The International Association of Athletics Federations recognizes the importance of nutritional practices in optimizing an Athlete's well-being and performance. Although Athletics encompasses a ...diverse range of track-and-field events with different performance determinants, there are common goals around nutritional support for adaptation to training, optimal performance for key events, and reducing the risk of injury and illness. Periodized guidelines can be provided for the appropriate type, amount, and timing of intake of food and fluids to promote optimal health and performance across different scenarios of training and competition. Some Athletes are at risk of relative energy deficiency in sport arising from a mismatch between energy intake and exercise energy expenditure. Competition nutrition strategies may involve pre-event, within-event, and between-event eating to address requirements for carbohydrate and fluid replacement. Although a "food first" policy should underpin an Athlete's nutrition plan, there may be occasions for the judicious use of medical supplements to address nutrient deficiencies or sports foods that help the athlete to meet nutritional goals when it is impractical to eat food. Evidence-based supplements include caffeine, bicarbonate, beta-alanine, nitrate, and creatine; however, their value is specific to the characteristics of the event. Special considerations are needed for travel, challenging environments (e.g., heat and altitude); special populations (e.g., females, young and masters athletes); and restricted dietary choice (e.g., vegetarian). Ideally, each Athlete should develop a personalized, periodized, and practical nutrition plan via collaboration with their coach and accredited sports nutrition experts, to optimize their performance.
Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function, and performance. However, there is limited evidence to support many of these ...claims, and the efficacy and safety of many products is questionable. The variety of nutritional aids considered for use by track-and-field athletes includes sports foods, performance supplements, and therapeutic nutritional aids. Support for sports foods and five evidence-based performance supplements (caffeine, creatine, nitrate/beetroot juice, β-alanine, and bicarbonate) varies according to the event, the specific scenario of use, and the individual athlete's goals and responsiveness. Specific challenges include developing protocols to manage repeated use of performance supplements in multievent or heat-final competitions or the interaction between several products which are used concurrently. Potential disadvantages of supplement use include expense, false expectancy, and the risk of ingesting banned substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement use is recommended. The authors conclude that it is pertinent for sports foods and nutritional supplements to be considered only where a strong evidence base supports their use as safe, legal, and effective and that such supplements are trialed thoroughly by the individual before committing to use in a competition setting.
We describe a protocol for forming an artificial lipid bilayer by contacting nanoliter aqueous droplets in an oil solution in the presence of phospholipids. A lipid monolayer forms at each oil-water ...interface, and when two such monolayers touch, a bilayer is created. Droplet interface bilayers (DIBs) are a simple way to generate stable bilayers suitable for single-channel electrophysiology and optical imaging from a wide variety of preparations, ranging from purified proteins to reconstituted eukaryotic cell membrane fragments. Examples include purified proteins from the α-hemolysin pore from Staphylococcus aureus, the anthrax toxin pore and the 1.2-MDa mouse mechanosensitive channel MmPiezo1. Ion channels and ionotropic receptors can also be reconstituted from membrane fragments without further purification. We describe two approaches for forming DIBs. In one approach, a lipid bilayer is created between two aqueous droplets submerged in oil. In the other approach, a membrane is formed between an aqueous droplet and an agarose hydrogel, which allows imaging in addition to electrical recordings. The protocol takes <30 min, including droplet generation, monolayer assembly and bilayer formation. In addition to the main protocol, we also describe the preparation of Ag/AgCl electrodes and sample preparation.
•The control of immune function is regulated by substrate disposal.•Exercise and nutrients directly affect the immunometabolism of immune cells.•Adenosine monophosphate–activated protein kinase and ...mammalian target of rapamycin regulated the energy sensor and fate of immune cell.
The immune system plays a key role in controlling infections, repairing injuries, and restoring homeostasis. Immune cells are bioenergetically expensive during activation, which requires a tightly regulated control of the metabolic pathways, which is mostly regulated by two cellular energy sensors: Adenosine monophosphate–activated protein kinase and mammalian target of rapamycin. The activation and inhibition of this pathways can change cell subtype differentiation. Exercise intensity and duration and nutrient availability (especially glucose and glutamine) tightly regulate immune cell differentiation and function through Adenosine monophosphate–activated protein kinase and mammalian target of rapamycin signaling. Herein, we discuss the innate and adaptive immune-cell metabolism and how they can be affected by exercise and nutrients.
We form an artificial lipid bilayer between a nanolitre aqueous droplet and a supporting hydrogel immersed in an oil/lipid solution. Manipulation of the axial position of the droplet relative to the ...hydrogel controls the size of the bilayer formed at the interface; this enables the surface density of integral membrane proteins to be controlled. We are able to modulate the surface density of the β-barrel pore-forming toxin α-hemolysin over a range of 4 orders of magnitude within a time frame of a few seconds. The concentration changes are fully reversible. Membrane protein function and diffusion are unaltered, as measured by single molecule microscopy and single channel electrical recording.
