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Fatigue and Recovery

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Penelope Cleghorn

on 15 April 2015

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Transcript of Fatigue and Recovery

What is Fatigue?
Fatigue is the inability to continue exercise at a given intensity due to physiological, biomechanical and/or psychological factors.

1. Accumulation of Metabolic By-Products
eg.
H+
(Hydrogen Ions)
Pi
(Inorganic Phosphate)
and
ADP
(Adenosine Diphosphate)
2. Fuel Depletion
Depending on the intensity and duration of the activity, different food fuels will be deleted eg. CP, muscle glycogen
2. Fuel Depletion
When exercising, your body uses fuels to produce energy to resynthesise ATP. The
INTENSITY
and
DURATION
of the activity will determine which food fuels are depleted when and by how much.
The Three Mechanisms of Fatigue
Unit 3 VCE Physical Education, Area of Study 2
Fatigue and Recovery
3. Thermoregulation
When the body is too hot, it can experience
hyperthermia,
which can also result in
dehydration
. Outside of its normal temperature, the body cannot function properly.
1. Accumulation of Metabolic By-Products
-How does
H+
cause fatigue?
-How does
Pi
and
ADP
cause fatigue?
-What is the
Lactate Inflection Point (LIP)
?
H+
H+ Accumulation
-Lactic Acid
is produced when the body uses Anaerobic Glycolysis to resynthesise ATP.

-When Lactic Acid is produced, it immediately
dissociates
(splits) into Lactate and H+. The accumulation of
H+
is what causes the fatigue in the body by impeding the muscular contractions.

Please Note:
-When Lactic Acid dissociates, equal amounts of Lactate and H+ are produced in a 1:1 ratio.
-Lactate is easily measured in the body, hence this reading is often used in graphs to demonstrate the level of fatigue in the body.
-Don't be fooled! Remember the H+ causes the fatigue
How does H+ cause fatigue?
-An accumulation of H+ leads to an increase in
muscle acidity
(decrease in pH).

-This
decreased pH level
decreases the amount of glycogen broken down in the muscle by inhibiting the
GLYCOLYTIC ENZYMES
hence the force and rate of muscular contractions decreases.
Accumulation of Pi
-When CP is broken down to resynthesise ATP via ATP-CP, not all of the P is used in this process. The 'extra' P is known as
inorganic Phosphate or Pi.
This is also a fatiguing metabolic by-product.
-Similar to H+, the Pi
inhibits the action of the muscles contracting
decreasing the force as the muscles contract.

The Lactate Inflection Point (LIP)
-When working aerobically, our body is able to
remove H+ and Lactate at the same rate that it is being produced
.

-When we increase our intensity, we
accumulate H+ at a greater rate than we can remove it which causes fatigue
.

-The greatest point at which production and remove of H+ is balanced is called the
Lactate Inflection Point.
Lactate Inflection Point (LIP)
The
greatest point
at which blood lactate production and blood lactate removal is balanced (equal).

In other words, the highest steady state of aerobic intensity.
Once you reach your LIP:
-decreased time to exhaustion
-increased anaerobic metabolism
-increased lactic acid accumulation
-increased H+ accumulation
-It is possible to prolong or
delay the LIP with Aerobic Training.

-This would be an advantage in longer distance events.

-LIP can determine the
highest intensity
an athlete can work at
without
producing greater amounts of H+ which would cause them to slow down and fatigue.
Summary:
-Increase in H+ causes acidosis in the muscle (decrease in pH).

-This inhibits the force and rate of muscular contractions.

-Causes fatigue.

Summary:
-Lactate Inflection Point (LIP) is the greatest point at which lactate production and lactate removal is balanced.

-Once you reach your LIP, you are closer to exhaustion.

-Athletes can delay their LIP through Aerobic Training.

-Athletes work just below their LIP, so they can work at their highest intensity for a longer period of time without causing them to fatigue.

