The Yo-Yo Intermittent Recovery Test (Level 1) to discriminate elite junior Australian football players

The Yo-Yo Intermittent Recovery (IR) Test is currently used to assess endurance performance in team sport athletes. However, to date, no data has been presented on its application to an elite junior Australian football (AF) playing group. Therefore, the aim of this study was to evaluate the Yo-Yo Intermittent Recovery Test Level 1 (IR1) ability to discriminate between junior AF players at two different playing standards and a group of non-athletic healthy males. Sixty age matched participants (16.6 ± 0.5 years) spread over three groups (20 per group): elite junior footballers; sub-elite junior footballers; and non-athletic healthy males participated in this study. Participants undertook a single Yo-Yo test performance on an indoor basketball court for each group. A one-way ANOVA with Scheffe's post hoc analysis revealed the elite junior footballers covered a significantly greater total distance (p < 0.001) and completed a significantly greater number of high-intensity efforts (p < 0.001) in comparison to their sub-elite counterparts, whilst both AF groups performed significantly better (p < 0.001) than the non-athletic healthy males. This study demonstrates the ability of the Yo-Yo IR1 to discriminate endurance performance between elite and sub-elite AF players, whilst further distinguishing AF players from a non-athletic healthy control group.

Influences of agricultural landuse and seasonal changes in abiotic conditions on invertebrate colonisation of riparian leaf detritus in intermittent streams

The structure and function of agricultural stream reaches with sparse riparian and floodplain vegetation differ from those of forested reaches, but may be ‘reset’ as these streams flow through reaches with forested riparian zones. We investigated whether invertebrate colonisation of River Red Gum (Eucalyptus camaldulensis) leaf packs in lowland intermittent streams was influenced by the adjacent reach-scale landuse (cleared farmland or forested reserve) within an agricultural catchment in Victoria, Australia. Further, we examined the influence of seasonal changes in hydrology and associated changes in abiotic conditions on the colonisation of leaves by repeating experiments over two summers and one spring. Across these experiments, there were no consistent differences in the structure of communities that colonised leaves in farmland and reserve reaches. In both seasons, most leaf colonists were collectors and few were shredders in both farmland and reserve reaches. Relative abundances of gastropod grazers were much higher in summer than in spring. The structure of invertebrate communities colonising leaves in the different reaches converged over time when streams flowed in spring, but diverged over time as the streams dried and abiotic conditions within disconnected pools became increasingly harsh in summer. Thus, patterns of leaf pack colonisation were influenced by the regional climate causing large seasonal changes in hydrology, but not by reach-scale landuse. The large-scale disturbances of agricultural landuse across the catchment and a supra-seasonal drought probably contributed to low diversities of invertebrate communities in the streams.

Impact on hemostatic parameters of interrupting sitting with intermittent activity

Introduction: Excessive sitting has been associated with an elevated risk of vascular conditions, particularly venous thrombosis. Interrupting sitting time with intermittent physical activity can reduce venous stasis; however, impacts on other aspects of thrombogenesis are less understood. Purpose: To examine the effects of interrupting sitting time on blood coagulation and blood volume parameters in sedentary, middle-age, overweight/obese adults (11 men and 8 women; age = 53.8 T 4.9 yr, body mass index = 31.2 T 4.1 kgImj2; mean T SD). Methods: The randomized three-period, three-treatment acute crossover trial consisted of uninterrupted sitting and sitting interrupted by 2-min bouts of either light- or moderate-intensity treadmill walking every 20 min. In each trial condition, blood samples were collected at baseline before the consumption of a standardized meal (j2 h) and postintervention (5 h). Results: Plasma fibrinogen increased from baseline with uninterrupted sitting (0.24 gILj1, 95% confidence interval = 0.13–0.34, P G 0.001). Lightintensity but not moderate-intensity activity breaks attenuated the increase by 0.17 gILj1 (95% confidence interval = 0.01–0.32, P G 0.05). There were no between-condition differences in prothrombin time, activated partial thromboplastin time, von Willebrand
factor, D-dimer, or platelet count. Uninterrupted sitting reduced plasma volume and increased hematocrit, hemoglobin, and red blood cell count; effects attenuated by both light- and moderate-intensity breaks (P G 0.05). White blood cell count increased with uninterrupted sitting and further increased with moderate-intensity breaks. Mean platelet volume increased with moderate-intensity but not lightintensity breaks or uninterrupted sitting. Conclusion: Uninterrupted sitting increased fibrinogen and reduced plasma volume, with associated increases in hemoglobin and hematocrit. Activity breaks attenuated these responses, indicative of an ameliorating influence on the procoagulant effects of uninterrupted sitting.

