## F-v profile in the game

In the previous article, we have seen how the force-velocity profile and the maximum power are fundamental parameters for sprint capacities and in particular the related horizontal components (3, 4).

We have also seen the relationship between force and speed during a maximal sprint (see fig. 1).

`Figure 1`

Is it possible to get the individual F-V profile (as obtained during a 30-m max sprint) even from the data of an official match? In this case, the fitness coaches could obtain the profile in an easier way, without having to perform a maximal test, generally not appreciated by the athletes.

Six players (FC SÜDTIROL – Italian third division) were monitored during a single league game. Figure 2 shows the summary graph relating to a player. For ease of reading, on the vertical axis, the acceleration has been inserted instead of the force, since the acceleration, neglecting the friction of the air, is linked to the force only by the mass of the individual.

```
Figure 2```

The blu dots refer to a maximal sprint (test). The red dots represent all the speed & acc combinations during the match (game). The upper limit of the dots during test and match obviously does not correspond to the straight line of the F-V model; therefore, F0 and V0 are not visible (see Fig. 1 and previous article). A first matter, in comparing the two models, consists in identifying the slope of the straight line obtained from the data of the match in order to identify with reasonable certainty the points F0 and V0 of the ideal model

The behaviour of the player of fig. 2 is quite clear:
– he didn’t reach the peak speed obtained in the test
– he was very close to the maximal acceleration obtained in the test.
In this case, the upper limit of the dots (red), which represent the game, could suggest that the slope of the ideal line F0-V0 is very similar to the one that could be drawn for the (blue) dots relating to the test.
On the other hand, the player shown in fig. 3 was almost able to reproduce during in the game the profile obtained in the test.

`Figure 3`

The player which is shown in fig. 4 has been able to reach higher acceleration peaks than those achieved during the test.

```
Figure 4```

The results obtained from the six monitored players are reported in table 1.

`Table 1`

There isn’t a substantial difference in the maximal speed obtained between the test and the game.
However, no athlete was able to reach the acceleration peaks achieved in the test (-6.27% on average). It could be reasonably linked to the fact that during the game it is difficult to start a sprint starting from a standstill; or that the game conditions (i.e. combine performance and technique) do not allow the “maximum power” to be fully expressed.

It would also be interesting to check if player 1, who managed to improve his maximum acceleration values in the game so well, during the test actually managed to fully express his potential. It is evident the importance of correctly motivating the players before asking them to perform a maximal test in order to then compare the data obtained with those of the games.
In conclusion, from these first results, using only the training and/or match data may be insufficient to construct the maximal PV ratio, although, as we have seen, there are some common points between the test and the game, such as the maximum speed and the slope of the two relationships.

The F-V profile from the match may not represent the maximal F-V profile of the athlete but can be considered a tool for comparing the athlete’s performance over time. It can be also useful to compare the performance before and during the return to play after an injury. Finally, it could be interesting to compare the F-V profile of an athlete with the average F-V profile of the teammates playing in the same position/role.

On the other hand, knowing the maximum sprint capacity of an athlete through the F-V relationship by means of a test also gives information on the quality of acceleration. In fact, some studies have shown that during a 4-second sprint (a typical action in football) with an equal force exerted on the ground, the athlete who obtains the greater distance is the ablest to orientate force forward (Morin et al, 2011). This topic will be discussed in the next article.

BIBLIOGRAPHY

MORIN, PASCAL, SAMOZINO. Technical Ability of Force Application as a Determinant Factor of Sprint Performance. Med Sci Sports Exerc. 2011 Sep;43(9):1680-8.

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