Basic Energy Systems Basic Energy Systems (Bioenergetics)(Bioenergetics)

The systems used to degrade fuels to The systems used to degrade fuels to provide the energy to form ATP are:provide the energy to form ATP are:

The The Oxidative systemOxidative system The The Glycolytic systemGlycolytic system The The ATP-PCr systemATP-PCr system

Muscle cells can produce ATP using any one or a Muscle cells can produce ATP using any one or a combination (IN MOST CASES) of the three combination (IN MOST CASES) of the three systemssystems

Anaerobic

The Energy ContinuumThe Energy Continuum

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Figure 4.1Figure 4.1

ATP-PCr SystemATP-PCr System

Relies on stored phosphagens as Relies on stored phosphagens as fuel - namely phosphocreatine fuel - namely phosphocreatine (PCr) - also called creatine (PCr) - also called creatine phosphate (CP)phosphate (CP)

PCr + ADP PCr + ADP ATP + CrATP + Crcreatine kinasecreatine kinase

Characteristics of ATP-Characteristics of ATP-PCrPCr

Anaerobic – occurs whether or not Anaerobic – occurs whether or not oxygen is presentoxygen is present

Creates Creates immediateimmediate ATP (high rate ATP (high rate ATP production)ATP production)– One enzyme reactionOne enzyme reaction

Characteristics of ATP-Characteristics of ATP-PCrPCr

Limited in ATP production Limited in ATP production capabilitiescapabilities– Can provide ATP for only 3 to 15 Can provide ATP for only 3 to 15

seconds of high intensity exercise seconds of high intensity exercise because stores of PCr are limitedbecause stores of PCr are limited

ATP AND PCr DURING SPRINTING

ATP-PCr SystemATP-PCr System

Dominates ATP production:Dominates ATP production:– During short-term, very high-intensity During short-term, very high-intensity

or all-out exercise (< 15 secs.)or all-out exercise (< 15 secs.) Tennis serve, high jump, power lifts, etc.Tennis serve, high jump, power lifts, etc.

Glycolytic SystemGlycolytic System

Glycolysis (lactic anaerobic)Glycolysis (lactic anaerobic) Glycolysis is an anaerobic pathway Glycolysis is an anaerobic pathway

that uses energy transferred from that uses energy transferred from glucoseglucose to rejoin P to rejoin Pii to ADP to form to ADP to form ATPATP

Glycolytic SystemGlycolytic System

Glucose Glucose

10 steps10 steps

Pyruvic Acid (aerobic conditions)Pyruvic Acid (aerobic conditions)

Lactic Acid (anaerobic conditions)Lactic Acid (anaerobic conditions)

ATP

ATP

Glycolytic System Glycolytic System

DominatesDominates ATP production from 15 ATP production from 15 seconds to 2 minutes of high-seconds to 2 minutes of high-intensity exerciseintensity exercise

Glycolytic System Glycolytic System CharacteristicsCharacteristics

Anaerobic Anaerobic Less immediate than ATP-PCr, but Less immediate than ATP-PCr, but

can provide ATP for longer (up to can provide ATP for longer (up to 2-3 minutes of high intensity 2-3 minutes of high intensity exercise)exercise)– Further contraction limited by lactic Further contraction limited by lactic

acid acid accumulationaccumulation

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Lactic AcidLactic Acid

Lactic acid levels in blood are a balance Lactic acid levels in blood are a balance between production and clearancebetween production and clearance

At low intensities, clearance = At low intensities, clearance = production, and levels remain at or near production, and levels remain at or near resting (1-2 mmol/L)resting (1-2 mmol/L)

At high intensities, the shuttle molecules At high intensities, the shuttle molecules cannot clear all the lactate produced, cannot clear all the lactate produced, and accumulation occursand accumulation occurs

Maximal value = ~ 8 mmol/L, but values Maximal value = ~ 8 mmol/L, but values as high as 32 mmol/L have been reportedas high as 32 mmol/L have been reported

