Fatigue and
Recovery
Mechanism
•
Understanding of the
multifactorial
mechanisms (including
fuel depletion,
metabolic by products
and thermoregulation)
association with
muscular fatigue, as a
Fatigue-Fuel Depletion
The multifactorial
mechanism of
fatigue…
… record some of
the key words and
messages in this
clip.
Fatigue…
… is an exercise-induced reduction in the
power-generating capacity of a muscle
and an inability to continue the activity.
…the onset and development of fatigue
depends on the type, intensity and duration
of activity, the muscle fibres being used the
type of muscular contractions and the
performers fitness levels.
The onset is dependant on…
 Type:
E.g. intermittent of continuous
 Intensity: E.g.
 Duration of activity:E.g.
 Muscle fibres being used:E.g.
 Type of muscular contractions:E.g
 Performers fitness levels: E.g
Classifying fatigue
 Fatigue
1.
2.
3.
4.

can be classified as
fuel depletion
accumulation of metabolic by-products
neuromuscular interruptions
elevated body temperature.
But remember it is often multifactorial
Fatigue is multifactorial (caused
by a combination of many factors)
Fuel Depletion
Neuromuscular Event
Metabolic By-Products
Elevated Body Temperature
List as many that you know in the boxes they belong in.
How many can you think of?
Fatigue is multifactorial (caused by a
combination of many factors)
Fuel Depletion
Neuromuscular Event
Intramuscular ATP
Decrease in CNS firing (rate and
intensity)
Phosphocreatine
Impaired sodium (Na+) and potassium
(K+) gradients
Muscle Glycogen
Blood Glucose
Metabolic By-Products
Elevated Body Temperature
H+ ions in plasma and muscles
Very high core temperature
Inorganic phosphate
Increased rates of dehydration
Adensine diphosphate (ADP)
Redistribution of blood away from
muscles to assist cooling=less blood/ 0
Ca+
Methods of generating ATP
during muscle activity
 Table
6.3 (p.149)
Lactic Acid- Good or Bad
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Read page 148
Define the term DOMS, Lactate Inflection Point,
Glycolysis, NAD +, acidosis
What is one benefit of lactic acid?
Explain the process of glycolysis with and without
oxygen
How is it that triathletes have near resting levels of
fatigue despite performing for hours?
How is training beneficial in accelerating lactate
clearance?
How does lactate and acidosis effect muscle
performance?
Passive vs active recovery. What is better?
Thinking things through…
1.
2.
3.
4.
5.
6.
List the metabolic consequence of supplying ATP via the
lactic acid system?
How is it possible for triathletes to have near-resting levels
of lactic acid despite performing for over a couple of
hours?
Explain how the accumulation of H+ is implicated in
muscle fatigue
Why are lactate levels tested regularly during training
sessions by physiologists, fitness advisors and coaches?
Explain how aerobic training reduces lactate
accumulation at any given workload and yet results in a
greater level of lactate accumulation during maximal
efforts.
What is lactic acid buffering?
Something else to consider…
1.
2.
3.
Study Figure 6.2. Explain the uptake of
oxygen and oxygen deficit for an
athlete 800m runner during an event
lasting 2 minutes
Study figure 6.4. Explain the oxygen debt
and its two parts, fast and slow.
List the fast and slow process of EPOC
Oxygen uptake during STEADY
STATE EXERCISE
Can you identify the location of oxygen deficit, steady state,
oxygen debt (EPOC)?
Define the following key terms
 Oxygen
Deficit
 Steady State and Plateaus
 Oxygen debt or EPOC
 VO2
 VO2 Max
 Buffering
 Myoglobin
Worksheet
LIP in terms of Steady State…
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The Beep Test CD comes with the ability to have
students run 5 minutes at Level 6, 8, 10 etc......
Rather than continuing with more rapidly occurring
beeps. Most people can handled level 6, this is due
to LIP not having been exceeded, there is energy
system interplay, abundance of fuels.
What would happen if you allow a 5 min break and
then complete next 5 minute set. What does this
mean in terms of LIP?
Few students could sustain 5 minutes at level 10 –
Once again, what is happening to lactate and
therefore hydrogen accumulation? If students can
keep up with this pace it’s clear they haven’t
triggered LIP.
Oxygen uptake with
increasing workload
What
predictions
can you
make
regarding this
individual’s
performance?
