Activity Profiles and Physiological Responses of Representative Tag Football Players in Relation to Playing Position and Physical Fitness

This study determined the physical fitness, match-activity profiles and physiological responses of representative tag football players and examined the relationship between physical fitness and the match-activity profile. Microtechnology devices and heart rate (HR) chest straps were used to determine the match-activity profiles of sixteen tag football players for five matches during the 2014 Australian National Championships. The relationships between lower body muscular power, straight line running speed and Yo-Yo intermittent recovery test level 2 (Yo-Yo IR2) and the match-activity profile were examined using Pearson’s correlation coefficients. Outside players had greater lower body muscular power (ES = 0.98) and straight line running speed (ES = 1.03–1.18) than inside players, and also covered greater very high-speed running (VHSR) distance/min (ES = 0.67) and reached higher peak running speeds (ES = 0.95) during matches. Inside and outside players performed a similar number of repeated high-intensity effort (RHIE) bouts and reported similar mean and maximum efforts per RHIE bout. However, there were differences between playing positions for mean and maximal RHIE effort durations (ES = 0.69–1.15) and mean RHIE bout recovery (ES = 0.56). Inside and outside players also reported small to moderate differences (ES = 0.43–0.80) for times spent in each HR zone. There were a number of moderate to very large correlations between physical fitness measures and match-activity profile variables. This study found lower body muscular power, straight line running speed and Yo-Yo IR2 to be related to the match-activities of representative tag football players, although differences between inside and outside players suggest that athlete testing and training practices should be modified for different playing positions.     

Number of Players and Relative Pitch Area per Player: Comparing Their Influence on Heart Rate and Physical Demands in Under-12 and Under-13 Football Players

The aim of the present study is to analyse the influence of different large-sided games (LSGs) on the physical and physiological variables in under-12s (U12) and -13s (U13) soccer players. The effects of the combination of different number of players per team, 7, 9, and 11 (P7, P9, and P11, respectively) with three relative pitch areas, 100, 200, and 300 m² (A100, A200, and A300, respectively), were analysed in this study. The variables analysed were: 1) global indicator such as total distance (TD); work:rest ratio (W:R); player-load (PL) and maximal speed (V_max); 2) heart rate (HR) mean and time spent in different intensity zones of HR (<75%, 75–84%, 84–90% and >90%), and; 3) five absolute (<8, 8–13, 13–16 and >16 Km h^-1) and three relative speed categories (<40%, 40–60% and >60% V_max). The results support the theory that a change in format (player number and pitch dimensions) affects no similarly in the two players categories. Although it can seem that U13 players are more demanded in this kind of LSG, when the work load is assessed from a relative point of view, great pitch dimensions and/or high number of player per team are involved in the training task to the U12 players. The results of this study could alert to the coaches to avoid some types of LSGs for the U12 players such as: P11 played in A100, A200 or A300, P9 played in A200 or A300 and P7 played in A300 due to that U13>U12 in several physical and physiological variables (W:R, time spent in 84–90%HR_max, distance in 8–13 and 13–16 Km h^-1 and time spent in 40–60%V_max). These results may help youth soccer coaches to plan the progressive introduction of LSGs so that task demands are adapted to the physiological and physical development of participants.     

Role of External and Internal Calcium on Heterocarrier-Mediated Transmitter Release

Abstract: Release-regulating heterocarriers exist on brain nerve endings. We have investigated in this study the mechanisms involved in the neurotransmitter release evoked by GABA heterocarrier activation. GABA increased the basal release of [³H]acetylcholine and [³H]noradrenaline from rat hippocampal synaptosomes and of [³H]dopamine from striatal synaptosomes. These GABA effects, insensitive to GABA receptor antagonists, were prevented by inhibiting GABA uptake but not by blocking noradrenaline, choline, or dopamine transport. Lack of extracellular Ca²⁺ or addition of tetrodotoxin selectively abolished the GABA-evoked release of [³H]noradrenaline, leaving unaffected that of [³H]acetylcholine or [³H]dopamine. 1,2-Bis(2-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA-AM) or vesamicol attenuated the release of [³H]acetylcholine elicited by GABA. Reserpine, but not BAPTA-AM, prevented the effect of GABA on [³H]dopamine release. Autoreceptor activation inhibited the GABA-evoked release of [³H]noradrenaline but not that of [³H]acetylcholine or [³H]dopamine. It is concluded that (a) the release of [³H]noradrenaline consequent to activation of GABA heterocarriers sited on noradrenergic terminals meets the criteria of a conventional exocytotic process, (b) the extracellular [Ca²⁺]-independent releases of [³H]acetylcholine and [³H]dopamine appear to occur from vesicles possibly through involvement of intraterminal Ca²⁺, and (c) autoreceptor activation only affects heterocarrier-mediated vesicular release linked to entry of extracellular Ca²⁺.     

