The aim of the present study was to investigate whether an internal and external focus of attention could promote greater postural stability. Also, we wished to explore how the process of postural control differs between groups of different levels of expertise.
In the present study there were no significant differences in the regularity of COP between three research groups during QS in both the AP and ML planes. This result is in line with other studies investigating the regularity of COP among athletes in trials which included a dual task condition (23), a more specific posture like a ballet position (24), or more demanding balance conditions like eyes closed or an unstable surface (25). In all mentioned works, the experimental conditions led to an increase in entropy among athletes compared to the CG. Maintaining an upright body posture is quite easy for all healthy participants. Therefore, we assumed that professional sports training does not transfer balance improvements to simple motor tasks or QS does not require “elite level” balance.
Biathletes were characterized by lower values of entropy, especially during the SP and AT trials and both in the AP and ML plane, compared to the other two groups, which confirms our first research hypothesis. This result stands in contrast with the research cited above, where an additional or more demanding balance task led to a decrease in COP regularity among athletes. However, we must consider a few important aspects of this examination. First, we cannot ignore the fact that for professional biathletes, SP and AT trials are a familiar position. Years of professional training made it more automatic and required less attentional resources. Therefore, additional tasks should not interfere significantly (or at least significantly less than not trained groups) with the main motor task. This claim corresponds well with Fitts’s Motor Learning Theory (34). According to the theory, after many years of sports training, biathletes reached the third (autonomous) stage of motor learning. It can be also observed in our results, specifically in the increased regularity of the COP signal during AT trials compared to QS and SP in the AP plane, as well as no significant changes between trials in ML plane. These outcomes are contrary to the CG and BG results, which are in line with the “constrained action hypothesis.” Introducing an internal and external focus led to a decrease in COP regularity in both groups. However, there were no differences between SP and AT trials. Therefore, the two types of additional focus included in this research triggered the same changes in COP structure, which does not confirm our second research hypothesis. However, there is strong evidence that biathletes present different postural control strategies, which ensures motor success.
To achieve good results, elite biathletes aim at decreasing postural and rifle sway in the SP (5). Performing a shot as soon as a stable position is obtained is a crucial factor for success (35). Efforts put towards following this strategy can be observed in the experimental data. Postural sway and the regularity irregularity of the COP signal tend to be positively correlated (36). This was also confirmed by research by Raffalt et al., who observed that sport rifle shooters are characterized by a higher regularity of the COP signal and lower body sway compared to non-shooters during single-legged standing. The same pattern of changes in the measured data can be also observed in our research; biathletes were characterized by a significantly more regular COP signal in positions closely related to their competition.
When competing, biathletes perform in quasi constant conditions. They use the same sportswear as during their training, the target is at a familiar distance, and they shoot only after they adjust to the environmental conditions and when they can stabilize their posture. From this perspective, we can say that biathletes’ posture is controlled mostly in a close-loop pattern even though shooting is a single short non-cyclic movement. In our study, it is even more clear in SP and especially during AT conditions as aiming was not followed by a shot. A main goal in order to achieve success in shooting is to minimize the movements of the gun barrel. This, however, requires a high level of postural stability (7). In addition, movement variability in a performed task diminishes in the process of professional training (37). Therefore, we can also expect that in experimental conditions biathletes will perform significantly better in this aspect compared to other groups. In the present study, as expected, biathletes were characterized by significantly lower values of SampEn during AT compared to QS. We can therefore conclude that their level of proficiency is reflected to some extent in our data. Another conclusion could be that well-developed postural control mechanisms can play a significant role in achieving success in a competition.
Based on the current research, Biathletes are characterized by more regular signal of COP. This means that they have more predictable, repetitive pattern of postural control. It is speculative whether to introduce additional disturbing external factors into the training regimen in order to push the limit a little further. There is a chance that the athlete, knocked out of the comfort zone, will perform worse due to the disturbance in their repetitive and known patterns. It seems to be enough that they have to deal with fatigue and changing weather conditions. Other aspects influencing the final result, like e.g. size of the aim, distance to target, shooting equipment and position, are constant. In our opinion one the aims of the training is to develop a postural control pattern, that ensures their sports success and overstimulation might decrease accuracy in shooting. For sure, we can monitor the progress by observing the changes in signal entropy over time, for example during training program which provides valuable information of athletes progress.
This study does present a few limitations. The main one would be that biathletes begin shooting in a heavily fatigued state after covering a certain cross-country distance. In our research, they performed a balance examination at full rest. Secondly, during their competition biathletes perform a shot after acquiring a good position, when in our study they had to stay in a position concentrated on the target for the desired time. Lastly, our results for the beginners group were closely related to the CG, which can suggest that three months of training is not sufficient for inducing changes in the postural control system.