Flood forecasting in large rivers with data-driven models

Results from the application of adaptive neuro-fuzzy inference system (ANFIS) to forecast water levels at 3 stations along the mainstream of the Lower Mekong River are reported in this paper. The study investigated the effects of including water levels from upstream stations and tributaries, and rainfall as inputs to ANFIS models developed for the 3 stations. When upstream water levels in the mainstream were used as input, improvements to forecasts were realized only when the water levels from 1 or at most 2 upstream stations were included. This is because when there are significant contributions of flow from the tributaries, the correlation between the water levels in the upstream stations and stations of interest decreases, limiting the effectiveness of including water levels from upstream stations as inputs. In addition, only improvements at short lead times were achieved. Including the water level from the tributaries did not significantly improve forecast results. This is attributed mainly to the fact that the flow contributions represented by the tributaries may not be significant enough, given that there could be large volume of flow discharging directly from the catchments which are ungauged, into the mainstream. The largest improvement for 1-day forecasts was obtained for Kratie station where lateral flow contribution was 17 %, the highest for the 3 stations considered. The inclusion of rainfall as input resulted in significant improvements to long-term forecasts. For Thakhek, where rainfall is most significant, the persistence index and coefficient of efficiency for 5-lead-day forecasts improved from 0.17 to 0.44 and 0.89 to 0.93, respectively, whereas the root mean square error decreased from 0.83 to 0.69 m.

The impact of continuous versus intermittent high frequency stimulation of the nucleus accumbens shell on ethanol preference and circadian locomotor activity in alcohol preferring rats

This study aimed to investigate the effect of different patterns of high-frequency stimulation at the nucleus accumbens shell on ethanol preference and circadian locomotor activity in adult male alcohol preferring (P) and nonpreferring (NP) rats.

Freshwater influences on hydrology and seagrass dynamics of intermittent estuaries

Many temperate estuaries have intermittently open and closed mouths, a feature that is often related to intermittent freshwater input. These systems, often overlooked due to their small size, can have large hydrological variability over medium-term time scales.

This variability presents potential difficulties for estuarine species particularly where anthropogenic alterations to freshwater flows can cause large deviations from natural patterns of tidal influence and inundation of habitat.

Influences of natural and hydrological variability on seagrasses were examined in two central Victorian estuaries with anthropogenically-modified but naturally-intermittent freshwater flows and mouth openings. Comparisons were focused on differences between an estuary with artificially-augmented freshwater inflow and an adjacent system, in which the volume and timing of inflows were altered by a reservoir. Eight additional estuaries in the region were also used to provide a context for these two main sites.

Hydrological changes during the three-year field component were affected by the ending of a drought and then a major flood a year later as well as by ongoing anthropogenic flow reduction and augmentation. These influences on hydrology were associated with an initially high seagrass coverage that was substantially reduced and showed signs of recovery only in the system that was affected by lower inflows. Such influences and responses also changed seasonally but to a much lesser extent than the responses to stochastic climatic events.

Natural flows were intermittent and varied substantially between years. Flooding flows represented up to 89% of the long-term annual average flow. Water quality was broadly typical of the region, with the exception of low pH in some tributaries, especially those of Anglesea estuary. Anthropogenic changes to flow were most evident at times of low natural flows and resulted in longer and more frequent periods of zero inflow to Painkalac estuary and a continual base flow to Anglesea. This base flow, from ponds containing coal ash, neutralised waters flowing from upstream and increased conductivity, except at times of high natural flow.

A three-state conceptual model of the magnitude and variability of water levels, based largely on the degree of tidal influence was identified and quantitatively assessed for the two estuaries that were the main focus of the study. These states in turn had a large influence on the area and inundation of benthic habitat. Floods tended to open the mouths of estuaries, which then remained tidal given sufficient flow to overcome sedimentary processes at the mouths. Low and zero inflow was a precondition for closure of the mouths of the estuaries. When closed, differences in inflow resulted in different endpoints in salinity patterns. From an initial pattern similar to a classic ‘salt wedge’, Painkalac estuary, with reduced inflow, quickly destratified and gradually became more saline, at times hypersaline. Anglesea estuary, with augmented flow, tended to remain stratified for longer until becoming completely fresh, given a long enough period of closure.

Episodic changes in the water quality of the estuaries were associated with different components of the freshwater flow regimes. At high flows, fresh waters of low pH with a high metal load entered Anglesea estuary. Except during the largest flood, when the estuary was completely flushed, this water was neutralised at the halocline and resulting in precipitation of metals. High flows into Painkalac were associated with elevated concentrations of clay-sourced suspended solids. During a closed period, with zero flow, a release of sediment-bound nutrients triggered by anoxia was observed in Painkalac, followed by an algal bloom.