Concomitant Effects of Ramadan Fasting and Time-Of-Day on Apolipoprotein AI,B, Lp-a and Homocysteine Responses during Aerobic Exercise in Tunisian Soccer Players

Objective

To examine the time-of-day and Ramadan fasting (RF) effects on serum apolipoprotein-AI (Apo-AI) and B (Apo-B), lipoprotein particles-a (Lp-a), high-sensitive C-reactive-protein (hs-CRP), and homocysteine (Hcy) during the Yo-Yo intermittent recovery test (YYIRT).

Design

Performance and biochemical measures were completed at two times-of-day (07:00 and 17:00 h), 1-week before RF (BR), the second week of RF (SWR), and the fourth week of RF (ER).

Setting

For each session, subjects performed the YYIRT, and blood samples were taken before and 3-min after the test for biochemical measures.

Participants

Fifteen soccer players.

Main Outcome Measures

Total distance during the YYIRT, core temperature, body composition, dietary intakes, lipid (HDL-C, LDL-C, Apo-AI, B and Lp-a) and inflammatory (hs-CRP and Hcy) profiles.

Results

Performances during the YYIRT were higher in the evening than the morning BR (P < 0.05), but this fluctuation was not observed during RF. Moreover, LDL-C, ApoB, and Lp-a were stable throughout the daytime BR. However, during RF, they decreased at 17:00 h (P < 0.05). Likewise, HDL-C and Apo-AI increased after the exercise and were higher at 17:00 h BR (P < 0.001). Moreover, these parameters increased during RF (P < 0.01). Furthermore, Hcy and hs-CRP increased during the exercise (P < 0.01) with higher evening levels BR. During ER, the diurnal pattern of Hcy was inversed (P < 0.001).

Conclusions

This study concluded that caloric restriction induced by RF seems to ameliorate lipid and inflammatory markers of cardiovascular health during intermittent exercise performed in the evening.     

Influence of Cervical Muscle Fatigue on Musculo-Tendinous Stiffness of the Head-Neck Segment during Cervical Flexion

Aim

The aim of this study is to determine if the fatigue of cervical muscles has a significant influence on the head-neck segment musculo-tendinous stiffness.

Methods

Ten men (aged 21.2 ± 1.9 years) performed four quick-release trials of flexion at 30 and 50% MVC before and after the induction of muscular fatigue on cervical flexors. Electromyographic activity was recorded on the sternocleidomastoids (SCM) and spinal erectors (SE), bilaterally. Musculo-tendinous stiffness was calculated through the quick-release method adapted to the head-neck segment.

Results

We noticed a significant linear increase of the head-neck segment musculo-tendinous stiffness with the increase of exertion level both before (P < 0.0001) and after the fatigue procedure (P < 0.0001). However, this linear relationship was not different before and after the fatigue procedure. EMG analysis revealed a significant increase of the root mean square for the right SCM (P = 0.0002), the left SCM (P < 0.0001), the right SE (P < 0.0001), and the left SE (P < 0.0001) and a significant decrease of the median power frequency only for the right (P = 0.0006) and the left (P = 0.0003) SCM with muscular fatigue.

Discussion

We did not find significant changes in the head-neck segment musculo-tendinous stiffness with fatigue of cervical muscles. We found a significant increase in EMG activity in the SCM and the SE after the induction of fatigue of the SCM. Our findings suggest that with fatigue of cervical flexors, neck muscle activity is modulated in order to maintain the musculo-tendinous stiffness at a steady state.     