E
HIGH INTENSITY, SHORT DURATION - CP Depletion
HIGH INTENSITY, LONG DURATION - Muscle Glycogen and Blood Glucose Depletion
Depletion of CP
-Once CP is depleted (after 10 seconds of maximal activity), there is an increased reliance on CHO and the anaerobic/aerobic systems to resynthesis ATP. This ATP is resynthesised at a slower rate, hence a decreased power and force produced by the muscles, hence decreased intensity.
Hence, body fatigues.
Hence, body fatigues.
Hence, body fatigues.
Depletion of Glycogen/Glucose
After approx. two hours of high intensity work using CHO to fuel the resynthesis of ATP, the CHO depletes meaning the body must now use Fats via Aerobic Lipolysis in the presence of Oxygen. This is a more complex chemical reaction, hence the rate of ATP is slower, hence the body must decrease its intensity.
Hence, body fatigues
Summary:
-When there is either CP or Glycogen/Glucose depletion, the body must use an alternative way to resynthesise ATP, via either a different Energy System or different food fuel.

-This affects the force and power produced by the muscles, meaning the body works at a lower intensity.

-Hence, the body fatigues.

3. Thermoregulation
-When the body experiences overheating

(
hyperthermia
) due to increase in ambient air temperature, the result is
dehydration
or a lack of fluids in the body.

-We must decrease intensity to try and bring body back with a normal temperature and fluid range.

-This causes fatigue.
T
Dehydration
Occurs when fluid loss exceeds fluid replenishment.
Increased core body temperature -
Increased sweating (increased blood to surface of skin and away from working muscles) -
Increased loss of electrolytes, salt and water -
Decreased blood plasma volume -
Increased Cardiac Activity (SV, Q) -Decreased intensity
Hence, body fatigues
Hyperthermia
Increased ambient air -
Increased body temp -
Increased blood flow to surface of skin to cool body down and away from working muscles -
Decreased oxygen and food fuels to working muscles -
Decreased waste removal -
Decreased ATP resynthesis -
Decreased intensity
Hence, body fatigues
R
Recovery
Once our body is fatigued, how do we restore our physiological and psychological function?

That is, how do we RECOVER?

Depending on the type of fatigue, this will affect the type of recovery we need.
ACTIVE RECOVERY
-Utilising same activity (muscle groups)
below 75% MAX HR
to maintain elevated HR and oxygen delivery to muscles to remove metabolic by-products.

-Also prevents
venous pooling
and
skeletal muscle pump
assists venous return
PASSIVE RECOVERY
-Complete rest and staying still.

-Optimal strategy to restore CP the
fastest.

-Dependent on amount of PC depleted

30 seconds replenishes 70% CP
3 minutes replenishes 98% CP
up to 10 minutes for full replenishment
NUTRITION
-Restores muscle/liver glycogen and blood glucose.

-Restores fluid and electrolytes lost through sweating.

-Repairs muscle tears through protein ingestion.
After the race...
-Consume 1g/KG of body weight of CHO within 1 hour of finishing race (eg. 75kg athlete, 75g of CHO - two large muffins)

-10-20g of protein within 2 hours of finishing ( eg. small cooked fish)

-For every 1kg of body weight lost, 1L of fluid (water or sports drink to be consumed)
So, which RECOVERY strategy is suited to which FATIGUE mechanism?
Accumulation of metabolic by products =
ACTIVE RECOVERY

Depletion of PC stores = PASSIVE RECOVERY

Depletion of glycogen stores =
NUTRITION

Hyperthermia =
PASSIVE RECOVERY/NUTRITION

Dehydration =
NUTRITION
Accumulation of ADP
-Again similar to H+ and Pi, additional ADP (that hasn't been resynthesised to ATP yet), causes a
decrease in speed and strength of muscular contraction
.
Hence, causes fatigue
VO2 MAX and LIP
-Elite Athlete will reach LIP at 85%-90% VO2 MAX

-Normal Athlete will reach LIP at 70%-80% VO2 MAX
Full transcript