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Introduction
The purpose of this paper was to review the concepts of
bioenergetics and the laws that govern energy transfers. Bioenergetics can
be defined as the study of all energy transfers in biological systems.
In
order to understand energy transfers within the biosphere (with a special
interest in human beings), the reader must grasp several correlated
concepts. The first three deal with systems, surroundings, and the
universe. A system can be defined as a functional unit or a particular
object or set of objects. This term can refer to a cell, organ, or the
reader of this paper. Further, the system can be closed or open. When
closed, the mass of the system is constant; when open, mass may enter or
leave. The reader has no further to look for an example of an open system
than the bodybuilder; namely in the off-season. The surroundings or
environment constitute everything outside of the system. Finally, the
universe is defined as the system combined with its environment.
First and Second Law of Thermodynamics
Thermodynamics deals with processes in which energy is transferred as heat
or work.
The first law of thermodynamics is the law of the conservation of
energy. That is, in any energy transfer, energy is neither created nor
destroyed but only changes in form. Energy is defined as the capacity to
do work; therefore the body cannot create energy, but can instead transfer
one form into another form. The potential energy (energy by position) held
between the bonds of an ATP molecule can be transferred to kinetic energy
or energy of motion. However, this leads into the second law of
thermodynamics. The second law of thermodynamics states that no energy
transfer is 100 percent efficient. Thus, when an athlete performs work
(curling a barbell) the reaction which catalyzes ATP
à
ATP + ADP + Pi + energy will not be 100 percent efficient. That is, the
energy can be fractionated into useable energy (kinetic) and non-useable
energy (heat).
As a result of the second law, it can be stated that the
entropy of the universe always increases in any energy transfer. Ludwig
Boltzmann, in the 1800s, is said to have discovered entropy, which states
that processes go toward a state of randomness. Entropy is denoted by the
symbol ‘S,’ therefore training, which speeds energy transfer rates, tends
to accelerate the randomness in the universe as heat is rapidly released
into the environment.
A notable consequence of increased work production is
therefore an increase in temperature. For a full review of
thermoregulation, see King (2004,
Thermoregulation). The reader should understand that temperature is
positively correlated with enzymatic reactions in biological systems.
Further, temperature is frequently measured in multiples of 10
(Almeida-Val, 1994, Bennett, 1984, Rall et al., 1990, Rome, 1990). The
change found as temperature increases by 10 degrees Celsius is known as
the Q10 effect. Enzymatic activity doubles with each multiple
of 10 increase. Therefore, though an athlete cannot utilize heat directly,
it can be used indirectly. Further, when dieting, the inefficiency of
energy transfer is quite advantageous. To understand why, efficiency needs
to be clearly reviewed. Efficiency is related to the concept of work. Work
done on an object by a force is defined as the product of the magnitude of
the displacement multiplied by the component of the force parallel to the
displacement (Giancoli, 1989). In simple terms, work is equal to force
multiplied by distance. Therefore, if an athlete were to ride on bicycle
ergometer, the investigator would first need to measure the circumference
of the wheel and then multiply this by the revolutions per minute for the
number of minutes the exercise was performed. Finally, the resistance
provided by the flywheel would need to be calculated. This is measured in
kilograms (or kiloponds). As an example:
Circumference of wheel = 5 meters
Revolutions per minute = 60
Total Minutes of Exercise = 20 minutes.
Resistance = 3 kp
Work = 3 X (60 X 5 X 15) = 13,500 kilogram-meters.
Note: 1 kilogram-meter is the amount of work done when moving one kilogram
a distance of 1 meter.
The work performed was therefore equivalent to 13, 500 kilogram-meters.
Energy is required to perform work; in fact, energy is defined as the
capacity to perform work and is measured in calories. One calorie is the
amount of energy it takes to raise one gram of water 1 degree Celsius.
