Download Aerobic System

EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
ADENOSINE TRIPHOSPHATE (ATP):

The energy required by the body to sustain life and for the contraction of muscles to
produce movement is derived from the food we eat.

When food is digested, it is broken down into chemical compounds including
carbohydrates, fats, and proteins. These chemicals compounds contain energy.
FOOD
Carbohydrates

Fats
Proteins
The energy contained in carbohydrates, fats, and protein cannot be used directly by the
body. Instead it is used to form a chemical compound called adenosine triphosphate
(ATP).
ATP:
ADENOSINE


P
P
P
ATP is stored in small amounts in all muscle cells.
It is the energy released, during the breakdown of ATP into adenosine diphosphate (ADP)
and the third phosphate, which represents the immediate source of energy that can be
used by the muscle cells to perform work.
BREAKDOWN OF ATP INTO ADP + P:
ADENOSINE
P
P
P
ENERGY RELEASED
ATP
→ ADP + P
SOURCES OF ATP:



ATP can be stored in the muscles in only small amounts.
Once this store has been used up, the body must supply the muscle with more ATP for it
to continue working.
The supply of ATP is limited by the intensity and duration of the physical activity.
Primary source of ATP: carbohydrates, which are broken down to glucose and glycogen.
Secondary source of ATP: fats, which are broken down into fatty acids.
Extreme source of ATP: proteins, only under extreme conditions (triathlons)
2 PATHWAYS FOR ENERGY PRODUCTION
ANAEROBIC PATHWAY
ATP-CP Energy System
AEROBIC PATHWAY
Lactic Acid Energy
System
Aerobic Energy System
SUMMARY OF THE 3 ENERGY SYSTEMS:
Characteristic
1. Oxygen
requirements
for energy
source
reaction
2. Energy source
for ATP
production
ATP-CP System
Anaerobic – no oxygen
required
Lactic Acid System
Anaerobic – no oxygen
required
Aerobic System
Aerobic – oxygen
required in the reaction
Chemical fuel - Creatine
Phosphate (CP)
Food source Carbohydrates
Glycogen
3. Duration of
energy system
4. Intensity
Up to 10 seconds
1 to 3 minutes
Food source Carbohydrates
Fat
Protein
>5 minutes
Maximal intensity (>95%)
High, sub-maximal
intensity (85-95%)
Sub-maximal intensity
(85%)
5. Recovery time
until repeat
effort
CP replenishments: 3-5
minutes
 50% in first 30 secs
 Rest recovery best
Removal of lactic acids to
rest levels.
 With active recovery:
- 50% removal in 15 mins
- 95% removal in 30 mins
 With passive
recovery:
- 50% removal in 30 mins
- 95% removal in 60 mins
Restoration of body
glycogen stores:
 After competition of
more that 1 hr: 2448hrs
 After hard interval
training: 6-24hrs
6. Factors when
operating
maximally
7. Specific
sporting
examples
Depletion of ATP and CP
stores
Lactic acid accumulation
By product of water and
carbon dioxide

Any athletic field
event
100m sprint
Golf drive
Gymnastics vault
Volleyball spike
Tennis serve


400m in athletics
Consecutive
basketball fast
breaks
Rally in squash
Repeated leads by
full-forward
Netball centre






Marathon
Cross-country skiing
Triathlon
AFL mid-fielder
2000m rower
Water polo player
Running up 1 flight of
stairs
Carrying heavy
shopping to the car
Sprinting for the train

