Min Steady State Research Articles

IMPACT OF CASEIN PROTEIN CONTAINING L-TRYPTOPHAN AND MELATONIN ON SLEEP QUALITY AND ENERGY EXPENDITURE

Increases in morning resting energy expenditure (REE) have been observed following late evening ingestion of protein. However, the impact of late night protein supplementation containing melatonin and L-Tryptophan has yet to be examined. PURPOSE: The purpose of this study is to determine the impact of the ingestion of pre-sleep casein protein supplement that contains L-Tryptophan and melatonin (PRO) on sleep quality, energy expenditure prior, during, and post exercise. METHODS: Aerobically active females (n = 13; age = 22.6 ± 1.9 yrs; ht = 1.65 ± 0.06 m; wt = 60.5 ± 9.6 kg; % bf = 22.5 ± 4.3; VO2max = 44.1 ± 5.3 ml/kg/min) participated in the study. In a cross-over design, PRO (Casein; 34.3g; 140 kcal; 289mg L-Tryptophan; 1mg Melatonin) or placebo (PLA) (cocoa powder; 10g; 20 kcal) were ingested 30 min prior to sleep. Sleep quality and perceived satiety were assessed using 10cm sliding scale the following morning. REE was measured for 30 minutes with at least 5 min of steady state before and after exercise. The exercise protocol consisted of 20 min of aerobic exercise on a treadmill at 40-50% of VO2max. Total calories during exercise were used to compare exercise energy expenditure (EEE). For the statistical analyses, Paired-samples t-tests and two-way repeated measures ANOVA. Results were considered significant at ≤ 0.05. RESULTS: Sleep quality during PRO was not significantly different than the PLA trial (61.6 ± 21.5 mm vs 68.4 ± 20.5 mm; p = 0.39). Perceived satiety during PRO was not significantly different than PLA (29.6 ± 8.2 mm vs 23.9 ± 6.6 mm; p = 0.43). EEE during PRO was not significantly different than PLA (112.1 ± 20.4 kcals vs 112.2 ± 21.8 kcals; p = 0.91). The main effects (supplement: p = 0.93; time: p = 0.15) and the interaction (Supplement x Time: p = 0.75) for REE pre and post exercise in PRO and PLA were not significantly different. CONCLUSIONS: No changes were observed ingesting PRO prior to sleep on next morning EEE and REE before and after exercise. Future investigations should examine the effects of relative (g/kg bw) pre-sleep protein containing tryptophan and melatonin ingestion on next morning EEE.

Feasibility Of Self-paced Intermittent Hypoxic Exercise As An Exercise Intervention In Obese Populations

BACKGROUND: We have previously shown for a healthy population, that in hypoxic conditions equivalent to 3500 m, self-paced intermittent best effort walking results in ~32 % greater oxygen cost (VO2) compared to matched work steady state walking. By combining a self-paced intermittent protocol with recumbent cycling, suggested to be a more comfortable exercise mode for obese populations, some perceived barriers to exercise (e.g. lack of time, discomfort) could be mitigated against, whilst increasing the exercise stimulus. PURPOSE: To determine if self-paced intermittent recumbent cycling performed in normobaric hypoxia increases oxygen cost and energy expenditure (EE) compared to matched work and duration steady-state exercise, and is a tolerable exercise mode for obese populations. METHOD: Fourteen tier 2 obese participants (4 men; 39 ± 13 yr; 165.1 ± 8.1 cm; 95.2 ± 16.1 kg; BMI: 34.9 ± 5.0 kg/m2) completed 3 exercise trials separated by 7 days. Trials were performed on a recumbent cycle ergometer and in a normobaric hypoxic chamber (FiO2 0.135). After determination of hypoxic ventilatory threshold (VT) and maximal power output (Wmax), participants completed one 20 min steady state (SS) cycle at 90 % VT, and one self-paced intermittent (INT) cycle. During INT, participants performed periods of maximal work at Wmax and could stop and rest as many times as necessary before completing the distance covered during SS. Breath-by-breath data were collected by a metabolic cart, and heart rate and arterial oxygen saturation were monitored throughout. Time to complete SS and INT were compared by Wilcoxon signed-rank test, and physiological data were compared by paired t-test. RESULTS: Time to complete the exercise bouts was similar (SS: 1200 ± 00 s vs INT: 1421 ± 441 s, p = 0.14). INT elicited a 30% higher VO2 (SS: 1779.46 ± 320.19 L; INT: 2553.77 ± 1097.65 L) and EE than SS [0.89 ± 0.38 MJ (212.81 ± 91.47 kcal) vs. 0.62 ± 0.11 MJ (148.29 ± 26.68 kcal)], p = 0.03). CONCLUSION: The self-paced INT protocol was completed by all obese participants without incident or complaint, and induced a 30% increase in EE compared to a comparable duration of work performed at 90% VT. Further work is required to compare long-term adherence and weight loss/metabolic responses to this mode of exercise completed in both normoxic and hypoxic conditions.