Conversion factors allow the investigator to calculate the amount of
calories needed to perform a specific quantity of work. It is known that
0.00234 Kilocalories are needed to perform one kilogram-meter of work.
Therefore all that needs to be done is to multiply this conversion factor
by the amount of work done like so:
13, 500 X 0.00234 = 31.59 kcals
Therefore in 20 minutes, if the body was 100 percent
efficient, the participant would have metabolized approximately 32 kcals,
and that is at a substantial work rate! If they continued for 3 hours they
would only have burned 192 calories, which is absolutely nothing! However,
as stated, the athlete is not 100 percent efficient. In order to find
efficiency, the oxygen consumed must be measured, as it is required for
energy production. In the above example, a typical 02 consumption may have
been 1.90 liters of 02 per minute. Using another conversion factor, liters
of 02 can be converted to calories metabolized. This measurement is known
as indirect Spirometry. Direct Spirometry would be to measure the amount
of heat dissipated (See Wilson, 2004:
Acute & Chronic Endocrine Responses to Exercise ). Once the amount of
02 consumed is found, you multiply it by the conversion factor 5.047 Kcal.
This is due to the fact that for every liter of 02 consumed, 5.047 Kcals
are used when carbohydrates are the source of fuel. To illustrate the
point:
(1.90 liters a min X 5.047) X 20 minutes of exercise = 192
calories
To find the efficiency of the activity, you simply divide the actual
calories utilized into the calories needed to perform the work, like so:
32 / 192 = 0.16
Multiply this by 100 to get a percentage and you get 16 percent
efficiency. Therefore this particular athlete would have actually burned
192 calories. The energy not used to perform work was dissipated as heat,
which adheres to the second law of thermodynamics.
Further, the above calculation of efficiency is known as ‘Gross
Efficiency.’ If resting energy is factored in, the efficiency of the task
would be slightly higher, but the point is clear.
What is interesting to note is that various activities can
be performed at optimal efficiency, and suboptimal efficiency. By
manipulating this variable, the athlete can actually increase the amount
of calories utilized to perform the task! As an illustration, performing a
stationary bike at 109 % of leg length is the most efficient way to
perform the task. Variance from this will lower the efficiency
correspondingly.
Reactions
Energy transfers can be fractionated into exergonic and
endergonic reactions. Exergonic reactions release energy into the
environment and are also called spontaneous reactions. When this results
in the release of heat, it is an exothermic reaction. An endergonic
reaction is one in which energy is absorbed; this is also called a
non-spontaneous reaction. Spontaneous refers to a process that will occur
on its own without added energy. Non- spontaneous reactions require
energy; that is, endergonic or energy-consuming reactions are coupled to
exergonic or energy-releasing reactions. For example, the splitting of ATP
to ADP + Pi + energy + heat is an exergonic (specifically exothermic)
reaction which can be used to phosphorylate free creatine to creatine
phosphate or CP. The energy state of the reactant creatine is lower than
the energy state of the product creatine phosphate, and is therefore
classified as being endergonic. The energy state of products ADP + Pi is
lower than the energy state of the reactant ATP, and is therefore
classified as an exothermic reaction. However, when ADP is phosphorylated,
it absorbs energy and the reaction is exergonic.
The measure of the heat content of a substance is known as
‘Enthalpy.’ Enthalpy is denoted by the symbol ‘H.’ (note: Enthalpy can
also be defined as the internal energy of a system + the product of V and
Pressure.) This paper is concerned with a concept known as change in
enthalpy. Change in enthalpy is denoted as
where
is the Greek letter delta, and stands for change. Of prime
importance to biological reactions is the concept of free energy. Free
energy is the amount of energy in a substance that can perform work. Free
energy is denoted by the symbol G, named after Willard Gibbs, who is a
father of bioenergetics as it is understood today. The greater the free
energy, or available energy, the greater amount of work that can be done.
During a reaction, the change in enthalpy is equal to a
change in entropy + the change in free energy. Or:
DH =
G + S
These concepts have extreme importance in understanding bioenergetics.
