Soccer is a multifaceted team sport that requires well-developed speed, agility, balance and power to be played at an elite level [1
]. In addition to possessing high levels of physical fitness, knowledge about the game and a good decision-making process are the key abilities [2
]. The modern game is characterized by dynamic movements such as short and long sprints, impulsive reactions and quick changes-of-direction (CoD) [6
]. Actions such as these are known to determine soccer performance and can be divided into categories related to sub-maximal speed, acceleration and CoD [7
]. High level CoD performance requires a combination of speed, balance, muscular power and coordination [8
Previous cross-sectional studies examined the relationship between jump [9
], balance [9
], sprint [7
] and CoD performances in soccer. According to these studies, jump performance accounted for 45% of the variance in CoD performance in elite soccer players [13
]. In addition, there is evidence that sprint and CoD performances were moderately correlated (25–35% of shared variance) in elite players [13
]. Furthermore, Yanci et al. [7
] showed that the correlation between jumping and CoD varied depending on the characteristics of test types. Similarly, Sekulic et al. [12
] reported moderate to large correlations (0.40–0.58) between CoD and balance performances in male soccer players.
It is unknown why the above discrepancies between studies exist though one plausible, yet unresearched, factor could be the different physiological profiles associated with players’ playing positions [15
]. For instance, strikers and full backs spend 20–40% more time sprinting than do midfielders or defenders [1
]. Despite this, just one study, in recreational soccer players, conducted by Goral et al. [8
], revealed that CoD performance was significantly worse in the midfielders compared with the goalkeepers (p
< 0.05) and strikers (p
< 0.05). Based upon the agility t
-test results, midfielders were found to be significantly faster than goalkeepers (p
< 0.05), whilst no differences were identified between players in other positions (p
> 0.05). Thus far, several studies have examined the CoD performances of elite soccer players. However, the lack of studies that have evaluated CoD characteristics of soccer players, according to their on-field position, must be addressed. To optimise soccer-specific performance testing and training, research should be conducted to evaluate the relationship between CoD performance determinants, such as linear sprint speed and jump performances, with respect to a player’s position [1
]. In light of the above, the main aim of this study was to determine the associations between measures of CoD, with and without the ball, and linear sprint speed, jump performance, and dynamic balance, with respect to playing position, in elite male soccer players. With regard to the relevant literature, we hypothesized that there would be significant differences in these factors across playing positions, potentially due to the varied demands imposed within position [8
We believe this study is the first to examine the relationship between a CODAT test, with and without the ball, and proxies of speed, jump performance, and dynamic balance in elite soccer players. Overall, moderate to large correlations were observed between CODAT tests and linear sprint times, jump performance and dynamic balance. Additionally, there were differences in these associations dependent on players’ on-field positions.
As expected, the results of this study demonstrate that the balance, jump performance, speed and CoD relationship in elite soccer players differ according to the specific demands of soccer play. In this way, short sprint speed is an important determinant of a player’s ability to change direction whether they are in possession of the ball or without the ball. On this basis, short sprint speed should be a priority for coaches to address as it is likely to be important across all situational variables within a game of soccer.
Previously, several CoD, jumping, balance and speed tests in elite soccer players were proposed as necessary assessments for that sport [8
]. However, few studies have examined the possible relationships between these outcome measures with regard to players’ positions. Our results support the findings previously reported by Kapidzic et al. [6
], who found a significant correlation between the 10-m acceleration test and the zig-zag preplanned CoD test results (r = 0.34; p
= 0.01). The strong influence of sprinting performance on CoD scores is a logical consequence of the nature of this test, as it is considered a preplanned agility test with a moment of zero velocity occurring throughout test execution.
Although different combinations of plyometric, strength and complex training could assist in the development of this capacity for elite soccer players [29
], the focus of neuromuscular training should be towards improving CoD by simultaneously developing jump performance, acceleration, and maximal sprinting speed capacities [11
]. In this way, a coach can adopt several complementary training modalities, such as short sprint and plyometric training, which can independently contribute to the development of CoD in soccer players. Future studies should focus on collecting longitudinal data to confirm the current observations regarding the development of CoD within elite soccer players.