Development, optimization, and evaluation of tamsulosin nanotransfersomes to enhance its permeation and bioavailability

Tamsulosin (TM) is a drug used for benign prostatic hyperplasia. This drug produces undesired side effects on oral administration due to fluctuation in the plasma level. Therefore, a transdermal delivery system is beneficial. Lipid-based systems revolutionized the transdermal route of drug delivery. Among them, nanotransfersomes, which have flexible and elastic membranes enabling them to improve skin permeation. Therefore, in the present study, we aimed to optimize nanotransfersomes by the statistical design of experiments in order to optimize the quantities of tamsulosin (drug), Lipoid S100 (lipid), and sodium deoxycholate SDC (edge activator). The responses were particle size, entrapment efficiency, and ex-vivo steady-state flux. The optimized formulation was characterized and evaluated for pharmacokinetic parameters. The results indicated that optimum nanotransfersome by the software consisted of tamsulosin (0.4664 mg), lipoid S100 (59.30 mg), and SDC (58.96 mg) showed 60 nm particle size, 42% entrapment, and 7.2 mcg/cm2.min steady state flux. Nanotransfersomes appeared spherical and uniform in TEM image. The stability index of the optimized formula was 85%. The enhancement in bioavailability was well significant when compared to the marketed tablet. Overall, the nanotransfersomes have proved as an efficient transdermal delivery system for tamsulosin.

Perception of Carbohydrate Availability Augments High-Intensity Intermittent Exercise Capacity Under Sleep-Low, Train-Low Conditions.

The authors tested the hypothesis that perception of carbohydrate (CHO) availability augments exercise capacity in conditions of reduced CHO availability. Nine males completed a sleep-low train model comprising evening glycogen-depleting cycling followed by an exhaustive cycling protocol the next morning in the fasted state (30min steady state at 95% lactate threshold followed by 1-min intervals at 80% peak power output until exhaustion). After the evening depletion protocol and prior to sleeping, subjects consumed (a)a known CHO intake of 6g/kg body mass (TRAIN HIGH) or (b)a perceived comparable CHO intake but 0g/kg body mass (PERCEPTION) or a known train-low condition of 0g/kg body mass (TRAIN LOW). The TRAIN HIGH and PERCEPTION trials were conducted double blind. During steady state, average blood glucose and CHO oxidation were significantly higher in TRAIN HIGH (4.01 ± 0.56mmol/L; 2.17 ± 0.70g/min) versus both PERCEPTION (3.30 ± 0.57mmol/L; 1.69 ± 0.64g/min, p < .05) and TRAIN LOW (3.41 ± 0.74mmol/L; 1.61 ± 0.59g/min, p < .05). Exercise capacity was significantly different between all pairwise comparisons (p < .05), where TRAIN LOW (8 ± 8min) < PERCEPTION (12 ± 6min) < TRAIN HIGH (22 ± 9min). Data demonstrate that perception of CHO availability augments high-intensity intermittent exercise capacity under sleep-low, train-low conditions, though this perception does not restore exercise capacity to that of CHO consumption. Such data have methodological implications for future research designs and may also have practical applications for athletes who deliberately practice elements of training in CHO-restricted states.

Does Pattern of Drink Intake Affect Exogenous Carbohydrate Oxidation During Prolonged Submaximal Running?

Marathons and half-marathons usually position drink stations every 5 km, providing opportunity for fast runners to consume fluid and carbohydrate approximately every 15-20 min. In recent attempts to break the marathon world record, drinks have been provided at more frequent intervals, often in smaller volumes. PURPOSE: To determine how the pattern of carbohydrate ingestion during running affects exogenous carbohydrate oxidation rates and measures of gastrointestinal (GI) comfort. METHODS: Twelve well-trained male runners (27 ± 7 y, 67.9 ± 6.7 kg, V̇O2peak: 68 ± 7 mL/kg/min) completed three exercise trials of 100 min steady state running at 70% V̇O2peak. During the first trial, 200 mL water was consumed every 20 min and results were used for background correction of 13CO2 breath enrichment. In the final two trials a 1 L volume of a 10% dextrose solution, enriched with [U-13C] glucose, was consumed at a rate of either 200 mL every 20 min (CHO-20) or 50 mL every 5 min (CHO-5). Expired breath and venous blood samples were collected at rest and every 20 min during exercise. Subjective scales of GI comfort were recorded at regular intervals. RESULTS: Exogenous carbohydrate oxidation rates were higher after 80 (0.58 ± 0.16 v 0.48 ± 0.16 g/min; P =0.020) and 100 min (0.67 ± 0.14 v 0.58 ± 0.15 g/min; P =0.016) of running in CHO-20 compared to CHO-5. During exercise, total carbohydrate oxidation rates were similar between trials and remained within a range of 2.0 to 2.5 g/min (P>0.168). Oxidation of endogenous carbohydrate was lower in CHO-20 (1.87 ± 0.37 v 2.08 ± 0.44 g/min; P<0.05). Serum glucose concentration increased above 5 mmol/L after drink ingestion, remaining elevated throughout exercise with no difference between trials (P =0.095). There were no differences in reported symptoms of GI comfort (P >0.05), with no subject reporting severe symptoms (all < 6) in either trial. CONCLUSIONS: Ingestion of a larger volume of carbohydrate solution at less frequent intervals increased exogenous carbohydrate oxidation rates, resulting in similar rates of total carbohydrate oxidation but with reduced contribution from endogenous carbohydrate stores.

