1,144 research outputs found
Reflectance spectra of Fe(2+)-Mg(2+) disordered pyroxenes: Implications to remote-sensed spectra of planetary surfaces
The reflectance spectra of Fe(2+)-Mg(2+) disordered orthopyroxenes are relevant to surfaces of terrestrial planets onto which basaltic magma has been extruded. If cooling rates of basalt lava flows were fast, equilibrium iron intersite partitioning may not have been achieved so that abnormal enrichments of Fe(2+) ions in M1 sites would occur. The two intense pyroxene Fe(2+) site CF bands in the 1 micron and 2 micron regions would continue to dominate the the reflectance spectra so that the pyroxene composition and structure type would be readily identified in telescopic spectral profiles. However, abnormal intensification of the Fe(2+)/M1 site CF band at 1.20 microns could lead to the false identification of olivine in remote sensed spectra because in pyroxene-olivine mixtures the inflection around 1.20 microns is the only spectral feature for detecting the presence of olivine. The identification of iron-bearing plagioclase feldspars, too, would be obscured by the pyroxene Fe(2+)/M1 site CF band at 1.20 microns. Such interference would be a major problem if in situ reflectance spectra could be measured on the surface of Venus where ambient temperatures are as high as 475 C. Disordering of Fe(2+) and Mg(2+) ions comparable to that in the orthopyroxenes used in this spectral chemical study might be expected in low Ca pyroxenes occurring on the Venusian surface. Researchers conclude that Fe(2+)/M1 site spectral features need to be carefully assessed in remote-sensed spectra before deductions are made about the presence of olivine on planetary surfaces
An update on accumulating exercise and postprandial lipaemia: translating theory into practice
Over the last two decades, significant research attention has been given to the acute effect of a single bout of exercise on postprandial lipaemia. A large body of evidence supports the notion that an acute bout of aerobic exercise can reduce postprandial triacylglycerol (TAG) concentrations. However, this effect is short-lived emphasising the important role of regular physical activity for lowering TAG concentrations through an active lifestyle. In 1995, the concept of accumulating physical activity was introduced in expert recommendations with the advice that activity can be performed in several short bouts throughout the day with a minimum duration of 10 minutes per activity bout. Although the concept of accumulation has been widely publicised, there is still limited scientific evidence to support it but several studies have investigated the effects of accumulated activity on health-related outcomes to support the recommendations in physical activity guidelines. One area, which is the focus of this review, is the effect of accumulating exercise on postprandial lipaemia. We propose that accumulating exercise will provide additional physical activity options for lowering postprandial TAG concentrations relevant to individuals with limited time or exercise capacity to engage in more structured forms of exercise, or longer bouts of physical activity. The benefits of accumulated physical activity might translate to a reduced risk of cardiovascular disease in the long-term. Copyright © 2013 The Korean Society for Preventive Medicine
High intensity interval exercise and postprandial triacylglycerol
