This study investigates the relationship between reactive agility and reaction speed, sprint speed, and muscle strength and their contribution to Y-shaped agility test and reactive agility test (RAT) performance in handball players. Seven handball players performed a Y-shaped agility test and RAT, simple and choice-based reaction time test, reaction test to fast and slow generated visual stimuli, 5 m and 20 m sprint tests, a 505 Agility test, a squat jump, a countermovement jump, and a drop jump. The results reveal a significant relationship between the times for the Y-shaped agility test and the 20 m sprint (r = 0.777, p = 0.040, R = 0.604), as well as the time for the 505 Agility test (r = 0.770, p = 0.043, R² = 0.593), and RSI (r = −0.755, p = 0.050, R² = 0.570); however, no relationship was found with parameters pertaining to reaction speed. RAT performance did not significantly correlate with RSI, time in the 505 Agility test, squat jump height, time in the 20 m sprint, and reaction time to fast generated visual stimuli, although large effect sizes were found (r > 0.5). It seems that the contribution of sensory and motor components depends on the structure of the agility test. While the Y-shaped agility test is mainly determined by sprinting, the change of direction speed, and reactive strength, there is the tendency for the reactive agility test to be determined by strength, speed, and visual reaction time.

This study evaluates the effect of 8 weeks of the stable and unstable resistance training on muscle power. Thirty-three healthy men recreationally trained in resistance exercises, randomly assigned into two groups, performed resistance exercises either under stable or unstable conditions for 8 weeks (three sessions per week). Before and after 4 and 8 weeks of the training, they underwent squats and chest presses on either a stable surface or on a BOSU ball and a Swiss ball respectively with increasing weights up to at least 85% 1RM. Results showed significant improvements of mean power during chest presses on a Swiss ball at weights up to 60.7% 1RM after 4 and 8 weeks of the instability resistance training. Mean power increased significantly also during squats on a BOSU ball at weights up to 48.1% 1RM after 4 but not 8 weeks of instability resistance training. However, there were no significant changes in mean power during bench presses and squats on a stable support surface after the same training. These findings indicate that there is no cross effect of instability resistance training on power produced under stable conditions. This confirms and complies with the principle for specificity of training.

This study investigates differences in power and velocity at different loads and power and force at different velocities during trunk rotations in athletes who practice sports with rotational demands on the trunk. Athletes of combat (n = 23), fighting (n = 39), ball (n = 52) and water sports (n = 19) with a mean age of 23.8 ± 1.5 years performed standing trunk rotations on each side with bars of different weights (from 1 kg up to 50 kg) placed on their shoulders. The findings showed significant between-group differences in mean power in the acceleration phase of trunk rotations, especially at higher weights (≥10.5 kg) or lower velocities (≤334.2 rad/s). The power at 10.5 kg was significantly higher in fighting than water (p = 0.035; d = 0.86), combat (p = 0.001; d = 1.53) and ball sports athletes (p = 0.001; d = 1.48), with no significant differences between the two latter groups; at 15.5 kg, it was higher in water than combat (p = 0.027; d = 0.91) and ball sports athletes (p = 0.009; d = 1.17) but not those in fighting sports; and at 20 kg, it was higher in water than combat (p = 0.013; d = 0.98) and ball sports athletes (p = 0.006; d = 1.33), with no significant differences with those in fighting sports. This testing is sensitive in discriminating between athletes of various sports, which may reflect the specificity of their training, including trunk rotations at various velocities under different load conditions.

The paper presents the possibilities offered by the ePEDlab platform supporting teaching of electrical drive. A case of using this open educational resources for self-study or distance education is presented. The paper focuses on the power quality aspects in electrical drives. The teaching process based on interactive lectures, computer simulation exercises and experimental exercises is described in the paper. The ePEDlab platform presents interactive lectures divided into two courses (for users with different level of knowledge). The courses present idea of operation, block schemes, description of control methods, features, power electronic converters and aspects of power quality in electrical drives. The paper presents examples of interactive lectures focused on power quality aspects and operation of DC and AC drives. Then prepared simulation models, used during self-study process for this aspects are showed. These models ensure a rich form of results presentation, can be parametrized during exercise realization and are tightly connected with the experimental part of the course. Last part of the paper presents possibility of experimental verification of the theory with aspects of distance measurement of the drive operation. The summary indicates the possibility of using remote access to teaching materials, including the experimental part, used during lockdown.