP per turn

Oxidative Phosphorylation

ATP formation in the presence of O2occurs in mitochondriaEach NADH produces 2.5 ATPEach FADH produces 1.5 ATP34% efficiency of aerobic respiration66% of energy released as heat

Electron Transport Chain

shuttles Electrons on 1 side and H+ on the other side to set up a voltage gradient to form ATP

B-oxidation

process of converting fatty acids into Acetyl-CoAFFA broken into 2 carbon segments requires O2 to be present for breakdown and 1 ATP to prime Fatty Acid1 turn= 1 NADH + 1 FADH2 = 4 ATP

N/2

equals the # of 2 Carbon acetyl groups formed

N/2 -1

number of turns of Beta-oxidation cyclesubtract 1 ATP from priming

Rate-Limiting enzymes

An enzyme that regulates metabolic pathwayHigh levels of ATP inhibit ATP productionLow levels of ATP and high levels of ADP+Pi stimulate ATP production1) Creatine Kinase2) Phosphofructokinase- glycolysis3) Cytochrome oxidase4) Phosphorylase- glycogenolysis5) Adenylate Kinase

Short-term, High-Intensity activities have a

greater contribution of anaerobic energy systems

Long-Term, Low to Moderate-Intensity exercise

majority of ATP produced from aerobic sources

Resting O2 consumption

0.25 L/min3.5 ml/kg/min

Rest to exercise transitions

Oxygen uptake increases rapidlyInitial ATP production through anaerobic pathways- ATP-PC system- Glycolysis

O2 deficit

lag in O2 uptake at the beginning of exercisealso occurs when increase in intensity

Trained Subjects

These kind of subjects have a smaller O2 deficithave better aerobic bioenergetic capacityresults in less production of Lactate and H+

Recovery form exercise

O2 uptake remains elevated above rest during recovery from excercise O2 debtEPOC

O2 debt

repayment for O2 deficit at onset of exerciseHas a Rapid Portion and a Slow portion

EPOC

excess post-exercise oxygen consumptiononly about 20% of elevated O2 used is to "repay" deficit

Rapid portion of O2 debt

Resynthesis of stored PCReplenishing muscle and blood O2 stores

Slow" portion of O2 debt

- Elevated heart rate and breathing = ↑ energy need- Elevated body temperature = ↑ metabolic rate- Elevated epinephrine and norepinephrine = ↑ metabolic rate - Conversion of lactic acid to glucose (gluconeogenesis)

Factors contributing to EPOC

Resynthesis of PC in muscleLactate conversion to glucoseRestoration of muscle and blood oxygen storesElevated body temppost-exercise elevation of HR and breathingElevated hormones

EPOC is Greater Following ______________ Intensity Exercise

HigherBecauseincrease body tempgreater decrease of PC + ATPgreater blood lactate accumulation (OBLA)higher blood epinephrine and norepinephrineincrease HR and breathinggreater work internal work

Doing light exercise _____________ blood lactate faster than sitting or standing

decreases

First 1-5 seconds of exercise

ATP produced via ATP-PC system and Adenylate Kinase ReactionAnaerobic

Intense exercise longer than 5 seconds

shifts ATP production to glycogenolysis and glycolysisanaerobic

Events lasting longer than 45 seconds

ATP production through ATP-PC, glycolysis, and aerobic systemsincrease in duration = more aerobic and less anaerobic

Exercise > 10 min

ATP production primarily from aerobic metabolismupward drift in VO2 uptake overtimeincrease body temp and blood epinerphrine/nprepinephrineincrease HR and breathing

O2 uptake increases _______ ________________ until maximal O2 uptake is reached

+ linearly

Factors that influence VO2 max

maximum ability of CV system to deliver O2 to muscleability of muscles to use O2 and produce ATP Endurance training typically show high VO2 max

Lactate Threshold

point where lactic acid rises exponentially during incremental exercisenormally at about 50-60% VO2 max in untrained subjectsNormally higher work rates (65%-80% VO2 max) in endurance trained subjectsalso called Onset of Blood Lactate Accumulation (OBLA)blood lactate levels reaches 4 mmol/L

Mechanisms of Lactate Threshold

Accelerated Glycolysis- NADH produced faster than shuttled to mitochondriaRecruitment of Fast-Twitch Fibers- LDH isozyme in fast fibers promotes lactic acid formationReduced Rate of Lactate Removal- results in more accumulation of lactate in blood

If H+ cannot enter mitochondria then ___________ + H+ forms lactate to enable glycolysis to continue

pyruvate

Practical Uses of the Lactate Threshold

1) prediction of performance 2) planning training programs = marker of training intensity and choose training HR based on LT

Can Lactate Cause muscle Soreness?What Does Cause DOMS (delayed onset muscle soreness)?

