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Biomedical subjects

M Gleeson

Publications and source records attributed to M Gleeson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Carbohydrate and fluid intake affect the saliva flow rate and IgA response to cycling.

PURPOSE: The purpose of this study was to examine the effect of regular CHO beverage ingestion and restricted fluid intake on various salivary parameters during prolonged cycle exercise. METHODS: In a randomized block design, 15 recreationally active men cycled for 2 h at 60% VO2max on three occasions, separated by 1 wk. On the CHO and placebo (PLA) treatments, subjects consumed either a glucose (60 g x L(-1)) or placebo drink before (400 mL), during (150 mL every 15 min), and after (400 mL) the exercise. On the restricted fluid intake (RFI) treatment subjects were given a total of 200 mL of placebo fluid to take as desired every 15-min during the exercise. Timed, unstimulated saliva samples were collected preexercise, at 1, 1.5, and 2 h of exercise and at 1 h postexercise. Blood samples were obtained from a subset of 8 subjects preexercise, postexercise, and at 1 h postexercise. RESULTS: Postexercise plasma glucose levels were 18% and 20% lower on the PLA and RFI treatments, respectively, compared with the CHO treatment (P < 0.01). Saliva flow rates were significantly higher on the CHO treatment compared with the RFI treatment at 1.5 h and 2 h of exercise (P < 0.01 and P < 0.05, respectively). Salivary IgA (s-IgA) concentration was significantly lower on the CHO treatment compared with the RFI treatment throughout the exercise (P < 0.05). No other differences were seen between treatments for either saliva flow rate or s-IgA concentration. Neither s-IgA secretion rate, alpha-amylase activity, nor alpha-amylase secretion rate were affected by treatment. CONCLUSIONS: These findings suggest that CHO and fluid intake influence the s-IgA and saliva flow rate response to prolonged submaximal exercise.

Adult↗
PubMed2000

Special feature for the Olympics: effects of exercise on the immune system. Overview: exercise immunology.

The review articles in this special feature reflect the current status of knowledge in the field of exercise immunology, with a focus on how exercise affects the human immune system and the health implications for resistance to infections and neoplastic diseases. In an Olympic year, the emphasis of exercise immunology research tends to be on elite athletes and the prevention of infections in the quest for optimum performance. However, research presented in this issue also covers recreational athletes, as well as highlighting the benefits of exercise for our ageing population.

Disease Susceptibility↗
PubMed2000

Special feature for the Olympics: effects of exercise on the immune system: modification of immune responses to exercise by carbohydrate, glutamine and anti-oxidant supplements.

Immunosuppression in athletes involved in heavy training is undoubtedly multifactorial in origin. Training and competitive surroundings may increase the athlete's exposure to pathogens and provide optimal conditions for pathogen transmission. Heavy prolonged exertion is associated with numerous hormonal and biochemical changes, many of which potentially have detrimental effects on immune function. Furthermore, improper nutrition can compound the negative influence of heavy exertion on immunocompetence. An athlete exercising in a carbohydrate-depleted state experiences larger increases in circulating stress hormones and a greater perturbation of several immune function indices. The poor nutritional status of some athletes may predispose them to immunosuppression. For example, dietary deficiencies of protein and specific micronutrients have long been associated with immune dysfunction. Although it is impossible to counter the effects of all of the factors that contribute to exercise-induced immunosuppression, it has been shown to be possible to minimize the effects of many factors. Athletes can help themselves by eating a well-balanced diet that includes adequate protein and carbohydrate, sufficient to meet their energy requirements. This will ensure a more than adequate intake of trace elements without the need for special supplements. Consuming carbohydrate (but not glutamine or other amino acids) during exercise attenuates rises in stress hormones, such as cortisol, and appears to limit the degree of exercise-induced immunosuppression, at least for non-fatiguing bouts of exercise. Evidence that high doses of anti-oxidant vitamins can prevent exercise-induced immunosuppression is also lacking.

Antioxidants↗
PubMed2000

Special feature for the Olympics: effects of exercise on the immune system: exercise effects on mucosal immunity.