Effects of 7-Day Ketone Ingestion and a Physiological Workload on Postural Stability, Cognitive, and Muscular Exertion Measures in Professional Firefighters

Background: Postural stability and cognitive performance are challenged in firefighters. The purpose of this investigation was to examine the impact of 7-day ketone supplementation on postural stability, cognitive performance, and muscular activation before and after a physiological workload. Methods: Nine professional firefighters completed two experimental sessions (pre- and post-workload) in a counterbalanced, double-blind design. Participants ingested either a ketone salt (KS) or placebo (PLA) daily for seven days, and had an eighth ingestion 30 min prior to testing. Each experimental testing consisted of maximal voluntary contractions (MVIC) for four muscles (knee flexors—BF, extensor—VM, ankle dorsiflexors—TA, and plantar flexors—MG) using electromyography and postural stability testing (eyes open (EO), eyes closed (EC), and eyes open-dual-task using a FitLight™ system (EOT)), before (pre-workload) and after (post-workload) a simulated physiological workload. The workload consisted of 35 min steady state exercise at 60% of peak oxygen consumption wearing firefighter personal protective equipment (PPE). Results: Significant differences were limited to time effects (pre-workload vs. post-workload), with no differences between groups (KS vs. PLA). Significantly lower muscle activity in VM, TA, and MG during MVIC, greater postural sway and muscle activity in BF during EC and EOT, and slower response time during EOT were evident post-workload. Conclusions: A 7-day ketone supplementation does not impact postural stability, muscle activity, and cognitive tasks, but a fatiguing workload causes significant performance reduction.

Methods for data analysis of resting energy expenditure measured using indirect calorimetry.

The aim of this study was to test the accuracy of different methods of resting energy expenditure (REE) data analysis using indirect calorimetry (IC) during traditional (30 min) and abbreviated (10 min) protocols. Fifteen women and 15 men (21-34 y of age) completed two consecutive 30-min IC measurements. Body composition was measured using dual-energy x-ray absorptiometry. The reference method for REE analysis was 5 min in steady state (SS) during 30 min (first 5 min discarded). REE measurements were randomized to define a reference or testing method. An interval method was defined using 25, 20, and 15 min (with first 5, 10, and 15 min discarded, respectively), during 30 min, and 5 min (first 5 min discarded) during 10-min intervals. The SS method was defined using 5 min in SS (first 5 min discarded) during 30 min, 5, 4, and 3 min in SS during 10-min (first 5 min discarded) intervals. Interval methods during 30 min and SS and interval methods during 10 min demonstrated large bias with significantly high REEs compared to the reference method (78.8-109.0 kcal/d, all P < 0.001). Testing methods demonstrated large upper limits of agreement between 225.2 and 322.8 kcal/d. No mean differences (P > 0.05), small bias (14.3 kcal/d), and narrow limits of agreement (-125.8 to 154.4 kcal/d) were observed between 5-min SS during 30 min and the reference method. All interval methods and SS methods during 10 min overestimated REE. We recommend using 5-min SS during 30 min. The measurement may be repeated until all participants achieve SS.

