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UNIT 3: AREA OF STUDY 2

PHYSIOLOGICAL RESPONSES TO PHYSICAL ACTIVITY

TOPIC 1: FOODS, FUELS AND ENERGY SYSTEMS Energy from muscular contraction comes from Adenosine Triphosphate. An acceptable abbreviation is ATP.

ATP --> ADP + Pi + energy ATP is stored in the muscle. You have approximately 90 grams. This is good for 2-3 all-out maximal contractions. (2-3 sec.) An activity like the vertical jump would use stored ATP. Once ATP splits and energy is released it becomes ADP (Adenosine Di-phosphate). ATP needs to be regenerated/replenished if exercise is to continue past 2 seconds. Energy from the food we consume is used as fuel(s) by the three energy systems to replenish ATP.

QUESTION 12 What is ATP and what does it provide? Solution

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THE ROLE OF CARBOHYDRATES Carbohydrates are stored as glycogen (Muscle Glycogen or Liver Glycogen). Transported in the blood as glucose. Glycogen is the body’s preferred fuel when exercising. Another term used for fuel is substrate. Why is glycogen preferred when exercising at moderate/high intensities? Requires less oxygen to release energy compared to triglycerides (fat). An 80 kg person may have stored: Muscle glycogen 400 grams.

Liver Glycogen 100 grams = 500 grams = 2000 calories.

1 hour of steady running = 700 calories.

Therefore glycogen would run out at just under 3 hours of continuous steady running.

Thus, the importance of Carbohydrate (fuel) Replenishment: What could you use to replenish fuel during the run? Gels and sports drinks are very effective. But the body/stomach can only absorb 300 – 500 calories per hour. In hot conditions you burn/use calories at a higher rate but your absorption of calories is even slower.

THE ROLE OF FATS Converted into Triglycerides – stored in the muscle – stored as Adipose tissue. Transported as Free Fatty Acids. Preferred fuel at rest and low intensity exercise – as sufficient oxygen is available. This results in a much greater yield of ATP. Not the preferred fuel when exercising at higher intensities as free Fatty Acids are transported quite slowly and a greater amount of oxygen is needed to breakdown them down compared to glycogen.

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THE ROLE OF PROTEINS Broken down into amino acids and stored in the muscle. Main functions are growth and repair, enzyme production. Not normally used as a fuel source for ATP production. Only used in extreme circumstances.

Food Fuels Broken down into? Storage Sites Transported as?

Carbohydrates Glycogen

Muscle Liver

Glucose

Fats Triglycerides

Muscle Adipose Tissue

Free Fatty Acids

Protein Amino Acids Muscle

THE CONTRIBUTION OF FUELS At Rest – 2/3 Triglycerides & 1/3 Glycogen. Exercise – preferred fuel = glycogen Why? But if you can metabolise triglycerides at higher exercise intensities (glycogen

sparing) this is a distinct advantage to the athlete. Why? Substrate – an alternative term for fuel. 1 Fat molecule fully broken down = a yield of 441 ATP.

1 Glucose molecule fully broken down = a yield of 36 ATP. The ranking of carbohydrate – Glycemic Index – High GI / Low GI.

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CARBOHYDRATE LOADING Method: CHO intake 3 - 5 days before major competition.

quantity & quality of training. Why? – Glycogen stores have super-compensated (over-flowing).

Performance enhancing – greater fuel stores – prolong performance/not faster.

Disadvantages – could body weight; in water storage with extra glycogen (feel stiff / heavy).

QUESTION 13 What is Carbohydrate Loading? Solution

GLYCOGEN SPARING

QUESTION 14 (a) Describe the graph. (b) What is Glycogen Sparing?

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‘HITTING THE WALL’ QUESTION 15 (a) What does this term refer to? (b) What type of athlete or event might this happen? (c) What is the effect on performance and why? (d) How might an athlete avoid “Hitting the Wall”?

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THE ATP-CP ENERGY SYSTEM Fast rate of ATP production & Small yield / capacity Type of activity = Short duration/High Intensity – (100 metre sprint) Fuel= PC stored in muscle replenished via passive recovery 30 sec. 70% replenished 3 min. 100% replenished Source of CP red meat, eggs

QUESTION 16 What are the benefits of being aerobically fit with regard to the ATP-CP system? Solution QUESTION 17 (a) What is the advantage of this system? (b) What is the disadvantage of this system?

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THE LACTIC ACID ENERGY SYSTEM Fast rate of ATP production & Small yield (but greater than the ATP-CP system) Type of activity = Duration (up to 75 sec) High Intensity. Video (400 metres). Activated at the start of intense exercise.

Fuel = Glycogen.

Metabolic fatiguing by-products (H+).

Insufficient O2 pyruvic acid lactic acid. Increasingly important system when intensity increases above 85% HR max (Lactate Inflection Point / Lactate Transition Point LT2). Glucose molecule is not fully broken down = 2 ATP produced.

QUESTION 18 What is the major limiting factor of this system? Solution

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THE AEROBIC ENERGY SYSTEM Slow rate of ATP production & Large yield Type of Activity – At rest / low & sub-maximal intensity. – from 75 sec when intensity is continuous and of a high intensity. Two major fuels (triglyceride/glycogen).

3 Stages – one glucose molecule = fully broken down via:

Aerobic Glycolysis (2 ATP).

Krebs Cycle (2 ATP).

Electron Transport System (32 ATP) = Total = 36 ATP produced.

