Energy system contribution in a maximal incremental test: correlations with pacing and overall performance in a 10-km running trial

This study aimed to verify the association between the contribution of energy systems during an incremental exercise test (IET), pacing, and performance during a 10-km running time trial. Thirteen male recreational runners completed an incremental exercise test on a treadmill to determine the respiratory compensation point (RCP), maximal oxygen uptake (V˙O2max), peak treadmill speed (PTS), and energy systems contribution; and a 10-km running time trial (T10-km) to determine endurance performance. The fractions of the aerobic (WAER) and glycolytic (WGLYCOL) contributions were calculated for each stage based on the oxygen uptake and the oxygen energy equivalents derived by blood lactate accumulation, respectively. Total metabolic demand (WTOTAL) was the sum of these two energy systems. Endurance performance during the T10-km was moderately correlated with RCP, V˙O2maxand PTS (P<@0.05), and moderate-to-highly correlated with WAER, WGLYCOL, and WTOTAL (P<0.05). In addition, WAER, WGLYCOL, and WTOTAL were also significantly correlated with running speed in the middle (P<0.01) and final (P<0.01) sections of the T10-km. These findings suggest that the assessment of energy contribution during IET is potentially useful as an alternative variable in the evaluation of endurance runners, especially because of its relationship with specific parts of a long-distance race.

Anaerobic performance in ice hockey : the effect of skate blade radius of hollow

The purpose of the study was to investigate the effect of skate blade radius of hollow (ROH) on anaerobic performance, specifically during the acceleration and stopping phases of an on-ice skating test. Fifteen, male Junior B hockey players (mean age 19 y ± 1.46) were recruited to participate. On-icc testing required each participant to complete an on-ice anaerobic performance test [Reed Repeat Skate (RRS)) on three separate days. During each on-ice test, the participant's skate blades were sharpened to one of three, randomly assigned, ROH values (0.63 cm, 1.27 cm, 1.90 cm). Performance times were recorded during each RRS and used to calculate anaerobic variables [anaerobic power (W), anaerobic capacity (W), and fatigue index (s, %)). Each RRS was video recorded for the purpose of motion analysis. Video footage was imported into Peak Motus™ to measure kinematic variables of the acceleration and stopping phases. The specific variables calculated from the acceleration phase were: average velocity over 6 m (m/s), average stride length (m), and mean stride rate (strides/s). The specific variables calculated from the stopping phase were: velocity at initiation of stopping (rn/s), stopping distance (m), stopping time (s). A repeated measures ANOV A was used to assess differences in mean performance and kinematic variables across the three selected hollows. Further analysis was conducted to assess differences in trial by trial performance and kinematic variables for all hollows. The primary findings of the study suggested that skate blade ROH can have a significant effect on kinematic variables, namely stride length and stride rate during the acceleration phase and stopping distance and stopping time during the stopping phase of an on-ice anaerobic performance test. During the acceleration phase, no significant difdifferences were found in SR and SL across the three selected hollows. Mean SR on the 1.27 cm hollow was significantly slower than both the 0.63 cm and 1.90 cm hollows and SL was significantly longer when skating on the 1.27 cm hollow in comparison to the 1.90 cm hollow. During the stopping phase, stopping distance on the 0.63 cm hollow (4.12 m ± 0.14) was significantly shorter than both the 1.27 cm hollow (4.43 m ± 0.08) (p < 0.05) and the 1.90 cm ho])ow (4.35 m ± 0.12) (p < 0.05). Mean ST was also significantly shorter when stopping on the 0.63 cm hollow then both the 1.27 cm and 1.90 cm hollows. Trial by trial results clearly illustrated the affect of fatigue on kinematic variables; AV, SR, IV decreased from trial 1 to 6. There was no significant effect on anaerobic performance variables during the RRS. Altering the skate blade ROH has a significant and practical affect on accelerating and stopping performance will be discussed in this paper.