Heart Rate Variability in Marathon Runners During Steady State Exercise and a Graded Exercise Test

Heart rate variability (HRV) analysis offers insight into health status, where greater HRV is associated with better cardiovascular function. Unlike most HRV techniques, which require stationarity of data (e.g., rest), detrended fluctuation analysis (DFA) does not. However, DFA may require a larger data set for reliable results. DFA captures both short- (DFAα1) and long-term fluctuations (DFAα2). A reliable technique to measure HRV using a brief, submaximal exercise session could serve as a simple method of assessing health and adaptability. PURPOSE: To compare HRV using DFA during a 3-min steady state (SS) run versus a longer graded exercise test (GXT). METHODS: Forty recreational runners (21.1 ± 1.6 years, 27f) completed a 2-mile (3.218-km) time trial (TT) prior to, and after 18 weeks of training for a 42.2-km marathon. Subjects performed a SS run at 75% of TT velocity for 6 min followed by an incremental GXT. Paired samples t tests were used to compare pre- and post-DFA measures, TT, and VO2max, and to compare DFA scores for the final 3 min of SS with the full GXT. Delta scores were calculated for all variables. Correlations between the changes were assessed using Pearson’s RESULTS: When comparing SS and GXT, post-DFAα1 and α2 and pre-DFAα1 were different. (p ≤ 0.001). During SS, DFAα1 decreased from pre- to post-testing (0.947 ± 0.248, 0.835 ± 0.261; p ≤ 0.018) whereas DFAα2 did not change: (1.224 ± 0.188, 1.291 ± 0.207; p = 0.150). For the full GXT, neither DFAα1 or DFAα2 changed with training. Subjects improved in TT (15.5 ± 2.0, 14.3 ± 1.6; p ≤ 0.001) and VO2max (50.4 ± 7.2, 52.7 ± 7.0; p = 0.002). DFA scores for SS and GXT were significantly correlated (r = 0.59 to 0.70, p ≤ 0.001) with the exception of the DFAα2 post-test (r = 0.25, p = 0.122). The changes from pre- to post-test during SS and GXT were correlated (DFAα1: r = 0.60, p ≤ 0.001; DFAα2: r = 0.32, p = 0.044). CONCLUSION: DFAα1 during SS decreased with training, indicating increased short-term HRV. While SS and GXT yielded different DFA scores, the correlations between the scores during SS and GXT and the correlations between the changes suggest that the SS data captures information related to the larger data set. Further research is needed to determine whether the differences between SS and GXT scores are due to the smaller data set or the higher exercise intensity during GXT.

Influence of myocardial oxygen demand on the coronary vascular response to arterial blood gas changes in humans.

It remains unclear if the human coronary vasculature is inherently sensitive to changes in arterial Po2 and Pco2 or if coronary vascular responses are the result of concomitant increases in myocardial O2 consumption/demand ([Formula: see text]). We hypothesized that the coronary vascular response to Po2 and Pco2 would be attenuated in healthy men when [Formula: see text] was attenuated with β1-adrenergic receptor blockade. Healthy men (age: 25 ± 1 yr, n = 11) received intravenous esmolol (β1-adrenergic receptor antagonist) or volume-matched saline in a double-blind, randomized crossover study and were exposed to poikilocapnic hypoxia, isocapnic hypoxia, and hypercapnic hypoxia. Measurements made at baseline and after 5 min of steady state at each gas manipulation included left anterior descending coronary blood velocity (LADV; Doppler echocardiography), heart rate, and arterial blood pressure. LADV values at the end of each hypoxic condition were compared between esmolol and placebo. The rate-pressure product (RPP) and left ventricular mechanical energy (MELV) were calculated as indexes of [Formula: see text]. All gas manipulations augmented RPP, MELV, and LADV, but only RPP and MELV were attenuated (4-18%) after β1-adrenergic receptor blockade ( P < 0.05). Despite attenuated RPP and MELV responses, β1-adrenergic receptor blockade did not attenuate the mean LADV vasodilatory response compared with placebo during poikilocapnic hypoxia (29.4 ± 2.2 vs. 27.3 ± 1.6 cm/s) and isocapnic hypoxia (29.5 ± 1.5 vs. 30.3 ± 2.2 cm/s). Hypercapnic hypoxia elicited a feedforward coronary dilation that was blocked by β1-adrenergic receptor blockade. These results indicate a direct influence of arterial Po2 on coronary vascular regulation that is independent of [Formula: see text]. NEW & NOTEWORTHY In humans, arterial hypoxemia led to an increase in epicardial coronary artery blood velocity. β1-Adrenergic receptor blockade did not diminish the hypoxemic coronary response despite reduced myocardial O2 demand. These data indicate hypoxemia can regulate coronary blood flow independent of myocardial O2 consumption. A plateau in the mean left anterior descending coronary artery blood velocity-rate-pressure product relationship suggested β1-adrenergic receptor-mediated, feedforward epicardial coronary artery dilation. In addition, we observed a synergistic effect of Po2 and Pco2 during hypercapnic hypoxia.