ATP RE-SYNTHESIS

Intensity (rate) Duration (yield)

Anaerobic Energy Systems

High Intensity = Fast rate of production

Short duration = small yield (amount of ATP)

Aerobic Energy System

Low / sub-maximal = Slow rate of production

Long Duration = large yield

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SUMMARY OF THE THREE ENERGY SYSTEMS

Characteristic ATP-CP System Lactic Acid System Aerobic System

Fuel Source Creatine Phosphate Glycogen Glycogen / Triglyceride /Protein

Intensity High 95% High 85% of Max HR

Rest / Low / Sub-max 85% max HR

Predominant For? (maximal/continuous)

0 – 10 sec 15 – 75 sec 75 sec plus

Peak Power 5 sec 15 sec

ATP Produced 0.7 ATP for each CPmolecule

2 ATP for each glucose molecule

36 ATP = Glycogen 441 ATP= Triglyceride molecule

By-Products Pi (inorganic phosphate + ADP

Lactic Acid = Lactate + Hydrogen Ions ADP

CO2 + H2O + Heat

Related Fitness Component

Anaerobic Capacity / Power

Muscular Strength

Muscular Power

Agility

Dynamic Flexibility

Anaerobic Capacity / Power

Local Muscular Endurance

Muscular Power Agility (with repeated efforts)

Aerobic Endurance

Local Muscular Endurance

Static Flexibility

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THE ENERGY SYSTEM INTERPLAY Key points to remember: All three energy systems are activated at the start of exercise. The predominant system is determined by the intensity and duration of the exercise. The intensity and duration will also determine the rate and yield of ATP production

All three systems are activated at the start of exercise. The predominant system is determined by the Intensity and Duration of the activity.

OTHER FACTORS AFFECTING THE PROPORTIONS OF ENERGY SYSTEMS

Used in any given exercise activity are: Level of fitness (whether adaptations to training have included enhancement of

relevant enzymes – which would for example postpone levels of lactate accumulation).

Availability of O2 and food fuels.

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EXAMPLE Explain interplay of all three systems evident in the training of an athlete as follows: 6 x 15 m sprints every 30 seconds. Solution "all energy systems would be activated at the onset of exercise, the ATP-PC system would be predominant for the first 4 high intensity, short duration sprints; however, since PC stores are being depleted by these sprints, and the recovery time provided is not sufficient to fully replenish PC stores, the lactic acid system would begin to contribute more and more with every sprint. The 5th and 6th sprints would see the lactic acid system become the most predominant in supplying ATP. The aerobic system would be contributing minimally during the sprint periods because they are of such a high intensity, however it would be predominant during the 30 second rest periods as they are passive and of low intensity. The aerobic system during these rest periods would help in supplying oxygen to muscles to help replenish PC and breakdown/oxidise H+."

Duration (min:sec) 22.3 49.3 1:53 3:55

Intensity (% VO2max) 201 151 113 103

% Aerobic 29 43 66 84

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QUESTION 19 In reference to the graph: (a) Describe the graph. (b) Explain why the running speed of the athlete would be much faster in the 200 m

compared to the 1500 m? (refer to the energy systems) (c) Why is the oxygen deficit relatively the same for all events? Concept of a finite capacity (d) How is it possible that all athletes are able to run at greater than 100% of VO2 max? QUESTION 20 VCAA 2007 Question 8

The study below shows the relative contributions of energy production from the anaerobic and aerobic energy systems. It was found, for each duration of maximal work the subject exhausted their anaerobic energy supply. Fill in the table with the estimated energy release from the aerobic and anaerobic energy systems.

Duration (maximal intensity work) seconds

Total Energy Release ml / kg

Aerobic ml / kg

Anaerobic ml / kg

60 100 50 50

120 150

180 200

4 Marks

Concept of a finite capacity – the Anaerobic Energy systems have a limited capacity to produce ATP (limited stores of CP that cannot be replenished until you stop) – the LA system is also limited by the accumulation of fatiguing by-products. Extended question have tended to concentrate on – The Energy System Interplay (a) Use the data to support/justify the use of the three energy systems in a particular sport. (b) Describe the interplay in a selected sport. (2009 VCAA – Surfing competition).

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AREA OF STUDY 2: PHYSIOLOGICAL REQUIREMENTS OF PHYSICAL ACTIVITY

TOPIC 2: THE MECHANISMS RESPONSIBLE FOR THE

ACUTE RESPONSES TO EXERCISE

To meet the increased energy demands when the body transitions from rest to exercise, there is a combined / coordinated response from our respiratory, cardiovascular and muscular systems. The rapid response from the body to meet these changes in energy demand are the bodies acute responses.

RESPIRATORY SYSTEM

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VE = TV x BF Where: VE = Ventilation (litres of air / minute) TV = Tidal Volume (air / breath) BF = Breathing Frequency The acute response to exercise is linear. As exercise intensity (energy requirements) increase – so too does Ventilation.

TYPICAL ACUTE RESPONSES QUESTION 21 Complete the following table

VE = TV BF

Rest

Exercise

The primary mechanism during exercise is a neural input that likely originates from the same area of the brain that is telling the skeletal muscles to exercise. This would explain the rapid increase and decrease of minute ventilation (VE) with the onset and cessation, of exercise. However, a "fine tuning" of exercise VE is accomplished primarily by the peripheral chemoreceptors, that detect increases in H+, CO2 and heat.

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QUESTION 22 Describe the graph.