Running up 4 flights
of stairs
Running 300m to
catch a bus
Chopping wood




Shopping
Gardening
Dancing
Ironing
8. Everyday
activity
examples













SOURCES OF ENERGY TO PERFORM WORK
FOOD
IS DIGESTED INTO
CARBOHYDRATES
FATS
PROTEINS
USED TO FORM CHEMICAL COMPOUND
ATP
ADENOSINE
P
P
P
CHEMICAL ENERGY
BREAKING OF PHOSPHATE BONDS GIVES ENERGY
ADENOSINE
P
P
P
ENERGY RELEASED
ATP →ADP + P
ENERGY RELEASED IS USED BY MUSCLES TO WORK
POSITIVES & NEGATIVES OF THE 3 ENERGY SYSTEMS
ATP-CP System
Positives
Stored onsite – ‘ready to go’
Negatives
Only available for a very short time (up to
10 sec.)
Maximal intensity exercise
Anaerobic – ‘without oxygen’
No performance inhibiting by-products
Quick to recover (100% in 3 min.)
Lactic Acid System
Positives
Negatives
Anaerobic – ‘without oxygen’
Lactic Acid accumulation retards
muscular contraction
Acts quickly
Short lived (approx. 60-90 sec.)
High Intensity
Can only use glycogen as a fuel source
Aerobic System
Positives
Negatives
Prolonged energy source
Needs oxygen (which takes time to
deliver)
No fatiguing by-products
Slow to increase oxygen delivery
Capable of breaking down 3 fuels
Is only dominant during sub-maximal
activity
EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
SUMMARY OF THE 3 ENERGY SYSTEMS
ENERGY SYSTEM
ATP-CP
LACTIC ACID SYSTEM
AEROBIC SYSTEM
ATP-PC
Alactacid
phosphagen
Lactacid
Anaerobic Glycolysis
Oxygen
Type
Anaerobic
Anaerobic
Aerobic
Fuel
CP
Carbohydrate
Carbohydrate
Fat
Protein
Very Limited
Limited
Limited
Up to 10 seconds
20 – 90 seonds
2-3 minutes plus
Instant
Quick
Slow
N/A
Lactic Acid
CO2
H2O
Limiting Factor
CP depleted
Lactic Acid
accumulation – fatigue
Insufficient O2 supply
or fuel (carbohydrate)
Recovery Time
50% in 30 seconds
100% in 3 minutes
Active – 45 minutes
Passive – 90 minutes
None – although 24-48
hours to replenish
carbohydrate, fluid etc.
Alternative names
ATP production –
capacity
Duration that
maximal energy
production can occur
ATP Production –
Speed
By-product of Energy
Production
EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
MAXIMUM OXYGEN CONSUMPTION (VO2 MAX)
VO2 Max = the volume of oxygen consumed by the body for energy production. It is measured
in litres of oxygen consumed per minute (L/min).
If an athlete were to slowly increase exercise intensity, there would be a corresponding
increase in oxygen consumption until they reached maximum oxygen consumption (VO2 Max)
– the region where oxygen uptake peaks despite further increases in exercise intensity (refer
to the following diagram).
Because larger people tend to consume more oxygen than smaller people (purely because of
their larger size), VO2 Max is usually expressed as a Relative VO2 Max in millilitres of oxygen
consumed per kilogram of body weight per minute (ml/kg/min). This allows for the comparison
of different-sized individuals. For example, in the following diagram the athlete’s peak VO2
Max value was 3.6 litres per minute. If the athlete undergoing this test had a mass of 68kg,
then their average relative oxygen consumption would be calculated as follows:
3.6L/min x 1000 = 3600ml
3600/68kg = 52.9ml/kg/min
The VO2 Max is an important indicator in determining a person’s capacity for the aerobic
resynthesis of ATP, with elite endurance athletes having higher values than other sports
performers. Untrained individuals would have a VO2 Max of approximately 40ml/kg/min, while
values exceeding 70ml/kg/min or beyond are only achieved by superbly conditioned
endurance athletes.
EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
ANAEROBIC THRESHOLD (AT)
Anaerobic Threshold (AT) = the maximum intensity of steady state exercise (% VO2 max)
that a person can sustain without a rapid increase in the accumulation of lactic acid.
It should be noted that exercise intensities approaching VO2 max can only be achieved
through the dominant use of the lactic acid system with subsequent formation and
accumulation of lactic acid.
Generally speaking, the most common reference point for anaerobic threshold is thought to be
when blood lactate levels exceed 4 ml per litre of blood.
Because there is no actual threshold point where aerobic processes simply ‘stop’ and
anaerobic processes simply ‘begin’, anaerobic threshold is more correctly referred to as the
Onset of Blood Lactic-acid Accumulation (OBLA).
A person’s anaerobic threshold, or OBLA, has a large impact on the athletic performance. It
determines the maximum exercise intensity they can maintain for an extended period of time
without the fatiguing effects of lactic acid accumulation. Generally speaking, individuals with
higher AT or OBLA values (expressed as a % of their VO2 max) are the better endurance
performers. Through training, VO2 max and anaerobic threshold can be improved.
EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
OXYGEN DEFICIT
Oxygen Deficit = the period of time at the start of exercise where the level of oxygen
consumption is below the necessary level to supply ATP aerobically. Because it takes 2-3
minutes to increase the O2 supply sufficiently, the two anaerobic systems must provide the
required ATP during this time, thus creating an oxygen deficit.
EXERCISE PHYSIOLOGY – ENERGY SYSTEMS

Aerobic and Anaerobic Energy: ATP-CP System, Lactic Acid System, Aerobic System.
OXYGEN DEBT OR EXCESS POST-EXERCISE OXYGEN CONSUMPTION (EPOC)
Oxygen Debt or EPOC = the period of time after exercise where O2 consumption will remain
elevated to allow the body to slowly return to pre-exercise levels. During this stage, the heart
and lungs continue to deliver O2 to the body to rebuild energy supplies. This is usually seen at
the end of a race where a runner will pant vigorously.
There 2 components of EPOC:
ALACTACID COMPONENT (fast) = the O2 consumed in early recovery to replenish ATP-CP
stores and to re-supply oxygen bound to myoglobin. This process is accomplished very
quickly; 30 seconds for 50% replenishment and 3 minutes for 100%.
LACTACID COMPONENT (slow) = the extra O2 is consumed and used to breakdown and
remove lactic acid that has accumulated, resynthesise glycogen, restore body temperature
and normal breathing. This process can take 1-2 hours to be completely repaid, however an
active recovery can speed up the process.
Continuous activity post-exercise (at about 55-60% VO2 max) will speed up the removal of
lactic acid.
o It prevents blood pooling in the extremities
o It allows the skeletal muscles to oxidise some of the lactic acid for energy
(70%)
o An elevated heart rate keeps blood circulation to the liver high, assisting with
the conversion of lactic acid back to glycogen.