The effect of ice slurry ingestion on body temperature and cycling performance in competitive athletes

The effects of pre cooling on endurance performance are widely known. In contrast, the approach of cooling during endurance exercise in combination with pre-exercise cooling has been poorly understood. The purpose of the present study was to determine whether the effects of precooling and cooling during exercise enhance exercise performance compared to the ingestion of a thermo-neutral beverage (20 °C) or precooling alone in cycling performance. This was an experimental study using a randomised crossover design in which 7 cyclists underwent three trials comprising of 45 min steady state cycling (SS) at 70% VO2 max and a subsequent 10 km time trial (TT) in hot conditions (32 °C, 50% relative humidity). Rectal temperature (Tre), heat storage (HS), heart rate (HR), blood lactate concentration (BLA) and thermal sensation (TS) were measured. The intervention consisted of: (1) ingestion of thermo-neutral beverage before and during SS cycling (TN), (2) ingestion of ice slurry beverage and application of iced towels (precooling) prior to exercise, and then ingestion of thermo-neutral beverage during SS (PRE) and (3) precooling strategy as above plus ice slurry ingestion during SS cycling (PRE + MID). The intake of thermo-neutral or ice slurry beverage (14 g/kg) occurred over 30 min before and every 15 min during SS cycling. There was no significant difference in TT performance between all the conditions (P =0.72). However, PRE and PRE + MID caused a significant decrease in Tre (P < 0.05) from TN during exercise. Accordingly, both precooling and a combination of precooling and mid-cooling during exercise in hot conditions may be a practical and effective way of reducing core temperature. Future studies should investigate longer distance events and timing of ice slurry ingestion.

Effects of carbohydrate mouth rinse and caffeine on high-intensity interval running in a fed state.

The current study aims to identify if mouth rinsing with a 6% carbohydrate mouth-rinse (CMR) solution and mouth rinsing and ingestion of caffeine (CMR+CAFF) can affect exercise performance during steady-state (SS) running and high-intensity intervals (HIIT) in comparison with a 0% control solution (PLA) when in a fed state. Eight recreationally trained males completed 3 trials (CMR, CMR+CAFF, and PLA) of 45 min SS running and an HIIT protocol (90% peak treadmill velocity) until fatigue in a double blinded, repeated-measures study. Participants ingested a capsule of either CAFF or PLA before and after SS. Participants received a 25-mL bolus of carbohydrate solution (CMR and CMR+CAFF trials) or taste-matched PLA (PLA trial) prior to HIIT protocol and after every second effort. Heart rate and lactate responses were recorded throughout the SS and HIIT protocol. CMR+CAFF was significantly different when compared with PLA (p = 0.001; Cohens d = 1.34) and CMR (p = 0.031; Cohens d = 0.87) in relation to distance covered before fatigue. Although there was no significant difference between CMR and PLA, there was a small benefit for CMR (p = 0.218; Cohens d = 0.46). Results indicate that CMR and ingestion of CAFF leads to improvements in performance during interval sessions while participants were in a fed state. These findings indicate that the regular use of CMR can decrease the risk of gastrointestinal distress reported by athletes, which can be applicable to athletes in a real-world setting.

Evaluation of a short protocol for indirect calorimetry in females with eating disorders and healthy controls

To enable clinicians to identify the clinical picture and treatment progress and to adjust eating plans according to personal energy needs, it is important to know the patient's correct resting metabolic rate (RMR). Indirect calorimetry (IC) is the preferred method for assessment of RMR, but long duration of measurement increases the load on the patients, and reduces the effectiveness in clinical and scientific settings. Further; not all patients reach a valid RMR according to the suggested best practice protocol, with 5min of steady state (SS) where respiratory gas volume exchange varies less than 10%. The aim of this study was to evaluate the possibility for an abbreviated RMR protocol and SS criterion. Forty two women diagnosed with bulimia nervosa or binge eating disorder (eating disorder group, ED), originally recruited for an outpatient treatment study, and 26 age and gender matched healthy controls (HC) were studied during a single, prolonged IC measurement. Participants rested for 10min in supine position wearing a two-way breathing facemask, before a continuous measurement period of 20min. Results from a standard 5min SS criterion was compared to an abbreviated 3min SS criterion. Both SS-criteria were evaluated through three different SS protocols (<10% variation in respiratory gas exchange), being: 1) measurement during the first 3 or 5min, 2) measurement after discarding the first 5min, and 3) the lowest identified RMR during the 20min of measurement. About 50% of the participants reached an early SS in both the defined SS minute criteria. Participants reaching a valid SS throughout the 20min of measurement increased from ∼90% to 100% with an abbreviated 3min SS. With a 5min SS criterion, the median (range) RMR for the 3 protocols were 1639.9 (1239.2), 1508.8 (1457.6) and 1500.6 (1328.8) respectively for the ED group, and 1702.2 (1239.4), 1608.4 (1076.4) and 1594.8 (1029.2) respectively for the HC group, (p>0.05 for all between-group analysis). With a 3min SS criterion, the median (range) RMR were 1533.6 (1298.2), 1461.2 (1406.1), and 1395.8 (1447.3) respectively for the ED group and 1681.7 (1332.4), 1613.7 (1266.0) and 1523.1 (1050.3), respectively for the HC group, (p>0.05 for all between-group analysis). Lowest measured RMR was different compared to the other two SS protocols in both the ED- and the HC group, and for both the 5min- and the 3min SS criteria, respectively (p<0.04). Furthermore, a SS of 3min resulted in lower RMR compared to 5min SS (p<0.00) and an increased number of participants classified as hypo-metabolic (RMRmeasured/RMRcalculated<0.9). An abbreviated measurement protocol to identify the lowest RMR using IC was not successful. Abbreviating the SS criteria from 5 to 3min, resulted in a lower RMR, hence encouraging further examination of the validity of shorter SS criterion than practiced today. Registered in Clinical Trials by id-number NCT02079935, and approved by the Norwegian Regional Committee for Medical and Health Research Ethics with id-number 2013/1871. The trial in which control persons were recruited, is approved by the Norwegian Regional Committees for Medical and Health Research Ethics with the id-number 2016/1718, and prospectively registered in Clinical Trials with the id-number NCT03007459.