Glutamine is an important fuel for some cells of the immune system. In situations of stress, such as clinical trauma, starvation, or prolonged, strenuous exercise, the concentration of glutamine in ...blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Provision of glutamine or a glutamine precursor has been found to decrease the incidence of illness in endurance athletes. To date, it has not been established precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated.
Prolonged, exhaustive exercise frequently leads to an increased incidence of upper respiratory tract illness (URTI) which is linked to transient immunodepression. We investigated potential ...biochemical markers of stress and fatigue, and URTI symptoms as a surrogate of immunodepression, in US Marines undergoing intensive winter training at altitude. Selected plasma amino acids and leptin (pLep) were measured as possible markers of fatigue and immunodepression, together with nonesterified fatty acids (pNEFA) and total antioxidant capacity (pTAC). Changes were observed in plasma free tryptophan (pFT), pGln, pLep, pNEFA, pTAC but not branched chain amino acids (pBCAA). pFT decreased markedly. Resting pGln decreased overall after one month at altitude. pGln routinely decreases 1-2 hrs after prolonged exercise. Importantly, we observed early morning decreases in pGln, suggesting a cumulative effect of prolonged activity, stress, and fatigue. Concomitantly, individuals with highest illness scores had the greatest pGln decrease: low pGln may therefore be associated with a diminished stress tolerance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK, VSZLJ
1 Hypoxia Research Unit, Health and Exercise Sciences
Research Laboratory, School of Applied Sciences, University of
Glamorgan, South Wales, CF37 1DL; 2 Cellular Nutrition
Research Group, ...University Department of Biochemistry, University
of Oxford, Oxford, OX1 3QU; and 3 Gastroenterology Laboratory,
Department of Medicine, Royal Postgraduate School, Hammersmith
Hospital, London, United Kingdom W12 ONN
The purpose of
the present investigation was to determine the independent effects of
hypoxia and physical exercise on peripheral cholecystokinin (CCK)
metabolism in humans. Thirty-two physically active men were
randomly assigned in a double-blind manner to either a normoxic (N;
n = 14) or hypoxic (H; n = 18) group.
During the acute study, subjects in the H group only participated in two tests, separated by 48 h, which involved a cycling test to exhaustion in normobaric normoxia and normobaric hypoxia (inspired O 2 fraction = 0.21 and 0.16, respectively). In the
intermittent study, N and H groups cycle-trained for 4 wk at the same
relative exercise intensity in both normoxia and hypoxia. Acute
normoxic exercise consistently raised plasma CCK during both studies by 290-723%, which correlated with increases in the plasma ratio of
free tryptophan to branched chain amino acids ( r = 0.58-0.71, P < 0.05). In contrast, acute hypoxic
exercise decreased CCK by 7.0 ± 5.5 pmol/l, which correlated with
the decrease in arterial oxygen saturation ( r = 0.56, P < 0.05). In the intermittent study, plasma CCK
response at rest and after normoxic exercise was not altered after
physical training, despite a slight decrease in adiposity. We conclude
that peripheral CCK metabolism 1 ) is more sensitive to acute
changes than chronic changes in energy expenditure and 2 ) is
potentially associated with acute changes in tissue P O 2 and metabolic precursors of cerebral
serotoninergic activity.
5-hydroxytryptamine; satiety; caloric intake; adipose tissue; aerobic capacity
Athletes undergoing intense, prolonged training or participating in endurance races suffer an increased risk of infection due to apparent immunosuppression. Glutamine is an important fuel for some ...cells of the immune system and may have specific immunostimulatory effects. The plasma glutamine concentration is lower after prolonged, exhaustive exercise: this may contribute to impairment of the immune system at a time when the athlete may be exposed to opportunistic infections. The effects of feeding glutamine was investigated both at rest in sedentary controls and after exhaustive exercise in middle-distance, marathon and ultra-marathon runners, and elite rowers, in training and competition. Questionnaires established the incidence of infection for 7 d after exercise: infection levels were highest in marathon and ultra-marathon runners, and in elite male rowers after intensive training. Plasma glutamine levels were decreased by ∼20% 1 h after marathon running. A marked increase in numbers of white blood cells occurred immediately after exhaustive exercise, followed by a decrease in the numbers of lymphocytes. The provision of oral glutamine after exercise appeared to have a beneficial effect on the level of subsequent infections. In addition, the ratio of T-helper/T-suppressor cells appeared to be increased in samples from those who received glutamine, compared with placebo.
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