The present review examines the effects of exercise on mucosal immunity in recreational and elite athletes and the role of mucosal immunity in respiratory illness. Habitual exercise at an intense level can cause suppression of mucosal immune parameters, while moderate exercise may have positive effects. Saliva is the most commonly used secretion for measurement of secretory antibodies in the assessment of mucosal immune status. Salivary IgA and IgM concentrations decline immediately after a bout of intense exercise, but usually recover within 24 h. Training at an intense level over many years can result in a chronic suppression of salivary immunoglobulin levels. The degree of immune suppression and the recovery rates after exercise are associated with the intensity of exercise and the duration or volume of the training. Low levels of salivary IgM and IgA, particularly the IgA1 subclass, are associated with an increased risk of respiratory illness in athletes. Monitoring mucosal immune parameters during critical periods of training provides an assessment of the upper respiratory tract illness risk status of an individual athlete. The mechanisms underlying the mucosal immune suppression are unknown.

Exercise↗
PubMed2000

Effect of oral glutamine supplementation on human neutrophil lipopolysaccharide-stimulated degranulation following prolonged exercise.

Recent studies have shown that neutrophils can utilize glutamine and that glutamine supplementation can improve neutrophil function in postoperative and burn patients. The present study investigated the influence of oral glutamine supplementation on stimulated neutrophil degranulation and oxidative burst activity following prolonged exercise. Subjects, 7 well-trained men, reported to the laboratory following an overnight fast and cycled for 2 hrs at 60% VO2max on two occasions a week apart. They were randomly assigned to either a glutamine or placebo treatment. For both trials, subjects consumed a sugar-free lemon drink at 15-min intervals until 90 minutes, then a lemon flavored glutamine drink (GLN) or sugar-free lemon drink (PLA) was consumed at 15-min intervals for the remaining exercise and the 2-hr recovery period. Venous blood samples were taken pre-, during, and postexercise. Glutamine supplementation had no effect on the magnitude of postexercise leukocytosis, the plasma elastase concentration following exercise (which increased in both trials), or the plasma elastase release in response to bacterial stimulation (which fell in both trials). Neutrophil function assessed by oxidative burst activity of isolated cells did not change following exercise in either trial. These findings therefore suggest that the fall in plasma glutamine concentration does not account for the decrease in neutrophil function (degranulation response) following prolonged exercise.

Administration, Oral↗
PubMed2000

Mucosal immune responses and risk of respiratory illness in elite athletes.

This review focuses on studies of mucosal immunity in elite athletes and specifically addresses the role of mucosal immunity in respiratory illness and associations with the intensity, volume, and duration of exercise. Habitual exercise at an intense level can cause suppression of mucosal immune parameters. Salivary IgA and IgM concentrations decline immediately after a bout of intense exercise and usually recover within 24 hours. Training at an intense level can result in a chronic suppression of mucosal immunoglobulin levels. The degree of suppression is associated with the intensity of the exercise and the duration or volume of the training. Low levels of salivary IgM and IgA, particularly the IgA1 subclass are associated with an increased risk of respiratory illness. Monitoring mucosal immune parameters during critical training periods and establishing personal profiles for individual athletes may provide an assessment of the risk status of an athlete for URTI and allow effective management by the athlete and coach. The nature of the respiratory illnesses in some elite athletes is still uncertain. Recent data indicate viral reactivation may be a significant cause of the respiratory symptoms. Despite suppression of mucosal immune parameters, elite athletes are capable of normal responses to novel oral vaccinations, indicating that mucosal immune mechanisms are intact.

Exercise↗
PubMed2000

The scientific basis of practical strategies to maintain immunocompetence in elite athletes.

