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Energy Transfer in the Body

Refer to text for more detail.

Energy Metabolism

 Energy   the capacity or ability to perform work.

Energy is required for muscle contraction and other biological work such as digestion, nerve conduction, secretion of glands, etc.

 Metabolism   the sum total of all chemical reactions

occurring in the body.

Biologic Work in Humans

 Mechanical Work

 Transport Work

 Chemical Work

Adenosine Triphosphate (ATP)

The most common immediate energy currency of the cell (the all purpose nucleotide)

Nitrogen Carbon Phosphorous Oxygen

Metabolic Production of ATP   Aerobic Processes

processes which require the presence of oxygen delivered by the blood

Adenosine Triphosphate Adenosine Diphosphate

Nitrogen Carbon Phosphorous Oxygen

Energy +Pi

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ATP ADP + P + Energy

CP C P Energy

i

i

ATPase

CreatineKinase

! "###

! "### + +

Biologic Work

ATP-CP (Phosphagen) System

Principle of Coupled Reactions

All-out power for approximately 10 seconds

Anaerobic Glycolysis The Glycolytic System

Glucose

2 Pyruvate

Lactate Lactate

10 chemical reactions Net production of 2 or 3 ATP molecules

Glucose  Glucose can be made available in the

muscle cells for breakdown to lactate principally by two methods:   glucose molecules may pass from the

blood through the muscle cell membrane into the cell interior (net 2 ATP), or

  the glucose can be split from glycogen stores in the muscle cell itself (net 3 ATP).

 Glycogen is stored in liver and muscle tissue.

Anaerobic Glycolysis   Anaerobic glycolysis can produce ATP rapidly to

help meet ATP requirements during severe exercise when oxygen demand is greater than oxygen supply

  High rates of ATP production by glycolysis cannot be sustained for very long (40-60 sec.)

  Low muscle pH is associated with hydrogen ion concentration and lactate formation

  High acidity is believed to contributes to the acute muscular discomfort experienced during intense exercise.

Predominates in all-out efforts 30-90 seconds

50-200 meters

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Aerobic Processes Aerobic Carbohydrate Breakdown

Acetyl Coenzyme A

Pyruvic Acid

Electron Transport Chain

Krebs Cycle

Glucose

Pyruvate Lactate

Anaerobic Conditions

Aerobic Conditions

Pyruvate

Glycolysis (2 ATP)

Glycolysis (2 ATP)

No O2 available

36 ATP +CO2 +H2O

Krebs cycle Electron TC

O2 available

Total ≈ 38 ATP

Wall of Mitochondria ATP Yield

 Do not worry about specific yields of ATP.  Depending on whether glycogen or

glucose is used and depending on which shuttle system is used to transport NADH molecules to the mitochondria you can get yields of 36 to 40 ATP.

 The main thing is to see the approximate increase in ATP yield between anaerobic breakdown (2 or 3 ATP) versus aerobic breakdown (36-40 ATP)

Predominates in the majority of daily activities and lower intensity, long-duration sports. An all-out effort of 2 minutes is approximately 50% aerobic and 50% anaerobic

Aerobic Breakdown of a Glycogen Molecule

Glycogen Glucose Pyruvate Acetyl - CoA Kreb's cycle Electron Transport C + O2

CO2 + H2O + ATP

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Energy Release From Fat  The actual fuel reserves from stored fat

represent approximately 80,000 to 100,000 kcal of energy in an average size male or female.

  In contrast, the carbohydrate energy reserve is less than 2,000 kcal, of which 1,500 kcal are stored as muscle glycogen, 400 kcal as liver glycogen, and about 80 kcal of glucose are in the blood.

Aerobic Breakdown of Fatty Acids

Fat Fatty acids Beta oxidation Acetyl-CoA Kreb's cycle Electron Transport C + O2

CO2 + H2O + ATP

Less efficient than carbohydrate in terms of energy per O2 used

Energy Release From Protein  Research findings indicate that protein

breakdown above the resting level occurs during exercise of long duration when carbohydrate stores become low.

  It has been suggested as much as 15% of the energy during strenuous long duration exercise can come from protein.

Aerobic Breakdown of Proteins

Protein" Amino acids Deamination Kreb's cycle Electron Transport Chain + O2

CO2 + H2O + ATP

% phosphagen anaerobic

% glycolytic anaerobic

% aerobic

5 seconds 85 10 5 10 seconds 50 35 15 30 seconds 15 65 20 60 seconds 8 62 30 2 minutes 4 46 50 4 minutes 2 28 70 10 minutes 1 9 90 30 minutes Negligible 5 95 60 minutes Negligible 2 98 120 minutes Negligible 1 99

Relative contribution of aerobic and anaerobic energy during maximal physical activity of various durations.

