Echocardiographic assessment of cardiovascular physiology of preterm miniature piglets supported with a pumped artificial placenta system.

OBJECTIVES: We evaluated fetal cardiovascular physiology and mode of cardiac failure in premature miniature piglets on a pumped artificial placenta (AP) circuit. METHODS: Fetal pigs were cannulated via the umbilical vessels and transitioned to an AP circuit composed of a centrifugal pump and neonatal oxygenator and maintained in a fluid-filled biobag. Echocardiographic studies were conducted to measure ventricular function, umbilical blood flow, and fluid status. In utero scans were used as control data. RESULTS: AP fetuses (n = 13; 102±4d gestational age [term 115d]; 616 ± 139 g [g]; survival 46.4 ± 46.8 h) were tachycardic and hypertensive with initially supraphysiologic circuit flows. Increased myocardial wall thickness was observed. Signs of fetal hydrops were present in all piglets. Global longitudinal strain (GLS) measurements increased in the left ventricle (LV) after transition to the circuit. Right ventricle (RV) and LV strain rate decreased early during AP support compared with in utero measurements but recovered toward the end of the experiment. Fetuses supported for >24 h had similar RV GLS to in utero controls and significantly higher GLS compared to piglets surviving only up to 24 h. CONCLUSIONS: Fetuses on a pump-supported AP circuit experienced an increase in afterload, and redistribution of blood flow between the AP and systemic circulations, associated with elevated end-diastolic filling pressures. This resulted in heart failure and hydrops. These preterm fetuses were unable to tolerate the hemodynamic changes associated with connection to the current AP circuit. To better mimic the physiology of the native placenta and preserve normal fetal cardiovascular physiology, further optimization of the circuit will be required.

Foam rolling and tissue flossing of the triceps surae muscle: an acute effect on Achilles tendon stiffness, jump height and sprint performance - a randomized controlled trial.

This study aimed to investigate an acute effect of foam rolling and tissue flossing of the Triceps Surae muscle on Achilles tendon stiffness, jump height and sprint performance at different time points. The participants were academic athletes (n = 32) aged between 22 and 24 years; randomly allocated into two groups: foam rolling (ROLL) and tissue flossing (FLOSS). The participants were tested at baseline and 5-min, 15-min, 30-min, 45-min, and 60-min after ROLL and FLOSS for Achilles tendon stiffness (ATstiffeness) at three reference locations: (1) tendon's origin, (2) ankle joint height and (3) intermuscular septum of the gastronomies muscle; countermovement jump (CMJ); and sprint performance at 15-m (SPRINT15 m). The analysis of stiffness revealed a significant decrease in ATstiffness from baseline to Post-60 (p ≤ 0.001) for three locations in the FLOSS group (p ≤ 0.001). In FLOSS, a significant increase was observed from Post-15 to Post-60 (all p≤0.001) in CMJ. We found also a significant decrease in SPRINT15 m in FLOSS in all-time points (p ≤ 0.001), however, SPRINT15 m decreased in Post-5 min, Post-15 min, and Post-30 min (p ≤ 0.001 for all) in ROLL. The current study suggested that both groups enhanced performance up to 60 min after the intervention, caused by mitigating excessive stiffness.

Effects of Plyometrics Training on Muscle Stiffness Changes in Male Volleyball Players.

