Introduction to Exercise Physiology

Hippocrates (460 -377 BC) “Father of Preventative Medicine”

Galen (131 - 201 AD) most well-known & influential

physician “Laws of Health”

Galen

Wrote about: benefits of exercise

deleterious effects of sedentary living

Galen Surgically repaired torn tendons &

muscle

Recommended rehabilitation therapies

Recommended exercise regimes

Laws of Health (circa 140 AD)

1. Breathe fresh air2. Eat proper foods3. Drink the right beverages4. Exercise5. Get adequate sleep6. Have a daily bowel movement7. Control one’s emotions

Exercise Physiology History

Harvard (late 19th century)

Department of Anatomy, Physiology, and Physical Training

B.S Degree (1891 - 1898)

This Course in Exercise Physiology

Designed to heighten your awareness of:

General Health and Wellness

Preventative Medicine

This Course in Exercise Physiology

Identify strengths & weaknesses of the latest fitness “crazes” and diets

Nutrition I

Galen:“Eat proper foods”“Drink the right beverages”

Macronutrients Carbohydrates (CHO)

Lipids

Proteins

Function of Macronutrients Structural

Functional

Common Element Carbon (C)

Carbohydrates (CHO) Carbon (C) Hydrogen (H) Oxygen (O) (CH2O)n

Monosaccharides single sugar molecule basic unit of CHO categorized by # of carbons:

- trioses- tetroses- pentoses- hexoses

Monosaccharides glucose (dextrose) - blood sugar fructose - fruit sugar galactose - milk sugar

Glucose main energy source produced :

- thru digestion of complex CHO

- in liver via gluconeogenesis

Glucose

absorbed in small intestine

Cells

Glycogen

Lipids

Oligosaccharides disaccharides

GLUCOSE

Fructose

Glucose

Galactose Lactose

Maltose

Sucrose

Polysaccharides

Polysaccaharides

Plant Animal

Plant Polysaccharides

Plant Polysaccaharides

Starch Fiber

Starch storage form of CHO complex CHO most impt. dietary source of CHO grain bread, cereal, pasta

Fiber Nonstarch polysaccharide resistant to human digestion make up structural components of

plants cellulose

Fiber Linked w/ lower obesity, DM, intestinal

disorders, HD, serum cholesterol aid in gastrointestinal function (bulk):

- scraping gut wall- dilute harmful chemicals- transit time

rate of digestion of CHO

Animal Polysaccharides Stored Glucose

Glycogen

Liver Muscle

CHO in the body

375 - 475 grams

Muscle

(325 grams)Liver

(90 - 110 grams)

Blood Glucose

(5 grams)

Glycogen Utilization directly by muscle

liver blood glucose (glyogenolysis) muscle

Glycogen Regulation blood glucose insulin

(pancreas[])

cellular uptake of blood glucose

Glycogen Regulation blood glucose glucagon

(pancreas[])

break-down of glycogen blood glucose

Glycogen Regulation very sensitive to changes in diet

- depleted quickly- reserved quickly

upper limit = 15g /1 kg

excess is stored as lipids

CHO intake 40 - 60% sucrose (table sugar) vs. fructose

(plant sugar) fructose

- fewer calories- does not stimulate insulin

secretion- taken up by muscle w/o insulin

stable blood glucose

Role of CHO energy source

preserve tissue proteins (structure)

CHO starvation gluconeogenesis- protein glucose- glycerol (lipids) glucose

Role of CHO allows for efficient lipid metabolism blood glucose lipid mobilization incomplete lipid catabolism ketone

bodies (ketosis / acidosis) seen w/:

- CHO starvation- DM

Role of CHO proper function of CNS

efficient nerve tissue metabolism

CHO and Exercise

Intense exercise (> 80% HRmax): Initially (5-10 min.) mm. glycogen via

anaerobic means 1 hour of intense exercise

55% glycogen 2 hours

100% use of BG

CHO and Exercise

Moderate exercise (60-79% HRMax) initially all glycogen later 40-50% of energy is glycogen

