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Purpose: The development of a motion capture system leads to fast and accessible ways of precise testing of athletes and their motor abilities. The striking performance in martial arts and combat sports requires measuring velocity in the context of successful contact with the target. The aim of this study was to present the novel kinematic target effect coefficient and its possible use as a speed accuracy benchmark of performance based on the example of taekwon-do roundhouse and frontal kicks. Methods: The stereophotogrammetry motion capture setup consists of 10 infrared cameras (NIR Vicon MX-T40). Analysis includes 180 kicks (roundhouse and frontal kicks) performed by 15 adult participants on a master level in taekwon-do. The kinematic target effect comparison includes two targets – a training shield and a table tennis ball hanging from the ceiling. Markers were placed on the lower extremities of participants. Spatial-temporal variables were registered for both kicking legs, techniques, and target types. Results: Both roundhouse and frontal kicks revealed target and marker dependent differences during its execution. The kinematic target effect coefficient values differ for the specific marker and kick type. Conclusion: The wireless motion capture systems could be helpful in the training process and an athlete’s evaluation before sports competitions.

Background Anxiety could be felt even in objectively peaceful situations, but a vision of conflict could result in increased stress levels. In this article, we aimed to identify hidden patterns of mental conditions and create male profiles to illustrate the different subgroups as well as determinants of anxiety levels among them in accordance with proximity to a possibility of direct exposure to military action. Methods A sample of Ukrainian males, in duty as conscripts to military service (n = 392, M±SD = 22.1±5.3) participated in a survey. We used the 36-Item Short Form Health Survey, and State-Trait Anxiety Inventory. In addition to psychological indices, social-demographic data were collected. To discover the number of clusters, the k-means algorithm was used, the optimal number of clusters was found by the elbow algorithm. For validation of the model and its use for further prediction, the random forest machine-learning algorithm, was used. Results By performing k-means cluster analyses, 3 subgroups were identified. High values of psychological indices dominated in Subgroup 2, while lowest values dominated in Subgroup 3. Subgroup 1 showed a more even distribution among the indices. The strength of the relevance and main determinants of the prediction of the presented model mostly consisted of mental qualities, while socio-demographic data were slightly significant.

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BackgroundThe back kick (in taekwon-do terminology referred to as dwit chagi) is considered a powerful weapon in taekwon-do sparring. This paper attempts to identify the kinematic factors affecting the efficiency of the back kick on the basis of values obtained for foot and knee velocities and the duration of the kick. Material/MethodsThe study was based on 3 taekwon-do athletes (aged 16.3 ±0.6 years; weight 66.0 ±7.9 kg; height 172.0 ±7.0 cm). The case study relied on an Italian system called Smart-D, manufactured by BTS S.p.A., used for complex movement analysis. ResultsThe mean resultant velocity of the dwit chagi determined in this study was 6.00 ±1.39 m/s, and the kick's duration was 0.77 ±0.46 s. The mean maximum velocity was developed at the length of the leg equal to ca. 80% of its maximum length value. ConclusionsThe study shows that the resultant velocity of the kick correlates with the location of the foot (r = -0.86) and its velocity when aiming at the target (r = 0.98). Duration of the kick depends on the velocity of chambering up the knee (r = -0.65) and its extension directed at the target (r = -0.73) as well as the foot take-off (r = -0.69) and its lifting (r = -0.50) velocities.