fatique and excercise
TRANSCRIPT
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What is Fatigue?
Temporary loss of strength and energy resulting
from hard physical or mental work; "growing
fatigue was apparent from the decline in theexecution of their athletic skills
Feeling of tiredness or weariness usually
associated with performance decrement
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What is Fatigue?
A feeling of tiredness or weariness resulting in a
decreased capacity for physical and mental work
A condition that results when the body cannot
provide enough energy for the muscles to
perform a task
Physical weariness resulting from exertion
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Fatigue
Fatigue is caused by:
- The type of activity
- Muscle Fibre type (White fast twitch/Red slow twitch)
- The type of muscle contraction
The intensity of exercise
The duration of exercise
The level of fitness
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Types of Fatigue
Local pain or heaviness at the muscle eg:
sore bicep from doing 100 bicep curls
General can be both physical and mentalfatigue, eg: exhausted from training
Long term over training and will lead to
injury
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Fatigue refers to the inability to continue
exercise at a given intensity
decrease in muscular performance usually seen as a
failure to maintain or develop a certain expected force
or power.
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Central versus Peripheral
Where does fatigue occur?
Central fatigue
Proximal to the motor unit
Peripheral fatigue
Residing within the motor unit
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Central Fatigue
Brain and spinal cord; CNS fatigue
Studies that used voluntary exhaustion and then
additional electrical stimulation
After voluntary exhaustion, electrical stimulation
evoked sizable force production
Central location of fatigue
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Peripheral Fatigue
Fatigue occurring within the local motor unit;
local fatigue
Studies that fatigued a muscle with electrical
stimulation to the point of no muscle twitch
Muscle action potentials were relatively unaffected
Peripheral location of fatigue (but not at the NMJ)
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So, where does fatigue occur?
In both central and peripheral locations. The location of fatigue is intensity-dependent
Lower-intensity, longer duration fatigue will primarily
occur centrally Higher-intensity, short duration fatigue will primarily
occur peripherally
Example Why do we slow down during the course
of a 1600 m race? Do we slow down?
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Causes of Fatigue
1. Fatigue of energy generating systems within
and external to muscle
2. Accumulation of metabolic by-products &failure of the muscular contractile mechanism
3. Disturbances to homeostasis
4. Central or peripheral nervous system
dysfunction
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1. Fatigue of energy generating
systems
within and external to muscle
Muscle glycogen depletion
Liver glycogen depletion
Depletion of fat stores
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Depletion of Fuels
CP and Glycogen is the dominate fuel used for high intensity activities.
Once these fuels run out your body can no longer work at high intensityand must resort to fats. This is not as efficient and causes the athlete toslow down or stop.
CP stores will last continually for 10 seconds.
Your body has enough Glycogen stores for 90 180 minutes of continualexercise.
Anaerobic glycolysis will last continually at high intensity for 30-100seconds or for as long as the individual can with stand the increasing byproducts
High intensity activities require fast twitch muscle fibre (white) thatfatigue faster than slow twitch (Red).
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2. Accumulation of metabolic by-
products & failure of the muscular
contractile mechanism
Lactic acid accumulation Phosphocreatine depletion and phosphate
accumulation
Hypoxia/impaired of oxygen delivery Disturbance to calcium metabolism
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Disturbance to calcium metabolism
Both mechanisms thought to
be important in developmentof fatigue during prolonged
exercise
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By-Products
ADP
Inorganic phosphate (Pi)
Pyruvic Acid
Lactic Acid (LA)
Hydrogen ions (H+)
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By-Products
ADP
Produced by the break down of ATP
By-ProductInorganic Phosphate (Pi)
Produced from the breakdown ofCP
Pi is leading cause of fatigue in muscles
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By-Product
Pyruvic Acid
Formed when the body creates ATP through
Anaerobic glycolysis.
Pyruvic Acid will not cause fatigue and canactually be used to create ATP when there is
plenty of oxygen present. Stage two of aerobic
system, Krebs Cycle
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By-Product
Lactic Acid
Lactic Acid is produced when Pyruvic Acid is not converted toATP through Krebs cycle, from high intensity anaerobicactivity.