The functioning of the immune system is affected by stress. An accumulation of stress in elite athletes may lead to chronic immunosuppression and hence increased susceptibility to opportunistic infections. Therefore, athletes, coaches, and their medical support personnel are seeking guidelines to reduce the risk of illness, which, when it occurs, is likely to compromise training and competition performance. Training strategies to minimize the risk of immunosuppression need to consider the management of training volume and intensity, training variety to overcome monotony and strain, a periodised and graded approach to increasing training loads, and provision of adequate rest and recovery periods. In order to limit the effects of psychological stress, athletes should be taught self-management and coping skills. Benefit may be gained from monitoring athletes' responses to the psychological and psychosocial stresses of high-level training and competition. Nutritional considerations should emphasize the need for adequate intakes of fluid, carbohydrate, protein, and micronutrients. Limiting initial exposure when training or competing in adverse environmental conditions (heat, humidity, cold, altitude or polluted air) and acclimatizing where appropriate will reduce the effects of environmental stress. Other behavioral, lifestyle changes such as good hygiene practice, may limit transmission of contagious illnesses by reducing exposure to common sources of infection. Medical support including regular check ups, appropriate immunization, and prophylaxis may be particularly important for athletes who are at high risk of succumbing to recurrent infection.

Animals↗
PubMed2000

The measurement of IgA and IgG transglutaminase antibodies in celiac disease: a comparison with current diagnostic methods.

Celiac disease (CD) is an inflammatory disorder of the small intestine induced by cereal prolamins. The demonstration of IgA endomysial antibodies (EMA) is currently the most reliable serological screen for CD. The antigenic target is transglutaminase. The aim of this study was to develop an ELISA assay for the detection of antibodies to transglutaminase (TGA), and to assess the sensitivity and specificity of TGA for the detection of celiac disease against the benchmarks of jejunal biopsy, antigliadin antibodies (AGA) and EMA. Sera from 57 patients with celiac disease were tested for IgA and IgG TGA, IgA EMA, IgA and IgG AGA, and the total IgA level. The sensitivity, specificity, predictive value and concordance of AGA, EMA and TGA were assessed against the gold-standard biopsy result. IgG plus IgA TGA offered 100% sensitivity in CD patients for whom no dietary intervention had been commenced, with a specificity of 61%. The sensitivity of TGA dropped from 100 to 79% after dietary restriction. In patients on no gluten restriction, there was 100% agreement between TGA and EMA, and 100% agreement between TGA and AGA for the IgA isotype. The false-positive rate for TGA was 53% in Down's syndrome patients and 25% in patients with systemic autoimmune disorders. We conclude that testing for TGA is a reliable diagnostic serology for celiac disease, with improved sensitivity compared with established methods. The results suggest that serial TGA measurements may be a more and accurate marker for dietary compliance than AGA, but prospective studies are required.

Autoantibodies↗
PubMed1999

Salivary IgA subclasses and infection risk in elite swimmers.

The concentrations of total IgA, IgA1 and IgA2 were measured in saliva collected from 25 elite swimmers in the early and late phases of a 7 month training season and compared with the number of respiratory infections during the season. The IgA1 concentrations in the early phase of the training season were significantly associated (P = 0.01) with the number of respiratory infection episodes during the training season. The lower the concentration of IgA1, the greater the number of infection episodes. Swimmers with four or more infections during the training season had significantly lower salivary IgA1 concentrations than those with less than four infection episodes (P = 0.01). The proportion of IgA1 in the saliva of the elite swimmers (80%) was higher than for normal non-exercising adults (60%). A small proportion of athletes had salivary IgA2 concentrations below the detection limit of the assay and the mean concentration of IgA2 was significantly lower than the concentrations for a normal adult population (P = 0.01). This study suggests that measurement of IgA subclasses, in particular IgA1, at the commencement of a training season may predict infection risk in elite swimmers.

Adolescent↗
PubMed1999

Effects of exercise intensity, duration and recovery on in vitro neutrophil function in male athletes.