Effects of sample solvent composition and injection volume on chromatographic peak profiles of methyl w- benzimidazolecarbamate and 3-butyl1-2,4-dioxo[1,2-a]-s- triazinobenzimidazole in RP-HPLC

The effects of sample solvent composition and the injection volume, on the chromatographic peak profiles of two carbamate derivatives, methyl 2-benzimidazolecarbamate (MBC) and 3-butyl-2,4-dioxo[1,2-a]-s-triazinobenzimidazole (STB), were studied using reverse phase high performance liquid chromatograph. The study examined the effects of acetonitrile percentage in the sample solvent from 5 to 50%, effects of methanol percentage from 5 to 50%, effects of pH increase from 4.42 to 9.10, and effect of increasing buffer concentration from ° to 0.12M. The effects were studied at constant and increasing injection mass and at four injection volumes of 10, 50, 100 and 200 uL. The study demonstrated that the amount and the type of the organic solvents, the pH, and the buffer strength of the sample solution can have a pronounced effect on the peak heights, peak widths, and retention times of compounds analysed. MBC, which is capable of intramolecular hydrogen bonding and has no tendency to ionize, showed a predictable increase .in band broadening and a decrease in retention times at higher eluting strengths of the sample solvent. STB, which has a tendency to ionize or to strongly interact with the sample solvent, was influenced in various ways by the changes in ths sample solvent composition. The sample solvent effects became more pronounced as the injection volume increased and as the percentage of organic solvent in the sample solution became greater. The peak height increases for STB at increasing buffer concentrations became much more pronounced at higher analyte concentrations. It was shown that the widely accepted procedure of dissolving samples in the mobile phase does not yield the most efficient chromatograms. For that reason samples should be dissolved in the solutions with higher aqueous content than that of the mobile phase whenever possible. The results strongly recommend that all the samples and standards, regardless whether the standards are external or internal, be analysed at a constant sample composition and a constant injection volume.

The influence of myosin regulatory light chain phosphorylation on the contractile performance of fatigued mammalian skeletal muscle

ABSTRACT The myosm regulatory light chain (RLC) of type II fibres is phosphorylated by Ca2+ -calmodulin dependent myosin light chain kinase (skMLCK) during muscular activation. The purpose of this study was to explore the effect of skMLCK gene ablation on the fatigability of mouse skeletal muscles during repetitive stimulation. The absence of myosin RLC phosphorylation in skMLCK knockout muscles attenuated contractile performance without a significant metabolic cost. Twitch force was potentiated to a greater extent in wildtype muscles until peak force had diminished to ~60% of baseline (37.2 ± 0.05% vs. 14.3 ± 0.02%). Despite no difference in peak force (Po) and shortening velocity (Vo), rate of force development (+dP/dt) and shortening-induced deactivation (SID) were almost two-fold greater in WT muscles. The present results demonstrate that myosin RLC phosphorylation may improve contractile performance during fatigue; providing a contractile advantage to working muscles and protecting against progressive fatigue.

Mediating Influence of Physical Fitness on the Relationship between Academic Performance and Motor Proficiency

We explored the potential mediating influence of physical fitness on the relationship between academic performance and motor proficiency in children. 1864 students (F:926, M:938, age 11.91 (SD:0.34). Academic achievement was derived from an average of standardized tests of reading, writing, and math. The Bruininks-Oseretsky Test of Motor Performance (short-form) determined motor proficiency. Fitness (peak oxygen uptake) was established with the Léger 20-m Shuttle Run Test. OLS regression identified several significant predictors of academic performance. After controlling for age (p=0.0135), gender (p<0.0001), and parental education (p<0.0001), motor proficiency (p<0.0001), was significant. After adding physical fitness (p=0.0030) to the model the effect of motor proficiency remained significant however the point estimate was reduced from 0.0034 (p<0.0001) to 0.0026 (p<0.0001). These results suggest that physical fitness plays a mediating role on the relationship between academic performance and motor proficiency although both aerobic fitness and motor proficiency have independent roles.

