Effects of Postactivation Performance Enhancement on The Vertical Jump in High-Level Volleyball Athletes.

The objective of this study was to evaluate the effects of a training session with and without an intervention of postactivation performance enhancement (PAPE) on countermovement jump (CMJ) height, perceived recovery status (PRS), and ratings of perceived exertion (RPEs), followed by a specific volleyball training session. The sample consisted of sixteen professional male volleyball players, with an average age of 26.8±6.1 years and average height of 195.9±6.7 cm, randomly divided into a group with PAPE intervention (GPAPE) (n=8), and a control group (CTRL) without PAPE intervention (n=8). The control group carried out the training session with plyometric exercises, and the GPAPE added conditioning protocols for PAPE to plyometric training, followed by a technical tactical volleyball session. At the end of the training session, there was an increase of 16.3% in the height of the CMJ in the GPAPE, while the CTRL showed a decrease of 5% in the height of the CMJ. PRS and RPE variables did not differ between the groups. It was concluded that PAPE had a positive effect on the height of the vertical jump after plyometric training, which was maintained until the end of the technical and tactical volleyball session.

Does Complex Training Enhance Vertical Jump Performance and Muscle Power in Elite Male Volleyball Players?

PURPOSE: The authors aimed to compare the effects of 4 weeks jump versus complex training methods on lower limb muscle power and maximal isokinetic torque of knee extensors and flexors in elite male volleyball players. METHODS: Sixteen male volleyball players were allocated into 2 groups, jump training (n = 8; 27.0 [5.7] y, 94.3 [7.6] kg) and complex training (with induction of postactivation performance enhancement, n = 8; 26.6 [3.6] y, 94.2 [6.3] kg). All individuals performed jump training 2 sessions/wk, and the complex group received induction training with postactivation performance enhancement and jump training. RESULTS: After 4 weeks, an increase in countermovement jump height (jump: 49.0 [1.2] to 52.7 [2.1] cm and complex: 49.2 [1.1] to 53.3 [1.9] cm; P = .009) and power (jump: 29.5 [1.1] to 34.3 [1.4] W and complex: 30.4 [0.9] to 34.4 [1.08] W; P = .001) was observed without significant differences between groups and without significant group × time interaction (P > .05). Also, no significant difference was observed between and within groups for the isokinetic peak torque at low speeds (60 and 180°s), although total muscle work and knee extensor/flexor ratio increased from pretraining to posttraining at 300° seconds similarly in both groups. CONCLUSION: The findings indicate that jump performance and power, knee extensor/flexor ratio, and total muscle work increased after 4 weeks of jump and complex training. However, the inclusion of heavy resistance stimulus did not elicit any additional improvements in the vertical jump performance and isokinetic strength of elite volleyball players.

Jump performance and mechanics after a regular training bout in elite volleyball players.

BACKGROUND: Volleyball is a complex intermittent sport characterized by short explosive technical movements, many of which involve vertical jumping. The assessment of mechanical jumping variables in relation to both injury prevention and performance enhancement through the use of wearable technologies is becoming a new training tool among professional volleyball players. METHODS: The present study aimed to assess the vertical jumping mechanics before and after a controlled load (volume and intensity) of a routine volleyball training session among male professional players. Twelve male elite professional volleyball players (23.7±4.9 years, 198.1±6.2 cm, 92.2±10.3 kg) of national and international level belonging to the same Brazilian first league team were recruited. Biomechanical analysis of vertical unilateral countermovement jump (CMJ) and bilateral CMJ tests were performed before and after a routine training session of these players at their usual training court. An inertial orientation sensor placed at the third lumbar vertebra was employed for biomechanical data collection. RESULTS: In relation to the unilateral CMJ, a 10% decrease (P=0.02) in the vertical ground reaction force after training compared to pretraining values was observed. However, no significant differences were observed in the remaining outcomes. Regarding the bilateral CMJ, no significant differences were observed in all assessed outcomes. CONCLUSIONS: Our findings showed no evidence of fatigue after a controlled regular in season volleyball training session in professional players. In addition, this volleyball training session induced a significant reduction in the vertical ground reaction force during unilateral CMJ in volleyball players.

A comparison of the internal and external load demands imposed on professional soccer referees in FIFA's current model of physical test in relation to games.

BACKGROUND: Based on the need to investigate the demands imposed on referees in the current model of physical evaluation and during professional games, this study's objective was to compare these demands in the physical test versus the games. METHODS: Thus, it evaluated the heart rate, distance covered, time, and speed of all 14 referees in the physical test and during Brazil's first division state championship games using a Global Positioning System enabled heart rate monitor. RESULTS: The maximum heart rate (HRmax) and maximum speed were higher in the physical test (183.86±12.79 bpm) and (26.80±0.96 km/h), respectively, than in the games (170.25±17.71 bpm) (P=0.008) and (24.27±1.68 km/h) (P=0.001), respectively. In the HRmax zone ≥90 and ≤100%, the time and percentage distance were greater in the physical test (47.87±16.60% and 58.57±22.78%), respectively, than in the games (17.82±18.29% and 18.84±18.92%, respectively; P<0.001). However, in the speed zone <13 km/h, the time and the percentage distance were longer in the game (93.73±1.26% and 86.13±2.31%), respectively, than in the physical test (68.73±12.31% and 39.65±9.74%, respectively; P<0.001). CONCLUSIONS: Thus, it is concluded that the professional referees perform at greater intensities during the physical test than in the games. In contrast, the demands for intensities corresponding to aerobic metabolism are greater in games or equal to those in physical testing, depending on the intensity reference.

Factors influencing self-selected walking speed in fibrotic interstitial lung disease.