Dariusz, M, Krzysztof, M, Pawel, C, Edward, S, Marek, K, Tomasz, S, Dorota, B, Rektor, Z, and Jan, C. Effects of plyometrics training on muscle stiffness changes in male volleyball players. J Strength Cond Res 33(4): 910-921, 2019-We investigated whether 6 weeks of specific plyometric training (PT) impacts on changes in muscle stiffness and enhances the vertical jumping ability as the indirect evaluation of the explosive power of the lower extremities of male volleyball players. Sixteen male collegiate volleyball players participated in this experiment. Regular PT was performed twice per week for 60-90 minutes each time. During each PT session, heart rate and muscle stiffness data were collected. Two series of 10 single measurements of each muscle (23 points of the front and back legs) were measured the day before the first enhanced training session and after completing each week of PT. Participants were tested for maximum effort in vertical jumping using the squat jump (SJ) with hands on thighs, countermovement jump (CMJ), and CMJ with a 2-step to 3-step approach. Jumping motor ability tests were completed. Data were collected 1 day before PT. The last measurement was performed 3 days after completing the last week of PT. The 6-week PT program only had an effect on the statistically relevant increase in muscle stiffness in the tibialis anterior (highest value, 593.86 ± 60.24 N·m) and quadriceps. Improvements in the explosive power of leg muscles resulted in a significant increase in the vertical jumping ability; there were improvements in SJ and CMJ (p = 0.0338 and p = 0.0007, respectively). If PT involves a moderate workload and if players never exceed the intensity target of the workout, then less muscle stiffness and muscle soreness may occur.

Achievable radiation reduction during pediatric cardiac catheterization: How low can we go?

OBJECTIVES: To assess the effectiveness of radiation-reduction measures implemented during pediatric catheterization, and provide data on the radiation doses for common interventional and diagnostic procedures, indexed to body weight. BACKGROUND: Ionizing radiation exposure must be minimized to "as low as reasonably achievable," by instituting radiation-limiting techniques and knowledge of expected radiation exposure. METHODS: Radiation-reduction measures included pulsed-fluoroscopy at 7.5 pulses/second (0.032-0.045 µGy/pulse), an air-gap magnification technique for children<20 kg, operator awareness, and additional exposure reduction techniques through projection optimization. Radiation doses for procedures performed between 2007 through 2014 were retrospectively reviewed, including dose area product (DAP) and DAP/kg of body weight for 25 procedural types. Median doses were compared with those previously published from other large centers and multi-institutional databases and assessed for changes over time. RESULTS: Reviewed were 5,196 cases, which included 2,819 interventional, 710 endomyocardial biopsies and 1,667 diagnostic studies, documenting a significant difference in exposure between various procedures and body weights. The absolute exposure was significantly greater in larger children (e.g., for ductal closure median DAP/kg: 17 µGy*m2/kg 10-20 kg children vs. 37 µGy*m2 /kg for those>30 kg, P<0.001). Dose exposure using radiation-reduction techniques were the lowest reported in the literature for all procedure types compared (e.g. median DAP for pulmonary valvuloplasty 163 µGy*m2 vs. 405 to 1,230 µGy*m2 reported by 3 large centers). Reduction of fluoroscopy acquisition to 7.5 pulses/second nearly halved radiation exposure (P<0.001). CONCLUSIONS: Implementing a radiation dose reduction and awareness program can lead to documented reduction in exposure, across a variety of procedures performed by multiple operators.

Functional connectivity between core and shoulder muscles increases during isometric endurance contractions in judo competitors.

PURPOSE: The aim of this study was to assess the surface electromyogram (SEMG) changes within and between muscles of the torso and shoulder region during static endurance contraction in elite judokas. We hypothesized an increased functional connectivity of muscles from the shoulder and torso regions during sustained isometric contraction. METHODS: Twelve healthy, right-handed judo competitors participated in the study. The SEMG signals from the dominant trapezius (upper, middle and lower part), deltoideus anterior, serratus anterior, and pectoralis major muscles were recorded during isometric endurance contraction consisting of bilateral arm abduction at 90°. The normalized mutual information (NMI) was computed between muscle pairs as an index indicating functional connectivity. RESULTS: The NMIs increased significantly during endurance test for 10 of the 15 muscle pairs (P < 0.001). CONCLUSION: We concluded that the increases in NMIs highlighted functional changes in the interplay between core and shoulder muscles during an endurance contraction in elite judokas.

Analysis of male volleyball players' motor activities during a top level match.

