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The Different Types of Fatigue

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The Different Types of Fatigue


According to McArdle, Katch and Katch, Exercise Physiology , 4th
edition, Fatigue is defined as “ the decline in muscle tension
capacity with repeated stimulation”. Simply it means that as the
athlete progresses in his/her activity, muscle tiredness accompanied
by laboured breathing sets in and this would result in decreasing
performance in the said activity as it progresses further.

Fatigue is the result of many factors, each of which is the direct
result of the activity or exercise that produces it. As we know it ,
voluntary muscle action is the result of a chain of events involving
the following areas in the following order:

1 The central nervous system involving proximal motor neurons (mainly
in the brain)

2 The peripheral nervous system within the motor units ( ie motor
neurons, peripheral nerves, motor end plates and muscle fibers)

3 The neuromuscular junction

4 The muscle fiber function

Now when this chain of events between the central nervous system and
the muscle fiber junction is interrupted, fatigue would result.

Muscle Fatigue occurs when muscular performance is impaired ie when
the muscles fail to maintain a certain workload . This fatigue is
caused by a depletion of energy fuel such as glycogen or PC,
accumulation of lactic acid and a dramatic increase of H+
concentration in the active muscles in trained and untrained
individuals during prolonged high intensity exercise. Local muscular
fatigue occurs in the fast twitch fibers ( type II) rather than in the
slow twitch fibers ( type I ).

Nutrient Fatigue occurs when the active muscle fibers experience a
major reduction in glycogen content during prolonged sub maximal
exercise.

Neural fatigue occurs at the neuromuscular junction when an action
potential fails to cross over from the motor neuron to the muscle
fiber.

There are several factors that cause fatigue and they are:

1 Depletion of Phosphocreatine

As we know it that energy for muscular contraction is supplied by ATP
and its continual resynthesis. When Phosphocreatine is rapidly
depleted during the time the muscles are subjected to repeated maximal
contractions, the body’s ability to replace the spent ATP is
hindered. As a result of this, the muscles are deprived of sufficient
ATP to sustain the muscle contractions and fatigue and the subsequent
deterioration in performance results.

2 Production of Lactic Acid

Lactic Acid is the by product of anaerobic lactic glycolysis. In the
process of glycolysis, glycogen is broken down to pyruvic acid. As
glycolysis is carried out without oxygen , the pyruvic acid is changed
to lactic acid which causes fatigue. The presence of lactic acid in
the blood will decrease the pH value of the blood making it more
acidic and thus will affect the muscle and neural function. Onset of
Blood Lactate Accumulation ( OBLA ) will occur at about 55% VO2max for
the untrained athlete and at 80% for the trained athlete. Therefore,
it is seen that lactic acid accumulation will occur in the muscles
during prolonged and high intensity exercise. The hydrogen ions will
break away from the lactic acid leaving the lactate behind which
causes the sensation of pain in the muscles and fatigue. This is
experienced in short high intensity exercise nsuch as running the
400metres sprint. What happens is that the breakaway hydrogen ions
will increase the acidity in the muscles causing a decrease in the pH
value. The decreased pH will inhibit the action of the glycolytic
enzymes thus preventing further release of energy from glycogen.

3 Neural Transmission Failure

During maximal muscle contraction, the neural transmission frequency
is high and as a result of this maximum tension in the muscles occurs
through the recruitment of many muscle fibers. When this happens, the
fast twitch fibers find it difficult to maintain tension probably due
to the impairment of neuromuscular transmission at the nerve endings
in the muscle and fatigue occurs quickly in about 2 to 6 secs. The
impairment could be due to an accumulation of extracellular potassium
ions which would change the electrical potential across the muscle
membrane and the nerve endings. The fatigue so caused in a localized
muscle group, is short in duration . In a sprint event, the recovery
may be longer but in a training environment, several sprint
repetitions would be possible if there is provision for recovery
periods inbetween repetitions.

4 Depletion of Calcium Ions

When slow twitch fibers are recruited for exercise, fatigue would
still result but at a slower pace than in high intensity exercise.
Fatigue in this case is thought to be caused by the impaired
electrical activity and the chemical changes that induce muscle
shortening .The ability to sustain muscular contractions is reduced
and this is thought to be caused by the depletion of intracellular
calcium ions that paly an important role in the contraction process.
Post exercise diet and recovery activities would be needed for the
athlete to recover from this type of fatigue.

5 Depletion of Glycogen

In prolonged exercise that lasts for several hours, fatigue develops
as glycogen becomes depleted in the slow twitch fibers and the fast
twitch fibers are recruited maximally. When this occurs, further
recruitment of fast twitch muscle fibers is no longer possible to
compensate the decline of activity in the slow twitch fibers and power
output from the muscles begin to decline thus affecting performance.
Recovery from this type of fatigue would take days depending on the
type of activity and the severity of the damage to muscles that has
occurred.