The Influence of Attentional Focus on the Self-Efficacy-Performance Relationship in a Continuous Running Task

The self-efficacy-performance relationship in continuous sport tasks has been shown to be significantly reciprocal yet unequal with stronger influences in the performance-to-self-efficacy pathway rather than self-efficacy-to-performance pathway (e.g., LaForge-MacKenzie & Sullivan, 2014b). Bandura (2012) suggested that sociocognitive variables may influence this relationship. Attention as a sociocognitve factor may bias the processing of performance and self-efficacy information (Bandura, 1982, 1997; Bandura & Jourden, 1991). As confidence and attention are important aspects of peak running performance (Brewer, Van Raalte, Linder, & VanRaalte, 1991), the primary purpose of the present study was to examine the self-efficacy-performance relationship under three conditions of attentional focus. The secondary purpose was to examine self-efficacy and performance as separate constructs under the same conditions of attention. Participants ran continuously for one kilometer in one of three randomly assigned attentional focus conditions: internal-focus (n = 51), external-focus (n = 50), and control (n = 49). Self-efficacy was assessed using a one-item measure every 200 meters. Path analyses examining the primary objective revealed significant self-efficacy-to-performance pathways in all conditions: external-focus (p < .05, βs ranging from -.17 to -.32), internal-focus (p < .05, βs ranging from -.26 to -.36), and control (p < .05, βs ranging from -.29 to -.42). Significant reciprocal relationships were absent in all conditions. ANOVAs examining the secondary objectives found significantly faster performance in the control condition at the start (F (2, 147) = 3.86, p < .05) and end of the task (F (2, 147) = 3.56, p < .05). Self-efficacy was significantly higher in the internal-focus condition at the end of the task (Self-Efficacy 4 (F (2, 147) = 3.21, p < .05) and Self-Efficacy 5 (F (2, 147) = 4.74, p < .05). In contrast to previous within-trial research (e.g., LaForge-MacKenzie & Sullivan, 2014b) self-efficacy-to-performance effects were more significant and robust than performance-to-self-efficacy effects. These results provided support for Bandura’s (2012) suggestion that sociocognitive factors may have the ability to alter the causal structure of the self-efficacy-performance relationship, proposing complexities in the self-efficacy-performance relationship (Sitzmann &Yeo, 2013). Results were discussed from both theoretical and applied perspectives.

Force potentiation as a modulator of contractile performance: Implications for control of skeletal muscle force and energetics of work

This thesis investigated the modulation of dynamic contractile function and energetics of work by posttetanic potentiation (PTP). Mechanical experiments were conducted in vitro using software-controlled protocols to stimulate/determine contractile function during ramp shortening, and muscles were frozen during parallel incubations for biochemical analysis. The central feature of this research was the comparison of fast hindlimb muscles from wildtype and skeletal myosin light chain kinase knockout (skMLCK-/-) mice that does not express the primary mechanism for PTP: myosin regulatory light chain (RLC) phosphorylation. In contrast to smooth/cardiac muscles where RLC phosphorylation is indispensable, its precise physiological role in skeletal muscle is unclear. It was initially determined that tetanic potentiation was shortening speed dependent, and this sensitivity of the PTP mechanism to muscle shortening extended the stimulation frequency domain over which PTP was manifest. Thus, the physiological utility of RLC phosphorylation to augment contractile function in vivo may be more extensive than previously considered. Subsequent experiments studied the contraction-type dependence for PTP and demonstrated that the enhancement of contractile function was dependent on force level. Surprisingly, in the absence of RLC phosphorylation, skMLCK-/- muscles exhibited significant concentric PTP; consequently, up to ~50% of the dynamic PTP response in wildtype muscle may be attributed to an alternate mechanism. When the interaction of PTP and the catchlike property (CLP) was examined, we determined that unlike the acute augmentation of peak force by the CLP, RLC phosphorylation produced a longer-lasting enhancement of force and work in the potentiated state. Nevertheless, despite the apparent interference between these mechanisms, both offer physiological utility and may be complementary in achieving optimal contractile function in vivo. Finally, when the energetic implications of PTP were explored, we determined that during a brief period of repetitive concentric activation, total work performed was ~60% greater in wildtype vs. skMLCK-/- muscles but there was no genotype difference in High-Energy Phosphate Consumption or Economy (i.e. HEPC: work). In summary, this thesis provides novel insight into the modulatory effects of PTP and RLC phosphorylation, and through the observation of alternative mechanisms for PTP we further develop our understanding of the history-dependence of fast skeletal muscle function.

