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To date, no investigation has studied the effect of acute intake of caffeinated chewing gum on volleyball performance. Therefore, the aim of this investigation was to establish the impact of caffeinated chewing gum ingestion on physical performance in female volleyball players. Twelve high-performance volleyball female athletes participated in a randomized, crossover, placebo-controlled, and double-blind experiment. Each athlete performed two identical experimental sessions after a) ingestion of ~6.4 mg/kg of caffeine via caffeinated chewing gum, b) ingestion of non-caffeinated chewing gum as a placebo. After the ingestion of gum, athletes performed a volleyball game, and performance was assessed by a notational analysis. Just before and after the game, jump performance during block and attack actions was evaluated. The number of points obtained and the number of errors committed during serve, reception, attacking, and blocking actions were unaffected by the ingestion of caffeinated chewing gum (p from 0.066 to 0.890). However, caffeinated chewing gum increased jump attack height in comparison to the placebo (pre-game 46.0 ± 7.2 vs. 47.2 ± 6.7 cm, p = 0.032; post-game 46.3 ± 7.6 vs. 47.5 ± 6.9 cm, p = 0.022, respectively). Caffeinated chewing gum did not modify block jump height (pre-game 32.7 ± 5.5 and 33.0 ± 4.3 cm, p = 0.829; post-game: 34.8 ± 6.1, 35.4 ± 6.1 cm, p = 0.993, respectively). The ingestion of ~6.4 mg/kg of caffeine via caffeinated chewing gum was effective for improving jump attack performance in women volleyball athletes. However, this effect was not translated into better volleyball performance during a game.

The goal of the study was to determine the differences between volitional and maximal movement tempo during resistance exercise. Ten healthy men volunteered for the study (age = 26.4 ± 4.8 years; body mass = 93.8 ± 9.6 kg; barbell squat one-repetition maximum (1RM) = 175 ± 16.7 kg; bench press 1RM = 140.5 ± 26.8 kg). In a randomized order, the participants performed six sets of the barbell squat and the bench press exercise at progressive loads from 40% to 90%1RM (step by 10%) under two testing conditions: with volitional movement tempo or with maximal movement tempo. The three-way repeated measures ANOVA showed a statistically significant multi-interaction effect for time under tension (p0.001), peak bar velocity (p = 0.04) and for mean bar velocity (p0.001). There was also a statistically significant main effect of movement tempo for time under tension (p0.001), peak bar velocity (p0.001) and for mean bar velocity (p0.001). The post hoc analysis for main effect of tempo revealed that time under tension was significantly longer for volitional compared to maximal tempo (0.84 vs 0.67 s, respectively), peak bar velocity was significantly higher for maximal compared to volitional tempo (1.24 m/s vs 0.90 m/s, respectively), and mean bar velocity was significant higher for maximal compared to volitional tempo (0.84 m/s vs 0.67 m/s, respectively). The presented results indicate that there were significant differences between volitional and maximal movement tempos in time under tension and bar velocity (peak and mean), as well as significant differences in those variables between the two exercises. Therefore, the velocity of movement and time under tension is related to movement tempo, external load and type of exercise used.

Introduction. The main goal of this study was to examine the effect of acute intake of 3 mg/kg/body mass (b.m.) of caffeine (CAF) on countermovement jump (CMJ) performance in recreationally trained women habituated to CAF. Material and Methods. 17 healthy recreationally trained women habitually using CAF participated in the study. The experiment followed randomized, cross-over, double-blind design under three different conditions: control test (CONT) or consumed placebo (PLAC) or consumed 3 mg/kg/b.m. of CAF (CAF-3). Each participant performed 2 sets of 2 CMJ. The following variables were recorded: concentric peak velocity (PV), peak power (PP) and jump height (JH). Results. The two-way repeated measure ANOVA (substance × set) revealed no statistically significant interaction and main effects for all measured variables between conditions. In comparison to the CONT and PLAC, the intake of CAF-3 was not effective at increasing PV (p = 0.533), JH (p = 0.417) and PP (p = 0.871) during 2 sets of the CMJ. Conclusions. This study suggests that 3 mg/kg/b.m. of CAF did not improve CMJ height in recreationally trained women habituated to CAF. Furthermore, the level of athletic performance might be considered a factor in regard to CAF ergogenicity.

The main goal of the present study was to evaluate the acute effects of blood flow restriction (BFR) at 70% of full arterial occlusion pressure on strength-endurance performance during the bench press exercise. The study included 14 strength-trained male subjects (age = 25.6 ± 4.1 years; body mass = 81.7 ± 10.8 kg; bench press 1 repetition maximum (1RM) = 130.0 ± 22.1 kg), experienced in resistance training (3.9 ± 2.4 years). During the experimental sessions in a randomized crossover design, the subjects performed three sets of the bench press at 80% 1RM performed to failure with two different conditions: without BFR (CON); and with BFR (BFR). Friedman’s test showed significant differences between BFR and CON conditions for the number of repetitions performed (p < 0.001); for peak bar velocity (p < 0.001) and for mean bar velocity (p < 0.001). The pairwise comparisons showed a significant decrease for peak bar velocity and mean bar velocity in individual Set 1 for BFR when compared to CON conditions (p = 0.01 for both). The two-way repeated measures ANOVA showed a significant main effect for the time under tension (p = 0.02). A post-hoc comparisons for the main effect showed a significant increase in time under tension for BFR when compared to CON (p = 0.02). The results of the presented study indicate that BFR used during strength-endurance exercise generally does not decrease the level of endurance performance, while it causes a drop in bar velocity.

We present security vulnerabilities in the remote voting system Helios. We propose Apollo, a modified version of Helios, which addresses these vulnerabilities and could improve the feasibility of internet voting.