Anaerobic ATP Anaerobic ATP ProductionProduction

ATP-PCr and Glycolysis, collectively ATP-PCr and Glycolysis, collectively called the ANAEROBIC energy called the ANAEROBIC energy systems, work together to provide systems, work together to provide ATP during exercise that is too ATP during exercise that is too intense for all the needed ATP to be intense for all the needed ATP to be made aerobically (supramaximal made aerobically (supramaximal exercise)exercise)– Aerobic systems also begin to Aerobic systems also begin to

contribute (minorly) within the first 10 contribute (minorly) within the first 10 seconds of exerciseseconds of exercise

Oxidative SystemOxidative System

AerobicAerobic breakdown of food fuels breakdown of food fuels (CHO, FATS, some PRO)(CHO, FATS, some PRO)

AerobicAerobic Glycolysis or Beta Oxidation Glycolysis or Beta Oxidation

Krebs CycleKrebs Cycle

Electron Transport ChainElectron Transport Chain

AEROBIC GLYCOLYSIS AND THE ELECTRON TRANSPORT CHAIN

Oxidative System Oxidative System CharacteristicsCharacteristics

Has a much higher ATP yield than either Has a much higher ATP yield than either anaerobic systemanaerobic system– Can produce ATP almost indefinitely provided Can produce ATP almost indefinitely provided

adequate fuel and oxygen are availableadequate fuel and oxygen are available Responds more slowly than either Responds more slowly than either

anaerobic system (low rate of ATP anaerobic system (low rate of ATP production, but high capacity)production, but high capacity)– Can’t produce enough ATP quickly enough to Can’t produce enough ATP quickly enough to

support high-intensity exercisesupport high-intensity exercise

Major Differences Major Differences between Energy between Energy

SystemsSystems Fuel(s) used Fuel(s) used Oxygen requirementOxygen requirement Rate of ATP productionRate of ATP production

– High (ATP-PCr)High (ATP-PCr)– Moderate (glycolytic)Moderate (glycolytic)– Low (oxidative)Low (oxidative)

Amount of ATP produced (and therefore Amount of ATP produced (and therefore the length of time each can fuel the length of time each can fuel activity)activity)

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Figure 4.2Figure 4.2

Key Point to RememberKey Point to Remember

When discussing energy systems, When discussing energy systems, it is important to remember that it is important to remember that the time ranges on the continuum the time ranges on the continuum for each energy system are based for each energy system are based upon maximal or all-out efforts at upon maximal or all-out efforts at optimal paces optimal paces

Longest distance in a given time Longest distance in a given time periodperiod

ExampleExample The ATP-PCr system will dominate ATP The ATP-PCr system will dominate ATP

production for the first 15 seconds of an production for the first 15 seconds of an activity that can only be performed for activity that can only be performed for 15-30 seconds because it is such a high 15-30 seconds because it is such a high intensity activity that it cannot be intensity activity that it cannot be performed for a longer time periodperformed for a longer time period

Walking for 15-30 seconds does not Walking for 15-30 seconds does not require a maximal effort and so is NOT require a maximal effort and so is NOT predominately fueled by the ATP-PCr predominately fueled by the ATP-PCr system even though it only lasts for only system even though it only lasts for only 15 seconds. 15 seconds.

ExampleExample

Maximal effort and optimal paces will differ Maximal effort and optimal paces will differ between a sprint and a marathon, because between a sprint and a marathon, because the time frame differs (30 seconds vs. 3 the time frame differs (30 seconds vs. 3 hours). One must judge the optimal pace hours). One must judge the optimal pace that will elicit the best performance. A that will elicit the best performance. A sprinter should not jog the first few sprinter should not jog the first few seconds; nor should a marathon runner seconds; nor should a marathon runner sprint the first few seconds. That would sprint the first few seconds. That would not be maximal effort or optimal pacing, not be maximal effort or optimal pacing, and therefore the energy system being and therefore the energy system being used could not be precisely assessed. used could not be precisely assessed.

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1. Laboratory procedures – BIOPSY or 1. Laboratory procedures – BIOPSY or blood draws for lactate analysisblood draws for lactate analysis

2. Tests of anaerobic power and 2. Tests of anaerobic power and capacitycapacity

a.a. Wingate Anaerobic Test Wingate Anaerobic Test (WAT)(WAT)

b.b. Mararia-Kalamen Stair Mararia-Kalamen Stair ClimbClimb

c.c. Field testsField tests

Measurement of Anaerobic Measurement of Anaerobic MetabolismMetabolism

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