The effect of the year of wheat variety release on productivity and stability of performance on two organic and two non-organic farms

Nineteen wheat cultivars, released from 1934 to 2000, were grown at two organic and two non-organic sites in each of 3 years. Assessments included grain yield, grain protein concentration, protein yield, disease incidence and green leaf area. The superiority of each cultivar (the sum of the squares of the differences between its mean in each environment and the mean of the best cultivar there, divided by twice the number of environments; CS) was calculated for yield, grain protein concentration and protein yield, and ranked in each environment. The yield and grain protein concentration CS were more closely correlated with cultivar release date at the non-organic sites than at organic sites. This difference may be attributed to higher yield levels with larger differences among cultivars at the non-organic sites, rather than to improved stability (i.e. similar ranks) across sites. The significant difference in the correlation of protein yield CS and cultivar age between organic and non-organic sites would support evidence that the ability to take up mineral nitrogen (N) compared to soil N has been a component of the selection conditions of more modern cultivars (released after 1989). This is supported by assessment of green leaf area (GLA), where more modern cultivars in the non-organic systems had greater late-season GLA, a trend that was not identified in organic conditions. This effect could explain the poor correlation between age and protein yield CS in organic compared to non-organic conditions where modern cultivars are selected to benefit from later nitrogen (N) availability which includes the spring nitrogen applications tailored to coincide with peak crop demand. Under organic management, N release is largely based on the breakdown of fertility-building crops incorporated (ploughed-in) in the previous autumn. The release of nutrients from these residues is dependent on the soil conditions, which includes temperature and microbial populations, in addition to the potential leaching effect of high winter rainfall in the UK. In organic cereal crops, early resource capture is a major advantage for maximizing the utilization of nutrients from residue breakdown. It is concluded that selection of cultivars under conditions of high agrochemical inputs selects for cultivars that yield well under maximal conditions in terms of nutrient availability and pest, disease and weed control. The selection conditions for breeding have a tendency to select cultivars which perform relatively better in non-organic compared to organic systems.

The real-time optimisation of DNO owned storage devices on the LV network for peak reduction

Energy storage is a potential alternative to conventional network reinforcementof the low voltage (LV) distribution network to ensure the grid’s infrastructure remainswithin its operating constraints. This paper presents a study on the control of such storagedevices, owned by distribution network operators. A deterministic model predictive control (MPC) controller and a stochastic receding horizon controller (SRHC) are presented, wherethe objective is to achieve the greatest peak reduction in demand, for a given storagedevice specification, taking into account the high level of uncertainty in the prediction of LV demand. The algorithms presented in this paper are compared to a standard set-pointcontroller and bench marked against a control algorithm with a perfect forecast. A specificcase study, using storage on the LV network, is presented, and the results of each algorithmare compared. A comprehensive analysis is then carried out simulating a large number of LV networks of varying numbers of households. The results show that the performance of each algorithm is dependent on the number of aggregated households. However, on a typical aggregation, the novel SRHC algorithm presented in this paper is shown to outperform each of the comparable storage control techniques.

Control methodologies: Peak reduction algorithms for DNO owned storage devices on the Low Voltage network

The Distribution Network Operators (DNOs) role is becoming more difficult as electric vehicles and electric heating penetrate the network, increasing the demand. As a result it becomes harder for the distribution networks infrastructure to remain within its operating constraints. Energy storage is a potential alternative to conventional network reinforcement such as upgrading cables and transformers. The research presented here in this paper shows that due to the volatile nature of the LV network, the control approach used for energy storage has a significant impact on performance. This paper presents and compares control methodologies for energy storage where the objective is to get the greatest possible peak demand reduction across the day from a pre-specified storage device. The results presented show the benefits and detriments of specific types of control on a storage device connected to a single phase of an LV network, using aggregated demand profiles based on real smart meter data from individual homes. The research demonstrates an important relationship between how predictable an aggregation is and the best control methodology required to achieve the objective.