First, recall that in any reaction, entropy, or randomness of a system,
increases. Further, energy is neither created nor destroyed but only
changes form. Therefore, when exercising, the change in enthalpy results
in more and more unavailable energy and less and less free or available
energy. This energy will need to be replaced at some point if activity is
to continue. An additional concept that should be understood is that of
equilibrium. A reaction has reached equilibrium when change in enthalpy is
equal to zero available energy + entropy. That is, entropy in the
reaction has peaked. Therefore, the greater the
separation the reactants are from equilibrium, the greater the amount of
free energy available to perform work will be. As an athlete trains, the
amount of available energy continually decreases, and the amount of
entropy increases. Of course the athlete should be sensitive to how that
energy is stored, how quickly a particular form of potential energy is
depleted, and how quickly it is replenished. An interesting term used to
describe the form of energy used while training is known as Respiratory
Exchange Ratio (RER). The Respiratory exchange ratio is defined as the
amount of carbon dioxide produced divided by the quantity of oxygen
consumed.
C02produced * 02consumed-1
The ratio gives the experimenter information in regards to
fuel utilization during exercise.
The RER is a reflection of the chemical composition of the
three varying substrates; that is carbohydrates, lipids (fats), and
proteins. Reliance on 100 percent carbohydrate produces a ratio of 1.0. As
an illustration:
Glucose (C6H1206)
à Utilizes 6 molecules of 02
à
Resulting in production of 6 molecules of C02
6 C02 produced / 602consumed = 1.0
The RER when fat is being used 100 percent of
the time is approximately 0.7, while the ratio of protein at 100 percent
is 0.8. From this the reader should understand that carbohydrates are the
most efficient fuel during exercise, as they require less oxygen to
metabolize than fat or protein. However, fat has a greater store of
potential energy.
Further, by obtaining the RER the investigator can know what
percentage of fuels are used during specific exercise sessions and match
their diet specifically to that ratio.
There are various forms
of exercise, which can be fractionated into submaximal continuous,
interval, supramaximal, isometric, and dynamic. Submaximal is in reference
to the percentage of V02 max utilized. V02 max is defined as the highest
amount of oxygen a participant can take in, transport, and utilize to
produce ATP aerobically while breathing air during heavy exercise;
therefore submaximal would be a fraction of the maximum. For example,
biking lightly would be anything below 50 % V02 max. Intensity is the
term to describe the level at which the participant trains relative to
their maximum level of V02. The higher the percentage of V02 max, the
greater the intensity.
Supramaximal is work performed above 100 % V02 max. The higher the level
is above maximal, the greater the reliance on anaerobic energy sources,
and the shorter the activity can continue, as will be explained in the
energy continuum aspect of this series. Isometric exercise refers to a
stationary contraction of the musculature in which neither shortening or
lengthening occurs, while dynamic is in reference to external resistance
training with varying movements.
In general, the lower
the athlete is in submaximal work loads, the closer the RER will be to
7.0, and the closer the individual is to maximal the closer they will be
to a RER of 1.0. In fact, one of the criteria for a maximal V02 max
testing is an RER of 1.0. As a second generality, a longer duration may
lower the RER; that is, the session will progressively rely on fat stores
as duration lengthens. External resistance training will yield an RER of
approximately 1.0, for reasons seen when discussing glycolysis. The main
carbohydrate source utilized during max exercise is glycogen. In fact,
there is a high correlation between glycogen storage and duration and
intensity while external resistance training (Wilson, 2004, Pre Contest
Preparation). It is for this reason that carbohydrates should be a major
food source for bodybuilders, or any athlete who relies on an RER of 1.0.
Further, the fallacious protocol of fat and fiber post-workout, combined
with fructose seems even more ludicrous in this light. This is due to the
fact that the participant is utilizing a replacement cocktail which quite
simply does not replace what was used! For a full review of the fallacy of
post-workout suicidal strategies, see Knowlden (2004,
Scientific Investigation into Post Workout Meal ).
A further consequence of thermodynamic principles is the
topic of mass gain. As stated, the bodybuilder is an open system. Since
entropy is constantly increasing, it follows that for the many endergonic
reactions which occur to build macromolecules such as contractile tissue,
a number of exergonic reactions are also occurring in which the net effect
is greater disorder of the universe for greater order of the system
itself. Further, if the system expels more energy than is consumed, then
the end result will be an overall lowered availability of stored energy in
the body, with the intent of that stored energy being taken from
subcutaneous tissue. However, the equation is not as simple as it may
sound. To effectively diet, participants in the dieting program should
understand at what moments energy will be consumed to its greatest extent.