/ lipid (aerobic) later - glycogen BG and lipid

CHO and Exercise

Continued exercise: depletion of glycogen and BG

systemic fatigue (“bonking”, “hitting the wall”)

CHO and Exercise

In general, w/ an activity : use of muscle glycogen (anaerobic

glycolysis) as initial energy concurrent release of glucose (liver)

Effect of Diet on Muscle Glycogen diet low in CHO quicker time to

fatigue

high fat/low CHO diets energy endurance

Effect of Diet on Muscle Glycogen

Initial muscle glycogen (g/100 g muscle)

Tim

e to

exh

aust

ion

(min

utes

)

1 4

50

200

Low CHO

Normal Diet

High CHO

Bergstrom J. et. al. Diet, muscle glycogen and physical performance. Acta Physiol. Scand., 71: 140, 1967.

CHO and Exercise

What nutrient to use is determined by:1. Exercise intensity2. Exercise duration3. Fitness status4. Nutritional status

CHO Balance & Exercise

Fuel

Exercise

sympatheticresponse

LiverGlycogenoly

sisAnaerobic

Glucose

BG

glycogenphosphorylase

Muscle Glycogenolysi

sAnaerobic

Glucose

LipidsGlucose BG

CHO and Exercise

Exercise Time (minutes)

Leg

Glu

cose

Upt

ake

(mM

/min

)

10 40

1.0

4.0Heavy Exercise

Moderate Exercise

Mild Exercise

Felig P, Wahren J. Fuel Homeostasis in exercise. N. Engl. J Med., 293: 1078, 1975.

Lipids (Fats) same elements as CHO

different linking and > H:O ratio

Lipids

Lipids

Simple Compound Derived

Simple Lipids triglycerides - most plentiful

> 95% of body fat

Triglycerides glycerol

fatty acids

Fatty Acids saturated

- holds many H atoms- animal products- snacks

Fatty Acids unsaturated

- usually plant sources- mono- canola, olive peanut- poly- safflower, sunflower,

soybean, corn- hydrogenation - saturated-

like (margarine, lard)

Compound Lipids triglyceride + other chemicals phospholipids (phosphate &

nitrogenous base)- help control movement

across cell membrane- structural integrity- blood clotting- myelin sheaths

Compound Lipids Glycolipids (FA + CHO + N) Lipoproteins (protein +

triglycerides / phosolipids)- main form of lipid transport

Lipoproteins Chylomicrons - transports lipid-

soluble vitamins (A, D, E, & K) HDL - 50% protein / 20% lipid /

20% cholesterol LDL VLDL - 95% lipid - transports

triglycerides

HDL vs. LDL LDL

- deliver cholesterol to arterial walls- structural changes in walls

HDL- “reverse transport of cholesterol” liver

HDL vs. LDL Total cholesterol is not the issue

ratio of HDL to LDL

cholesterol:HDL (HDL:LDL) risk of CAD

exercise & smoking HDL

Derived Lipids from simple & compound lipids

cholesterol - only in animals

Cholesterol found in plasma membrane

exogenous - obtained thru diet

endogenous - synthesized by cells

Cholesterol endogenous - produced by:

- liver (70%)- arterial walls- intestinal walls

Functions of Cholesterol building of plasma membranes precursor for

vitamin Dadrenal gland hormonesestrogen, androgen, progesterone

impt. in formation of bile egg yolk, red meat, organ meat,

shellfish, dairy products

Cholesterol and CAD serum cholesterol + LDL CAD other risk factors: genetics, HBP, smoking, reduce cholesterol thru:

- diet ( saturated fat / unsaturated fat)

- exercise and weight control- medication

1:2 (cholesterol reduction:CAD risk)

Dietary Intake of Lipids 30% of total energy content

- 70-80% = unsaturated fats - (mono = poly)

Role of Lipids largest store of energy

protection

thermal insulation

Lipids as an Energy Source 1 gram yields 9 calories at rest can yield 80-90% of energy concentrated energy source