This study aimed to investigate the walking economy and possible factors influencing self-selected walking speed (SSWS) in patients with fibrotic interstitial lung disease (ILD) compared to controls. In this study, 10 patients with ILD (mean age: 63.8 ± 9.2 years, forced expiratory volume in the first second: 56 ± 7% of predicted) and 10 healthy controls underwent resting pulmonary function tests, cardiopulmonary exercise, and submaximal treadmill walking tests at different speeds. The walking economy was assessed by calculating the cost-of-transport (CoT). Dynamic stability was assessed by stride-to-stride fluctuations using video recordings. Patients with ILD showed reduced peak oxygen uptake with a tachypneic breathing pattern and significant oxygen desaturation during exercise. The CoT did not differ between the groups (p = 0.680), but dyspnea and SpO2 were higher and lower, respectively, in patients with ILD at the same relative speeds. SSWS was reduced in ILD patients (2.6 ± 0.9 vs. 4.2 ± 0.4 km h-1 p = 0.001) and did not correspond to the energetically optimal walking speed. Dynamic stability was significantly lower in patients with ILD than in healthy controls, mainly at lower speeds. Patients with ILD presented a similar cost of transport compared to healthy controls; however, they chose lower SSWS despite higher walking energy expenditure. Although walking stability and dyspnea were negatively affected, these factors were not associated with the slower walking speed chosen by individuals with ILD.

Gamma spectrometry of iodine-125 produced in IEA-R1 nuclear reactor, using HPGe detector and fixation into epoxy matrix disc.

Few places in the world produce iodine-125. In Brazil, the first production was achieved by using the IEA-R1 nuclear reactor located at Nuclear and Energy Research Institute - IPEN. To verify the quality of iodine-125 produced, and the amount of contaminants such as iodine-126, cesium-134 and caesium-137 among others, iodine-125 samples were immobilized into epoxy matrix disc, with the same geometry of a barium-133 reference radioactive source, used to calibrate an HPGe detector. The HPGe detector has a thin carbon composite window, which allows measure the iodine-125 photopeaks, between 27.1 and 35.4 keV. The method employed here was successful in producing and measurement of iodine-125.

Kinematic Comparison of the Roundhouse Kick Between Taekwondo, Karate, and Muaythai.

ABSTRACT: Diniz, R, Del Vecchio, FB, Schaun, GZ, Oliveira, HB, Portella, EG, da Silva, ES, Formalioni, A, Campelo, PCC, Peyré-Tartaruga, LA, and Pinto, SS. Kinematic comparison of the roundhouse kick between taekwondo, karate, and muaythai. J Strength Cond Res 35(1): 198-204, 2021-The roundhouse kick (RHK) is frequently executed in taekwondo, karate, and muaythai because of its high technical effectiveness during combat. The purpose of this study was to compare kinematic characteristics during RHK performance between taekwondo, karate, and muaythai athletes. Forty-seven male athletes (25.5 ± 4.7 years, 1.75 ± 0.1 m, and 75.8 ± 11.5 kg) volunteered to participate (taekwondo: 17; karate: 15; and muaythai: 15). Self-selected distance from target, mean and peak fifth metatarsus linear velocity (LV5mean; LV5peak), mean and peak hip (HAVmean; HAVpeak) and knee (KAVmean; KAVpeak) angular velocities, as well as target linear acceleration (TLA) were analyzed with a 3D video motion analysis system. Comparisons between modalities were performed with 1-way analysis of variances and Bonferroni's post hoc test (α = 0.05). Self-selected distance was lower in muaythai compared with taekwondo and karate (p < 0.001). Also, karate had greater LV5mean compared with muaythai (p = 0.001), and muaythai showed higher HAVmean than karate (p = 0.011). In addition, HAVpeak was greater in muaythai than in taekwondo and karate (p < 0.001). No differences were found for KAVmean, KAVpeak, and TLA. Although it is similarly described between modalities, RHK showed distinct kinematic characteristics between taekwondo, karate, and muaythai. Based on these results, coaches and athletes can improve their RHK technique according to the specificities of each combat sport. Specifically, it is suggested that combat strategies should aim to increase the distance from the opponent during combat for muaythai athletes, whereas taekwondo and karate athletes should focus on decreasing it.

Correction: Pilates training improves 5-km run performance by changing metabolic cost and muscle activity in trained runners.

[This corrects the article DOI: 10.1371/journal.pone.0194057.].

Pilates training improves 5-km run performance by changing metabolic cost and muscle activity in trained runners.

PURPOSE: Strength training improves distance running economy and performance. This finding is based predominantly on maximal and explosive strength programmes applied to locomotor muscles, particularly on the lower limbs. It is not certain whether a minimization of metabolic cost (Cmet) and an improvement in running performance is feasible with strength training of the postural and trunk muscles. METHODS: Using kinematic, neuromuscular and metabolic measurements of running at two different speeds before and after a 12-week Pilates training programme, we tested the hypothesis that core training might improve the running Cmet and performance of trained runners. Thirty-two individuals were randomly assigned to the control group (CG, n = 16) or the Pilates group (PG, n = 16). RESULTS: Confirming our hypothesis, a significant improvement (p<0.05) was observed for running performance in the PG (pre: 25.65±0.4 min; post: 23.23±0.4 min) compared to the CG (pre: 25.33±0.58 min; post: 24.61±0.52 min). Similarly, the PG (4.33±0.07 J.kg-1.m-1) had better responses than the CG (4.71±0.11 J.kg-1.m-1) during post-training for Cmet. These findings were accompanied by decreased electromyographic activity of the postural muscles at submaximal running intensities in the PG. CONCLUSIONS: Overall, these results provide a rationale for selecting strength training strategies that target adaptations on specific postural and locomotor muscles for trained distance runners.