The present study aims to assess motor activity of volleyball players using an original video recording method developed by the authors. Twenty-eight volleyball players taking part in 4 matches of the Polish Volleyball League were examined. The recorded data were analyzed in view of the mean total distance covered by volleyball players on different court positions during a match, set, and rally. The results showed that volleyball players cover the mean total distance of 1221 ± 327 m (mean ± SD) in a 3-set match, and 1757 ± 462 m in a 4-set match. A statistically significant difference (p ≤ 0.005) was found between the distance covered by the middle blockers and setters, defenders, spikers, and libero players in a match and in a set. The study revealed a tendency to lengthen the distance by the players in the final sets, which is indicative of the extended time of individual rallies. The mean distance covered in a single rally amounted to 10.92 ± 0.9 m in 4 matches (between 9.12 and 12.56 m). Considering the limited size of the field of play, volleyball players cover relatively long distances during a match and individual sets, with the shortest distance covered by middle blockers, and the longest by setters. From a practical application point of view, detailed topographic analysis of a player's movements on the court as well as precise data on the time of activity and rest breaks provide the coach with valuable information on the ways of development of arrhythmic, changing and dynamic training loads.

The effectiveness and types of serves used in elite women's and men's volleyball in the 2021/2022 season.

In elite volleyball, the serve takes an offensive form, aiming to directly score a point or significantly hinder the opponent from launching an attack. Which is why the research aimed to compare the type and effectiveness of the serve in the main round of Tauron and PlusLiga in the 2021/2022 season and update the current knowledge on the types of serves by function and gender. The study analysed observation consisted of 314 women's and men's matches. VolleyStation Pro v 1.29.5; Volleystation z o. o. Poland. Data from the main round matches that took place in the 2021/2022 season in the Polish elite league PlusLiga (182 men's matches) and Tauron Liga (132 women's matches) were used, and the regular season consisted of 2 rounds. The average percentage effectiveness of the serve in women was higher (E = 22%) than in men (E = 15%). In women, only 3 types were observed (JS, JF and W), as much as 86% of all the serves were JF serves. In men, as many as 5 types (JS, JF, FJS, FJF and W), of which over 67% were dynamic JS serves (jumping serve). The serve element has been modified over the years to obtain better effects conducive to winning. Ranging from increasing the speed of the serve, eliminating the serves from the spot in favor of the jump serves, to the use of serves to hide the correct hit of the ball ("Fake"-FFJ, FJS).

Kinematics of Two Special Endurance Trials: A Methodological Contribution to 400-m Performance.

This study aimed to determine changes in the kinematics of sprint steps based on progressive muscular fatigue during high-intensity 350-m and 500-m trials. Twelve elite healthy male 400-m sprinters with a minimum of six years of regular sprint training experience were recruited. They were divided into two groups for the experiment: a 350-m and a 500-m trial group. Time and kinematics of sprinting step motion for specific segments, i.e., starting to final stages of each trial, were obtained using the Opto Jump-Microgate optical measurement system. The starting phase of each sprint was defined as the section without muscular fatigue (noF), and the final phase was the sprint under muscular fatigue (onF). Each last 25 m of the 50-m evaluated section containing ten complete running steps was selected for detailed statistical analysis. Various patterns of temporal and spatial variables of sprinting efforts were observed between 350-m and 500-m trials. Each trial result was influenced by significant individual changes (p < 0.05). All variables indicated that the two distances differed significantly in terms of running kinematics. This was confirmed by significant differences in the mean step frequency (p < 0.001), which presented a difference of 11.75%, and the mean step speed (p < 0.001). As a result of these changes, a hierarchical intermittent endurance training pattern was defined. The research concluded that special endurance (intermittent sprints) based on 350 m differed significantly in kinematics from sprints over 500 m. Therefore, it should be assumed that the distance of 350 m is more similar in its kinematics to the 400-m competition. This should encourage coaches and athletes to apply a 350-m distance in training developing special endurance, especially in the pre-competitive and competitive periods.

Impact of Right Ventricular Pressure Overload on Myocardial Stiffness Assessed by Natural Wave Imaging.