This review examined if high intensity interval exercise (HIIE) reduces postprandial triacylglycerol (TAG) concentrations. Fifteen studies were identified, in which the effect of interval exercise conducted at an intensity of >65% of maximal oxygen uptake was evaluated on postprandial TAG concentrations. Analysis was divided between studies which included supramaximal exercise and those which included submaximal interval exercise. Ten studies examined the effect of a single session of low-volume HIIE including supramaximal sprints on postprandial TAG. Seven of these studies noted reductions in postprandial total TAG area under the curve the morning after exercise of between ~10%-21% compared with rest but three investigations found no significant difference in TAG concentrations. Variations in the HIIE protocol used, inter-individual variation or insufficient time post-exercise for an increase in lipoprotein lipase activity are proposed reasons for the divergent results among studies. Five studies examined the effect of high-volume submaximal interval exercise on postprandial TAG. Four of these studies were characterised by high exercise energy expenditure and effectively attenuated total postprandial TAG concentrations by ~15%-30% but one study with a lower energy expenditure found no effect on TAG. The evidence suggests that supramaximal HIIE can induce large reductions in postprandial TAG concentrations but findings are inconsistent. Submaximal interval exercise offers no TAG metabolic or time advantage over continuous aerobic exercise but could be appealing in nature to some individuals. Future research should examine if submaximal interval exercise can reduce TAG concentrations in line with more realistic and achievable exercise durations of 30 minutes per day
Staging of the cognitive decline in Alzheimer's disease: Insights from a detailed neuropsychological investigation of mild cognitive impairment and mild Alzheimer's disease
Increasing meal frequency in combination with exercise mitigates postprandial triacylglycerol
Background: This study examined how manipulating meal frequency, with and without
exercise, affects postprandial triacylglycerol (TAG). Methods: Fourteen sedentary men
completed four 2-day trials in a non-counterbalanced random crossover order: (i) consumption of
one large high fat milkshake without exercise (1-CON); (ii) consumption of two smaller high fat
milkshakes without exercise (2-CON); (iii) consumption of one large high fat milkshake with
exercise (1-EX); and (iv) consumption of two small high fat milkshakes with exercise (2-EX) –
total energy intake was standardized across trials. On Day 1, participants rested (1-CON and 2- CON) or walked briskly for 60 minutes (1-EX and 2-EX). On Day 2, participants consumed
either a single large high-fat milkshake (75% fat) (1-CON and 1-EX) for breakfast or two
smaller iso-energetic milkshakes (2-CON and 2-EX) for breakfast and lunch. Plasma TAG were
measured fasting and for 7 hours after breakfast. Results: Peak incremental TAG was 30%
lower on 2-EX than 1-CON (P = .041; d = 0.38). Postprandial TAG increased more rapidly in
the first 4 hours in 1-CON than other trials, but at 6 hours TAG was exaggerated in 2-CON
compared with 1-CON. Conclusions: Increasing meal frequency after exercise, without altering
overall fat intake, attenuates postprandial TAG
Pre-diabetes in overweight youth and early atherogenic risk
PURPOSE: To compare atherogenic lipoprotein particles and vascular smooth muscle biomarkers in overweight youth with pre-diabetes (PD) vs. normal glucose tolerance (NGT).
METHODS: 144 adolescents (60 black, 84 white; 102 female; PD=45, NGT=99) aged 10-19 years underwent a fasting blood draw and 2-h OGTT. Lipoprotein particle size and subclass concentration and vascular smooth muscle biomarkers (ICAM-1, VCAM-1 and E-selectin) were compared between youth with PD and NGT.
RESULTS: Compared with NGT, PD adolescents had smaller LDL (mean±SE: 20.5±0.1 vs. 21.0±0.1 nm; P=0.002) and HDL (8.62±0.05 vs. 8.85±0.04 nm; P=0.013) size and elevated medium small (159.2±10.3 vs. 123.8±6.4 nmol/L; P=0.037) and very small (626.3±45.4 vs. 458.5±26.4 nmol/L; P=0.032) LDL particle concentrations, after adjustment for race and BMI. Further adjusting for fasting insulin or visceral adiposity obviated these differences between the groups except for LDL size. ICAM-1 and E-selectin did not differ in youth with PD but correlated with LDL and HDL size, and small LDL particle concentrations.