Short-Duration Performance Acceptance Test of Parabolic Trough Solar Field: A Case Study

Extensive solar field performance testing is often required as part of the plant commissioning process in order to ensure that actual solar field performance satisfies both technical specifications and performance guarantees between the involved parties. In this study, short duration (15 min) steady state performance acceptance test for Kuraymat integrated solar combined cycle (ISCC) solar field was carried out in agreement with the general guidelines of the earlier National Renewable Energy Laboratory (NREL) report on parabolic trough (PT) collector fields (Kearney, 2011, “Utility-Scale Parabolic Trough Solar Systems—Performance Acceptance Test Guidelines,” National Renewable Energy Laboratory, Golden, CO, NREL Report No. SR-5500-48895 and Kearney, 2010, “Development of Performance Acceptance Test Guidelines for Large Commercial Parabolic Trough Solar Fields,” National Renewable Energy Laboratory, Golden, CO, NREL Report No. SR-5500-49367) which is in full agreement with the plant documentations provided by FLAGSOL (2010, “Specification: Performance Test Procedure. Plant Documentations,” Customer Doc-ID: KU1-FLG-000-QP-M-001). This work includes measurement of the thermal power output of PT system under clear sky conditions over a short period during which thermal steady state conditions exist. The methodology of the solar field testing is presented while a special consideration is provided for the model formulation and uncertainty associated with the measured data. The measured results together with the associated uncertainties were compared with model predictions. All tests for both northern and a southern collector subfields that satisfy the test conditions are accepted based on acceptance test evaluation criteria.

The effect of minimalist, maximalist and energy return footwear of equal mass on running economy and substrate utilisation

The aim of the current study was to explore the effects of minimalist, maximalist and energy return footwear of equal mass on economy and substrate utilisation during steady state running. Ten male runners completed 6 min steady state runs in minimalist, maximalist and energy return footwear. The mass of the footwear was controlled by adding lead tape to the lighter shoes. Running economy, shoe comfort, rating of perceived exertion and % contribution of carbohydrate to total calorie expenditure were assessed. Participants also subjectively indicated which shoe condition they preferred for running. Differences in shoe comfort and physiological parameters were examined using paired samples t-tests, whilst shoe preferences were tested using a chi-square test. The results showed firstly that running economy was significantly improved in the energy return (35.9 ml∙kg/min) compared to minimalist footwear (37.8 ml∙kg/min). In addition % carbohydrate was significantly greater in the minimalist (76.4%) in comparison to energy return footwear (72.9%). As running economy was improved and carbohydrate utilisation reduced in the energy return in comparison to minimalist footwear, the current investigation shows that these footwear are more economical when shoe mass is controlled.

Part 1 – Coronary angiography with gadofosveset trisodium: a prospective feasibility study evaluating injection techniques for steady-state imaging