The large decline in seagrass extent that was observed in both estuaries was closely related to floods and the subsequent reductions in potential habitat associated with the tidal states that followed. Analysis of historical patterns of extent against rainfall records suggested that periods of drought and extended mouth closures were related to establishment and expansion of beds. This model was similar to that described for South African estuaries and contrasted with more-seasonal patterns reported for local marine embayments.

Rates of in situ decomposition of seagrass detritus showed a mix of seasonal and disturbance-driven patterns of change, depending on estuary. Variability of these rates on a scale of 100s of metres was typically not significant, but there were a few episodes that were highly significant. A negative correlation between decomposition rate and seagrass extent was also observed. A novel technique for assessing cellulose decomposition potential in sediment, adapted from soil science, proved to be a useful tool for estuarine research. Results from this component of the study highlighted both small-scale variability that was inconsistent through time, and also stable differences in decomposition potential between depths and estuaries that were consistent with differences in hydrological state and salinity.

Given the relative lack of knowledge about processes in intermittent estuaries, particularly those relating to changes in freshwater inflow, results from this study will be of value both locally and for similar systems elsewhere. Locally, it is likely that flow regimes to both Anglesea and Painkalac estuaries will be reduced, following closure of the mine power station at Anglesea and due to increased demand from the reservoir above Painkalac. There is potential to manage flows from each of these sources to minimise downstream effects. Regionally, and globally, there are many intermittent estuaries in areas with Mediterranean-type climates. It has been predicted that the climates of these regions will become drier but with an increase in intensity of storm events, both of which have ramifications for flow regimes to estuaries. It is hoped that results of this study will contribute to more informed management of intermittent estuaries in the context of these likely changes.

Unilateral bicep curl hemodynamics: low-pressure continuous vs high-pressure intermittent blood flow restriction

 Light-load exercise training with blood flow restriction (BFR) increases muscle strength and size. However, the hemodynamics of BFR exercise appear elevated compared with non-BFR exercise. This questions the suitability of BFR in special/clinical populations. Nevertheless, hemodynamics of standard prescription protocols for BFR and traditional heavy-load exercise have not been compared. We investigated the hemodynamics of two common BFR exercise methods and two traditional resistance exercises. Twelve young males completed four unilateral elbow flexion exercise trials in a balanced, randomized crossover design: (a) heavy load [HL; 80% one-repetition maximum (1-RM)]; (b) light load (LL; 20% 1-RM); and two other light-load trials with BFR applied (c) continuously at 80% resting systolic blood pressure (BFR-C) or (d) intermittently at 130% resting systolic blood pressure (BFR-I). Hemodynamics were measured at baseline, during exercise, and for 60-min post-exercise. Exercising heart rate, blood pressure, cardiac output, and rate–pressure product were significantly greater for HL and BFR-I compared with LL. The magnitude of hemodynamic stress for BFR-C was between that of HL and LL. These data show reduced hemodynamics for continuous low-pressure BFR exercise compared with intermittent high-pressure BFR in young healthy populations. BFR remains a potentially viable method to improve muscle mass and strength in special/clinical populations.

Constraints upon the response of fish and crayfish to environmental flow releases in a regulated headwater stream network

In dry climate zones, headwater streams are often regulated for water extraction causing intermittency in perennial streams and prolonged drying in intermittent streams. Regulation thereby reduces aquatic habitat downstream of weirs that also form barriers to migration by stream fauna. Environmental flow releases may restore streamflow in rivers, but are rarely applied to headwaters. We sampled fish and crayfish in four regulated headwater streams before and after the release of summer-autumn environmental flows, and in four nearby unregulated streams, to determine whether their abundances increased in response to flow releases. Historical data of fish and crayfish occurrence spanning a 30 year period was compared with contemporary data (electrofishing surveys, Victoria Range, Australia; summer 2008 to summer 2010) to assess the longer-term effects of regulation and drought. Although fish were recorded in regulated streams before 1996, they were not recorded in the present study upstream or downstream of weirs despite recent flow releases. Crayfish (Geocharax sp. nov. 1) remained in the regulated streams throughout the study, but did not become more abundant in response to flow releases. In contrast, native fish (Gadopsis marmoratus, Galaxias oliros, Galaxias maculatus) and crayfish remained present in unregulated streams, despite prolonged drought conditions during 2006-2010, and the assemblages of each of these streams remained essentially unchanged over the 30 year period. Flow release volumes may have been too small or have operated for an insufficient time to allow fish to recolonise regulated streams. Barriers to dispersal may also be preventing recolonisation. Indefinite continuation of annual flow releases, that prevent the unnatural cessation of flow caused by weirs, may eventually facilitate upstream movement of fish and crayfish in regulated channels; but other human-made dispersal barriers downstream need to be identified and ameliorated, to allow native fish to fulfil their life cycles in these headwater streams.