Effect of Fatigue on Hamstring Reflex Responses and Posterior-Anterior Tibial Translation in Men and Women

Anterior cruciate ligament (ACL) rupture ranks among the most common injuries in sports. The incidence of ACL injuries is considerably higher in females than in males and the underlying mechanisms are still under debate. Furthermore, it has been suggested that muscle fatigue can be a risk factor for ACL injuries.We investigated gender differences in hamstring reflex responses and posterior-anterior tibial translation (TT) before and after fatiguing exercise. We assessed the isolated movement of the tibia relative to the femur in the sagittal plane as a consequence of mechanically induced TT in standing subjects. The muscle activity of the hamstrings was evaluated. Furthermore, isometric maximum voluntary torque (iMVT) and rate of torque development (RTD) of the hamstrings (H) and quadriceps (Q) were measured and the MVT H/Q as well as the RTD H/Q ratios were calculated.After fatigue, reflex onset latencies were enhanced in women. A reduction of reflex responses associated with an increased TT was observed in females. Men showed no differences in these parameters. Correlation analysis revealed no significant associations between parameters for TT and MVT H/Q as well as RTD H/Q.The results of the present study revealed that the fatigue protocol used in this study altered the latency and magnitude of reflex responses of the hamstrings as well as TT in women. These changes were not found in men. Based on our results, it is conceivable that the fatigue-induced decrease in neuromuscular function with a corresponding increase in TT probably contributes to the higher incidence of ACL injuries in women.     

The Effects of a 6-Week Strength Training on Critical Velocity,Anaerobic Running Distance, 30-M Sprint and Yo-Yo Intermittent Running Test Performances in Male Soccer Players

The objectives of this study were to examine the effects of a moderate intensity strength training on changes in critical velocity (CV), anaerobic running distance (D''), sprint performance and Yo-Yo intermittent running test (Yo-Yo IR1) performances. Methods: two recreational soccer teams were divided in a soccer training only group (SO; n = 13) and a strength and soccer training group (ST; n = 13). Both groups were tested for values of CV, D'', Yo-Yo IR1 distance and 30-m sprint time on two separate occasions (pre and post intervention). The ST group performed a concurrent 6-week upper and lower body strength and soccer training, whilst the SO group performed a soccer only training. Results: after the re-test of all variables, the ST demonstrated significant improvements for both, YoYo IR1 distance (p = 0.002) and CV values (p<0.001) with no significant changes in the SO group. 30-m sprint performance were slightly improved in the ST group with significantly decreased performance times identified in the SO group (p<0.001). Values for D'' were slightly reduced in both groups (ST -44.5 m, 95% CI = -90.6 to 1.6; SO -42.6 m, 95% CI = -88.7 to 3.5). Conclusions: combining a 6-week moderate strength training with soccer training significantly improves CV, Yo-Yo IR1 whilst moderately improving 30-m sprint performances in non-previously resistance trained male soccer players. Critical Velocity can be recommended to coaches as an additional valid testing tool in soccer.     

External and Internal CO2 Transport in Lemanea: Interactions with the Kinetics of Ribulose Bisphosphate Carboxylase

The rate of photosynthesis by the freshwater alga Lemanea mamillosais proportional to CO₂ concentration, virtually to the pointof saturation, and inversely proportional to the radius of thethallus. By contrast, the CO₂ response curve of very thin slicesof the thallus is a rectangular hyperbola with a (lower) halfsaturation concentration of 10 mmol m^–3. For the intactplant, the kinetics of CO₂ fixation are strongly masked by internalCO₂ transport limitations, although the maximum rate of photosynthesisis probably determined by the rate of supply of ribulose bisphosphate(RuBP). The flow of water over the alga becomes turbulent atwater velocities greater than about 90 mm s^–1 and thethallus stretches significantly at higher water velocities.In its natural habitat, therefore, the external unstirred layerwill be thin (< 10 µm) and the thallus will be stretched,leading to rapid external and increased internal rates of CO₂transport from the bulk solution. The estimated maximum rateof CO₂ transport is commensurate with the maximum rate of photosynthesis(i.e. the rate of supply of RuBP). Key words: Transport limitations, Kinetics of CO₂ fixation     

