The aim of the present study was to determine if an inertial measurement unit placed on the metatarsal part of the foot can provide valid and reliable data for an accurate estimate of vertical jump height. Thirteen female volleyball players participated in the study. All players were members of the Republic of Serbia national team. Measurement of the vertical jump height was performed for the two exemplary jumping tasks, squat jump and counter-movement jump. Vertical jump height estimation was performed using the flight time method for both devices. The presented results support a high level of concurrent validity of an inertial measurement unit in relation to a force plate for estimating vertical jump height (CMJ t = 0.897, p = 379; ICC = 0.975; SQJ t = −0.564, p = 0.578; ICC = 0.921) as well as a high level of reliability (ICC > 0.872) for inertial measurement unit results. The proposed inertial measurement unit positioning may provide an accurate vertical jump height estimate for in-field measurement of jump height as an alternative to other devices. The principal advantages include the small size of the sensor unit and possible simultaneous monitoring of multiple athletes.

The Aim. The aim of this paper is to define the contractile characteristics of maximal isometric handgrip force and to establish possible differences between the students of the Universities of Chelyabinsk and Belgrade. The secondary aim is to create a practically applicable initial model in order to explore the mentioned characteristics in the future. Material and methods. For the purposes of this research, the overall sample of 225 subjects was tested. 91 subjects were from Russia and 134 were from Serbia. The results were gathered using a strain gage and a standardized isometric handgrip test protocol. The contractile properties of HG muscle force were measured in relation to three different contractile dimensions: the maximal muscle force (Fmax), the maximal explosive muscle force (RFDmax), the time need for achieving maximal (tFmax) and maximal explosive (tRFDmax) muscle force. Results. This study has shown that there are no generally statistically significant differences for all observed variables of HG contractile characteristics between tested Russian and Serbian students. Based on the results of the present study, six different models of the equation for evaluation of HG contractile characteristics of female and male students, i.e. young adults, were made. All defined models are highly statistically significant, accurate and sensitive in the prediction of the general distributive position of an individual or particular group of subjects in relation to the measured contractile characteristics. Conclusions. The obtained results can generally indicate the stability of potential to exert the given contractile characteristic in relation to the population of similar evolutionary (Slavs) at different geographical background.

This paper aims to determine the relationship between the measures of shooting performance handgrip strength and weapon kinematics during different phases of the shot. The research included 35 participants who performed shooting sessions on 6 and 15 m shooting distance. Moderate (r > 0.388, p < 0.05) correlations were found between the handgrip strength and shooting performance. In the interval 1.0–0.1 s before the shot moderate correlations of weapon acceleration, accuracy and precision were determined (r > 0.310, p < 0.05) at the 6 m distance. Moderate correlations of shooting precision and rotational speed were found for the shooting distance 15 m for the same time interval (r > 0.413, p < 0.05). Moderate to high correlations of shooting accuracy, precision and weapon kinematics were found for both shooting distances (r > 0.405, p < 0.05) in the time interval 0.1–0.0 s. Absolute handgrip strength was a superior predictor of shooting performance than relative strength. Precision was more related to handgrip strength than accuracy and this relationship was more pronounced with distance. Correlations of shooting performance and rotational speed indicate high influence of the rotational component of weapon movement on the result.

The aim of this paper is to determine the discriminative potential of the IMU-based system for the measurement of rapid hand movement properties, i.e., relevant kinematic variables in relation to different groups of participants. The measurement of the kinematics of the rapid hand movement was performed using a standard hand tapping test. The sample in this research included a total of 70 female participants and was divided into 3 subsamples. The discriminant analysis has identified two functions, DF₁ and DF₂, that explain 91.1 and 8.1% of the variance, respectively. The differences between the examined subsamples originate from the variables grouped in DF₁, which were statistically significant (p≤0.000). In relation to this function, the national volleyball team centroid position was shifted with -1.108 and -1.968 standard deviation values from the control group and youth volleyball team, respectively. The difference between control and Voll_Youth groups was -0.860 standard deviation value. The factors with the greatest discriminative potential among the groups represent the temporal characteristics of the rapid hand movement, i.e., the time elapsed between the onset of the movement and the first and second tap, as defined by the variables t1 and t2, respectively. The established findings clearly indicate that IMU sensors are practically applicable in relation to the sensitive measurement of rapid arm movement capability of female athletes.

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.