9/24/2015

The match is an irregular interval load

The match is an irregular interval load


The football match is an open skills-based sport activity of acycled intervals. Open skills mean that the movement of the player is determined by the movement of the opponents and teammates. The acycled intervals are created by irregular distances and directions of various speed. These intervals may change by the game of the team, both as distances and intensity concerned. The average of the movement speed of an adult player is 6-7 km/h in 90 minutes. This movement intensity is equal to the speed of a faster walk. I must refer to an earlier article on analysis of matches, it can be observed well also here, that the football player performs more than half of the match with low intensity even in the highest leagues.
Each and every impact requires increased energy investment from the system due to the changing speed of movement and intensity of movement. The movement of the player is most similar to car driving. A car „consumes“ much more fuels during city transport, where it starts, stops, accelerates and slows down. Just like in a football match. 10-12 km of straightforward line running at a balanced speed and 10-12 km of movement performance, made up of 8-10 m sections with many changes of directions and speed cannot be compared. There is a significant difference between the two types of practices, investigating both the physiological effect and the coordination work.
The speed of movement of the football player changes dynamically. The high-speed work of several seconds is followed by a shorter-longer performance of moderate intensity. The proportion of the fast and slow work performance within the sections is one of the most important parts of the physical capacity. If the period of 45-55 minutes spent with active movement is broken down to 1,000 meters, running of 1,000 meter would take 4 minutes and 10-30 seconds. The distribution of load of this kind is not precise, because the athlete performs the active movement in 90 minutes in intervals of irregular speed. High intensity work, repeated at least once a minute, significantly determines the performance of work.

If the player can „gain strength“ quickly, his „condition is good“. Frequent repeat of the dynamic sections (figure 1) highly influences every movement performance. Characteristics of complex movements are changing direction, speed and force. 
Figure 1. GPSport. Papp 2011.






Due to the acyclic character of the football movement, the speed of movement and the related load cannot be evaluated with the cyclic-like running movement. The frequent changes of direction and speed occurring during the short intervals cause increased effort to a the musculature. This is why the value of cardiac frequency per minute is 130-140 during a straight line running of 10 km/h, while if the athlete turns or changes direction several times during the running at a speed of 10 km/h, the former value increases to 150-160. The stops and slowdowns - depending on the direction of the movement -, require even by one and a half-twice as much efforts from the football player than the accelerations. Their total effect improves the rate of the effort along with the load on the circular system.
Plenty of efforts affect the player in several seconds, but their duration is really short.
The movement of a player can be followed in the following graphic (figure 2) in an interval of 5 seconds. The rate of the forces (g) appearing during the complex movement is shown by three lines. The negative values show the rate of the force performed during a slowdown on the graphic. It can be observed well, that the player performs a bigger force during the up and down movement (red line) during acceleration, while during the side movements (green line), he must use the biggest force to stop. There is a similar effect in case of the back and forth movements (yellow line) as well. The football player must use more strength to stop or slow down while his body is in swing. In a match situation, the success of football-specific speed is determined rather by the speed of stop-slowdown than the skill of acceleration.
The volume of the forces (g) appearing during the movement changes depending on intensity of the movement. - g shows the volume of the force exercised during the slowdown and stop, while +g shows the volume of the force during acceleration. The complex stimuli affect the player in a quick and complex form, the reactions to the stimuli appearing in a millisecond are involuntary, however they cause contraction and muscle tension. The stimuli reach the musculature- and nervous system so quickly that they cannot be reacted to consciously. To the „training of reactions like this“ one of the most effective forms of training is the so-called reactive or plyometric force training. The effect mechanisms of „slowdown“ of movement (anisometric excentric), „stopping and keeping“ of the athlete (isometric) and „acceleration“ of the athlete (anisometric concentric) can be modelled here well. The relation of the nervous- and musculature system and the movement coordination level significantly influence success. Even 15-25 complex stimuli may affect the musculature in 5 seconds, arriving from several directions and it uses the speed of the contraction and relaxation of the muscle at a high level.
Figure 2.  GPSports Systems, Papp 2012.

The significant efforts during the complex movements increase the rate of load on the system. It is shown in the reaction of the circulatory system. While a uniformly straightforward movement leads to moderate cardiovascular reaction, a movement of short intervals at the same speed increases the cardiac frequency better. 
Table 3. (Bloomfield 2007Summary of a survey. Number of turns and changes of 
directions has been broken down to positions. It can be seen well, that defenders or forwards perform the most turns and changes of directions. It may play a more important role in training of football players, if a certain type of training, broken down to positions, is applied. In case of players moving the most right around the gate, the distances are shorter, but they include more changes of directions than in case of left and right defenders. The movements of the players on the left and right of the field are longer, thus the physical load is nearly the same, however with different characteristics.
The differentiated training is the basis of maximal improvement of performance. By the following table we can determine, how much the players should exercise of each given type of movements. The earlier articles discussed the physiological effects, now the character of movement will be put in focus. The practices must be different from one another both in technique and load on the circulatory system and the musculature. In certain sections of weekly exercises, it is practical to have the players performed different workouts in accordance with their positions. This way also the performance of the football player is improved better during a match.
 It can be observed in the abovementioned published table, that players playing in center of the midfield run more than their team mates footballing in the middle of the defense area. But it cannot be considered as their load is bigger than those of the middle defenders. The defenders - on the basis of the measurement of Bloomfield - perform by 20% more changes of directions and these mean a bigger effort to the system.

Table 3. Bloomfield 2007.
Turns
Forward
Midfielder
Defender
¼ turn
625
495
647
½ turn
94
96
92
¾ turn
5
8
4
Complete turn
7
9
0
Complex change of direction
20
10
17
Total changes of direction
748
608
822


Barros et al. (2007) compared the movement intensities of the players in the Brazilian championship (table 4). The movements performed in various speed domains were significantly different. The performances of 55 players were summarized and they were analyzed from speed of a walk to the zone of sprint runs. However Bloomfield and Barros investigated teams of different football cultures, the various physical profile of the positions was common in every survey. Those players were especially different from the average of the team, who play directly in front of the gate. Despite the shorter quantity of movements, the shorter distances include more turns and parallel to this more stops and starts. Therefore the physical activity of these football players is similarly high as that of their mates, who run more. The playing activity, reducing to a smaller area assumes an increased muscle work and anaerobic win of energy.


Table 4. Barros 2007.
Position
0 -11 km/h
11-14 km/h
14-19 km/h
19-23 km/h
>23 km/h
Total
movements


Half-time
1
Half-time
2
Half-time
1
Half-time
2
Half-time
1
Half-time
2
Half-time
1
Half-time
2
Half-time
1
Half-time
2

Centre
back
2860 m
2628 m
705
m
586 m
718 m
622 m
295 m
265 m
191 m
161 m
9029 m
Left or