Duration of Maximal ExerciseSeconds Minutes10 30 60 2 4 10 30 60 120

% anaerobic 90 80 70 50 35 15 5 2 1% aerobic 10 20 30 50 65 85 95 98 99

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% Max Power

Phosphagen

Lactic

Energy Production Continuum

The text graph shows this on logarithmic scale

Lactate

Aerobic

Figure 6.5 in text

ATP ADP + P + Energy

CP C P Energy

i

i

ATPase

CreatineKinase

! "###

! "### + +

ATP-Creatine Phosphate System

For a max 1 second effort you do not really need to resynthesize much ATP – you have enough in the muscle already

General Characteristics of the Three Energy Systems

Power Capacity Energy System Moles

ATP per minute

Total moles of ATP

available ATP-PC (phosphagen) 3.6 0.7 Glycolytic 1.6 1.2 Aerobic System 1.0 90.0

Table 6.3: Estimated Maximal Power Output and Capacity of the Three Energy Systems

Aerobic Power ≈ 28% of Peak Phosphagen System Power

Glycolytic System power ≈ 44% Peak Phosphagen Power

(Some researchers report this value to be higher ≈ 60%)

Capacity and Power of the Three Energy Systems (Untrained Male Subjects)

ATP ProductionEnergy System Capacity Power

(total moles) (moles/min)Phosphagen (ATP/PC) 0.6 3.6Anaerobic gylcolysis 1.2 1.6Aerobic (oxidative) Theoretically Unlimited 1.0

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Rankings of Rate and Capacity of ATP Production

Power Capacity System rate of ATP

production capacity of ATP

production ATP-PC

(phosphagen) 1 4

Anaerobic glycolysis 2 3 Oxidation of

carbohydrates 3 2

Oxidation of fats and proteins

4 1

Human Power Output (energy systems)

Graph from “Champion Athletes” Wilkie 1960

Energy Transfer in Exercise

The energy systems previously discussed are related to all human activity. We now need to relate this information specifically to exercise.

Time Motion Studies

English 1st Division (Premier) PlayersPosition and Distance Covered (in meters)

Activity Mid-field Full-back Striker Centre-back AverageJog 4042 2907 2769 2908 3157Cruise 2159 1588 1752 1596 1774Sprint 1063 787 1068 829 937Walk 2034 2293 2310 1774 2103Back 507 670 498 652 582

Total 9805 8245 8397 7759 8552

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Ajax Amsterdam Data

Soccer Activity Percentage of Total Match Time

Walk 20-30%

Jog 30-40%

Run 15-25%

Sprint 10-15% (18%)

Backwards 4-8%

Duration Classification Predominate Energy Supplied By

1-4 seconds Anaerobic ATP (in muscles)

4-20 seconds Anaerobic (ATP-PC/Glycolytic)

ATP + PC + Some muscle glycogen

20-45 secs Anaerobic (Glycolytic/ATP-PC)

ATP + PC + Muscle glycogen

45-120 secs Anaerobic (Glycolytic)

Muscle glycogen

120-240 secs Aerobic + Glycolytic

Muscle glycogen + a little from other fuels

>240 secs Aerobic Muscle glycogen + Fatty Acids + Protein

Predominant Energy Pathways 0s 4s 10s 30s 3 min +

ATP

ATP-CP

ATP-CP + glycolytic

Aerobic endurance

Strength Power

Sustained Power

Anaerobic Power Endurance

Oxygen

Five Areas of the Energy Continuum Performance

Time Intensity of Event

Major Energy System(s)

Types of Activity

0-6 seconds Very Intense

ATP-CP Jumping, throwing, kicking, 50 metre sprints, base-running

6-30 seconds

Intense ATP-PC and Glycolytic

100-200 metre sprints

30 seconds– 2 minutes

Heavy Glycolytic 600-800 metres run, ice hockey shifts, box lacrosse shifts, 100-metre swim

2-3 minutes Moderate Glycolytic and oxidative

800-100 metre runs

>3 minutes Light Oxidative systems

Running > 1000 metres, distance cycling, cross country skiing, swimming > 200-m

% phosphagen anaerobic

% glycolytic anaerobic

% aerobic

5 seconds 85 10 5 10 seconds 50 35 15 30 seconds 15 65 20 60 seconds 8 62 30 2 minutes 4 46 50 4 minutes 2 28 70 10 minutes 1 9 90 30 minutes Negligible 5 95 60 minutes Negligible 2 98 120 minutes Negligible 1 99

Primary Metabolic Demand From Sports or Activity Phosphagen

System Anaerobic Glycolysis

Aerobic Metabolism

Baseball High Low - Basketball High Moderate to High - Field Events High - - Field Hockey High Moderate Moderate Football (American) High Moderate Low Ice Hockey High Moderate Moderate Lacrosse High Moderate Moderate Marathon (42 km) Low Low High Soccer High Moderate Moderate Tennis High Moderate - Volleyball High Moderate - Wrestling High High Moderate Weight Lifting High Low Low

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Average VO2 max (ml/kg.min) for Non-Athletes and Athletes Group or Sport Age Male Female

Non-athletes 10-19 47-56 38-46 20-29 43-52 33-42 60-69 31-38 22-30

Baseball 18-32 48-56 Cycling 18-26 62-74 47-57 Football 20-36 42-60 - Gymnastics 18-22 52-58 36-50 Ice Hockey 10-30 50-63 - Rowing 20-35 60-72 58-65

From Chapter 5 – you should see a high positive correlation between a sport with a high demand on the oxidative system and the athletes VO2 max.