Competition for Antigen between Th1 and Th2 Responses Determines the Timing of the Immune Response Switch during Mycobaterium avium Subspecies paratuberulosis Infection in Ruminants

Johne''s disease (JD), a persistent and slow progressing infection of ruminants such as cows and sheep, is caused by slow replicating bacilli Mycobacterium avium subspecies paratuberculosis (MAP) infecting macrophages in the gut. Infected animals initially mount a cell-mediated CD4 T cell response against MAP which is characterized by the production of interferon (Th1 response). Over time, Th1 response diminishes in most animals and antibody response to MAP antigens becomes dominant (Th2 response). The switch from Th1 to Th2 response occurs concomitantly with disease progression and shedding of the bacteria in feces. Mechanisms controlling this Th1/Th2 switch remain poorly understood. Because Th1 and Th2 responses are known to cross-inhibit each other, it is unclear why initially strong Th1 response is lost over time. Using a novel mathematical model of the immune response to MAP infection we show that the ability of extracellular bacteria to persist outside of macrophages naturally leads to switch of the cellular response to antibody production. Several additional mechanisms may also contribute to the timing of the Th1/Th2 switch including the rate of proliferation of Th1/Th2 responses at the site of infection, efficiency at which immune responses cross-inhibit each other, and the rate at which Th1 response becomes exhausted over time. Our basic model reasonably well explains four different kinetic patterns of the Th1/Th2 responses in MAP-infected sheep by variability in the initial bacterial dose and the efficiency of the MAP-specific T cell responses. Taken together, our novel mathematical model identifies factors of bacterial and host origin that drive kinetics of the immune response to MAP and provides the basis for testing the impact of vaccination or early treatment on the duration of infection.     

理气调补汤对运动性疲劳大鼠血清皮质醇和白细胞介素2影响的研究

目的:通过观察理气调补汤对运动性疲劳大鼠血清皮质醇(C)和白细胞介素2(IL-2)水平的影响,以期揭示中药理气调补汤促进运动性疲劳恢复的作用机理.方法:健康雄性SD大鼠30只,随机分为对照组(Ⅰ组)8只、单纯运动组(Ⅱ组)11只、中药运动组(Ⅲ组)11只.实验时Ⅲ组每天定时定量中药灌胃1ml/100g体重,Ⅰ组、Ⅱ组灌胃相同剂量的生理盐水.实验采用游泳运动训练方式.6周末力竭训练后24h分离血清测定C和IL-2含量.结果:Ⅲ组大鼠游泳至力竭的时间较Ⅱ组显著延长;Ⅱ组和Ⅲ组大鼠血清IL-2浓度均显著低于Ⅰ组,但Ⅲ组大鼠血清IL-2浓度显著高于Ⅱ组;血清C浓度Ⅱ组显著高于Ⅰ组,Ⅲ组较Ⅱ组显著降低.结论:大强度运动训练可能导致HPA轴释放过量皮质醇,从而使免疫功能受到抑制.理气调补汤能够调节疲劳大鼠的HPA轴适应性,降低C的过量释放,维持免疫功能稳定,延缓疲劳的发生.     

Influence of Phthalates on in vitro Innate and Adaptive Immune Responses

Phthalates are a group of endocrine disrupting chemicals, suspected to influence the immune system. The aim of this study was to investigate the influence of phthalates on cytokine secretion from human peripheral blood mononuclear cells. Escherichia coli lipopolysaccharide and phytohemagglutinin-P were used for stimulation of monocytes/macrophages and T cells, respectively. Cells were exposed for 20 to 22 hours to either di-ethyl, di-n-butyl or mono-n-butyl phthalate at two different concentrations. Both diesters were metabolised to their respective monoester and influenced cytokine secretion from both monocytes/macrophages and T cells in a similar pattern: the secretion of interleukin (IL)-6, IL-10 and the chemokine CXCL8 by monocytes/macrophages was enhanced, while tumour necrosis factor (TNF)-α secretion by monocytes/macrophages was impaired, as was the secretion of IL-2 and IL-4, TNF-α and interferon-γ by T cells. The investigated phthalate monoester also influenced cytokine secretion from monocytes/macrophages similar to that of the diesters. In T cells, however, the effect of the monoester was different compared to the diesters. The influence of the phthalates on the cytokine secretion did not seem to be a result of cell death. Thus, results indicate that both human innate and adaptive immunity is influenced in vitro by phthalates, and that phthalates therefore may affect cell differentiation and regenerative and inflammatory processes in vivo.     