BACKGROUND: Right ventricular (RV) hemodynamic performance determines the prognosis of patients with RV pressure overload. Using ultrafast ultrasound, natural wave velocity (NWV) induced by cardiac valve closure was proposed as a new surrogate to quantify myocardial stiffness. OBJECTIVES: This study aimed to assess RV NWV in rodent models and children with RV pressure overload vs control subjects and to correlate NWV with RV hemodynamic parameters. METHODS: Six-week-old rats were randomized to pulmonary artery banding (n = 6), Sugen hypoxia-induced pulmonary arterial hypertension (n = 7), or sham (n = 6) groups. They underwent natural wave imaging, echocardiography, and hemodynamic assessment at baseline and 6 weeks postoperatively. The authors analyzed NWV after tricuspid and after pulmonary valve closure (TVC and PVC, respectively). Conductance catheters were used to generate pressure-volume loops. In parallel, the authors prospectively recruited 14 children (7 RV pressure overload; 7 age-matched control subjects) and compared RV NWV with echocardiographic and invasive hemodynamic parameters. RESULTS: NWV significantly increased in RV pressure overload rat models (4.99 ± 0.27 m/s after TVC and 5.03 ± 0.32 m/s after PVC in pulmonary artery banding at 6 weeks; 4.89 ± 0.26 m/s after TVC and 4.84 ± 0.30 m/s after PVC in Sugen hypoxia at 6 weeks) compared with control subjects (2.83 ± 0.15 m/s after TVC and 2.72 ± 0.34 m/s after PVC). NWV after TVC correlated with both systolic and diastolic parameters including RV dP/dtmax (r = 0.75; P < 0.005) and RV Ees (r = 0.81; P < 0.005). NWV after PVC correlated with both diastolic and systolic parameters and notably with RV end-diastolic pressure (r = 0.65; P < 0.01). In children, NWV after both right valves closure in RV pressure overload were higher than in healthy volunteers (P < 0.01). NWV after PVC correlated with RV E/E' (r = 0.81; P = 0.008) and with RV chamber stiffness (r = 0.97; P = 0.03). CONCLUSIONS: Both RV early-systolic and early-diastolic myocardial stiffness show significant increase in response to pressure overload. Based on physiology and our observations, early-systolic myocardial stiffness may reflect contractility, whereas early-diastolic myocardial stiffness might be indicative of diastolic function.

Psychomotor performance of elite volleyball players during a game.

Prior studies have found that reaction time and movement time increase with fatigue (measured by blood lactate concentration) in laboratory situations. The study tested whether these relationships occurred for reaction time and movement time of elite volleyball players during a training game. Components of the players' psychomotor performance (reaction time, movement time) and physiological parameters (heart rate, blood lactate concentration) were analyzed. Fourteen male, adolescent volleyball players participated in the study. Reaction time and movement time were measured with the Optojump measurement system during the game in off-the-court periods. All measurements were performed during a pre-game test and during each of the four sets of the game. During Set 1, players' reaction time decreased significantly compared with the pre-game test indicating a likely warm-up effect. Blood lactate concentration increased significantly across sets. However, the players' reaction times remained constant across sets. The studied players did not exceed the psychomotor fatigue threshold anytime during the entire game. These findings indicate that the amount of training (20 hours a week) done by elite players is sufficient to prevent threshold fatigue levels that create significant decreases in psychomotor performance.

Influence of jump height on the game efficiency in elite volleyball players.

The aim of the study was to verify the impact of the jump height measured during the serve, attack and block on their effectiveness. The analysis of the literature and observations lead to the hypothesis that despite the similarities in men's and women's volleyball, the nature of the way of playing between women and men differs. The observation covered 39 male and 24 female elite volleyball players. We used a proprietary software tool, namely OpenCV to assess the jump height library. The analysis was performed on the jump serve height (SJH), attack jump height (AJH), and block jump height (BJH). The following analysis was performed to confirm the differences in the height of the jump and partially confirm the hypothesis. The main difference between men's and women's volleyball is how the serve, attack and block jump height affect winning or losing match sets. In male volleyball players, there is a decrease in the parameters of SJH, AJH and BJH in subsequent sets of matches, while in female volleyball players this relationship is reversed. For men, it seems reasonable to strive to increase the height of a jump to maximize effective offensive actions, as well as to maintain the developed performance throughout a match. In women's volleyball, it is worth using such training measures that allow players would achieve their maximum jumping abilities from the first set, and the main training goal should be focused on the technique and tactics of the whole team.

