Previous studies, where high-level fencers changed targets during the lunges showed that when the number of possible responses is increased during attacks (uncertainty), simple reaction times (RT) and choice reaction times (CRT) also increase, but do not affect the coordination of the movement pattern (Gutierrez-Davila et al., 2013a; 2013b).
In both studies, we have confirmed that the velocity of the center of mass (CoM) at the end of the horizontal acceleration phase decreased as uncertainty increased. Despite this, we should exercise caution when making this statement, since the reduction in speed of the CoM could be related to the adjustments made when increasing the CRT. We should indicate that the CRT required to process the target change occurs during the acceleration phase.
The protocols used in the two mentioned studies do not permit us to confirm the independent effect of the uncertainty regarding the speed of the CoM, in addition to the methodological drawbacks posed by the fact of comparing velocity values among different movement patterns (with or without a target change). In this work, the methodology was designed to test the independent effect of uncertainty on the velocity of the CoM. To do this, under the two experimental conditions, we used attack actions where no target change occurred and uncertainty was considered to be the level of probability that an error might result from that attack action, implying an inhibition of the planned movement pattern.
This type of uncertainty, due to the probability of error during the execution of the planned movement pattern, is common in fencing and is related to the tactical component whereby is possible to reduce uncertainty and execute a rapid and precise movement pattern (Borysiuk and Waskiewicz, 2008; Czajkowski, 2009).
The relevance of the tactical component in fencing goes far beyond trying to reduce the uncertainty prompted by the stimuli that trigger the response and thereby shorten the time to process information (Schmidt and Lee, 2011; Stein, 2008), as the fencer also uses tactics to predict the defensive action of the opponent during the attack. In this way, it is possible to reduce uncertainty during the movement time and execute a predetermined attack action meant to mislead the opponent.
In view of the above, when we analyze attack actions in fencing against distant targets, the concept of anticipation refers to a conscious action, as part of the tactical component or strategic expectancy, through which the opponent's defensive movements are predicted during the attack (Gao et al., 2009). In this predictive sense, we could consider that the attacker's probabilities of anticipating the defender will depend on the level of uncertainty that the fencer has before beginning the attack.
The influence that this type of uncertainty has during attack actions in fencing could be explained by certain findings in cognitive neuroscience. Currently, two main pathways are believed to transmit the visual information gathered through the primary visual cortex to other cortical areas. Each of these routes provides information with different uses and functions for the visual perception of objects (Goodale and Westwood, 2004; Milner and Goodale, 1995; Ungerleider and Mishkin, 1982). The dorsal pathway or system (directed towards the posterior parietal lobule) identifies the location of objects and their movements while the ventral visual pathway or system (directed towards the cortex of the inferior temporal lobule) is responsible for identifying objects.
For sports movements requiring anticipation, Van der Kamp et al., (2008) have described how the visual perception of information sources that regulate the reaction response (RR) require the synchronized interaction of the two visual systems, each serving its respective function. Both systems work at different points in space and time. That is, the information used by the dorsal stream is immediate, relatively rapid, and associated with automatic movements in which it is not necessary to be conscious of how the movement is made or of what type of information is used (Goodale and Westwood, 2004). In contrast, the ventral stream is associated with explicit consciousness, enabling the identification of the action most appropriate to reach the target. The ventral stream can also at times have a certain control over movement when the situation is not completely favorable to the dorsal system, as may occur in situations involving uncertainty during an action (Goodale and Westwood, 2004).
Despite the above-mentioned differences, the two systems work in close coordination (Glover, 2004; Van der Kamp et al., 2008), although, depending on the situation, the control of the movement can be dominated more by one visual stream. Therefore, when an attack action has a high probability of beating the opponent (without uncertainty), the movement pattern is made automatically without the need for conscious movement (Gao et al., 2009). In this situation, the dorsal visual system would control the movement. In contrast, uncertainty in the attack (the probability of error due to an unexpected defensive action by the opponent) would require continuous visual information concerning the defensive actions of the opponent. This situation would require mastery of the ventral system and thus a reduction in the speed to maintain the precision of the action.
The aim of this study is to determine the effect that uncertainty due to the possibility of error caused by an unexpected action by the opponent during the simple lunge in fencing exerts on the temporal parameters of the reaction response as well as on the speed of the execution. According to the above-mentioned researchers, the hypothesis is that the uncertainty due to an unforeseen action by the opponent during the execution of a programmed movement pattern will increase the temporal patterns of the response reaction and reduce the speed of the center of mass.
The participants were 18 fencers (14 male and 4 female) with over five years' competitive experience at regional level. Ten of them were specialists in epee and the other eight were specialists in foil (age 25.1 [+ or -] 6.5 years; height 1.75 [+ or -] 0.08 m; mass 70.5 [+ or -] 10.9 kg). All of the participants were informed about the study and their participation and gave their written consent to participate in this study, following the guidelines of the Ethics Commission of the University.
Two Dinascan/IBV force platforms, A and B, (Institute de Biomecanica de Valencia, Valencia, Spain) were used, operating at 500 Hz, permitting the recording of the horizontal component of the reaction force from each force platform, ([F.sub.AX] and [F.sub.BX]). A video camera, Casio EX FH20, at 70 Hz recorded the sagittal plane of the fencers, from which the position of their CoM was determined before starting the movement. A projector connected to a computer with an external programmable card projected a black circle (the target), 0.1 m in diameter onto the geometric center of a white screen of 0.7 x 0.55 m, which acted as a plastron. The geometric...