SPORTS PHYSIOLOGY “Energy Systems”

Key terms you must know:• Energy• Adenosine triphosphate (ATP)• Adenosine diphosphate (ADP)• ATP Splitting• Carbohydrate

- Glucose, Glycogen• Fat (lipids)

- Triglycerides, FFA’s• Protein• Anaerobic• Aerobic• Glycolysis

• ATP / PC System• Phosphocreatine (PC)• Lactic Acid System• Onset of Blood Lactate

Accumulation (OBLA)• Anaerobic Threshold (AT)• Aerobic System• Krebs Cycle • Electron Transport Chain• Mitochondria• Energy Continuum• Slow / Fast Twitch Muscle Fibres

Energy?• Can be defined as “the ability to do work.”

• Measured in kilojoules (kJ) or Calories (C). 1kJ = 24 Calories

• ATP – is the chemical compound that serves as the immediate source of energy for most energy consuming reactions in the body, including: muscular contraction, processing food, tissue growth & repair, production of hormones as well as nerve conduction.

ENERGY (catabolism of

ATP)

Nerve conduction

Digesting & processing of food

Hormone manufacture

Building new body tissues (growth)

Muscular contraction

Repairing body tissues

Energy for skeletal muscle contractions

• Energy for the cross-bridges to pull.* Myosin and Actin filaments work together to create movement as cross-bridges are formed.

Sliding Filament Theory

http://www.youtube.com/watch?v=gJ309LfHQ3M

What is ATP?• ATP is the energy source for all

muscular effort, whether for a small subconscious movement such as the blinking of an eye, or planned repetitive effort in weight training.

• ATP = Adenosine + 3 Phosphates. ‘Tri’ meaning three

• The phosphates are linked to adenosine via high energy bonds.

• When these high energy bonds break, a phosphate separates from ATP and energy is released for muscular effort.

• This can be simplified as:ATP ADP + Pi + Energy

• Also known as ‘ATP Splitting’

Adenosine + 3 Phosphates

ATPAdenosine + 2 Phosphates

ADP

P PP P PAA + Energy+ Pi

High energy bonds (12,000 Calories)

Rebuilding ATP

• A muscle fibre stores only a limited amount of ATP!

• ‘ATP Splitting’ is reversible process, whereby ADP undergoes phosphorylation (rejoins with a phosphate) with the assistance of energy to resynthesize ATP:

Adenosine + 2 Phosphates

ADPAdenosine + 3 Phosphates

ATP

Energy

+ Pi + PPPP PA A

CHO ProteinFat

Energy for rest and activity

The body can create energy (ATP) under two mainconditions:

1. Rest conditions,• Where there is sufficient oxygen available for the body to continue to

function at resting level.

2. Active conditions,• Where physical exertion means there is insufficient oxygen available for

the body to continue to function at a particular level without a marked increase in oxygen intake either during or after the effort. These conditions occur during anaerobic activity and aerobic activity.

ATP production during rest conditions• Rest is when the body is not under physical stress and when breathing and

heart rates are low and stable.• The body has an abundant supply of oxygen, so preference is to produce

ATP from the breakdown of fat (as no fatiguing by-products).- ⅔ ATP from breakdown of fats (but with greater O2)

- ⅓ ATP from the breakdown of CHOs• Occurs in the Mitochondria – bean shaped ‘power house’ of the cell.• End products of this aerobic respiration are: CO2, H2O & Heat

ATP production during activity

• ‘Activity’ in physical education is a wide ranging term that refers to any physical state more exertive than rest. The ATP produced during activity depends on a number of factors:

1. The length of time (duration) of the exercise2. How hard an athlete works (intensity) in the exercise bout3. How well-developed his/her cardiorespiratory system is (aerobic

fitness)4. The degree of recovery in between successive bouts of exercise.

• REMEMBER: due to the time it takes to get necessary O2 into the lungs, absorption into the bloodsteam & transportation to working muscles, our bodies sometimes must make use of anaerobic systems.

Sources of ATP• ATP is an end product in your diet. All the food, processed drinks and

water that you consume contain nutrients that your body requires for:- Healthy growth- Repair of body ‘wear and tear’ from everyday activities- Energy for all body functions.

• The components of a healthy diet are:- Carbohydrates- Fat- Protein- Vitamins & Minerals- Water

• ATP can be created from any carbohydrate, fat or protein.