The impact of location and type on the performance of Low-Voltage network connected Battery Energy Storage Systems

This paper assesses the impact of the location and configuration of Battery Energy Storage Systems (BESS) on Low-Voltage (LV) feeders. BESS are now being deployed on LV networks by Distribution Network Operators (DNOs) as an alternative to conventional reinforcement (e.g. upgrading cables and transformers) in response to increased electricity demand from new technologies such as electric vehicles. By storing energy during periods of low demand and then releasing that energy at times of high demand, the peak demand of a given LV substation on the grid can be reduced therefore mitigating or at least delaying the need for replacement and upgrade. However, existing research into this application of BESS tends to evaluate the aggregated impact of such systems at the substation level and does not systematically consider the impact of the location and configuration of BESS on the voltage profiles, losses and utilisation within a given feeder. In this paper, four configurations of BESS are considered: single-phase, unlinked three-phase, linked three-phase without storage for phase-balancing only, and linked three-phase with storage. These four configurations are then assessed based on models of two real LV networks. In each case, the impact of the BESS is systematically evaluated at every node in the LV network using Matlab linked with OpenDSS. The location and configuration of a BESS is shown to be critical when seeking the best overall network impact or when considering specific impacts on voltage, losses, or utilisation separately. Furthermore, the paper also demonstrates that phase-balancing without energy storage can provide much of the gains on unbalanced networks compared to systems with energy storage.

The medieval climate anomaly and Byzantium: a review of the evidence on climatic fluctuations, economic performance and societal change

At the beginning of the Medieval Climate Anomaly, in the ninth and tenth century, the medieval eastern Roman empire, more usually known as Byzantium, was recovering from its early medieval crisis and experiencing favourable climatic conditions for the agricultural and demographic growth. Although in the Balkans and Anatolia such favourable climate conditions were prevalent during the eleventh century, parts of the imperial territories were facing significant challenges as a result of external political/military pressure. The apogee of medieval Byzantine socio-economic development, around AD 1150, coincides with a period of adverse climatic conditions for its economy, so it becomes obvious that the winter dryness and high climate variability at this time did not hinder Byzantine society and economy from achieving that level of expansion. Soon after this peak, towards the end of the twelfth century, the populations of the Byzantine world were experiencing unusual climatic conditions with marked dryness and cooler phases. The weakened Byzantine socio-political system must have contributed to the events leading to the fall of Constantinople in AD 1204 and the sack of the city. The final collapse of the Byzantine political control over western Anatolia took place half century later, thus contemporaneous with the strong cooling effect after a tropical volcanic eruption in AD 1257. We suggest that, regardless of a range of other influential factors, climate change was also an important contributing factor to the socio-economic changes that took place in Byzantium during the Medieval Climate Anomaly. Crucially, therefore, while the relatively sophisticated and complex Byzantine society was certainly influenced by climatic conditions, and while it nevertheless displayed a significant degree of resilience, external pressures as well as tensions within the Byzantine society more broadly contributed to an increasing vulnerability in respect of climate impacts. Our interdisciplinary analysis is based on all available sources of information on the climate and society of Byzantium, that is textual (documentary), archaeological, environmental, climate and climate model-based evidence about the nature and extent of climate variability in the eastern Mediterranean. The key challenge was, therefore, to assess the relative influence to be ascribed to climate variability and change on the one hand, and on the other to the anthropogenic factors in the evolution of Byzantine state and society (such as invasions, changes in international or regional market demand and patterns of production and consumption, etc.). The focus of this interdisciplinary

