#### Metabolic power: is it all so simple? (part 1)

A performance analysis based on metabolic power values

Recently the estimate of metabolic power has started playing a key role in the conditioning training of soccer players. Even though the approach we adopted has its own limitations and has been widely debated since 2005, there’s no doubt that the evaluation of metabolic power is very useful for calculating energy expenditure during phases of play characterized by frequent accelerations and decelerations. The metabolic power required for these phases can undergo significant variations and may reach peaks of 100 W∙kg-1, a value which corresponds to an oxygen demand of 290 ml /kg min and can thus be considered higher than any possible maximum value of oxygen consumption. Indeed, taking into consideration the average value of metabolic power produced during an exercise may be useful to understand its intensity.

Those who adopt this approach for the first time may find convenient to refer to metabolic power as the single parameter for some considerations concerning training intensity. Nevertheless, important data that the mere value of metabolic power is not able to emphasize might not be adequately taken into account due to oversimplification.

The analysis of a performance cannot be focused exclusively on the research of a certain average value of metabolic power, since this method may be significantly misleading. As a matter of fact, metabolic power varies according to:

- the role of the player: the difference between a central defender and a midfielder may be higher than 4 W∙kg-1 during a match. Thus it’s not logical to set an average team value which should be valid for all the players;
- the kind of exercise performed: submaximal interval trainings produce an average power that is much higher than that estimated in small-sided games during which the exertion perceived by the players is considerably higher. In this case, the average metabolic power value cannot be satisfactory enough to describe in details the exercise;
- the relationship between exercise and recovery;
- the dimensions of the pitch and the number of players involved in the training.

Thus, it is clear that whether a player reaches or not the average metabolic power value (which is the same for all of us) is not relevant to the real effectiveness of the training.

In the next articles we’re going to tackle some fundamental issues which will contribute to clarify these concepts. Specifically, we’re going to deal with the following topics:

- SUBJECTIVITY: athletic characteristics can differ according to subjects. The maximal aerobic power values in a soccer team may vary up to 30% and the same training exercise performed by more athletes at the same average power has a different relative intensity for each of them.
- REQUIRED POWER AND ACTUAL AEROBIC POWER: what is the aim of the training drill and which are the metabolic pathways targeted by exercise?
- METABOLIC POWER AND OTHER IMPLICATIONS: which are the parameters that distinguish an effective drill from an ineffective one? We’re now discussing about athletic goals, but it’s important to bear in mind that in team sports an exercise can be considered effective if it has satisfied certain technical and tactical demands.

The second part of this article will deal with “The issue of subjectivity“.

August 10th, 2015 – Here the podcast “The calculation of metabolic power” (Prof. di Prampero interviewed by Dr Andy Franklyn-Miller).