NoMicroscopic injury to muscle fibers and inflammation

LDH isoforms

LDH has 5 isoforms1) Heart Like = favors lactate removal (LDH H4)2) Fast Twitch = favors more lactate (LDH M4)3) Slow Twitch = have more heart type and thus produce less lactate (H3 M1)

What formula is used to calculate Fuel Utilization Estimate During SS exercise

Respiratory exchange ratio (RER or R)R= VCO2/VO2R for fat = ~.7R for glucose = 1must be at steady state

Estimate of fuel utilization during excercise

.85 = 50/50< .85 = more fat used>.85 = more carbs being usedincrease in intensity = > % of CHO used

What is the primary fuel source for Low intensity exercise? (<30% VO2 max)

fats

What is the primary source for high intensity excercise? (>70% VO2 max)

carbs

crossover concept

shows shift from fat to CHO metabolism as exercise intensity increasesshows shift from CHO to fat with decrease in exercise intensity

__________________ intensity exercise is best for burning fat

Higher best intensity to burn fat is @ 50-60% VO2 max

Prolonged, low-intensity exercise

Shift from carbohydrate metabolism toward fat metabolismfats burn in the flame of carbsGlycogen degraded during prolonged exercise

muscle glycogen

Primary source of carbohydrate during high-intensity exerciseSupplies much of the carbohydrate in the first hour of exercise

As muscle glycogen declines more __________________________ is needed

blood glucose

blood glucose

found in liver

intramuscular triglycerides

primary source of fat at moderately high exercise intensity

Plasma FFA comes from _________________________

adipose tissue lipolysisbecomes more important as muscle triglyceride levels decline in long-duration excercise

______________ in muscle glycogen usage at higher % intensity and __________________ in usage of fat

increase decrease

diet intake influences the amount of ______________________ stored in the liver and the muscle

glycogenLow CHO is badCarbohydrate storage is in limited supply

The liver can convert alanine to ___________________ used for CHO

glucose

Lactate

can be used as a fuel source by skeletal muscle and heart can be converted to glucose in liver

Lactate Shuttles

Lactate produced in 1 tissue and used by another

Cori Cycle

the cycle of lactate to glucose between the muscle and liverliver takes 2 lactates and forms 1 glucoseGLuconeogenesis helps to keep blood glucose up

neuroendocrine system

- Endocrine system releases hormones via ductless glands into blood- Nervous system-nerve releases neurotransmitter directly to target cell and is short lasting

Hormones

any substance that enters the bloodbinds to a receptor that alters activity of tissues (includes endocrines)work on specific hormone receptorsAmino acid derivativesPeptides/proteinSteroids

The effect of a hormone on a tissue is determined by ______________________________ and ______________________________

Plasma concentration Number of active receptors

Plasma concentration is determined by

1) Rate of secretion hormone2) Rate of metabolism3) Amount of transport proteinmore protein to carry less free hormoneonly free hormone level has an effect on receptor4) Changes in plasma volumeMore volume less concentration or vise versa

Hormone receptors magnitude of effect is dependent on

1) hormone concentration2) Number of receptors on the cell3) Affinity of receptor for hormone

Downregulation

decrease receptor number in response to high hormone concentration

Upregulation

increase receptor # in response to low hormone concentration

Mechanisms of Hormone Action

1) Activation of genes to alter protein synthesis2) Activating 2nd messengers in cell membrane3) Altering membrane transport

2nd messengers in cell membrane include

Cyclic AMPCa++Inositol triphosphate (IP3)Diacylglycerol (DAG)

Steroid hormone action

works to alter gene expression in the nucleusHormone to receptor to nucleus

Cyclic AMP 2nd messenger mechanism

hormone binds to receptor and activates receptorsends signal to enzyme to form cAMPcAMP activates PKAeffects lots of cell responses