The associations observed between horizontal jumping, balance test performance and CoD ability suggest the influence of neuromuscular factors involved in rapid CoD, in addition to some cognitive abilities [11
]. In addition, the biomechanical and physiological similarities between jumping and CoD, which are observed throughout each “stop-and-go” movement during these actions, could be the reason behind the positive associations observed between jumping abilities and CoD scores. With these points taken together, a player must possess the physical attributes to efficiently negotiate the CoD demands of soccer, but also the cognitive capability to perceive and react within a very short timeframe during play. Thus, the influence of these factors on pre-planned CoD performance development and the use of further dynamic tests (on stabliometric platforms and using unstable surfaces) that mimic the nature of dynamic movement, should be considered in future studies with tests to determine true agility performance yet to emerge in the literature.
Concerning players’ specific field positions, some relevant and novel relationship were also found. Positional challenges are determined by the varying physical demands imposed on players during soccer matches in the different areas of the field. For instance, although full backs require high speed and muscular power to pass and evade opponents along a relatively straight course, midfielders must be able to accelerate with changes of direction on a more frequent basis [15
]. Information such as this could therefore be useful for the identification of game-specific strengths and weakness of players with regard to their specific playing position, thus facilitating a more focused training regime. On this, Brahim et al. [30
] showed that midfielders tend to have the best CoD ability. According to Boone et al. [15
], strikers are significantly faster than players in all other positions. This was reinforced by Gil et al. [31
], who found that strikers were the fastest players on the team with goalkeepers being the slowest. Davies [32
] stated that players spend most of a game without possession, underlining the importance of addressing speed and agility both with, and without, the ball. Coaches must consider these differences in formulating training programs for players and our results further contribute to the knowledge on the highly variable challenges associated with the different playing positions in soccer.
One novel aspect of our findings was the significant association observed between balance and CoD test performances observed for all players. Thus, from these results, it may be suggested that the motor control required for optimal CoD in soccer is partially dependent on dynamic balance capabilities. Balance has rarely been studied in relation to CoD ability, although some researchers have previously noted its importance in enhancing CoD [10
], whilst others have recognised it as a characteristic of efficient CoD [29
]. The influence of balance on CoD could relate to one’s ability to accurately coordinate the timing and action of skeletal muscles [33
] thus maintaining appropriate postural stability and, therefore, the ability to maintain balance [22
]. This hypothesis could be further verified through analysis of the patterns of motion, along with the mechanical demands, of the shuttle run test that was performed. For the successful execution of this test, the ability to perform rapid accelerations and decelerations, and to quickly change position from side to side, as in soccer play, is crucial. Given that these actions cause frequent perturbations of the center of gravity, which requires efficient neuromuscular control, it is reasonable to assume that players’ ability to efficiently maintain dynamic balance may positively affect the high-speed athletic maneuvers required in soccer. It is interesting that CoDwb shared a weaker relationship with YBT in strikers and though it is unclear as to why this result occurred, coaches could consider this finding when formulating training programs for strikers, defenders and midfielders alike.
Accordingly, exercises to improve CoD, and to develop dynamic balance, must be given due consideration by coaches [34
] with potentially less emphasis placed on this in attacking players who are in possession of the ball. Moreover, further studies are required to appropriately evaluate the additive advantage of combining balance training with more traditional forms of speed and power training. Similarly, researchers should also consider the potential of alternative characteristics, such as anthropometrics and muscle strength, to impact upon YBT performances [22
This study is not without limitations; the sample size of each positional group was small. Therefore, this study is preliminary. However, it is difficult and almost impossible to recruit large sample sizes in elite sport, especially in a highly professionalized elite sport such as soccer. While our results provide interesting information for coaches and strength and conditioning specialists, they have to be interpreted with caution and should be verified in future studies. Another limitation related to the fact that only two teams from the same league were included; therefore, it is unknown if different results would be observed when including elite players from other countries and competitive levels.