A computational framework for uncertainty integration in stochastic unit commitment with intermittent renewable energy sources

The penetration of intermittent renewable energy sources (IRESs) into power grids has increased in the last decade. Integration of wind farms and solar systems as the major IRESs have significantly boosted the level of uncertainty in operation of power systems. This paper proposes a comprehensive computational framework for quantification and integration of uncertainties in distributed power systems (DPSs) with IRESs. Different sources of uncertainties in DPSs such as electrical load, wind and solar power forecasts and generator outages are covered by the proposed framework. Load forecast uncertainty is assumed to follow a normal distribution. Wind and solar forecast are implemented by a list of prediction intervals (PIs) ranging from 5% to 95%. Their uncertainties are further represented as scenarios using a scenario generation method. Generator outage uncertainty is modeled as discrete scenarios. The integrated uncertainties are further incorporated into a stochastic security-constrained unit commitment (SCUC) problem and a heuristic genetic algorithm is utilized to solve this stochastic SCUC problem. To demonstrate the effectiveness of the proposed method, five deterministic and four stochastic case studies are implemented. Generation costs as well as different reserve strategies are discussed from the perspectives of system economics and reliability. Comparative results indicate that the planned generation costs and reserves are different from the realized ones. The stochastic models show better robustness than deterministic ones. Power systems run a higher level of risk during peak load hours.

Modeling intermittent cycling performance in hypoxia using the critical power concept

PURPOSE: This study investigated the efficacy of an intermittent critical power model, termed the "work-balance" (W'BAL) model, during high-intensity exercise in hypoxia. METHODS: Eleven trained, male cyclists (mean ± SD; age 27 ± 6.6 yr, V[Combining Dot Above]O2peak 4.79 ± 0.56 L.min) completed a maximal ramp test and a 3 min "all-out" test to determine critical power (CP) and work performed above CP (W'). On another day an intermittent exercise test to task failure was performed. All procedures were performed in normoxia (NORM) and hypoxia (HYPO; FiO2 ≈ 0.155) in a single-blind, randomized and counter-balanced experimental design. The W'BAL model was used to calculate the minimum W' (W'BALmin) achieved during the intermittent test. W'BALmin in HYPO was also calculated using CP + W' derived in NORM (N+H). RESULTS: In HYPO there was an 18% decrease in V[Combining Dot Above]O2peak (4.79 ± 0.56 vs 3.93 ± 0.47 L.min ; P<0.001) and a 9% decrease in CP (347 ± 45 vs 316 ± 46 W; P<0.001). No significant change for W' occurred (13.4 ± 3.9 vs 13.7 ± 4.9 kJ; P=0.69; NORM vs HYPO). The change in V[Combining Dot Above]O2peak was significantly correlated with the change in CP (r = 0.72; P=0.01). There was no difference between NORM and HYPO for W'BALmin (1.1 ± 0.9 kJ vs 1.2 ± 0.6 kJ). The N+H analysis grossly overestimated W'BALmin (7.8 ± 3.4 kJ) compared with HYPO (P<0.001). CONCLUSION: The W'BAL model produced similar results in hypoxia and normoxia, but only when model parameters were determined under the same environmental conditions as the performance task. Application of the W'BAL model at altitude requires a modification of the model, or that CP and W' are measured at altitude.

Rapid directional change degrades GPS distance measurement validity during intermittent intensity running

Use of the Global Positioning System (GPS) for quantifying athletic performance is common in many team sports. The effect of running velocity on measurement validity is well established, but the influence of rapid directional change is not well understood in team sport applications. This effect was systematically evaluated using multidirectional and curvilinear adaptations of a validated soccer simulation protocol that maintained identical velocity profiles. Team sport athletes completed 90 min trials of the Loughborough Intermittent Shuttle-running Test movement pattern on curvilinear, and multidirectional shuttle running tracks while wearing a 5 Hz (with interpolated 15 Hz output) GPS device. Reference total distance (13 200 m) was systematically over- and underestimated during curvilinear (2.61±0.80%) and shuttle (-3.17±2.46%) trials, respectively. Within-epoch measurement uncertainty dispersion was widest during the shuttle trial, particularly during the jog and run phases. Relative measurement reliability was excellent during both trials (Curvilinear r = 1.00, slope = 1.03, ICC = 1.00; Shuttle r = 0.99, slope = 0.97, ICC = 0.99). Absolute measurement reliability was superior during the curvilinear trial (Curvilinear SEM = 0 m, CV = 2.16%, LOA ± 223 m; Shuttle SEM = 119 m, CV = 2.44%, LOA ± 453 m). Rapid directional change degrades the accuracy and absolute reliability of GPS distance measurement, and caution is recommended when using GPS to quantify rapid multidirectional movement patterns.