Impact of marathon performance on muscles stiffness in runners over 50 years old.

Introduction: The research examines the relationship between marathon performance and muscle stiffness changes from pre to marathon in recreational runners aged 50+ years. Methods: Thirty-one male long-distance runners aged 50-73 years participated in the experiment. The muscle stiffness of quadriceps and calves was measured in two independent sessions: the day before the marathon and 30 min after the completed marathon run using a Myoton device. Results and Discussion: The 42.195-km run was completed in 4.30,05 h ± 35.12 min, which indicates an intensity of 79.3% ± 7.1% of HRmax. The long-term, low-intensity running exercise (marathon) in older recreational runners and the low level of HRmax and VO2max showed no statistically significant changes in muscle stiffness (quadriceps and calves). There was reduced muscle stiffness (p = 0.016), but only in the triceps of the calf in the dominant (left) leg. Moreover, to optimally evaluate the marathon and adequately prepare for the performance training program, we need to consider the direct and indirect analyses of the running economy, running technique, and HRmax and VO2max variables. These variables significantly affect marathon exercise.

Fatigue and Training Load Factors in Volleyball.

The purpose of this article was to determine the internal and external loads experienced by volleyball players in a weekly cycle during the competitive season. Using accelerometers, as well as subjective rating perceived exertion (RPE) and total quality recovery scale (TQR) questionnaires, eleven female athletes were monitored during five days of training sessions over the course of the 2021 season. The data were evaluated for trends during the start period in preparation for the championship tournament. Analysis of the accelerometer data revealed a relationship between RPE and session rating perceived exertion (s-RPE), as well as the number of total accelerations. It was reported that on the training days of the same well-being level, the jump number values were significantly different. The results suggest that monitoring athletes for the number of accelerations can be used to understand the needs of volleyball players and to improve the design of training and recovery days to optimize athletes' well-being.

Impact of the Addition of a Centrifugal Pump in a Preterm Miniature Pig Model of the Artificial Placenta.

The recent demonstration of normal development of preterm sheep in an artificial extrauterine environment has renewed interest in artificial placenta (AP) systems as a potential treatment strategy for extremely preterm human infants. However, the feasibility of translating this technology to the human preterm infant remains unknown. Here we report the support of 13 preterm fetal pigs delivered at 102 ± 4 days (d) gestation, weighing 616 ± 139 g with a circuit consisting of an oxygenator and a centrifugal pump, comparing these results with our previously reported pumpless circuit (n = 12; 98 ± 4 days; 743 ± 350 g). The umbilical vessels were cannulated, and fetuses were supported for 46.4 ± 46.8 h using the pumped AP versus 11 ± 13 h on the pumpless AP circuit. Upon initiation of AP support on the pumped system, we observed supraphysiologic circuit flows, tachycardia, and hypertension, while animals maintained on a pumpless AP circuit exhibited subphysiologic flows. On the pumped AP circuit, there was a progressive decline in umbilical vein (UV) flow and oxygen delivery. We conclude that the addition of a centrifugal pump to the AP circuit improves survival of preterm pigs by augmenting UV flow through the reduction of right ventricular afterload. However, we continued to observe the development of heart failure within a matter of days.

Allometric association between physical fitness test results, body size/shape, biological maturity, and time spent playing sports in adolescents.

Regular participation in strength and conditioning activities positively correlates with health-related benefits in sports (team and individual). Maturity offset (MO) is a recognized parameter in fitness outcome assessment. The aims of the present study are to analyze cross-sectional allometric development of motor performances in a sample of adolescents and relate scaled motor performance to the estimated amount and type of physical activity and biological maturity status in 771 subjects aged 14-19 years. Three physical fitness components were evaluated using field tests (standing broad jump, sit-ups, shuttle run). Extra hours of sport after school (EHS) and MO were the covariates. The model to predict the physical performance variables was: Y = a · Mk1 · Hk2 · WCk3 · exp(b · EHS + c · MO) · ε. Results suggest that having controlled for body size and body shape, performing EHS and being an early developer (identified by a positive MO slope parameter) benefits children in physical fitness and motor performance tasks.