Returning to a pre-exercise
state
 High
intensities = high EPOC
 EPOC has two stages; EPOC fast
replenishment and EPOC slow
replenishment
 EPOC fast is primarily restoration of PC
(taking 2-3 minutes)
 EPOC slow is primarily concerned with
removal of lactic acid though buffering
 See table 6.5 (p.154) for a summary
Likely Causes of fatigue
Predominant ES
Likely causes of Fatigue
Types of recovery
ATP-PC
Fuel depletion of ATP and
PC
Passive recovery
Lactic Acid
Accumulation of by
product
H+ ions
Inorganic Phosphates
Non dietary
Active recovery
Massage
Hydo/water based therapies
Aerobic
Fuel depletion
Glycogen stores, then fats
Elevated body
temperature
Causing dehydration and
blood flow away from
muscles
Dietary
High GI
Rehydration via sports drinks
Non-dietary
Active recovery
Massage
Hydro/water based therapy
Depletion of Fuel
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Only a factor when using the ATP-PC (PC depletion) and
predominantly aerobic events lasting over 1 hour
CHO is the only source of energy during maximal intensity
exercise but fats are used increasingly during prolonged
endurance events
Muscle glycogen is the first fuel, as this is depleted, the
muscles use glycogen stored in the liver, once this is
depleted it looks towards blood-born fats and stored fats.
The rate of energy production using glycogen is 50 to 100%
faster that the production using fats. This is due to a more
complex chemical reaction and great amounts of oxygen
required. Small amounts of glycogen is needed to actually
breakdown fats.
Protein can be used but only in extreme circumstances
lasting over 5 hours
Carbohydrate and Fat
utilisation during endurance
events
What would happen to the athletes performance once fat is
the predominant energy source? Why?
Metabolic By-products
H+ ions
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The negative effects on
performance associated with
lactate accumulation is due to 
the increase in hydrogen ions
The breakdown of glucose or

glycogen produces lactate
and H+ (1 for 1)
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The hydrogen ions makes the
muscle acidic
As the concentration increases 
the blood and muscles
become more acidic
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This acidic environment will slow
down enzyme activity and the 
breakdown of glucose itself
Inorganic Phosphate
During muscle contraction ATP is broken
down to ADT and P1 (inorganic
phosphate)
Both are released during the cross bridge
cycle of the sliding filament theory
explaining muscle contractions
P1 is linked to the power stroke of the
cross bridge cycle
P1 accumulation occurs rapidly during
high intensity exercise resulting in
decreased contractile force production
P1 reduces the amount of Ca that can
be released via the sodium-potassium
pump and hence slows contraction
ADP is released near the end of the cross
bridge cycle after the ATP split to release
energy
Accumulation of ADP causes a decrease
in the maximal velocity of shortening in
the cross bridge and an associated
reduction in power output
Neuromuscular Factors
Decreased CNS ‘firing’
 The brain detects fatigue and acidosis so
sends weaker signals to working muscles in
an effort to reduce intensity and slow down
the work rate of the muscles
 Less electrical stimulation created by
sending fewer signmald eill result in less force
and less frequent muscle contractions
 This is a self protection mechanism
Elevated Temperature
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Is only an issue while performing in environmental
conditions of high heat an humidity
Normal core temperature ranges from 36.5 to 37.5
degree Celsius
Hyperthermia is unusually high body temperature and
elevated core temperature and severely affects
performance
Muscles produce heat as they work
Our bodies must loose this heat via radiation,
conduction, convection and evaporation
Once the body looses 2-3% of it’s body weight through
sweating, thermoregulation is impaired (the bodies
ability to keep the core temp. within certain
boundaries
Physiological result of sweat
loss- see fig 6.9 (p.160)
Recovery Strategies
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Recovery aims to return the body to pre-exercise
conditions and reverse the effects of fatigue.
Efficient recovery strategies will enhance
adaptation to exercise loads as well as preparing
the athlete for future training.
Read pages 161-167. Summarise the following
recovery strategies
Refuelling: Phosphocreatine, muscle glycogen
and blood glucose
Metabolic by-product: Removal of H+ ions in
plasma and muscles and replenishing inorganic
phosphate (Pi) and Adenosine diphosphate (ADP)
Addressing neuromuscular factors.
Lowering body temperature.
Active vs Passive
Active
1.
Dietary refueling and
hydration
2.
Removal of H+ ions
3.
Rebounding P1 to ADP
4.
Addressing
nueronmuscular
factors
5.
Strategies for cooling
Passive
1. PC
Refueling
Application Tasks
1. Work the Web: Review of Sports Drinks on the Market (p.166)
http://www.choice.com.au/Reviews-and-Tests/Food-andHealth/Food-and-drink/Beverages/Sports-drinks-review-andcompare/Page/Introduction.aspx
Record Key Findings of the study.
2. Follow the following link
http://www.ausport.gov.au/ais/sssm/fatigue_and_recovery to
investigate the number of ways the AIS promotes performance
recovery. Record Key findings
3.Investigate Strategies for cooling . Record Key findings
http://www.coolmax.invista.com/
4. Student directed presentation on chosen fatigue management
strategy E.g. Compression garments, hydration, ice baths, etc!
Explain the scientific theory that underpins your chosen method