In the case of mankind, the answer is the basal metabolic rate, or the
amount of calories utilized to maintain a resting state. In fact, the
basal metabolic rate accounts for 70 percent energy expenditure. It is
prudent to therefore maintain or even increase this rate at all costs.
Energy Production Pathways and Mechanisms of
Phosphorylation
Biological work is fueled by three distinct energy pathways.
That is, the exergonic energy yielding reactions afforded by the
hydrolysis of ATP are provided by the phosphagen system (A Lactic
Anaerobic), glycolysis (Lactic Anaerobic), and oxidative phosphorylation.
The Phosphagen system and glycolysis are classified as anaerobic pathways,
in that they are not reliant on oxygen, while oxidative, as the name
implies, does depend on 02.
ATP, or adenosine triphosphate, is a high-energy compound, in which
potential energy is stored between chemical bonds. The process of adding a
phosphate group to an andenosine diphosphate group is known as
phosphorylation. Knowlden (2004) suggests that a more appropriate term is
‘charging.’ This charging effect is attributed to the very nature of the
ATP molecule, which is classified as a nucleotide. It is classified as
such as its constituents fit the definition. That is, the structure is
composed of the nitrogenous base -adenine, the sugar ribose, and a tri set
of phosphate groups.
The bonds between phosphate groups require energy to form,
as the actual groups themselves repell each other through a negative
charge mechanism. However, the nucleotide ADP and Pi are designed in such
a way that electrons can be shared so as to reduce energy states when
bonded. The reduced energy states formed are known as resonance hybrids, a
process which reverses when the phosphate group is removed. The effect is
similar to the loading of a dart gun. Energy is required to load the dart
into a gun and overcome the repelling forces provided by the spring
mechanism. Energy is then released as the trigger is pulled.
Anaerobic pathways work through a process known as substrate
level phosphorylation. This refers to a process where one molecule
directly donates a phosphate group to a second molecule. However, aerobic
metabolic pathways operate through oxidative phosphorylation. This process
utilizes a complex structure known as the electron transport chain, which
is able to harnesses energy via a process known as chemiosmotic coupling
(discussed in detail in future issues; however, for a review see Knowlden,
2003,
Eight Weeks To A Freakier Tibialis) to provide the energy capable of
phosphorylating ADP.
Control of the Rate of Energy Pathways
The rate of pathway operation is dependent on enzymatic
catalytic activity. The human body is designed to react quickly to various
energy demands, and therefore enzymes are highly adaptable to both acute
and chronic demands placed on the physiological parameters. An enzyme is a
complex that speeds or catalyzes a reaction without actually being
affected by the reaction itself.
As was mentioned, spontaneous reactions will occur in a
downhill manner, or without added input. However, the processes that
promote these exergonic reactions are too slow to keep up with the
maintenance of homeostatic function in the biological organism. Though
these reactions occur spontaneously, they also require the input of
energy. At first this seems contradictory, but it is quite the opposite.
Molecules are always in a state of random thermal motion. As they randomly
move, collisions occur, which affords the energy required for the reaction
to take place.
The energy barrier, which must be overcome, is known as ‘Activation
Energy.’ Enzymes are able to lower the Activation Energy drastically,
thereby increasing the rate of reaction.
A diagrammatical format of how enzymes react with substrates
is as follows:
Enzyme + Substrate(s)
ßà
Enzyme-substrate complex
ßà
Product + Enzyme
Note that in the above diagram the reactions are reversible. This is an
important concept, in that it signifies the fact that if the enzyme does
not have a high enough affinity for the substrates, it will not be able to
interact with it long enough to provide the mechanisms responsible for the
release of a product. Affinity refers to the binding capability that an
enzyme has for the substrate. Chronic adaptations in enzymes actually
increase the affinity of the complex to the substrate, thus enhancing the
direction of a reaction. It also shows that enzymes have the capability
of binding reversibly to a product, and re forming the original substrate.
For example, the enzyme Lactate Dehydrogenase can bind pyruvate, and two
hydrogens to form Lactic Acid. However, it can also reversibly bind Lactic
acid to release the products of pyruvate and 2H+.