CONCLUSIONS: Overweight adolescents with PD have an atherogenic lipoprotein profile of small LDL and HDL size and increased concentrations of small LDL, moderated by insulin resistance and visceral adiposity, but independently driven by dysglycemia for LDL size. Associations between smooth muscle biomarkers and lipoproteins could be an early signal heralding the atherogenic process. It remains to be determined if correction of dysglycemia and associated lipoprotein abnormalities in obese youth could prove effective in halting this process
Effects of caffeine supplementation on performance in ball games
Although a large body of evidence exists documenting the ergogenic properties of caffeine, most studies have focused on endurance performance. However, findings from endurance sports cannot be generalized to performance in ball games where, apart from having a high level of endurance, successful athletic performances require a combination of physiological, technical and cognitive capabilities. The purpose of this review was to critically evaluate studies that have examined the effect of a single dose of caffeine in isolation on one or more of the following performance measures: total distance, sprint performance, agility, vertical jump performance and accuracy in ball games. Searches of three major databases resulted in 19 studies (invasion games: 13; net-barrier games: 6) that evaluated the acute effects of caffeine on human participants, provided the caffeine dose administered, and included a ball games specific task or simulated match. Improvements in sprint performance were observed in 8 of 10 studies (80%), and vertical jump in 7 of 8 studies (88%). Equivocal results were reported for distance covered, agility and accuracy. Minor side effects were reported in 4 of 19 studies reviewed. Pre-exercise caffeine ingestion between 3.0 and 6.0 mg/kg of body mass appears to be a safe ergogenic aid for athletes in ball games. However, the efficacy of caffeine varies depending on various factors, including, but not limited to, the nature of the game, physical status and caffeine habituation. More research is warranted to clarify the effects of caffeine on performance measures unique to ball games, such as agility and accuracy. It is essential that athletes, coaches and practitioners evaluate the risk-benefit ratio of caffeine ingestion strategies on an individual case-by-case basis
Increased complexities in visual search behavior in skilled players for a self-paced aiming task
The badminton serve is an important shot for winning a rally in a match. It combines good technique with the ability to accurately integrate visual information from the shuttle,
racket, opponent, and intended landing point. Despite its importance and repercussive
nature, to date no study has looked at the visual search behaviors during badminton
service in the singles discipline. Unlike anticipatory tasks (e.g., shot returns), the serve presents an opportunity to explore the role of visual search behaviors in movement
control for self-paced tasks. Accordingly, this study examined skill-related differences in
visual behavior during the badminton singles serve. Skilled (n D 12) and less skilled
(n D 12) participants performed 30 serves to a live opponent, while real-time eye movements were captured using a mobile gaze registration system. Frame-by-frame analyses of 662 serves were made and the skilled players took a longer preparatory time before serving. Visual behavior of the skilled players was characterized by significantly greater number of fixations on more areas of interest per trial than the less skilled. In addition, the skilled players spent a significantly longer time fixating on the court and net, whereas the less skilled players found the shuttle to be more informative. Quiet eye (QE) duration (indicative of superior sports performance) however, did not differ significantly between groups which has implications on the perceived importance of QE in the badminton serve. Moreover, while visual behavior differed by skill level, considerable individual differences were also observed especially within the skilled players. This augments the need for not just group-level analyses, but individualized analysis for a
more accurate representation of visual behavior. Findings from this study thus provide
an insight to the possible visual search strategies as players serve in net-barrier games. Moreover, this study highlighted an important aspect of badminton relating to deception and the implications of interpreting visual behavior of players
A single session of resistance exercise does not reduce postprandial lipaemia
This study investigated the effect of a single session of resistance exercise on postprandial lipaemia. Eleven healthy, normolipidaemic men aged 23 (SE 1.4) years performed two trials at least one-week apart in a counterbalanced randomized design. In each trial participants consumed a test meal (1.2g fat, 1.1g carbohydrate, 0.2 g protein and 68 kJ per kg body mass) between 08.00 and 09.00 following a 12 hour fast. The afternoon before one trial participants performed an 88 minute bout of resistance exercise. Prior to the other trial participants were inactive (control trial). Resistance exercise was performed using free weights and included 4 sets of 10-repetitions of each of 11 exercises. Sets were performed at 80% of 10 repetition maximum with a 2 minute work and rest interval. Venous blood samples were obtained in the fasted state and at intervals for 6 h postprandially. Fasting plasma triacylglycerol (TAG) concentration did not differ significantly between control and exercise trials (mean SE: 1.03 0.13 mmol•L-1 versus 0.94 0.09 mmol•L-1; respectively). Similarly the 6 h total area under the plasma TAG concentration versus time curve did not differ significantly between control and exercise trials (9.84 1.40 mmol•L-1•6 h versus 9.38 1.12 mmol•L-1•6 h; respectively). These findings suggest that a single session of resistance exercise does not reduce postprandial lipaemia
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