- high in H- relatively low H2O

50x > caloric reserve in fat than CHO spares use of protein as energy

Lipids and Vitamins

Transport medium for fat soluble vitamins (A, D, E, K)

Lipids and Diets

3.5 hours to digest

reduce hunger

Lipids and Exercise

Light to moderate exercise utilizes FFA

initiation of exercise:- initial in serum FFA- sympathetic hormones /

insulin- FFA release from adipose

Lipids and Exercise

moderate exercise for < 1 hour:CHO and lipid utilization is =

> 1 hour:> use of lipids as CHO deplete

continued moderate exercise:lipids may provide 80% of

energy

Lipids and Exercise Intensity

intensity- lipid utilization remains same- blood glucose & muscle

glycogen

@ 25% or 85% of max. exercise lipid utilization remains same

Lipids and Exercise Intensity

trained individuals - more efficient - mobilizing FFA- utilizing FFA

conserve glycogen reserves

Lipids and Exercise Intensity

0

50

100

150

200

250

Trained Untrained

Plasma FFA

Triglyceride

Glycogen

Blood Glucose

Tis

sue

O2 u

ptak

e (m

L/k

g. min

)

Lipid

Saltin B, Astrand PO. Free fatty acids and exercise. Am. J. Clin. Nutr., 57(suppl): 752S, 1993)

Training Effect

enzymes responsible for producing energy

improved transport of FFA thru membranes

altered transport of FFA ( proteins & enzymes)

proliferation of capillaries (vascularization)

Proteins

C, H, O, N (16%), S, P, Fe

amino acids chains

Amino Acids

8 essential (9 children)

nonessential - synthesized

Proteins

Sources:- eggs*, milk, meat, fish, poultry

- 67% from animals- cholesterol- saturated fat

- animal sources more complete- vary plant sources to achieve

variety

Proteins

Plant sources:- often high in CHO / fiber,

vitamins- low in cholesterol

Protein Consumption

excessive amounts not necessary 0.8 – 0.9 grams/kg BW 2-4 grams/kg of BW

(infants/children) +20 grams – pregnancy +10 grams - nursing

Amino Acid Supplementation

has NOT demonstrated:

increased muscle mass

improved muscular strength, power, or endurance

Protein in the Body

found in:- blood plasma- visceral tissue- muscle

important functional & structural roles no stores

Role of Amino Acids/Protein

12-15% of body mass building blocks of tissue

(anabolism) cells – plasma membrane,

internally collagen in hair, skin, etc. enzymes

Role of Amino Acids/Protein

blood plasma proteins-hemoglobin

genetic material (RNA/DNA) buffering muscle – actin, myosin

Protein Metabolism

catabolized @ rest for energy (2-5%)

deaminized first urea urine

excessive protein catabolism excessive H20 loss

Protein Utilization during Exercise

0

200

400

600

800

1000

1200

1400

1600

Rest High CHO Low CHO

Sw

eat u

rea

nitr

ogen

(m

g/h)

Lemon PWR, Nagel F. Effects of exercise on protein and amino acid metabolism. Med. Sci. Sports Exerc., 13: 141, 1981.

Protein Utilization during Exercise

Ala

nine

out

put f

rom

legs

(m

M/m

in.)

Felig P, Wahren J. Amino acid metabolism in exercising. J. Clin. Invest. 50: 2703, 1971.

0

20

40

60

80

100

120

140

160

180

Rest Mild Moderate Severe

Protein Metabolism

Nitrogen balance nitrogen (protein) in = nitrogen outPositive nitrogen balance nitrogen in > nitrogen out children pregnancy recovery 20 to resistance training

Protein Metabolism

Negative nitrogen balance- nitrogen in < nitrogen out- protein used as 10 energy

source - starvation – dietary

implications loss of LBM

Protein Metabolism Summary

occurs during endurance and resistance training exercise for energy utilization

20 CHO/Glycogen depletion additional quantities for heavy

resistance training??? additional food intake will probably

provide enough CHO and protein