Carbohydrates (CHOs)• Primary source of ATP for muscle contraction during exercise. • Broken down into glucose for transportation in the blood.• Stored as glycogen in the muscles and liver (~ 90 mins)• Excess is converted to fat and stored in adipose tissue.• Glycogen can then be used to power ATP production in both the

Lactic Acid and Aerobic Systems.• e.g. Grains, breads, pasta, fruit and vegetables.• Carbohydrate Loading – a nutritional strategy to maximise muscle

glycogen stores prior to endurance competition. e.g. Few days before competition:- decrease volume & intensity of training- increase CHO intake in diet (~70%)

Fats (Lipids)

• VERY energy dense (37 kJ/g) & produce large amounts of ATP.• BUT requires much more Oxygen, therefore must decrease work load.• Broken down to free fatty acids (FFAs), which circulate in the blood,

and triglycerides, which are found in the muscles and liver.• Excess stored largely as adipose tissue.• Energy from the breakdown of fats is used mainly at rest and periods

of low intensity sub-maximal exercise.• Secondary source of ATP for muscle contraction during exercise. • Under special conditions, however, an athlete may use fat earlier in the

activity to ‘spare’ the CHO stores and therefore enable high-level effort closer to the end of competition. (Glycogen sparing)

• e.g. dairy products, nuts, and oils.

Protein

• Made up of amino acids (i.e. Leucine, Tryosine, Lysine) – building blocks of our bodies (contain N,H & C).

• Stored in the muscles and adipose tissue.• Protein only minimally contributes to ATP production.• In extreme circumstances (such as starvation or ultra triathlon /

marathon events) when the body has severely depleted its supplies of CHO and fat, proteins become a viable source of ATP.

• e.g. meat, fish, eggs and dairy products.

Q: Why is protein the least preferred fuelsource for energy?

Fuels - SummaryFood Fuel Stored as SiteCarbohydrate(Primary Source when exercising due to efficiency)

• Glucose• Glycogen• Excess as fat

• Blood• Muscle & liver• Adipose Tissue

Fat(Primary Source at rest 66-75%, Secondary Source when exercising to CHO)

• Free Fatty Acids• Triglycerides• Fat

• Blood• Muscle• Adipose Tissue

Protein(Last resort situations only)

• Muscle amino acids• Excess as fat

• Skeletal Muscle• Adipose Tissue

Energy (ATP) Production

• There are 2 pathways for energy production:(1) Aerobic Pathway - in the presence of Oxygen

(2) Anaerobic Pathway - in the absence of Oxygen• There are 3 Energy Systems.

ATP-PC Systemhttp://www.youtube.com/watch?v=uCmNQQWlrc0

ATP-PC System• ATP-CP or Phosphagen System• Pathway: Anaerobic • Fuel: PCr (chemical) and Muscle ATP stores.• Intensity: High to maximal• Time of most effectiveness:

• By-products: None• Takes place in the muscle cell NOT Mitochondria.• ATP production: Small amounts instantly; > 1 ATP per mol. of PCr• Recovery:

• This energy pathway provides ATP for once off powerful, explosive efforts e.g. 100m sprint, tennis serve or a take off in long jump.

Q: List 5 activities from 5 completely different sports that would use the Phosphagen system.

ATP Resynthesis (ATP-PC)

http://www.youtube.com/watch?v=BR3dDO1Sz0E

ATP-PC System

is closely linked to several fitness components:• Muscular strength• Muscular power• Speed• Agility• Reaction Time

Q: Which muscle fibre type would this system predominantly recruit?

Q: Examples of Fitness Tests which assess this energy system might be?

Lactic Acid System

Lactic Acid System• Energy released from the breakdown of

glucose into Pyruvic Acid is the second means by which ADP + Pi reforms into ATP.

• From approx. 10-30 secs the ATP-PC System energy contribution diminishes to almost nothing, and anaerobic glycolysis becomes the predominant energy system.

• Anaerobic Glycolysis or Anaerobic Glycolytic system• Pathway: Anaerobic• Fuel: Glycogen (stored CHO)• Intensity: Near maximal • Time of most effectiveness:

• By-product: Lactic Acid• Takes place in the cell cytoplasm NOT Mitochondria.• ATP production: Limited amounts rapidly, 2 ATP per molecule of glycogen fuel.• Recovery: Lactic Acid removal dependant upon amount of energy used up & the method of recovery:

Approx. 30 secs – 2 mins

Q: List 3 different sporting examples which use the LA System.