Low ventilatory responsiveness to transient hypoxia or breath-holding predicts fast marathon performance in healthy middle-aged and older men.

The aim of this study was to test the utility of haemodynamic and autonomic variables (e.g. peripheral chemoreflex sensitivity [PCheS], blood pressure variability [BPV]) for the prediction of individual performance (marathon time and VO2max) in older men. The post-competition vasodilation and sympathetic vasomotor tone predict the marathon performance in younger men, but their prognostic relevance in older men remains unknown. The peripheral chemoreflex restrains exercise-induced vasodilation via sympathetically-mediated mechanism, what makes it a plausible candidate for the individual performance marker. 23 men aged ≥ 50 year competing in the Wroclaw Marathon underwent an evaluation of: resting haemodynamic parameters, PCheS with two methods: transient hypoxia and breath-holding test (BHT), cardiac barosensitivity, heart rate variability (HRV) and BPV, plasma renin and aldosterone, VO2max in a cardiopulmonary exercise test (CPET). All tests were conducted twice: before and after the race, except for transient hypoxia and CPET which were performed once, before the race. Fast marathon performance and high VO2max were correlated with: low ventilatory responsiveness to hypoxia (r = - 0.53, r = 0.67, respectively) and pre-race BHT (r = - 0.47, r = 0.51, respectively), (1) greater SD of beat-to-beat SBP (all p < 0.05). Fast performance was related with an enhanced pre-race vascular response to BHT (r = - 0.59, p = 0.005). The variables found by other studies to predict the marathon performance in younger men: post-competition vasodilation, sympathetic vasomotor tone (LF-BPV) and HRV were not associated with the individual performance in our population. The results suggest that PCheS (ventilatory response) predicts individual performance (marathon time and VO2max) in men aged ≥ 50 yeat. Although cause-effect relationship including the role of peripheral chemoreceptors in restraining the post-competition vasodilation via the sympathetic vasoconstrictor outflow may be hypothesized to underline these findings, the lack of correlation between individual performance and both, the post-competition vasodilation and the sympathetic vasomotor tone argues against such explanation. Vascular responsiveness to breath-holding appears to be of certain value for predicting individual performance in this population, however.

Achieving sustained extrauterine life: Challenges of an artificial placenta in fetal pigs as a model of the preterm human fetus.

Artificial placenta (AP) technology aims to maintain fetal circulation, while promoting the physiologic development of organs. Recent reports of experiments performed in sheep indicate the intrauterine environment can be recreated through the cannulation of umbilical vessels, replacement of the placenta with a low-resistance membrane oxygenator, and incubation of the fetus in fluid. However, it remains to be seen whether animal fetuses similar in size to the extremely preterm human infant that have been proposed as a potential target for this technology can be supported in this way. Preterm Yucatan miniature piglets are similar in size to extremely preterm human infants and share similar umbilical cord anatomy, raising the possibility to serve as a good model to investigate the AP. To characterize fetal cardiovascular physiology, the carotid artery (n = 24) was cannulated in utero and umbilical vein (UV) and umbilical artery were sampled. Fetal UV flow was measured by MRI (n = 16). Piglets were delivered at 98 ± 4 days gestation (term = 115 days), cannulated, and supported on the AP (n = 12) for 684 ± 228 min (range 195-3077 min). UV flow was subphysiologic (p = .002), while heart rate was elevated on the AP compared with in utero controls (p = .0007). We observed an inverse relationship between heart rate and UV flow (r2  = .4527; p < .001) with progressive right ventricular enlargement that was associated with reduced contractility and ultimately hydrops and circulatory collapse. We attribute this to excessive afterload imposed by supraphysiologic circuit resistance and augmented sympathetic activity. We conclude that short-term support of the preterm piglet on the AP is feasible, although we have not been able to attain normal fetal physiology. In the future, we propose to investigate the feasibility of an AP circuit that incorporates a centrifugal pump in our miniature pig model.