The aim of the present study was to compare the effects of exercise at 80% VO2max (resulting in fatigue within 1 h) with more prolonged exercise at a lower work rate (55% VO2max for up to 3 h) on blood neutrophil function and plasma concentrations of cortisol, glutamine and glucose. Eighteen healthy male subjects (mean+/-SD age 22.5+/-3.7 yrs, VO2max 60.1+/-6.6 ml x kg(-1) x min(-1)) cycled on an electrically braked ergometer at 80% VO2max to fatigue (37+/-19 min). On another occasion, separated by at least one week, subjects performed exercise on the same ergometer at 55% VO2max for 3 h or to fatigue, whichever was the sooner. Mean exercise time was 164+/-23 min. The order of the trials was randomised. Both exercise bouts caused significant (p<0.05) elevations of the blood leucocyte count and plasma cortisol concentration and reductions in the in vitro neutrophil degranulation response to bacterial lipopolysaccharide and oxidative burst activity. After exercise at the lower work rate for a longer duration, plasma cortisol concentration was higher, blood leucocyte and neutrophil counts were higher, blood lymphocytes, plasma glucose and indices of neutrophil function were lower than those observed at 80% VO2max. Plasma glutamine only fell significantly during recovery after the more prolonged exercise. We conclude that when exercise is very prolonged, the diminution of innate immune function is greater, or at least as great as that observed after fatiguing exercise at higher work rates. Furthermore, reductions in neutrophil function after exercise at 80% VO2max were not related to changes in the plasma glutamine concentration, although both plasma glutamine and neutrophil function were decreased at 1 and 2.5 h post-exercise in the long duration exercise trial.

Adult↗
PubMed1999

The effects of carbohydrate supplementation on immune responses to a soccer-specific exercise protocol.

The aim of this study was to determine the effect of carbohydrate (CHO) versus placebo (PLA) beverage consumption on the immune and plasma cortisol responses to a soccer-specific exercise protocol in 8 university team soccer players. In a randomized, counterbalanced design, the players received carbohydrate or placebo beverages before, during and after two 90 min soccer-specific exercise bouts (3 days apart) designed to mimic the activities performed and the distance covered in a typical soccer match. Blood and saliva samples were collected before, during and after the exercise protocol. Plasma lactate concentration increased to approximately 4 mmol x l(-1) at 45 and 90 min of exercise in both treatments (P<0.01). Plasma glucose concentration was significantly lower after 90 min of exercise with ingestion of the placebo than the carbohydrate (PLA: 4.57+/-0.12 mmol x l(-1); CHO: 5.49+/-0.11 mmol x l(-1); P<0.01). The pattern of change in plasma cortisol, circulating lymphocyte count and saliva immunoglobulin A secretion did not differ between the carbohydrate and placebo trials. Blood neutrophil counts were 14% higher 1 h after the placebo trial than the carbohydrate trial (PLA: 4.8+/-0.5x10(9) cells x l(-1); CHO: 4.2+/-0.5x10(9) cells x l(-1); P = 0.06), but the treatment had no effect on the degranulation response of blood neutrophils stimulated by bacterial lipopolysaccharide. We conclude that, although previous studies have shown that carbohydrate feeding is effective in attenuating immune responses to prolonged continuous strenuous exercise, the same cannot be said for a soccer-specific intermittent exercise protocol. When overall exercise intensity is moderate, and changes in plasma glucose, cortisol and immune variables are relatively small, it would appear that carbohydrate ingestion has only a minimal influence on the immune response to exercise.

Adult↗
PubMed1999

The effects of high-intensity intermittent exercise on saliva IgA, total protein and alpha-amylase.

