The Body in Swimming: Anaerobic Metabolism

Anaerobic Metabolism

Also known as anaerobic glycolysis, involves the process of glucose converting to lactic acid. ATP recycling during this period is much slower than the previously described ATP-CP system, this will mean that once this anaerobic metabolism becomes the main energy source athletes will be unable to maintain maximum speed. Anaerobic Metabolism, during Intense Swimming, occurs almost immediately, however, it does not become the main contributor of energy until the ATP-CP system depletes. Both anaerobic metabolism and ATP-CP energy source are both equal from approximately 3 to 10 secs of maximum effort. Thereafter, the creatine phosphate-ATP recycling ceases and anaerobic metabolism becomes the primary energy source – usually for the last 20 secs of maximum effort. During this transition, there is a decline in the swimmers power of approximately 10% (Newsholme etal. 1992).

Training Anaerobic Metabolism

Training does appear to increase both the quantity and activity of enzymes of anaerobic glycolysis (Costill, Fink, and Pollock 1976; Costill 1978; Jacobs et al. 1987). However, there is a contradiction to this. Sprint training provides an ideal platform to bring about improvements anaerobically, endurance training, on the other hand, seems to hinder this effect. This is the hardest hurdle to tackle when considering this form of training as many swimmers strive to improve both their endurance base and speed, however, the former seems to reduce the rate of anaerobic metabolism. It has been suggested that the anaerobic system is at it’s optimum when athletes are untrained – evidence cited from the fact many swimmers experience their best sprint performances after long breaks.

Other than those training solely for 50m events, all that swimmers training for greater lengths can hope for is to maintain their innate level of providing energy from anaerobic metabolism, although, large volumes of endurance work will most likely decline the swimmers level of anaerobic metabolism.

Taper may allow middle distance and distance swimmers to counter this effect, although, this may not be long enough and the swimmers innate ability may not return until endurance training has been significantly reduced or ceased for several weeks. Swimmers who have seen great improvements in their endurance, may see good performances despite the loss in speed. Sprinters on the other hand will not produce a good result if they cannot regain their speed.

In conclusion, anaerobic metabolism influences a swimmers speed more significantly than ATP-CP system, which only accounts for the first few seconds in a race. Developing a swimmers anaerobic ability should not be seen as a high priority in athletes who train for events greater than 50m as endurance training hinders and may even cause a decline in anaerobic metabolism, although, sprint training may maintain the swimmers innate ability. Sprinters must take great care in the volume of endurance training they do as it can take very long periods for a swimmer to regain his/hers innate ability. It could be argued that a sprinter’s training would be more effective if it had a greater focus toward improving muscular contraction and anaerobic metabolism rather than improving any aerobic capacity; if any at all.

Yours in Swimming,



The Body in Swimming: Training the ATP-CP System

Adenosine Triphosphate – ATP

ATP is made up of some protein, a chemical called adenosine and three molecules of phosphate shown below. These are joined together by energy to form ATP molecules. ATP is the only substance that can provide energy for our muscles to move, or contract. All the other chemicals that provide energy are used to rebuild ATP when it has broken down to release it’s own energy.


When the muscles require energy, they ‘call’ upon the ATP molecule to split from one of it’s phosphate molecules, releasing energy in the process. This leaves a molecule called Adenosine diphosphate (ADP), adenosine and the two remaining phosphate molecules.

To rebuild the ATP, and therefore, allow it to release energy once more, a phosphate molecule must be found as well as a form of energy. ATP can not move to muscles which are working from other parts of the body, therefore, when a molecule loses its energy (and some phosphate), other sources of energy must be found within the same fibre in order to avoid becoming severely fatigued – which all must be done almost immediately.

ATP does not just have to rely on finding another phosphate molecule, there are substitutes that can be used. This also applies to the energy source it acquires. For the purposes of this article, I will focus on one of the four chemicals: creatine phosphate.

Creatine Phosphate

This chemical provides the quickest source of energy and replacement phosphate to rebuild the ATP. It contains both creatine and one molecule of phosphate, with energy binding the two. These both combine with the ADP to allow the reformation of an ATP molecule and thus, energy for use in muscular contraction.

Although the rebuild process can be completed extremely fast, the drawback is that is can only be used for approximately 4-5 secs of max effort (di Prampero 1971) and therefore, a maximum rate of muscular contraction can only last for 4 to 6 secs.

A very small amount of CP is available afterward as phosphate and energy will be utilised in replacing ATP. Although, after a period of recovery and once all the ATP have been reformed, the left over phosphate will recombine with the creatine, formed with energy.

ATP-CP System in Training

Experts have, I feel, overstated the importance of training this system. Although it is observed that increasing the storages of ATP and CP results in athletes maintaing maximum speed for longer, the benefits are minor and would only likely be seen in 25 and 50m races.

Even in those shorter distances, it is hard to identify any reason why it would be important to develop this system. The normal rate of ATP-CP metabolism can provide energy for almost all of the maximum speed during a race, with the exception perhaps for the legs during the start or turns. The latter, however, is accommodated anyway as training alone will increase ATP and CP supplies as a by-product.

For even the improvements training the ATP-CP system would produce – likely less than 0.20 sec in a 25 or 50 event – time would be better spent developing other areas. Apart from technical training, a swimmer can significantly improve their maximum speed by increasing the size and strength of their muscle fibres (in particular groups) to improve power, and by recruiting fibres at a faster rate in an improved pattern. These can be both improved through land training and also in-water sprinting, the latter of which should be prioritised in order to allow muscle-fibre recruitment to occur in patterns which are in the correct sequence.

In short, the improvements seen in the ATP-CP system during training is sufficient enough not to require specific development. Training for maximum speed is better spent on technique and improving muscular strength as well as recruitment patterns.

Yours in Swimming,