Effects of High-Velocity Strength Training on Movement Velocity and Strength Endurance in Experienced Powerlifters with Cerebral Palsy.

The present study aimed to evaluate the effects of a 6-week high-velocity strength training (HVST) intervention on movement velocity and strength endurance in experienced powerlifters with cerebral palsy (CP). Eleven experienced powerlifters with CP and seven from a control group (CON), were subjected to 6-week HVST. An assessment of movement velocity and strength endurance was conducted one week before (T1) and one week after (T2) the 6-week training intervention. During testing, athletes performed a maximum number of bench press repetitions possible within 5 sets of 15 s each, with 1-min passive rest intervals in-between. The indicator of movement velocity was the weight pressed in the first 5 s (5sW) in all performed sets. Strength endurance was described by the total weight (TW) pressed during the test. 5sW in T2 was significantly higher as compared with T1 in the CP group only (T1 928.9 ± 342.9 kg vs. T2 1007.3 ± 324.6 kg; p = 0.016). TW in T2 was significantly higher as compared with T1, both in the CP group (T1 2550.5 ± 843.9 kg vs. T2 2809.8 ± 981.3 kg; p < 0.001) and in the CON group (T1 2300.7 ± 845.1 kg vs. T2 2468.9 ± 890.1 kg; p = 0.049). A 6-week program of HVST increased movement velocity in resistance trained CP athletes. The gains of strength endurance were observed in both groups.

Trapezius viscoelastic properties are heterogeneously affected by eccentric exercise.

OBJECTIVES: The aim of this study was to investigate the influence of eccentric exercise (ECC) on the spatial mapping of muscle stiffness and creep of the upper trapezius, using a quantitative myotonometry device. DESIGN: Two groups of 16 subjects participated in the experimental sessions. In part A, the test-retest reliabilities of muscle stiffness and creep were assessed. In part B, muscle stiffness and muscle creep were mapped before, immediately after and 24h after ECC when post-exercise soreness had developed. METHODS: The ECC protocol consisted of 50 eccentric contractions divided into 5 bouts of 10 contractions at maximum force level. RESULTS: The relative reliabilities of stiffness and creep measurements were found to be substantial to almost perfect. Muscle stiffness for musculotendinous sites increased at 24h after ECC while it decreased for muscle belly immediately after and 24h after ECC. Muscle creep for musculotendinous sites decreased, and for muscle belly sites increased, immediately after and 24h after ECC. CONCLUSIONS: For the first time, the present study showed sign of discrepancies in the effects of ECC on muscle stiffness and creep, underlining opposite changes in the musculotendinous and muscle belly viscoelastic properties of upper trapezius.

Effects of volleyball plyometric intervention program on vertical jumping ability in male volleyball players.

BACKGROUND: This study aimed to investigate the effect of a 6-week plyometric exercise training program on the development of lower limb explosive power in terms of vertical jumping ability in university level volleyball players. The study involved 9 male volleyball players from the AWF Wroclaw University Sports Club, with a minimum of 5 years of training and competition experience. The program consisted of various bounds, hops, and jumps in vertical, horizontal, and mixed directions. During the program, a progressive overload of plyometric intervention was applied. Lower limb explosive power in the form of vertical jumping ability was developed and tested. METHODS: The jumping ability was evaluated via 5 types of maximum-effort vertical jumps, using the Opto Jump system. In addition, once each week, the heart rate was recorded using a heart rate monitor (Polar RS300X GPS). RESULTS: The only significant correlation was found between squat jump and number of jumps and between counter movement jump and heart rate. CONCLUSIONS: From a practical standpoint, the improvement, which was noticed after 3 and 6 weeks, seems to optimal period for volleyball players adaptation to significant increased training load.