Pathways such as glycolysis are regulated by a number of
enzymes responsible for each step in the process. Interestingly enough,
enthalpy is measured collectively over each of these steps. According to
Hess’s Law, if a process can be written as the
sum of several steps (i.e. glycolysis), the enthalpy change of the process
equals the sum of the enthalpy changes of the individual steps.
The rate at which enzymes function is dependent upon the
catalytic rate, affinity, enzyme concentration, and substrate
concentration. The former have briefly been discussed. Enzyme
concentration is another example of a chronic adaptation to exercise
stress. That is, specific enzymes increase in concentration specifically
to the demands placed on the system. This will be discussed in metabolic
adaptations further in the series. Substrate availability can be regulated
acutely by the athlete. For example, after training, the greater the
supply of glucose provided to the musculature, the higher the synthetic
rate of glycogen via the enzyme glycogen synthase. Further, during
exercise, the greater the concentration of glucose in the cell, the faster
the rate of glycolysis will be. And the faster the rate, the greater the
athlete’s performance in weight training activities will be. This supply
of glucose is increased through diet and through endogenous hormone
secretion during training. For example epinephrine will stimulate the
breakdown of glycogen, which increases glucose concentration.
Enzymatic Regulation through Allosteric Reactive
Mechanisms
When
enzymes contain binding sites for molecules, which are not substrates,
they are known as covalent enzymes. When they contain more than one
binding site, they are referred to as multivalent enzymes. The molecules
that bind are known as modulators, and can either be inhibitory or
excitatory (increase catalytic rate). Enzymes are able to bind certain
substrates because of their specific shape. When bound to a modulator, the
enzyme undergoes a shape change known as a conformational change, or
allosteric reaction. Like substrates, modulator regulation is directly
correlated to the concentration of the modulator itself. Further, the
binding is again reversible and therefore subject to the law of mass
action, which states that as reactants increase relative to products, the
reaction will further increase the proportion of products. In this case,
however, the time that the modulator molecule is bound will increase.
Rate Limiting Enzymes
A rate-limiting enzyme can be defined as an enzyme whose
activity is directly proportional to the rate of an entire series of
enzymatic reactions contained within an energy pathway. One such enzyme is
Phosphofructokinase (PFK), which is an allosteric enzyme. As its rate
increases, the rate of glycolysis itself increases. When muscular
contraction increases, by necessity the bi products of that contraction
increase. ADP and Pi increase from the hydrolysis of ATP, and AMP
increases through the use of the phosphagen anaerobic system. These
byproducts bind to PFK and act as excitatory modulators. However, when ATP
and CP stores increase, they act to inhibit PFK. This makes sense, as the
need for energy production via glycolysis is lowered.
The implication is that rapid breakdown of ATP via muscular
contraction leads to rapid increases in glycolysis through such
mechanisms, as well as the Q-10 effect, enzyme concentration, and
substrate concentration.
Final Thoughts
Interestingly enough, the Bible discussed the second law of thermodynamics
millenniums ago. The Apostle Paul states:
Hebrews 1:10-12
10 And,
Thou, Lord, in the beginning hast laid the foundation of the earth; and
the heavens are the works of thine hands: 11 They shall perish; but thou
remainest;
and they all shall wax old as doth a garment;
12 And
as a vesture shalt thou fold them up, and they shall be changed: but thou
art the same, and thy years shall not fail.
The Universe is decaying (entropy is increasing to a maximum) on a daily
basis. Indecently, this fact demolishes the religion of evolutionism.
The law of cause and effect states that every effect must have had a
cause, and the definition for cause here is the chief agent causing
something to be made. So if one were to punch a dent into a wall, the
cause would be the participant’s fist and the effect was the dent in the
wall. To state that a dent came about without a cause would be to go
against all logic. Professor W.T. Stace (1934), in his A Critical
History of Greek Philosophy states:
Every student of logic
knows that this is the ultimate canon of the sciences, the foundation of
them all. If we did not believe the truth of causation, namely, everything
which has a beginning has a cause, and that in the same circumstances the
same things invariably happen, all the sciences would at once crumble to
dust. In every scientific investigation this truth is assumed (1934, p.
6).
