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The best way to develop your athlete's Energy Pathways

Brian Mackenzie provides some advice on the body's energy pathways and how to develop them.

Energy production is both time and intensity-related. Running at a very high-intensity, as in sprinting, means that an athlete can operate effectively for only a brief period. Running at a low-intensity, as in gentle jogging, means that an athlete can sustain activity for a long period. The training introduces another variable, and the sprinter who uses sound training principles can run at a high intensity for longer periods. Similarly, the endurance athlete who uses sound training methods can sustain higher intensities during a set period. There is a relationship between exercise intensity and the energy source.

Energy Pathways

D. Matthews and E. Fox, in their revolutionary book, "The Physiological Basis of Physical Education and Athletics", divided the running requirements of various sports into the following "energy pathways":

  • ATP-PC and LA, LA-02, and 02
  • ATP - Adenosine Triphosphate: a complex chemical compound formed with the energy released from food and stored in all cells, particularly muscles. Only from the energy released by the breakdown of this compound can the cells perform work. The breakdown of ATP produces energy and Adenosine Diphosphate (ADP)
  • PC - Phosphate Creatine: a chemical compound stored in the muscle, which when broken down aids in the manufacture of ATP. The combination of ADP and PC produces ATP
  • LA - Lactic acid: a fatiguing metabolite of the lactic acid system resulting from the incomplete breakdown of glucose. However, Noakes in South Africa has discovered that although excessive lactate production is part of the extreme fatigue process, it is the protons produced at the same time that restrict further performance
  • O2 means aerobic running in which ATP is manufactured from food, mainly sugar and fat. This system produces ATP copiously and is the prime energy source during endurance activities

These energy pathways are time duration restricted. In other words, once a specific time elapses the pathway is no longer used. There is some controversy about these limitations, but the consensus is:

Duration Classification Energy Supplied By
1-4 seconds Anaerobic ATP (in muscles)
4-20 seconds Anaerobic ATP + PC
20-45 seconds Anaerobic ATP + PC + Muscle glycogen
45-120 seconds Anaerobic, Lactic Muscle glycogen
120-240 seconds Aerobic + Anaerobic Muscle glycogen + lactic acid
240-600 seconds Aerobic Muscle glycogen + fatty acids

The result of muscle contraction produces ADP which, when coupled with PC regenerates ATP (PC is stored in the muscles). Actively contracting muscles obtain ATP from glucose stored in the bloodstream and the breakdown of glycogen stored in the muscles. Exercise for longer periods requires the complete oxidation of carbohydrates or free fatty acids in the mitochondria. The carbohydrate store will last approx. Ninety minutes and the free fatty store will last several days. 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 Anaerobic (ATP-CP) Energy System

Adenosine Triphosphate (ATP) stores in the muscle last for approximately 2 seconds and the resynthesis of ATP from Creatine/Phosphate (CP) will continue until CP stores are depleted approximately 4 to 5 seconds. This gives us around 5 to 7 seconds of ATP production.

To develop this energy system sessions of 4 to 7 seconds of high-intensity work at near-peak velocity are required. e.g.

  • 3 x 10 x 30m with recovery of 30 seconds/repetition and 5 minutes/set.
  • 15 x 60m with 60 seconds recovery
  • 20 x 20m shuttle runs with 45 seconds recovery

The Anaerobic Lactate (Glycolytic) System

Once the CP stores are depleted the body resorts to stored glucose for ATP, the breakdown of glucose or glycogen in anaerobic conditions results in the production of lactate and hydrogen ions. The accumulation of hydrogen ions is the limiting factor causing fatigue in runs of 300m to 800m.

Sessions to develop this energy system:

  • 5 to 8 x 300m fast - 45 seconds recovery - until pace significantly slows
  • 150m intervals at 400m pace - 20 seconds recovery - until pace significantly slows
  • 8 x 300m - 3 minutes recovery (lactate recovery training)

There are three different working units within this energy system: Speed Endurance, Special Endurance 1, and Special Endurance 2. Each of these units can be developed as follows:

Speed Endurance Special Endurance 1 Special Endurance 2
Intensity 95-100% 90-100% 90-100%
Distance 80-150 metres 150-300metres 300-600 metres
No of Repetitions/Set 2 to 5 1 to 5 1 to 4
No of Sets 2 to 3 1 1
Total distance/session 300-1200 metres 300-1200 metres 300-1200 metres
Example 3 x (60, 80, 100) 2 x 150m + 2 x 200m 3 x 500m

The Aerobic Energy System

The aerobic energy system utilises proteins, fats, and carbohydrates (glycogen) for resynthesising ATP. This energy system can be developed with various intensity (Tempo) runs. The types of Tempo runs are:

  • Continuous Tempo- long slow runs at 50-70% of maximum heart rate. This places demands on muscle and liver glycogen. The usual response by the system is to enhance muscle and liver glycogen storage capacities and glycolytic activity associated with these processes.
  • Extensive Tempo- continuous runs at 60-80% of maximum heart rate. This place demands on the system to cope with lactate production. Running at this level assists the removal and turnover of lactate and the body's ability to tolerate greater levels of lactate.
  • Intensive Tempo- continuous runs at 80-90% of maximum heart rate. Lactate levels become high as these runs border on speed endurance and special endurance. Intensive tempo training lays the base for the development of anaerobic energy systems.

Sessions to develop this energy system:

  • 4 to 6 x 2 to 5-minute runs - 2 to 5 minutes recovery
  • 20 x 200m - 30 seconds recovery
  • 10 x 400m - 60 to 90 seconds recovery
  • 5 to 10 kilometre runs

Energy System recruitment

Although all energy systems turn on at the same time, the recruitment of an alternative system occurs when the current energy system is almost depleted.

The following table provides an approximation of the percentage contribution of the energy pathways in individual sports. (Fox et al. 1993)

Sport ATP-PC and LA LA-O2 O2
Basketball 60 20 20
Fencing 90 10  
Field events 90 10  
Golf swing 95 5  
Gymnastics 80 15 5
Hockey 50 20 30
Distance running 10 20 70
Rowing 20 30 50
Skiing 33 33 33
Soccer 50 20 30
Sprints 90 10  
Swimming 1500m 10 20 70
Tennis 70 20 10
Volleyball 80 5 15

Article Reference

This article first appeared in:

  • MACKENZIE, B. (2003) The best way to develop your athlete's Energy Pathways. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 2 / June), p. 6-8

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (2003) The best way to develop your athlete's Energy Pathways [WWW] Available from: [Accessed

About the Author

Brian Mackenzie is a British Athletics level 4 performance coach and a coach tutor/assessor. He has been coaching sprint, middle distance, and combined event athletes for the past 30+ years and has 45+ years of experience as an endurance athlete.