BackgroundThe purpose of this study was to define an optimal injection protocol for 5–10 min duration navigator-based coronary MR angiography using an intravascular gadolinium-based contrast agent (GBCA), which is better suited for steady-state coronary MR angiography than conventional GBCAs.MethodsUsing projections from pharmacokinetic models of the intravascular concentration of gadofosveset, a dual-injection protocol was formulated and tested on 14 healthy human subjects. Modified Look-Locker inversion recovery (MOLLI) sequences were used for T1 mapping at 3 Tesla to evaluate the concentration of tracer in the aorta over the scanning interval.ResultsPharmacokinetic models for a bolus plus slow infusion technique at a 5, 10, and 15 min steady state intravascular concentration was compared to single bolus curves. The 70 %/30 % bolus/slow infusion technique resulted in the highest intravascular concentration over a 5 min scan duration. Similarly, the 60 %/40 % bolus/slow infusion technique was projected to be ideal for image acquisition duration of 5–10 min. These models were confirmed with T1 maps on normal volunteers. Arterial-venous mixing of contrast was achieved within 90 s of the beginning of the bolus.ConclusionsGadofosveset injection is optimized for the lowest intravascular T1 time for 5–10 min duration MR angiography by bolus injection of 60–70 % of the total dose followed by slow infusion of the remainder of the total dose. This protocol achieves rapid and prolonged steady state intravascular concentrations of the GBCA that may be useful for prolonged image acquisition, such as required for navigator-based coronary MR angiography at 3 Tesla. Trial registrationClinicalTrials.gov identifier: NCT01130545NCT01130545, registered as of May 25, 2010.

Intensify chemical reduction to remove nitrate from groundwater via internal microelectrolysis existing in nano-zero valent iron/granular activated carbon composite

A composite combination of nano-zero valent iron (nZVI) and granular activated carbon (GAC) was introduced to achieve nitrate transformation into nitrogen with minimum byproducts via chemical reduction. The results showed that nitrate removal was significantly intensified and GAC was an excellent partner of nZVI chemical reduction. Both the dispersion and long-term reactivity of nZVI were improved, and more than 80% of nitrate was removed at 10 g/L nZVI/GAC composite within 90 min in steady state. The byproducts of nitrite and ammonium formed in reduction process were below 0.008 and 0.04 mg/L, respectively, and nitrogen was the main end product, which was confirmed by X-ray photoelectron spectroscopy analysis. Moreover, the kinetic model of nitrate reduction by nZVI/GAC composite can be described well by pseudo-first-order reaction kinetic (R2 = 0.984). The intensification is closely related to the dispersion effect of GAC matrix to nZVI and the promotion effect to electrons transfer between nZVI and nitrate pollutant of internal iron–carbon microelectrolysis existing in such a composite. Therefore, the findings are very beneficial to develop an efficient and low-cost chemical remediation method for nitrate-contaminated groundwater.

Quantitative 4D Flow MRI during Hypoxia Identifies Non‐uniform Cerebrovascular Dysfunction in Young Adults with Metabolic Syndrome

Metabolic Syndrome (MetSyn) increases the risk of developing cerebrovascular diseases (e.g. stroke). We tested the hypothesis that MetSyn impairs cerebral dilation to hypoxia, and the attenuation would be observed primarily in the middle cerebral arteries. Macroscopic cerebral blood flow (CBF) was measured with a novel 4D Flow MRI approach at 3T using radial undersampling to quantify regional vasodilation to isocapnic hypoxia in 10 healthy controls (Con, 29±4 yrs) and 8 MetSyn patients (38±8 yrs). Blood pressure, O2 Saturation (SaO2), end‐tidal CO2 was measured and Cerebral Vascular Conductance (CVC=CBF/blood pressure*100mmHg) was calculated for five intracranial arteries: Middle [MCA] x2, Anterior [ACA] x2, and Basilar [BA] (ml/min/100mmHg). Hypoxia (5 min steady state) lowered SaO2 to ~85±2% (Fi O2 =0.1). End‐tidal CO2 was maintained (36±1 mmHg). Baseline CVC was 25% lower in MetSyn (750±57 Con vs. 562±75 MetSyn, p=0.03). Hypoxia increased total CVC (p&lt;0.001) but the increase was 50% lower in MetSyn (Δ 127±18 Con vs. 62±22 MetSyn, p=0.03). Hypoxic dilation differed substantially by region: the greatest relative impairment occurred in ACA (Δ 20±4 Con vs. 8±3 MetSyn, p=0.02). CVC in the MCA (Δ 29±7 vs. 15±6, p=0.08) and BA (Δ 28±6 vs. 17±8, p=0.13) were not significantly lower in MetSyn. Therefore, MetSyn patients exhibit impaired hypoxic vasodilator responses with the negative effects directed more to regions of the brain supplied by the ACA. This non‐uniform cerebrovascular dysfunction occurs early in adulthood, which may contribute to poor cerebral vascular outcomes in MetSyn.