Lactic Acid does not cause muscle fatigue but will increase pH. Increased pH will not cause muscle fatigue but will increase
recovery time.
LA will inhibit key enzymes from working producing slowerreaction times.
LA will inhibit calcium which is needed for musclecontractions.
LA can be used to produce ATP if oxygen is present throughKrebs cycle. LA can be good and produce ATP
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By-Product
Hydrogen ions (H+)
By-Product of Anaerobic Glycolysis
Inhibits muscular contractions.
Increases pH.
Inhibits enzymes that assist glycolysis
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3. Disturbances to homeostasis
Electrolyte concentrations and theircompartmentalisation
Concentrations of glucose in blood, muscle and
other tissues (e.g. brain) Muscle and systemic pH and osmolality
Temperature (especially muscle and brain)
C
oncentrations of FFA Blood and plasma volume
Hormone concentrations
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Dehydration
Loss of fluid from
- Sweat, the bodies natural response tothermoregulation
- vasodilation, the increase in size of capillaries toreduce heat.
Effected by
- Duration of exercise
- Environment eg. hot day, humid
- Athletes acclimatisation to conditions
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Dehydration will result in
Continual loss of water will increase body temperate.
An increase in body temperature will require the
body to increase sweat production and vasodilation.
This will result in more loss of water and higher
temperatures
Results in fatigue
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Effects of Dehydration
Cramps
Heat stress
Heat stroke
Fatigue
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Guidelines to avoid Dehydration
Be well hydrated before exercise up to several hours prior toexercise
Do not wait until you are thirsty as an indicator to dehydration
Cold water is absorbed faster
Drink at least 500ml 30 minutes before exercise Drink at least 200ml every 15 minutes while exercising
Drink at least 500ml to 1 litre of water after exercise
1 kilo of weight loss during exercise = 1 litre of water loss
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4. Central or peripheral nervous
systemdysfunction
Positive inputs External stimulation
Crowd
voice
Other competitors
Negative inputs Pain (e.g. muscles,joints)
Sensations of
breathlessness
Fatigue
Low brain glucoseinputs
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What factors affect the time to onset
of fatigue?
Intensity, duration and pattern of exercise
Fitness
Age
Body Condition
Environmental conditions
Heat, heat & humidity or cold
Altitude
Pollution
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Indicators of fatigue
Ataxia, stumbling, unwillingness to exercise
Pain
Weakness
Hyperthermia
Low blood glucose
Hypovolaemia
Low BP
Nerve dysfunction
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Indicators of fatigue
Hypoglycaemia
Muscle glycogen depletion
Liver glycogen depletion
Changes in muscle EMG output
Dehydration
Hypovolaemia
Electrolyte loss
Acid-base disturbance
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Fatigue versus Exhaustion
FATIGUE
Able to restart exercise
after a short restPhysiologically normal
Risk of pathology low
EXHAUSTION
Not able to continue to
exercise
Physiological extremes
Pathological changes
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Definitions of Exhaustion
Extreme fatigue
Serious weakening and loss of energy
The act of exhausting something entirely The depletion of energy stores resulting in
muscle fatigue to the point where physical
activity cannot be performed
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Recovery
The aim of recovery is to minimise the effects offatigue
It aims to
- Replenish CP and ATP stores
- Breakdown and remove LA
- Restore muscle and liver glycogen
- Rehydration replace lost water and electrolytes
- Repair damaged muscle tissue- Reduce oxygen debt
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Passive recovery
Athlete remains still or lies on the ground
Best for
- Replenishing muscle PC- Is the faster form of recovery
- 70% of PC restored in 30 seconds
- 95 % of PC restored in 120 seconds
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Active Recovery
Involves athlete moving walking after exercise.
This pumps oxygen to the working muscle
Oxygen is essential in:
- Breaking down and removing LA- Removing H+
- Removing Pi and removing
50% removal of LA takes 30 minutes with Passive recovery
50% removal of LA takes 15 minutes with Active Recovery