To achieve good performance, athletes need to synchronize a series of movements in an optimal manner. One of the indicators used to monitor this is the order of occurrence of relevant events in the movement timeline. However, monitoring of this characteristic of rapid movement is practically limited to the laboratory settings, in which motion tracking systems can be used to acquire relevant data. Our motivation is to implement a simple-to-use and robust IMU-based solution suitable for everyday praxis. In this way, repetitive execution of technique can be constantly monitored. This provides augmented feedback to coaches and athletes and is relevant in the context of prevention of stabilization of errors, as well as monitoring for the effects of fatigue. In this research, acceleration and rotational speed signal acquired from a pair of IMUs (Inertial Measurement Unit) is used for detection of the time of occurrence of events. The research included 165 individual strikes performed by 14 elite and national-level karate competitors. All strikes were classified as slow, average, or fast based on the achieved maximal velocity of the hand. A Kruskal–Wallis test revealed significant general differences in the order of occurrence of hand acceleration start, maximal hand velocity, maximal body velocity, maximal hand acceleration, maximal body acceleration, and vertical movement onset between the groups. Partial differences were determined using a Mann–Whitney test. This paper determines the differences in the temporal structure of the reverse punch in relation to the achieved maximal velocity of the hand as a performance indicator. Detecting the time of occurrence of events using IMUs is a new method for measuring motion synchronization that provides a new insight into the coordination of articulated human movements. Such application of IMU can provide additional information about the studied structure of rapid discrete movements in various sporting activities that are otherwise imperceptible to human senses.

Karate fighters are under constant pressure to find adequate scoring solutions in ever-changing combat conditions. Thus, technique improvement at high levels of mastery demands a novel approach to key data acquisition and in-depth analysis of more than just the impact phase in punch execution. With the aim of describing the kinematic and temporal structure of a reverse punch in the developmental phase, two wireless sensors were used for the acquisition of selected quantities in ten modalities performed by a continental and world medallist. The results show that the timeline of kinematic parameters may be a reliable factor regarding the efficiency of the reverse punch. The obtained hand results show a tendency towards maintaining greater levels of stability in comparison to the body. Additionally, the differences between parameters in relation to applied tests that replicated training and combat conditions were noted. The highest acceleration values were obtained in sliding motion preceding RP, with a partner holding chest punch pad, both static (7.35 ± 0.47 g₀) and dynamic (6.99 ± 1.23 g₀) tests. The same applies for velocity (8.39 ± 0.14 and 7.30 ± 1.28 m/s). The obtained results indicate the need for specific testing and an individual approach in the analysis of the techniques of elite competitors, along with the use of sensors in data acquisition. Such an approach may help improve the training and competition practice of karate fighters.

The aim of this paper is to define the population indicators of the nutritional status among the working population of the Republic of Serbia based on the value of Body Mass Index (BMI). The sample consisted of a total of 7.125 working subjects, among which 4.525 males (63.51%) and 2.600 females (36.49%). The subjects were from the following regions: Northern Serbia-Vojvodina, Capital city - Belgrade, Central Serbia, Western Serbia, Southern Serbia and Eastern Serbia. The average BMI values based on test groups of men and women were 26.53±4.07 and 24.07±5.09 kg
m-2, respectively. On the basis of the obtained results, it was determined that statistically significant BMI differences exist among subjects in general, i.e. in relation to gender (F=58.412, p<0.000), the age category (F=268.885, p<0.001) as well as the interaction of the given factors (F=18.203. p<0.000). In relation to the prevalence, for the female subsample, it was determined that 65.3% of the subjects are in the optimal weight category, 18.7% are overweight, 12.5% are obese and 3.6% of are in the underweight category. When it comes to the male test group, the underweight prevalence of 0.2% was established. Percentage of subjects in the categories of optimal weight, overweight and obesity was 37.9, 48.0 and 13.9%, respectively. The highest prevalence of overweight and obesity was found at the age of 60-65 years. In the male test group, it was determined that 45.2% of the subjects were pre-obese and 26.0% were obese. In relation to the female subsample, the prevalence of overweight was found to be at the level of 36.8%, while the prevalence of obesity was as high as 41.4%. On the basis of the defined models of nutrition status in relation to age, it was found that the established BMI growth constant is 0.0904 kg·m-2, that is 90.4 g
m-2 per year of life for the male subsample, while for the female subsample growth constant is at the level of 0.1767 kg
m-2, that is 176.7 g
m-2 per year of life.

The influence of joint motion on punch efficiency before impact is still understudied. The same applies to the relationship between the kinematic and temporal parameters of a reverse punch (RP) that determines a score. Therefore, the aim of this study was to investigate if the exclusion or inclusion of body segments affects the acceleration, velocity, rotation angle, and timeline of execution, and to examine the correlation between these quantities. Seven elite male competitors—senior European and World Championship medalists—participated in the in-field testing. Quantities were acquired in the developmental phase of RP through three modalities of execution. Synchronized real-time data were obtained using combined multimodal sensors and camera fusion. The main findings of the study have highlighted the significant differences in the temporal and kinematic variables of RP that arise from the modality of execution. Large and medium correlation coefficients were obtained between the examined variables of body and hand. In conclusion, the results show that measured parameters are affected by segmental body activation. Moreover, their interdependence influences punch execution. The presented interdisciplinary approach provides insightful feedback for: (i) development of reliable and easy-to-use technical solutions in combat sports monitoring; and (ii) improvements in karate training.

Compared to adults, children have longer simple reaction time (SRT) and choice reaction time (CRT) to simple and choice visual stimuli. Based on the available data, it can be concluded that this occurrence could be due to correlation between age and the information processing speed. Other factors may have an impact, too, such as the shorter attention span which children may have. Some studies indicate that karate favors the development of cognitive functions, including the RT. Therefore, the aim of the current study was to determine whether there is a difference in simple and choice reaction time between boys and girls of preadolescent and early adolescent age on the basic and premastery level of karate training. Testing involved 78 participants divided into four subgroups, in accordance with the gender and the level of training, using a custom designed RT measuring software, developed in LabVIEW 2012 software package. A two-way analysis of variance (Two-way ANOVA) confirmed no differences between boys' and girls' SRT scores, while the significant differences were found at the mastery criterion subsample level. When it comes to CRT, the differences were found at the boys' subsample level, as well as between genders on the basic level of training. It cannot be stated with absolute certainty whether the acquired differences are the result of karate training, some other physiological and cognitive phenomena or the maturation process. Consequently, the further research should involve a broader sample - the population of the physically inactive, as well as the children involved in other sports.