The Influence of External Real and White Noise on the LOTKA-VOLTERRA Model

The behaviour of a marginally stable predator-prey system, the LOTKA -VOLTERRA model is analyzed under the influence of parameter fluctuations. The cases of white and real noise are studied separately. It is shown that for white noise no stationary solution exists, but even for time tending to infinity explosion occurs only with zero probability. In the case of real noise the class of noise processes that permit a stationary solution is characterized by their spectral density. It turns out that this class consists of all stationary processes that do not contain the eigenfrequencies of the LOTKA -VOLTERRA system. It is shown that for all other real noise processes a resonance phenomenon occurs and the solutions grow unboundedly.     

Evaluation of Anaerobic Glucose Utilization by Escherichia coli Strains with Impaired Fermentation Ability during Respiration with External and Internal Electron Acceptors

Applied Biochemistry and Microbiology - The characteristics of anaerobic glucose utilization and metabolite production by recombinant Escherichia coli strains with impaired fermentation ability...     

Influence of body CO2 stores on ventilatory dynamics during exercise

Pulmonary CO2 flow (the product of cardiac output and mixed venous CO2 content) is purported to be an important determinant of ventilatory dynamics in moderate exercise. Depletion of body CO2 stores prior to exercise should thus slow these dynamics. We investigated, therefore, the effects of reducing the CO2 stores by controlled volitional hyperventilation on cardiorespiratory and gas exchange response dynamics to 100 W cycling in six healthy adults. The control responses of ventilation (VE), CO2 output (VCO2), O2 uptake (VO2), and heart rate were comprised of an abrupt increase at exercise onset, followed by a slower rise to the new steady state (t1/2 = 48, 43, 31, and 33 s, respectively). Following volitional hyperventilation (9 min, PETCO2 = 25 Torr), the steady-state exercise responses were unchanged. However, VE and VCO2 dynamics were slowed considerably (t1/2 = 76, 71 s) as PETCO2 rose to achieve the control exercise value. VO2 dynamics were slowed only slightly (t1/2 = 39 s), and heart rate dynamics were unaffected. We conclude that pulmonary CO2 flow provides a significant stimulus to the dynamics of the exercise hyperpnea in man.     

Circadian Rhythms: Influences of Internal and External Factors on the Period Measured in Constant Conditions1

The article reviews most of the data available on the period ? of freerunning circadian rhythms, measured in constant conditions. Emphasis is placed on the effects of light intensity and ambient temperature on ?, with references to influences of other external as well as internal factors. In the introduction, examples are given of spontaneous and induced variations in ? and its dependence on the experimental history. The discussion concentrates' largely on results obtained from arthropods and vertebrates.     

Internal and External Influences on Near-Surface Microbial Community Structure in the Vicinity of the Cape Verde Islands