Phospholipase C 2nd messenger mechanism

hormone binds to receptor sends signal to activate enzyme phosholipase C enzyme and DAG, IP3, and Ca++= 2nd messengers IP3, DAG and Ca2+

Insulin receptor

insulin binds to receptor and activates tyrosine phosphorylation (P).this leads to many steps within cell

major endocrine glands include

Hypothalamus and pituitary glandsThyroid and parathyroid glandsAdrenal glandsPancreasTestes and ovaries

Hypothalamus

controls (+ or -) secretions to pituitary gland

anterior pituitary gland

Adrenocorticotropic hormone (ACTH) -> adrenal gland --> cortisolThyroid-stimulating hormone (TSH) -> thyroid -> thyroxine (increases metabolism) Growth hormone -> all tissue

posterior pituitary gland

antidiuretic hormone (ADH) --> retains water and works on kidneysDecreases H2O loss from body to maintain plasma volumestimulated by increase plasma osmolarity and decrease in plasma volume (due to sweat loss and decrease plasma volume)increase during exercise . 60% VO2 max to maintain plasma volumerealtionship is curvilinear

thyroid gland

regulator of metabolismT3 and T4 modest increase exerciseT3 is more active form a permissive hormone

permissive hormone

hormone that assist other hormones

Growth hormone

from anterior pituitaryessential for growth of all tissuesmobilizes fatty acids from adipose tissuehelps maintain blood glucoseassists with gluconeogenesisSpares plasma glucose

growth hormone __________________________ during exercise

increases

Growth Hormone _____________________ with intensity

+ curvilinear

Beta-Endorphins

from hypothalamusInhibits insulin releasePromotes glucagon releaseassist in blood glucose regulationintensity > or equal to 70% VO2 max can increase circulating BELonger duration will increase BE further

adrenal cortex

via mineral corticoids to keep water and sodium salts elevated K+ or decrease in pressure will activate aldosterone via release of renin

Antiotensin II

a powerful vasoconstrictor that increases BP

Aldosterone

helps to control water and saltsincreases Na+ retention and H2OIncrease in NA+ to help Increase H2O retentionregualtion of blood volume and blood pressurestimulated by increase in K+ or decrease in plasma volume+linear

Adrenal Medulla

secretes catecholamines epinepphrine and norepinephrineE = 80%NE = 20%but more NE in blood than E due to spill over of NE from syp. nerves

epinephrine and norepinephrine

fast acting hormonesbind to adrenergic receptors Alpha and Betaassist in blood glucose maintenance during exercise (increases muscle glycogen breakdown and inhibits blood glucose uptake in non-active tissuesincrease during exercise + linear (related to increase in HR)

Beta 1 receptors

E=NE Increase cyclic AMPIncrease HR and Glycogenolysis

Beta 2 receptors

E>>>>NEincrease cyclic AMPIncrease HR and Glycogenolysis

Alpha 1 receptors

NE> or equal to E Increase CA++ increase vasoconstriction

Alpha 2 receptors

NE> or equal to E decrease cyclic AMP increase vasoconstriction-

There is a greater increase in _____________________ than __________________ during exercise by % and absolute amount

NE E

Epinephrine response to intensity of exercise is

positive linear increase overtime higher intensity = greater EE is much lower than NE

Catecholamines

regulate substrate mobilizationalso influence HR, BP, and blood flow NE>E (~6X higher)

Mineralcorticoids

from adrenal cortex aldosteronemaintence of plasma Na+ and K+

Glucocorticoids

Cotrisolregulation of plasma glucose Permissive

Cortisol

permissivemaintenance of plasma glucosepromotes use of FFA as fuel to spare glucoselow intensity decrease cortisol from 0intensity > 60% VO2 max increase in a positive linear manner

Pancreas

secretes insulin from beta cellssecretes glucagon from alpha cells

Insulin

fast actingpromotes storage of glucose, amino acids, and fatsplasma concentration decreases during exerciseinhibits glucagon

Glucagon

Fast actingmobilization of glucose and FFA fuels plasma concentration increases during exercise

Insulin __________________ overtime during exercise at steady state

decreasesat steady state

Insulin has the ______________ response to exercise intensity

smile

Trained athletes show a _________________ glucagon response

lower

Muscle Glycogen breakdown is under ___________________ control. Them being.....

triple1) AMP-metabolic2) Epinephrine- cyclic AMP - hormonal3) Ca++ - calmodulin - muscle contraction