Download ESCC 7 The Anaerobic Glycolytic Energy System

Specialist Certification Program
The Endurance Events
The Anaerobic Glycolytic
Energy System
An Overview of the Anaerobic Glycolytic Energy System

The Anaerobic Glycolytic Energy System. The Anaerobic Glycolytic energy system is a series of
reactions and physiological processes that produce the compound ATP from substrate. This ATP
is used to fuel muscular contractions. The system is classified as anaerobic because of the fact
that oxygen is not involved in these reactions. It is called the glycolytic system in reference to
the process of glycolysis, the breakdown of sugars. The anaerobic glycolytic energy system is
capable of producing energy at high rates for limited periods of time. Operation of the anaerobic
glycolytic energy system results in the accumulation of detrimental waste products that
eventually force intense work to cease. In conjunction with the alactic acid anaerobic system,
the glycolytic energy system can provide energy for high intensity exercise from 30 seconds to 2
minutes, depending upon an individual’s capacity and level of fitness.

Anaerobic Glycolytic Work Intensities. The anaerobic glycolytic energy system becomes
involved only in situations of high energy demand. This system supplies energy when work is
performed at intensities above the lactate threshold. Work intensities above below this level
result in complete oxidation of substrate and aerobic metabolism.

Substrate. Substrates are nutrient sources available in the organism to fuel cellular metabolism.
Anaerobic glycolysis uses glucose and glycogen exclusively as a substrate. Glycogen must be
converted to glucose for use, via a process called glycogenolysis. At high work intensities,
nutrients must come out of storage with the aid of enzymes and other proteins.
Glycolysis

Glycolysis. The dominate reaction of the anaerobic glycolytic energy system is known as
anaerobic glycolysis. Glycolysis is breakdown of glucose into pyruvate, producing ATP in the
process.

By Products. When glucose is incompletely oxidized, an acidic state in the muscle tissue results,
which limits muscular function the pyruvate lactic acid and hydrogen ions are produced. This is
due to the disassociation of the hydrogen ion (H+) from pyruvate to form lactic acid.

Buffering Capacity. A key cause of fatigue in the glycolytic system is the accumulation of
hydrogen ions, creating an acidic environment within the muscle cell. This is due to the
disassociation of the hydrogen ion (H+) from pyruvate to form lactic acid. The body contains
buffering substances which combine with these hydrogen ions to reduce the muscle fibers’
acidity and delay the onset of fatigue. These substances are sodium bicarbonate, muscle
phosphates and hemoglobin.

ATP Yield. In anaerobic metabolism, one glucose molecule produces a net gain of 2 ATP
molecules (4 ATP molecules are produced during glycolysis but 2 are required by enzymes used
during the process), making the glycolytic energy system much less efficient than the aerobic
energy system in this regard.
Anaerobic Glycolytic Adaptations to Training

Improved Glycolysis. Appropriate training results in enhanced glycolysis capabilities.

Improved Glycogenolysis. Appropriate training results in enhanced glycogenolysis capabilities.

Anaerobic Enzyme Adaptations. There are three primary enzymes that are enhanced by sprint
training. These are Phosphofructokinase, Phosphorylase, and Lactate Dehydrogenase. All three
of these enzymes showed increases in activity ranging from 10-25% with repeated 30-second
training bouts. Because both PFK and Phosphylase are essential to the anaerobic yield of ATP,
sprint training may enhance glycolytic capacity and allow the muscle to develop greater tension
for longer periods of time.

Phosphofructokinase. Phosphofructokinase (PFK) is the rate limiting enzyme that enhances
Glycolysis, the breakdown of Glucose to Pyruvic Acid. PFK activity increases in response to
training.

Phosphorylase. Phosphorylase is the enzyme that enhances the conversion of glycogen, e.g.
muscle glycogen, to glucose to enable Glycolysis to occur. Phosphorylase activity increases in
response to training.

Lactate Dehydrogenase. Lactate Dehydrogenase (LDH) is the enzyme that enhances the
reversible conversion of pyruvate to lactate. LDH activity increases in response to training.

Buffering Capacity Increases. Sodium Bicarbonate will release earlier and in greater volume due
to anaerobic training. Eight weeks of Anaerobic Glycolytic training has been shown to increase
the muscle buffering capacity by 12% - 50%. Changes in muscle buffering capacity are specific to
the intensity of the exercise performed. This increased buffering capacity allows trained athletes
to accumulate more lactate and hydrogen ions before performance is inhibited. Aerobic training
has no effect on buffering potential.

Increased Muscle Fiber Recruitment. The intense nature of glycolytic training results in
improved muscle fiber recruitment. With this improvement in the neuromuscular recruitment
process, the economy and efficiency increases significantly, improving performance at all
intensities.

Strength Gains. The intense nature of glycolytic training results in strength gains. These
strength gains come as a result of improved muscle fiber recruitment. This allows the muscle to
generate more force and maintain this force for a longer period of time, and economizes the
athlete’s use of energy.
Fatigue in the Anaerobic Glycolytic Energy System

Fatigue. Fatigue is a condition of diminished performance as a result of the physiological
processes associated with extensive work. Fatigue may interrupt many metabolic processes at
different sites throughout the body. Fatigue may be temporary, or it may be a chronic condition
that requires long recovery times.

Sources of Anaerobic Glycolytic Energy System Fatigue
o
Acidity. Acidity resulting from the accumulation of hydrogen ions, decreases metabolic
and contractile activity. Accumulation of H+ can cause fatigue at several sites and causes
several functional problems in the energy system.

Decreased PFK Activity. Hydrogen ions reduce the activity of the rate limiting
enzyme of glycolysis, phosphofructokinase (PFK). The accumulation of H+ will
decrease the functional capability of the PFK enzyme thus slowing down the
rate of fuel breakdown, glycolysis.

Action Potential Problems. H+ will affect action potential at the neuromuscular
junction. ATP, through the enzyme ATPase, is needed for the action potential
(sodium/potassium pump) or transmission of signal from the nervous system to
become muscular energy.
o

Acetycholine Release Problems. The rate of acetylcholine release is affected by
hydrogen ions. These inhibit the ability to recycle acetylcholesterase and
producing the rapid muscle contractions.

Calcium Competition. Another site of anaerobic fatigue is the accumulation of
H+ in the storage area for calcium. Calcium (Ca++) is necessary for the cross
bridging of myosin and actin that produces muscle contraction. Calcium must
compete with H+ for storage sites in the sarcoplasmic reticulum. This
competition between H+ and Ca++ results in a lack of Ca++ necessary to bind
troponin and permit actin-myosin interaction.

ATPase Problems. H+ ions also interfere with myosin and actin bridging by way
of ATPase enzyme interference. This limits the force of the contractions and the
duration of the contractions.
Electrolyte Fatigue. Potassium loss by contracting muscles may be a major factor in
fatigue encountered during maximal exercise. The lost potassium is taken up by other
tissues and returned to the fatigued muscle upon relaxation. This is done quickly as
evidenced by the rapid re-establishment of potassium levels in muscles cells despite a
high lactate response.
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