Electrical Evaluation of a Low Concentrating PVT Collector Based on Performance Ratio

Photovoltaic Thermal/Hybrid collectors are an emerging technology that combines PV and solar thermal collectors by producing heat and electricity simultaneously. In this paper, the electrical performance evaluation of a low concentrating PVT collector was done through two testing parts: power comparison and performance ratio testing. For the performance ratio testing, it is required to identify and measure the factors affecting the performance ratio on a low concentrating PVT collector. Factors such as PV cell configuration, collector acceptance angle, flow rate, tracking the sun, temperature dependence and diffuse to irradiance ratio. Solarus low concentrating PVT collector V12 was tested at Dalarna University in Sweden using the electrical equipment at the solar laboratory. The PV testing has showed differences between the two receivers. Back2 was producing 1.8 energy output more than Back1 throughout the day. Front1 and Front2 were almost the same output performance. Performance tests showed that the cell configuration for Receiver2 with cells grouping (6- 32-32-6) has proved to have a better performance ratio when to it comes to minimizing the shading effect leading to more output power throughout the day because of lowering the mismatch losses. Different factors were measured and presented in this thesis in chapter 5. With the current design, it has been obtained a peak power at STC of 107W per receiver. The solar cells have an electrical efficiency of approximately 19% while the maximum measured electrical efficiency for the collector was approximately 18 % per active cell area, in addition to a temperature coefficient of -0.53%/ ˚C. Finally a recommendation was done to help Solarus AB to know how much the electrical performance is affected during variable ambient condition and be able to use the results for analyzing and introducing new modification if needed.

The influence of temporal food restriction on the performance of isolated cardiac muscle

In this study we assessed the mechanical function of isolated left ventricular papillary muscles from 60 day-old male Wistar-Kyoto rats (WKY) subjected to different periods of food restriction (FR). The food-restricted animals (R) were fed 50% of the amount of diet consumed by the ad Libitum-fed rats (C). The cardiac muscles were studied after 30, 60, and 90 days (R-30, R-60 and R-90) of FR. The effect of FR on myocardial collagen concentration was also evaluated. The parameters from the three control groups that were statistically identical were combined and the control pool group (CP) was formed. The left ventricular weight-to-body weight ratio was lower in the R-30 and higher in the R-60 and R-90 in relation to their control groups. Hydroxyproline concentration was higher only in R-90 compared to CP and R-30. Myocardial mechanical function was the same in the C groups. The comparisons between CP and FR groups showed that: the muscles of R-30 presented increased resting tension and maximum rate of tension decline, and decreased velocity of shortening; the muscles of R-60 and R-90 groups showed a prolongation of the time to peak tension (TPT) and the time to peak shortening (TPS); and R-30 had an increased time from peak tension to 50% relaxation (RT1/2). Increases in TPT, TPS, and RT1/2 in groups R-60 and R-90 were significant in relation to R-30. In conclusion, while FR for 30 days produces disparate effects on myocardial performance, FR for 60 and 90 days prolongs the contraction period. The change of relaxation time in R-90 might be related to the increased myocardial collagen content. (C) 2001 Elsevier B.V. All rights reserved.

Production performance and egg quality of quails (Coturnix japonica) during several periods of the day

Three experiments were carried out to analyze the performance and egg quality of Japanese quails throughout the day when submitted to different lighting programs. In each experiment, birds were submitted to a period of 28 days for adaptation to the lighting program. During the following three days, each day - from 7 am to 7 pm or 9 pm - was divided into six or seven periods of two hours each, and the remaining hours corresponded to another single period. All birds were submitted to the same management practices, and received water and feed ad libitum. The experimental diet was formulated according to NRC (1994) standards. It was observed lower feed intake in the period of 9 pm to 7 am, and a higher incidence of lay from 3 pm to 7 pm, as opposite to hens, which peak of egg laying occurs during the morning. Some controversial results were found among experiments as to eggshell quality during the different periods of the day. Variation on the lighting program had little influence on the other performance and egg quality parameters.