Therefore, if it can be shown that the universe had a beginning it must
have had a cause (creator). And the evidence clearly points to this. As
discussed previously, the first two laws of thermodynamics state:
-
1st Law: The total amount of mass-energy in the
universe is constant.
-
2nd Law: The amount of energy available for work is
running out, or entropy is increasing to a maximum.
If
the total amount of mass-energy is limited, and the amount of usable
energy is decreasing, then the universe cannot have existed forever,
otherwise it would already have exhausted all usable energy. Therefore,
the universe had to have had a beginning.
·
Everything which has a beginning has a cause.
·
The universe has a beginning.
·
Therefore the universe has a cause
Further, Einstein’s general relativity shows that time is linked to matter
and space. Therefore time itself would have begun along with matter and
space. The Bible discusses the cause of the universe, and the origin of
time, space, and matter:
Genesis 1:1-2
1 In the beginning (time) God created
the heavens (space) and the earth (matter).
References:
V. M. Almeida-Val, L. T. Buck, and P. W. Hochachka
Substrate and acute temperature effects on turtle heart and liver
mitochondria Am J Physiol Regulatory Integrative Comp Physiol, Mar 1994;
266: R858 - 862.
A. F. Bennett
Thermal dependence of muscle function
Am J Physiol Regulatory Integrative Comp Physiol, Aug 1984; 247: R217 -
229.
J. A. Rall and R.
C. Woledge Influence of temperature on mechanics and energetics of muscle
contraction Am J Physiol Regulatory Integrative Comp Physiol, Aug 1990;
259: R197 - 203.
Stace, W.T. (1934), A Critical History
of Greek Philosophy (London).
Taylor, Richard (1967), “Causation,” The Encyclopedia
of Philosophy, ed. Paul Edwards (New York: Macmillan), 2:56-66.
Wald, George, The Origin of Life," in The Physics
and Chemistry of Life , 270 pp.
Horgan, John, 'In the
Beginning,'Scientific American, vol. 264 (February 1991), pp. 117-125.
Shapiro, Robert (1986), Origins—A Skeptics Guide to the Creation of Life
on Earth (New York: Summit).
Davies, Paul (1982), The Accidental
Universe (Cambridge: Cambridge University Press)
Hawking, Stephen (1988), A Brief
History of Time (New York: Bantam).
Dr Werner Gitt, in Information: The Third Fundamental
Quantity, (reprint from) Siemens Review, 56(6), November/December 1989.
Fred Hoyle, 'The Big Bang in Astronomy', New Scientist,
Vol.92, No. 1280, 1981, p. 527.
L. C. Rome
Influence of temperature on muscle recruitment and muscle function in vivo
Am J Physiol Regulatory Integrative Comp Physiol, Aug 1990; 259: R210 -
222.
King, Joe (2004)
Thermoregulation: Physiological Responses and Adaptations to Exercise in
Hot and Cold Environments. Journal of Hyperplasia Research, 4
Wilson, Jacob (2004) Acute & Chronic Endocrine Responses to Exercise
Induced Disruptions in Homeostasis Part One - Exercise Endocrinology
Principles and Catecholamines Journal of Hyperplasia Research, 4
Knowlden, Adam (2003) Eight Weeks To A Freakier Tibialis Journal of
Hyperplasia Research, 3
Knowlden, Adam
(2003) Scientific Investigation into the Rationality of Carbohydrate
Consumption Criterions in Correlation to Post-Training Anaerobic
Depletion
Patterns: A
series of sub-divisional essays. Journal of Hyperplasia Research, 3
Brooks G. (2000).
Intra and extra cellular lactate shuttle. Medicine and Science in
Sports and Exercise, 32, 790-9.
Brooks G. T.
Fahley, R. White, and K. Baldwin. (2000) Human bioenergetics and its
applications. (3rd ed) California: Mayfield Publishing.
Abernethy P., R.
Thayer, and A. Taylor. (1990) Acute and chronic responses of skeletal
muscle to endurance and sprint exercise: A review. Sports Medicine 10,
365-89.
Gladden L.
(2000) Muscle as a consumer of lactate. Medicine and Science in Sports
and Exercise, 32, 764-71.