50m Swim

Active 95% removal in 30mins

Passive 95% removal in 60mins

ATP Resynthesis (LA)

Comparison - Glycolysis

Aerobic Systemhttp://www.youtube.com/watch?v=PQMsJSme780

-

Aerobic System • This system includes the complete breakdown of glucose/fats/protein, using the processes of glycolysis/lipolysis + Krebs Cycle + ETC.

• Remember: When the body is at rest or during low intensity sub-maximal exercise, the demand for ATP is low and it is produced aerobically

• The energy from ATP resynthesis comes primarily from 2 fuel sources:- Fats (66-75%)- CHO (25-33%)

• Oxygen system or Aerobic Glycolysis.• Pathway: Aerobic (requires O2)• Fuel(s): Carbohydrate (glucose), Fats and then Protein.• Intensity: Sub-maximal • Time of most effectiveness:

• By products: H2O, CO2 + heat• Takes place in the Mitochondria• ATP production: unlimited amounts slowly.

• Recovery: Depends on intermittent or continuous recovery (high CHO intake is beneficial)

+ 5 minutes

CHO (Glucose) 38 ATPFats 460 ATP

Q: List 3 other sports which rely on the O2 System.

Krebs Cycle• In Aerobic Glycolysis, the Pyruvic acid breaks down in the presence of O2 (instead of producing Lactic Acid)• Sir Hans Krebs• Also known as the Citric Acid Cycle• Occurs in the Mitochondria (matrix)• Produces CO2. (C atoms)• 2 ATP made / 2 ATP pre Krebs Cycle

Electron Transport Chain• After the Krebs Cycle, the other major stage is the ETC.• Produces H2O and Heat (H and O mix)• 34 ATP made.

Aerobic Glycolysis = 38 ATP made

Aerobic Glycolysis

Q: Which muscle fibre type would this system recruit?

Comparison between SystemsCharacteristic ATP-PC Lactic Acid AerobicFuel/s ATP stores and

PhosphocreatineGlycogen CHO, Fats THEN

Protein

ATP production per molecule of energy source

Less than 1 Approx. 2 Glucose = 38Fats = 460

Speed / rate of ATP production

Small amounts instantly

Limited amounts rapidly

Unlimited amounts slowly

Intensity Maximal effort Near maximal (85-95%)

Sub-maximal(<85%)

Duration 0-10 secs 30 secs–2 mins 5 minutes+

Oxygen requirements Nil Nil O2 required

By products Nil Lactic acid H2O, CO2 and Heat

Characteristic ATP-PC Lactic Acid AerobicFatigue Fast fatigue Fast fatigue Slow fatigue

Muscle Fibre Type Fast twitch (white) Mainly fast twitch (white)

Slow twitch (red)

Speed of Muscle contraction

Very rapid Rapid Slow

Fitness components Muscular strength, react. time, power, agility, speed.

Local Muscular endurance

Cardio-respiratory endurance

Sporting Examples Golf Swing Tennis Serve 100m Sprint Javelin Throw Baseball Swing Volleyball Spike Football kick

400m Sprint 200m Sprint 50m Swim Gymnastics Floor Routine Repeated ‘break efforts’ in football, netball, b’ball etc.

Marathon Triathlon Cross-Country skiing 800m Swim 1500m Swim 2000m Rowing

Fitness Tests Vertical jump B’ball chest pass Grip strength 20-40m Sprints

Maximal push-up test (30secs) Maximal sit up test (60secs)

20m beep test 12 min run/walk

The Energy Continuum

• The Energy Continuum illustrates the ongoing and continual interplay between all 3 energy pathways and the fact that one system rarely acts in isolation.

• All 3 systems CAN operate at the same time providing different energy contributions depending on the intensity and duration of the activity.

Energy SystemATP-PC System 56 - - - - - -

Lactic Acid System 44 60 50 35 15 3 -

Aerobic System - 40 50 65 85 97 100

6s 30s 60s 2 min 5 min 30 min 60 min

Time

% Energy Contribution

Activities

1. Draw an accurate representation of the Energy Continuum diagram. Explain in detail, using 3 sporting examples to support your answer.

2. Make a list of the all the positives and negatives associated with the use of each Energy System.

3. Explain in detail the differences between Anaerobic and Aerobic Glycolysis – be sure to include the Krebs Cycle and Electron Transport Chain in your answer.

4. Write an equation to highlight the concept ‘ATP Splitting’. Explain. How is ATP resynthesized?

5. Discuss the recovery of all three Energy Systems.6. Read the article ‘Makings of a Winner’ and attached readings on

Energy Systems.