1. Energy System responses to acute exercise
Energy systems: phosphocreatine; lactic acid; aerobic; energy continuum; energy requirements of different sport and exercise activities
ATP PC
Lactic Acid
Aerobic

2. Energy Systems & Exercise: The Basics
ATP
Aerobic System
Lactic Acid/Anaerobic Glycolysis
ATP-PC (phosphagen)
0 sec 4 sec sec min min +
Strength – Power: power lift, shot put, golf swing
Sustained Power: sprints, fast breaks, football
Anaerobic Power – Endurance: m dash, 100 m swim
Aerobic Endurance: Beyond 800 m run
Immediate/short-term Aerobic-oxidative non-oxidative systems system

3. Fuel, Energy systems & Exercise
Anaerobic Energy System = Carbohydrates are the only fuel source
With prolonged exercise, Carbohydrates are the first fuel choice, as exercise continues, FAT becomes predominant :
As exercise intensity , energy supplied by Carbohydrates 
As duration , energy supplied by fat 
Protein is not a main fuel source except in an emergency :
As glycogen , energy supplied by protein 
Each system plays an important role in energy production:
All energy systems are “on” at all times
This gives us a variety of movements
The systems interact to supply Energy for the activity

4. Fuel, Energy systems & Exercise
% energy from CHO
increasing intensity of exercise
% energy from FAT
As exercise gets harder, the % energy from
oxidation of Carbohydrates goes UP sharply while the % energy from fat goes DOWN

5. Energy Systems on a Continuum!
‘All energy systems are “on” at all times’
All three energy systems contribute at the start of exercise but the contribution depends upon the individual, the effort applied or on the rate at which energy is used.
The following graph shows how the energy systems contribute to the manufacture of ATP over time when exercising at 100% effort.
The thresholds (T) indicate the point at which the energy system is exhausted - training will improve the thresholds times.

6. Energy Systems working together: 100m SPRINT
Energy Systems on a Continuum!
ADENOSINE
TRIPHOSPHATE
(ATP)
PHOSPHO-
CREATINE
(PCr)
GLYCOLYSIS
(ANAEROBIC;
CHO BREAKDOWN)
KREBS
CYCLE
(AEROBIC;
CHO, FAT, AND
PROTEIN
BREAKDOWN)
Energy Systems working together:
100m SPRINT
(10 seconds of maximal exercise)

7. Energy Systems on a Continuum! Energy Systems working together:
ADENOSINE
TRIPHOSPHATE
(ATP)
PHOSPHO-
CREATINE
(PCr)
GLYCOLYSIS
(ANAEROBIC;
CHO BREAKDOWN)
KREBS
CYCLE
(AEROBIC;
CHO, FAT, AND
PROTEIN
BREAKDOWN)
Energy Systems working together:
800 METER RUN (50 seconds)

8. Energy Systems working together: MARATHON 2.5 hours of exercise
Energy Systems on a Continuum!
ADENOSINE
TRIPHOSPHATE
(ATP)
PHOSPHO-
CREATINE
(PCr)
GLYCOLYSIS
(ANAEROBIC;
CHO BREAKDOWN)
KREBS
CYCLE
(AEROBIC;
CHO, FAT, AND
PROTEIN
BREAKDOWN)
Energy Systems working together:
MARATHON 2.5 hours of exercise

9. Sport, Exercise and Energy Systems
Anaerobic
70-80% Anaerobic
20-30%
Aerobic
Wt. Training
Stop & Go Sports
Jogging
Gymnastics
Tennis
Marathons
Football
Soccer
Cycling
Baseball
Field Hockey
Aerobic Dance

10. Energy System recruitment in Sport
ATP-CP and LA %
LA-Aerobic %
Aerobic
Basketball 60 20
Fencing 90 10
Field events
Golf swing 95 5
Gymnastics 80 15
Hockey 50 30
Distance running 70
Rowing
Skiing 33
Soccer
Sprints
Swimming 1.5km
Tennis
Volleyball
Table adapted from Fox E. L. et al, The Physiological Basis for Exercise and Sport, 1993