Exercise Physiology

•Driving force behind all types of work•Conversion of stored energy to mechanical energy

What Influences Athletic Ability?• Genetics• Training

• Training methodology

• Environment• Nutrition• Track/Arena

Surfaces• Shoes• Jockey• Etc.

ATHLETICABILITY

Heart sizeSkeletal muscle

properties

Anaerobic capacity

Gas exchange

Hemoglobinconcentration

Biomechanics

ENERGY

• Sources– Carbohydrates– Fats

• Effect on performance– ↓ energy = ↓ performance– Must meet energy requirement– Monitor body condition

• ↓ body condition = negative energy balance

Energy Metabolism

• Aerobic– With oxygen– Carbohydrate & fat– CO2, H2O & ATP

• Anaerobic– Without oxygen– Carbohydrate

(glycolysis)– Lactate & ATP

Muscle GlycogenBlood Glucose

Anaerobic Glycolysis

OxidativeMetabolism

Pyruvate Lactate

ATP

Free-Fatty Acids

CreatinePhosphate

Myokinaseand CPKReactions

CO2and Water

Lipolysis

Oxygen

Synthesis of ATP from aerobic and anaerobic metabolism.

Muscular System

Types of Muscle Fiber

• Type I• – Slow contracting• – ↓ glycolytic activity• – Fatigue resistant• – Aerobic metabolism• – Long term/low stress• work• – Endurance

• Type II• – Fast contracting• – Fatigue quickly• – ↑ Glycolytic activity• – Quick energy bursts• – Speed for longer• distances• – Primarily anaerobic

Breed Differences

Type I fibers Type II fibers

Energy For Muscle Contraction

• Walking– Slow contractions– Primarily type I

fibers– Fat primary energy

source (very efficient)

Energy For Muscle Contraction

• Trot and Canter– Increased contractions

• Increased contractions require more ATP

• Type II fibers• Fat cannot be

metabolized anaerobically

Anaerobic Glycolysis

• Fastest way to produce ATP

• Less efficient than aerobic glycolysis– Less ATP– Lactic acid produced– Decrease muscle pH– Fatigue/tying up

Horses that can generate a higher proportion of energy aerobically will

outperform horses with lower aerobic capacity

Estimated Types Of Energy Used

Event Preformed Energy

Anaerobic Aerobic

Racing QH 80% 18% 2%

Racing 1000 m 25% 70% 5%

Racing 1600 m 10% 80% 10%

Racing 2400 m 5% 70% 25%

Racing 3200 m 5% 55% 40%

Polo 5% 50% 45%

Estimated Types Of Energy Used

Event Preformed Energy

Anaerobic Aerobic

Barrel Racing 99% 4% 1%

Cutting 88% 10% 2%

Show Jumping 15% 65% 20%

3 Day (Cross Country)

10% 40% 50%

Endurance Rides 1% 5% 94%

Pleasure/Equitation

1% 2% 97%

Cardiovascular System

• Delivers blood to body– O2 from lungs– Nutrients from

GI tract

Cardiovascular System• Heart rate (HR)

– Resting 30-45– Exercising – 240 bpm max

• Stroke Volume (SV)– Volume of blood pumped per

beat– 800 – 900 mls

• HR X SV = Cardiac Output– Can pump > 250 li/min– Equivalent to 55 gal drum

Affect of Exercise On The Cardiovascular

System

• ↑ metabolic activity in limbs = ↑ blood flow• Three ways to increase blood flow

– Increase cardiac output• HR and CO proportional to running speed• Cannot ↑ HR beyond max

– Increase O2 carried in blood• Splenic dumping can double O2 carrying capacity

– Redistribute blood flow• ↑ to locomotive muscle• ↓ to kidneys and small intestines

Respiratory System

• Respiratory Rate – Resting - 8-20 breaths per min

• Exercise– ↑ O2 consumption– ↑ CO2 emission

• To increase air exchange– ↑ Respiratory rate

• RR linked to stride freq.• ↑ Tidal Volume (TV)

– Air inhaled or exhaled in a breath

Locomotor-Respiratory

Coupling (LRC)

• Galloping Horse– 150 Breaths– 12-15 liters of air

• Trotting Horse– 70-85 Breaths– 20-25 liters of air

Respiratory Problems• Laryngeal hemiplegia

– Partial paralysis of larynx– Inadequate gas exchange– Surgical treatment

• Chronic Obstructive Pulmonary Disease– Decreases respiratory rate– Hyperallerginc response to dust,

mold, irritants– House outdoors

• Exercise Induced Pulmonary Hemorrhage– Bleeding in lungs– Speeds above 14 m/s– Variable effects– Furosemide (Lasix)

Thermoregulation

• Importance– Evaporative Cooling

(Sweating)– Most important route

of heat dissipation– Requires ample

blood flow to carry heat from core to surface

• Thoroughbred (race)– 2.5 gal

• Endurance horse (50-100 miles)– 6-12 gal

• Three day event (dressage/cross country)– 5-6 gal

Thermoregulation

• ↑ Exercise intensity > ↑ heat load > ↑ need for heat dissipation

• Prevent dehydration to prevent thermal injury– Provision of adequate water– Normal diet– Salt & mineral supplement

Thermoregulation• Dehydration

– Electrolyte & pH disturbances– Fatigue– Gait incoordination (ataxia)– ↑ risk of orthopedic injury– Muscle damage– Death

• Supplement electrolytes– Beginning training program– Adjusting to high temperature

Types of Training

• Endurance– Enhances aerobic

system• High intensity/Quick

burst– Increases muscle mass– Strength training

Influence of Training

• ↑ heart size• ↓ HR at given speed• Quicker recovery to given heart rate• ↑ Capillaries

– ↑ O2 delivered to muscles• Increase aerobic capacity

Influence of Training

• ↑ Muscle Cell Mitochondria– ↑ O2 utilization per unit of muscle

• Muscle has quickest adaptation to training of all body tissues

Conditioning Times of Body Structures

0

5

10

15

20

25

Muscles Ligaments Bones

Unfit

Fit

Signs of Fatigue• Respiration rate > heart rate

– Inversion– Hyperventilating– Shallow breathing– Shock

• Muscle soreness (lactic acid buildup)• Ataxia• Deydration

Conditioning is A Process That Occurs Over Time