Average VO2 max (ml/kg.min) for Non-Athletes and Athletes

Group or Sport Age Male Female Skiing – Alpine 18-30 57-68 50-55 Skiing – Cross-country

20-28 65-95 60-75

Soccer 22-28 54-64 - Speed Skating 18-24 56-73 44-55 Swimming 10-25 50-70 40-60 Weight Lifting 20-30 38-52 - Wrestling 20-30 52-65

Oxygen Deficit

O2 Deficit VO2

(l/min)

Time Rest

Oxygen Debt

O2 Deficit

O2 Debt

Steady State O2 consumption

Exercise Recovery TIME

VO2

Resting VO2

O2 Deficit

Exercise Recovery TIME

O2 Debt

VO2 max

Oxygen Debt after Anaerobic Exercise

Oxygen Debt

O2 Deficit

O2 Debt

Exercise Recovery TIME

“Rapid” portion of debt

“Slow” portion of debt

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Figure 6.11 Lactate threshold and the onset of blood lactate (OBLA)

Recommended Recovery Times after Exhaustive Exercise Recommended Recovery Time

Recovery Process Minimum Maximum Restoration of ATP & CP 2 min 3 min Repayment of alactate O2 debt 3 min 5 min Restoration of O2-myoglobin 1 min 2 min Restoration of muscle glycogen 10 hr 46 hr (prolonged)

5 hr 24 hr (intermittent) Removal of lactate from 30 min 1 hr (exercise-rec) muscle and blood 1 hr 2 hr (rest-recover) Repayment of lactate O2 debt 30 min 1 hr

Ice Hockey Post-Game Recovery

  A light bike ride before/after exercise is a great way to warm-up or cool down along with stretching. Also, riding after a game helps to "flush out" lactic acid and other waste your muscles produce during activity; A cool-down flush ride should last around 10-min (often up to 30-min); Get your heart rate up around 140 bpm (Level II) for 5 min, then back off to a easy spin (Level I); You don't want to go hard enough to produce any more lactic acid (lactate); Stretch!!!

  This quote from” Paul Goldberg, of the Colorado Avalanche, February 1st, 2006.

Lactate does not cause muscle soreness   Despite the commonly

held belief that lactic acid (lactate) causes muscle soreness this has been discredited.

  Delayed onset muscle soreness is likely caused by damage to muscle fibers and associated connective tissue.

Getting a ball in the face also

causes soreness!

Blood Markers   If we take a blood sample from a runner the day

after a marathon, especially an ultra-marathon, we find that the levels of an enzyme called creatine kinase are very high. This is a marker of muscle damage as this particular enzyme "leaks" from damaged muscle.

  The "damage" is in the form of minute tears or ruptures of the muscle fibres. We can see this trauma to the muscle if a sample of muscle is examined microscopically.

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Blood Markers (cont.)   However, it is not just the muscle that is

damaged. By measuring hydroxyproline, it is possible to show that the connective tissue in and around the muscles is also disrupted.

  What this shows is that stiffness results from muscle damage and breakdown of connective tissue.

Stretching and DOMS

  There is no statistically strong evidence that stretching reduces post exercise muscle soreness.

  Intense stretching can cause muscle soreness.

Muscle Fatigue and Lactate   Lactic acid does not actually exist as an acid in

the body but rather as “lactate.   Producing lactate is a beneficial process since it

allows the regeneration of a coenzyme that ensures that energy production is maintained and exercise can continue (see text).

  Lactate also does not cause an increase in acidity (acidosis) within the muscle.

  When ATP is broken down to release energy for muscular contraction a hydrogen ion is released. This increases acidosis.

Muscle Fatigue and Hydrogen Ions   ATP-derived hydrogen ions are primarily

responsible for increases in acidity in the muscle.   High acidity is one factor that contributes to acute

muscular discomfort experienced during and shortly after intense exercise.

  However, recent evidence suggests fatigue is caused by calcium leaking into muscle cells from release channels within the muscle.

  Calcium helps control muscle contractions but after extended high-intensity exercise, channels in the muscle cells begin to leak calcium, which leads to weakened muscle contractions.

Muscle Fatigue & Calcium Channels   Leaked calcium also stimulates an enzyme that

attacks muscle fibers and also leads to fatigue and possible damage.

  However, as very high acidity could also cause damage to the cells the calcium leaks may be a protective mechanism to prevent muscle cell damage due to excessive acidity.

Neural Fatigue

 There is also the issue of Central Nervous System (CNS) fatigue.

 During intense repeated bouts of strenuous exercise neurotransmitters get depleted and reduces physical and cognitive performance.

 Central and peripheral fatigue factors are discussed in text Chapter 6.