Endurance

How to develop a good solid base on which to develop speed.

Brian Mackenzie explains the body's energy systems and the objective of endurance training.

A good base of endurance and strength is important before the specific speed and strength requirements of the athlete's sport/event can be developed, if you wish your athlete to ovoid injury. The objective of endurance training is to develop the energy production system(s) to meet the demands of the sport/event.

What are the energy production systems?

In the human body, food energy is used to manufacture adenosine triphosphate (ATP) the chemical compound that supplies energy for muscular contraction. Since ATP is in very low concentrations in the muscle, and since it decreases only to a minor extent, even in the most intense voluntary contraction, tightly controlled energy pathways exist for the continual regeneration of ATP as muscular contraction continues. For continuous exercise, ATP must be re-synthesised at the same rate as it is utilised. There are four types of endurance: Aerobic, Anaerobic, Speed and Strength endurance. A sound basis of aerobic endurance is fundamental for all events.

The distribution of aerobic to anaerobic endurance for the runner is approximately:

Aerobic Endurance

During aerobic work (aerobic means 'with oxygen') the body is working at a level that the demands for oxygen and fuel can be meet by the body's intake. The only waste products formed are carbon dioxide and water. These are removed as sweat and by breathing out.

Aerobic endurance can sub-divided as follows:

• Short aerobic - 2 minutes to 8 minutes (lactic/aerobic)
• Medium aerobic - 8 minutes to 30 minutes (mainly aerobic)
• Long aerobic - 30 minutes + (aerobic)

Aerobic endurance is developed through the use of continuous and interval running

• Continuous duration runs to improve maximum oxygen uptake (VO2max)
• Interval training to improve the heart as a muscular pump

Aerobic threshold

• The aerobic threshold, the point at which anaerobic energy pathways start to operate, is considered to be around 75% of the athlete's maximum heart rate. This is approximately 20 beats lower than the anaerobic threshold.

Anaerobic endurance

During anaerobic work (anaerobic means 'without oxygen'), involving maximum effort, the body is working so hard that the demands for oxygen and fuel exceed the rate of supply and the muscles have to rely on the stored reserves of fuel. In this situation waste products accumulate, the chief one being lactic acid. The muscles, being starved of oxygen, take the body into a state known as oxygen debt. The body's stored fuel soon runs out and activity ceases - often painfully. Activity will not be resumed until the lactic acid is removed and the oxygen debt repaid. Fortunately the body can resume limited activity after even only a small proportion of the oxygen debt has been repaid. As lactic acid is produced the correct term for this pathway is lactic anaerobic energy pathway. The alactic anaerobic pathway is the one in which the body is working anaerobically but without the production of lactic acid. This energy pathway can exist only so long as the fuel actually stored in the muscle lasts, approximately 4 seconds at maximum effort.

Anaerobic endurance can be sub-divided as follows:

• Short anaerobic - less than 25 seconds (mainly alactic)
• Medium anaerobic - 25 seconds to 60 seconds (mainly lactic)
• Long anaerobic - 60 seconds to 120 seconds (lactic +aerobic)

Using repetition work of relatively high intensity with limited recovery can develop anaerobic endurance.

Anaerobic threshold

The anaerobic threshold, the point at which lactic acid starts to accumulates in the muscles, is considered to be somewhere between 85% and 90% of your maximum heart rate.

Speed endurance

Speed endurance is used to develop the co-ordination of muscle contraction in the climate of endurance. Repetition methods are used with a high number of sets, low number of repetitions per set and intensity greater than 85% with distances covered from 60% to 120% of racing distance. Competition and time trials can be used in the development of speed endurance.

Strength endurance

All athletes need to develop a basic level of strength endurance. Examples of activities to develop strength endurance are - circuit training, weight training, hill running, harness running, Fartlek etc.

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 very short period of time.

Running at a low intensity, as in gentle jogging, means that an athlete can sustain activity for a long period of time. Training introduces another variable, and the sprinter who uses sound training principles is able to run at a high intensity for longer periods of time. Similarly, the endurance athlete who uses sound training methods can sustain higher intensities during a set period of time. There is a relationship between the exercise intensity and the energy source.

Energy Pathways

D. Matthews and E. Fox, in their book, "The Physiological Basis of Physical Education and Athletics", divides 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 ADP
• PC - Phosphate-creatine : a chemical compound stored in 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 restricted by time. In other words, once a certain time elapses that specific pathway is no longer used. There is some controversy about these limitations but the general consensus is:

The result of muscle contraction produces ADP which when coupled with PC (stored in the muscles) regenerates ATP. Actively contracting muscles obtain ATP from glucose stored in the blood stream and the breakdown of glycogen stored in the muscles. Exercise for longer periods of time requires the complete oxidation of carbohydrates or free fatty acids in the mitochondria. The carbohydrate store will last approx. 90 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 irons. The accumulation of hydrogen irons 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:

The Aerobic Energy System

The aerobic energy system utilises proteins, fats and carbohydrate (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 normal 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 places demands on the system to cope with lactate production. Running at this level assists the removal and turnover of lactate and 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 boarder 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 top 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 basically 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 certain sports. (Fox et al 1993)

About the Author

Brian Mackenzie is a UK Athletics level 4 performance coach and a coach tutor/assessor. He has been coaching sprint, middle distance and combined event athletes for the past 20+ years and has 35+ years experience as an endurance athlete. Brian can be contacted through his website at www.brianmac.co.uk

Article Reference

• Mackenzie B. (2003), "How to develop a good solid base on which to develop speed", Brian Mackenzie's Successful Coaching (ISSN 1745-7513), Issue 1

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