The effect of dietary nitrate supplementation on performance in trained male flatwater kayakers

Previous studies have reported that supplementation with nitrate-rich beetroot juice (BR) reduces the oxygen cost (VO 2 ) of submaximal cycling and running exercise and improves both exercise capacity and performance. To date, no study has investigated the performance effects of BR on sports which rely on the recruitment of large upper body muscle mass, such as flatwater kayaking. Purpose To determine the effects of dietary nitrate on parameters of performance in trained male kayakers. Methods Seven male kayakers completed four exercise trials consisting of an initial discontinuous graded exercise test to exhaustion and three performance trials using a kayak ergometer. The performance trials were composed of 15 min steady state exercise at 60% of maximum work rate, 5 × 10-second maximal sprints and, following a 5 min rest period, a 1 km time trial (TT). The first trial provided a baseline measurement and the second and third trials were preceded by ingestion of either 70 ml concentrated BR or tomato juice (placebo [PLA]) 3 h prior to exercise using a randomised cross-over design. Results Plasma nitrate (PLA: 34.1 ± 8.3 μM, BR: 152.0 ± 14.7 μM) and nitrite (PLA: 546.5 ± 76.0, BR: 702.9 ± 73.4 nM) were higher following ingestion of BR compared to PLA (both P 2 was lower in the BR trial than in the PLA trial (PLA: 35.8 ± 1.4 ml kg min −1 , BR: 34.6 ± 1.1 ml kg min −1 , P = 0.02). There was no difference in either peak power output in the maximal sprints ( P = 0.91) or TT performance between conditions (PLA: 4.6 ± 0.3 min, BR: 4.6 ± 0.3 min, P = 0.91 ). Conclusion In line with previous research, ingestion of BR reduced VO 2 during submaximal kayak exercise although contrastingly had no impact on kayak TT performance. These differences may be attributed to the specific physiological demands of sprint kayaking.

Influence of Chronic Dietary Carbohydrate Supplementation on Plasma Cytokine Responses to Exercise

This study examined the influence of 28 days of dietary carbohydrate (CHO) supplementation on plasma cytokine responses to cycle ergometry. Sixteen highly trained male cyclists and triathletes (age: 30.6+/-5.6 y; VO2max: 64.8+/-4.7 mL x kg(-1) x min(-1); mean+/-SD) participated in the study. One group (n=8) consumed a higher-CHO (8.5+/-1.7 g x kg(-1) body mass.day (-1)) diet for 28 days; a second group (n=8) consumed a moderate-CHO diet (5.3+/-0.4 g x kg (-1) x day (-1)). Total daily energy intakes were similar between the two groups. Cytokine responses to cycle ergometry were assessed prior to and again following the dietary intervention period. The cycle ergometry protocol involved 100 min steady state cycling at 70% VO2max followed by a time trial of approximately 30 min. Athletes were provided with 15 mL x kg (-1) x h (-1) of water during each trial. Blood samples were collected pre-, immediately post- and 1 h post-exercise for determination of plasma glucose and pro-inflammatory (IL-6, IL-8) and anti-inflammatory (IL-10, IL-1ra) cytokine concentrations. Cytokine responses to cycle ergometry were not substantially altered following the 28-day higher-CHO diet. In contrast, following the 28-day moderate-CHO diet, there were approximately 30-50% reductions (p=0.08-0.11) in anti-inflammatory cytokine responses post-exercise. These findings suggest that increased dietary CHO content alone does not effectively attenuate the pro-inflammatory cytokine response to exercise, however, there may be a small reduction in the anti-inflammatory cytokine response.

Impact of interval versus steady state exercise on nitric oxide production in patients with left ventricular dysfunction

Aim — The aim of the present study was to assess the impact of the interval exercise training (IET) vs. steady state exercise training (SSET) on nitric oxide production, through changes of circulating blood markers of endothelial function, including stable end-products of nitric oxide (NOx) and S-nitrosothiols (RSNOs) in patients with left ventricular dysfunction (LVD).Patients and methods — The impact of the IET vs. SSET on NOx and RSNOs production was assessed in a total of 31 (25 male, 6 female) patients with LVD (ejection fraction < 40%), who were admitted to our residential rehabilitation centre. Patients were randomised into an IET group (n = 18; 15 min interval exercise sessions, 2 times daily) and an SSET group (n = 13; 5-10 min steady state exercise sessions, 2 times daily), and exercised every day over a period of 3 weeks.The modified Saville-Griess method was used to determine NOx and RSNOs concentrations.Results — A significant increase was observed both for NOx (P < 0.05) and RSNOs (P < 0.001) in the IET group, as well as for RSNOs in the SSET group (P < 0.001). Both training methods were observed to significantly improve exercise capacity, as demonstrated for increased workload (P < 0.001 and P < 0.05 for the IET and SSET groups, respectively) and duration (P < 0.001 and P < 0.01 for the IET and SSET groups, respectively) of the exercise stress test at the end of the study.Conclusion — The results of the present study have demonstrated an increased nitric oxide production and improved exercise capacity in patients with left ventricular dysfunction, who were engaged in an interval exercise programme for three weeks, and clearly indicated an advantage of interval compared to steady state training method for cardiovascular rehabilitation.