Holloszy, J. O.,
and F. W. Booth. Biochemical adaptation to endurance exercise in muscle.
Annu. Rev. Physiol. 38: 273-291, 1976
D. L. Costill, E.
F. Coyle, W. F. Fink, G. R. Lesmes and F. A. Witzmann Adaptations in
skeletal muscle following strength training Journal of Applied Physiology,
Vol 46, Issue 1 96-99, Copyright © 1979 by American Physiological Society
Cadefau J,
Casademont J, Grau JM, Fernandez J, Balaguer A, Vernet M, Cusso R, Urbano-Marquez
A. Biochemical and histochemical adaptation to sprint training in young
athletes. Acta Physiol Scand. 1990 Nov;140(3):341-51.
Heigenhauser GJ,
Parolin ML., Role of pyruvate dehydrogenase in lactate production in
exercising human skeletal muscle. Adv Exp Med Biol. 1999;474:205-18.
J. Duncan
MacDougall, Audrey L. Hicks, Jay R. MacDonald, Robert S. McKelvie, Howard
J. Green, and Kelly M. Smith Muscle performance and enzymatic adaptations
to sprint interval training J Appl Physiol 84: 2138-2142, 1998;
8750-7587/98
Bessman SP. The
creatine phosphate energy shuttle--the molecular asymmetry of a "pool".
Anal Biochem. 1987 Mar;161(2):519-23.
Mujika I, Padilla
S. Detraining: loss of training-induced physiological and performance
adaptations. Part II: Long term insufficient training stimulus. Sports
Med. 2000 Sep;30(3):145-54.
Mujika I, Padilla
S. Detraining: loss of training-induced physiological and performance
adaptations. Part I: short term insufficient training stimulus. Sports
Med. 2000 Aug;30(2):79-87.
Brooks G. (2000).
Intra and extra cellular lactate shuttle. Medicine and Science in
Sports and Exercise, 32, 790-9.
Brooks G. T.
Fahley, R. White, and K. Baldwin. (2000) Human bioenergetics and its
applications. (3rd ed) California: Mayfield Publishing.
Abernethy P., R.
Thayer, and A. Taylor. (1990) Acute and chronic responses of skeletal
muscle to endurance and sprint exercise: A review. Sports Medicine 10,
365-89.
Gladden L.
(2000) Muscle as a consumer of lactate. Medicine and Science in Sports
and Exercise, 32, 764-71.
Holloszy, J. O.,
and F. W. Booth. Biochemical adaptation to endurance exercise in muscle.
Annu. Rev. Physiol. 38: 273-291, 1976
D. L. Costill, E.
F. Coyle, W. F. Fink, G. R. Lesmes and F. A. Witzmann Adaptations in
skeletal muscle following strength training Journal of Applied Physiology,
Vol 46, Issue 1 96-99, Copyright © 1979 by American Physiological Society
Cadefau J,
Casademont J, Grau JM, Fernandez J, Balaguer A, Vernet M, Cusso R, Urbano-Marquez
A. Biochemical and histochemical adaptation to sprint training in young
athletes. Acta Physiol Scand. 1990 Nov;140(3):341-51. Related
Articles, Links
Heigenhauser GJ,
Parolin ML., Role of pyruvate dehydrogenase in lactate production in
exercising human skeletal muscle. Adv Exp Med Biol. 1999;474:205-18.
J. Duncan
MacDougall, Audrey L. Hicks, Jay R. MacDonald, Robert S. McKelvie, Howard
J. Green, and Kelly M. Smith Muscle performance and enzymatic adaptations
to sprint interval training J Appl Physiol 84: 2138-2142, 1998;
8750-7587/98
Bessman SP. The
creatine phosphate energy shuttle--the molecular asymmetry of a "pool".
Anal Biochem. 1987 Mar;161(2):519-23.
Mujika I, Padilla
S. Detraining: loss of training-induced physiological and performance
adaptations. Part II: Long term insufficient training stimulus. Sports
Med. 2000 Sep;30(3):145-54.
Mujika I, Padilla
S. Detraining: loss of training-induced physiological and performance
adaptations. Part I: short term insufficient training stimulus. Sports
Med. 2000 Aug;30(2):79-87.
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