Microbial community structure in the subtropical north-east Atlantic Ocean was compared between 2 years and variation attributed to environmental variables. Surface seawater communities were analysed by flow cytometry and fluorescence in situ hybridisation. Probes specific to Alphaproteobacteria, Cyanobacteria, Gammaproteobacteria and Bacteroidetes identified 67–100% of cells. Due to natural variation in the study region due to the occurrence of major currents and islands, data could not be pooled but were instead divided between distinct water masses. Community structure did not differ greatly around the Cape Verde Islands between sampling periods but varied substantially in the open ocean, suggesting different environmental perturbations favour specific bacterial groups. Wind speed varied significantly between years, with moderate to strong breeze in winter 2008 and gales in winter 2006 (8.9 ± 0.2 ms⁻¹ and 16.0 ± 0.4 ms⁻¹, respectively). Enhanced wind-driven turbulence was associated with domination by the SAR11 clade of Alphaproteobacteria, which were present at 2.4-fold in the abundance of Prochlorococcus (41.8 ± 1.6% cells, compared to 17.7 ± 7.1%). Conversely, the calmer conditions of 2008 seemed to favour Prochlorococcus (40.0 ± 1.2% cells). Prochlorococcus high-light adapted clade HLI were only numerous during wind-driven turbulence, whereas oligotrophic-adapted clade HLII dominated under calm conditions. Bacteroidetes were most prominent in turbulent conditions (9.5 ± 1.3% cells as opposed to 4.7 ± 0.3%), as were Synechococcus. In 2008, a considerable dust deposition event occurred in the region, which may have led to the substantial Gammaproteobacteria population (22.5 ± 4.0% cells compared to 4.6 ± 0.6% in 2006). Wind-driven turbulence may have a significant impact on microbial community structure in the surface ocean. Therefore, community change following dust storm events may be linked to associated wind in addition to dust-derived nutrients.     

The Impact of Herbivory and Competition on Flowering and Survival during Saltmarsh Succession

Abstract: For succession, the establishment and turnover of plants, in terms of generative spreading and renewal, is of crucial importance. Especially the success of seedling establishment into the existing vegetation might be of prime importance for the further development of plant species composition. Flowering, on the other hand, is the necessary first step towards generative output and later seed set. In a chronosequential gradient of a saltmarsh succession, we investigated the performance of transplants of three common species under different conditions: Artemisia maritima, Atriplex portulacoides and Plantago maritima were transplanted as seedlings and mature plants into plots in early-, mid-, and late-successional stages (15, 30 and 40 years) on the Dutch island of Schiermonnikoog. Natural herbivory (by hares and geese) and neighbourhood competition were excluded in a factorial design. Flowering and survival rates of the three species were generally greatly reduced under natural conditions, compared to competition- and herbivory-free plots. The survival rates of Artemisia maritima and Plantago maritima reflect their position as early-successional species: early in succession, both show their highest survival and abundance. For late-dominant Atriplex portulacoides a different explanation has to be invoked for the medium-high survival and low abundance: probably winter grazing by hares and the importance of a high nitrogen supply rate, rather than flowering and survival, determine its low abundance in the early and mid-phase of this saltmarsh succession. Some long-term impacts of herbivores affecting flowering and survival are discussed.     

Influence of age and gender on cardiac output-VO2 relationships during submaximal cycle ergometry

Proctor, David N., Kenneth C. Beck, Peter H. Shen, Tamara J. Eickhoff, John R. Halliwill, and Michael J. Joyner. Influence ofage and gender on cardiacoutput-O₂ relationshipsduring submaximal cycle ergometry. J. Appl.Physiol. 84(2): 599-605, 1998.It is presentlyunclear how gender, aging, and physical activity status interact todetermine the magnitude of the rise in cardiac output(c) during dynamic exercise. To clarify this issue,the present study examined thec-O₂ uptake(O₂) relationship duringgraded leg cycle ergometry in 30 chronically endurance-trained subjects from four groups (n = 6-8/group): younger men (20-30 yr), older men (56-72yr), younger women (24-31 yr), and older women(51-72 yr). c (acetylene rebreathing), strokevolume (c/heart rate), and whole bodyO₂ were measured at restand during submaximal exercise intensities (40, 70, and ~90% of peakO₂). Baseline restinglevels of c were 0.6-1.2 l/min less in theolder groups. However, the slopes of thec-O₂relationship across submaximal levels of cycling were similar among allfour groups (5.4-5.9 l/l). The absolute cassociated with a given O₂(1.0-2.0 l/min) was also similar among groups. Resting andexercise stroke volumes (ml/beat) were lower in women than in men butdid not differ among age groups. However, older men and women showed areduced ability, relative to their younger counterparts, to maintainstroke volume at exercise intensities above 70% of peakO₂. This latter effect wasmost prominent in the oldest women. These findings suggest that neitherage nor gender has a significant impact on thec-O₂ relationships during submaximal cycle ergometry among chronically endurance-trained individuals.