Reference: 1 Nadel E.R. ( 1985) Psychological Adaptations to
Aerobic Training

2 Course Notes on Fatigue and Recovery provided by Blackburn College

3 Macardle, Katch and Katch , Exercise Physiology , 4th Edition

4 Part 2

The body of an athlete can recover from fatigue from participating in
a sprint event or a tennis match or a marathon race through the
following process:

1 Replacement of lost glycogen

2 Removal of lactic acid

3 Replacement of ATP

4 Replenishment of oxygen in myoglobin

For the replacement of glycogen, removal of lactic acid and
replacement of ATP, a large amount of oxygen would be needed and this
phenomenon id known as oxygen debt or post exercise oxygen
consumption. To adequately remove lactic from the blood a copius
amount of oxygen would be required.



Physiological Recovery
======================

For the three selected sports ie tennis, sprint and the marathon, the
replenishment of energy fuel and fluid is of utmost importance. CHO
loading is especially important before, during and after competition.
CHO loading will maximize glycogen stores and thus minimize the onset
of fatigue. The recommended intake of CHO is 1 gram per kg body weight
per hour during competition.

Replenishment of fluid loss to minimize the risk of dehydration is
also very important for the recovery process. For events lasting less
than 60 mins, water is sufficient to replace fluid loss. For tennis
and marathons, isotonic sports drinks such as Gatorade or 100 plus
will help to restore the electrolyte balance in the body and thus aid
in the recovery process. Zinc and Magnesium are important for muscle
repair and replacement. Potassium in conjunction with Sodium will help
to maintain fluid and electrolyte balance in the cells and is
important for nerve and muscle function. Potassium also helps to lower
blood pressure and a deficiency in Potassium would result on high BP,
dry skin , salt retention and irregular heartbeat. Deficiency in
Sodium would result in low blood sugar, dehydration, lethargy, and
heart palpitations leading to possible heart attacks. Therefore
Potassium and Sodium are very essential minerals that need to be
replaced quickly for recovery.



Physical Recovery
=================

Stretching and cooling down are very important for the recovery of the
athlete after a grueling tennis match, a competitive marathon or a
sprint. Stretching will improve posture and flexibility and it will be
good for the athlete to include stretching and cooling down to aid
quick recovery.

Cross training such as swimming light jogging and hydrotheraphy such
as saunas, massage and spas would stimulate the nerves and improve
blood circulation to aid quick recovery.



Psychological Recovery
======================

Athletes in the three events ie tennis , marathon and sprint could
listen to stimulating and calming music to help them to relax before
and after the event for optimal arousal and relaxation and recovery.

Proper breathing techniques while stretching will also help to relax
tense muscles thus aiding the recovery of the athlete.

Meditation would help the athlete to relax as well as calm the nerves
by reducing the noise to the brain. It would help the athlete to lower
the BP, heart and breathing rate, relaxes the muscles and controls
stress all of which are important for the athlete before and after the
competition.

Finally , imagery and visualization would help the athlete to invoke
the best performance and for relaxation.

Proposed Recovery For Tennis , Sprint( 100 metres) and Long Distance
Running

( Marathon )

SPORT

PHYSICAL

PSYSIOLOGICAL

PSYCHOLOGICAL

Sprint – 100 metres

To facilitate the removal of lactic acid in the muscles of the thighs
and for the relaxation of the sore muscles, sports massage is
proposed. In addition there should be plenty of rest and stretching to
loosen tight muscles and tendons.

Rest needed for the heart and respiration to return to normal and for
the clearing of lactic acid. Proper post event diet with high CHO and
electrolytes like Gatorade is important for recovery.

Listening to music or doing something else that is light not connected
with sport should help the athlete to relax. Meditation and relaxation
techniques to help the mind and body to relax would also help.

Distance Running

( Marathon )

To facilitate the removal of lactic acid in the muscles of the thighs
and legs and for the relaxation of the sore muscles, sports massage is
proposed. There should be plenty of rest and stretching to loosen
tight muscles and tendons and to clear lactic acid.

Rest needed for the heart and respiration to return to normal and for
the clearing of lactic acid. Proper post event diet with high CHO, Fat
for energy and electrolytes like Gatorade is important for recovery.

Listening to music or doing something else that is light not connected
with sport should help the athlete to relax. Meditation and relaxation
techniques to help the mind and body to relax would also help

Tennis

To facilitate the removal of lactic acid in the muscles of the arms
and legs and for the relaxation of the sore muscles, sports massage is
proposed. In addition there should be plenty of rest and stretching to
loosen tight muscles and tendons.

Rest needed for the heart and respiration to return to normal and for
the clearing of lactic acid. Proper post event diet with high CHO, Fat
for energy and electrolytes like Gatorade is important for recovery.

Listening to music or doing something else that is light not connected
with sport should help the athlete to relax. Meditation and relaxation
techniques to help the mind and body to relax would also help.

Reference : 1 Course Notes provided by Blackburn College

2 Nadel E R ( 1985), Physiological Adaptations To Aerobic Training

3 Scott Powers & Edward Haley , Exercise Physiology : Theory and
Application To Fitness and Performance , 5th Edition

4 McArdle, Katch and Katch, Exercise Physiology, 4th Edition

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