Ch5 (74 99)
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Transcript of Ch5 (74 99)
55C H A P T E R
Bioenergetics of Exercise and TrainingBioenergetics of Exercise and Training
Mike Conley
Chapter Outline
Essential terminology
Biological energy systems
Substrate depletion and repletion
Bioenergetic limiting factors in exercise performance
Oxygen uptake and the aerobic and anaerobic contributions to exercise
Metabolic specificity of training
Essential Terminology
Energy
Bioenergetics
Catabolism
Anabolism
Exergonic reactions
Metabolism
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
Adenosine monophosphate (AMP)Endergonic reactions
Chemical Structures of ATP, ADP, and AMPChemical Structures of ATP, ADP, and AMP
Energy stored in the chemical bonds of
adenosine triphosphate (ATP) is used to power
muscular activity. The replenishment of ATP in
human skeletal muscle is accomplished by
three basic energy systems: phosphagen,
glycolytic, and oxidative.
Phosphagen (Anaerobic) System
Occurs in the absence of molecular oxygen
Provides ATP for short-term, high-intensity activities
Is active in the start of all exercise regardless of intensity
Myosin ATPase and Creatine Kinase ReactionsMyosin ATPase and Creatine Kinase Reactions
Myokinase ReactionMyokinase Reaction
Glycolytic System
Breaks down carbohydrates to produce ATP that supplements the supply from the phosphagen system for high-intensity muscular activity
May go in one of two ways: fast glycolysis and slow glycolysis
During fast glycolysis, pyruvate is converted
to lactic acid, providing ATP at a fast rate
compared with slow glycolysis, in which
pyruvate is transported to the mitochondria for
use in the oxidative system.
Fast glycolysis has commonly been called
anaerobic glycolysis, and slow glycolysis,
aerobic glycolysis, as a result of the ultimate
fate of the pyruvate. However, because
glycolysis itself does not depend on oxygen,
these terms are not practical for describing the
process.
GlycolysisGlycolysis
The Cori CycleThe Cori Cycle
Lactate Threshold (LT) and Onset of Blood Lactate Accumulation (OBLA)Lactate Threshold (LT) and Onset of Blood Lactate Accumulation (OBLA)
Oxidative (Aerobic) System
Requires molecular oxygen
Uses primarily carbohydrates and fats as substrates
Provides ATP at rest and during low-intensity activities
The oxidative metabolism of blood glucose
and muscle glycogen begins with glycolysis. If
oxygen is present in sufficient quantities the
end product of glycolysis, pyruvate, is not
converted to lactic acid but is transported to the
mitochondria, where it is taken up and enters
the Krebs Cycle, or citric acid cycle.
Krebs CycleKrebs Cycle
Electron Transport ChainElectron Transport Chain
Metabolism of Fat, Carbohydrate, and ProteinMetabolism of Fat, Carbohydrate, and Protein
In general, an inverse relationship exists
between the relative rate and total amount of
ATP that a given energy system can produce.
As a result, the phosphagen energy system
primarily supplies ATP for high-intensity
activities of short duration, the glycolytic
system for moderate- to high-intensity activities
of short to medium duration, and the oxidative
system for low-intensity activities of long
duration.
Table 5.3 Effect of Event Duration on Primary Energy System Used
Duration Intensity Primary energyof event of event system(s)
0-6 s Very intense Phosphagen
6-30 s Intense Phosphagen and fastglycolysis
30 s-2 min Heavy Fast glycolysis
2-3 min Moderate Fast glycolysis andoxidative system
> 3 min Light Oxidative system
Table 5.4 Rankings of Rate and Capacity of ATP Production
System Rate of ATP Capacity of ATPproduction production
Phosphagen 1 5
Fast glycolysis 2 4
Slow glycolysis 3 3
Oxidation of carbohydrates 4 2
Oxidation of fats and proteins 5 1
1 = fastest/greatest; 5 = slowest/least
The extent to which each of the three energy
systems contributes to ATP production depends
primarily on the intensity of muscular activity
and secondarily on the duration. At no time,
during either exercise or rest, does any single
energy system provide the complete supply of
energy.
Low-Intensity, Steady-State Exercise MetabolismLow-Intensity, Steady-State Exercise Metabolism
EPOC = Excess postexercise oxygen uptake
High-Intensity, Non-Steady-State Exercise MetabolismHigh-Intensity, Non-Steady-State Exercise Metabolism
The use of appropriate exercise intensities
and rest intervals allows for the “selection” of
specific energy systems during training and
results in more efficient and productive
regimens for specific athletic events with
various metabolic demands.