The aim of this study was to assess the effect of an acute bout of high-intensity intermittent exercise on saliva IgA concentration and alpha-amylase activity, since this type of training is commonly incorporated into the training programmes of endurance athletes and games players. Eight well-trained male games players took part in the study. They reported to the laboratory after an overnight fast and performed a 60-min cycle exercise task consisting of twenty 1-min periods at 100% VO2max, each separated by 2 min recovery at 30% VO2max. Unstimulated whole saliva was collected over a 5-min period into pre-weighed tubes and analysed for total protein, saliva IgA and alpha-amylase. The saliva flow rate ranged from 0.08 to 1.40 ml x min(-1) at rest and was not significantly affected by the exercise. The performance of the intermittent exercise bout did not affect the saliva IgA concentration, but caused a five-fold increase in alpha-amylase activity (P<0.01 compared with pre-exercise) and a three-fold increase in total protein concentration (P<0.01). These returned to pre-exercise values within 2.5 h post-exercise. It has been suggested that IgA concentration should be expressed as the ratio to total protein concentration, to correct for any concentrating effect due to evaporative loss of saliva water when breathing through the mouth (as in strenuous exercise). The present study clearly demonstrates that this is not appropriate, since there is an increase in salivary protein secretion rate immediately after exercise (571+/-77 microg x min(-1) compared with 218+/-71 microg x min(-1) pre-exercise; P<0.05). The increased saliva alpha-amylase activity after exercise may improve the protective effect of saliva, since this enzyme is known to inhibit bacterial attachment to oral surfaces. The saliva alpha-amylase secretion rate was lower immediately pre-exercise than at any other instant, which may have been due to anticipatory psychological stress, although the subjects were all familiar with interval exercise. This emphasizes the need for true resting non-stressed control conditions in future studies of the effects of exercise on saliva constituents.

Adult↗
PubMed1999

Salivary IgA levels and infection risk in elite swimmers.

UNLABELLED: The effects of exercise on the immune system has been shown to be dependent on the level of fitness of the subjects, the degree of intensity, and the duration of the exercise. A reduction in salivary IgA levels occurs after individual sessions of exercise. PURPOSE: The purpose of this study was to assess the relationship between changes in salivary IgA and training volume, psychological stress, and infection rates in a cohort of 26 elite swimmers over a 7-month training period and to compare the changes with a group of 12 moderately exercising controls. METHODS: Salivary IgA concentrations were measured by an electroimmunodiffusion. Exercise gradings were assessed by a standardized aerobic-anaerobic rating system. Psychological stress/anxiety was evaluated by the Spielberger State-Trait Anxiety Inventory. Infections were physician-verified. RESULTS: Salivary IgA levels showed an inverse correlation with the number of infections in both elite swimmers and moderately exercising control subjects. The pretraining salivary IgA levels in swimmers were 4.1% lower for each additional month of training and 5.8% lower for each additional infection. The posttraining salivary IgA levels in swimmers were not significantly correlated with infection rates but were 8.5% lower for each additional 1 km swum in a training session and 7.0% lower for each additional month of training. The number of infections observed in the elite swimmers was predicted from regression models by the preseason (P = 0.05) and the mean pretraining salivary IgA levels (P = 0.006). The trends in pretraining salivary IgA levels over the 7-month season, calculated as individual slopes of pretraining IgA levels over time, were also predictive of the number of infections (P = 0.03) in the swimmers. CONCLUSIONS: These results indicate that measurement of salivary IgA levels over a training season may be predictive for athletes at risk of infection.

Adolescent↗
PubMed1999

Nutritional aspects of immunosuppression in athletes.

The literature suggests that a heavy schedule of training and competition leads to immunosuppression in athletes, placing them at a greater risk of opportunistic infection. There are many factors which influence exercise-induced immunosuppression, and nutrition undoubtedly plays a critical role. Misinterpretation of published data and misleading media reports have lead many athletes to adopt an unbalanced dietary regimen in the belief that it holds the key to improved performance. Some sports have strict weight categories, whilst in others low body fat levels are considered to be necessary for optimal performance or seen as an aesthetic advantage. This leads some athletes to consume a diet extremely low in carbohydrate content which, whilst causing rapid weight loss, may have undesirable results which include placing the athlete at risk from several nutrient deficiencies. Complete avoidance of foods high in animal fat reduces the intake of protein and several fat-soluble vitamins. On the other hand, diets with a very high carbohydrate content are usually achieved at the expense of protein. In addition, anecdotal and media reports have often promoted the supposed performance benefits of certain vitamins and minerals, yet most athletes do not realise that micronutrient supplementation is only beneficial when correcting a deficiency, and to date there is little scientific evidence to substantiate claims that micronutrients act as an ergogenic aid. Moreover, excessive intakes of micronutrients can be toxic. Deficiencies or excesses of various dietary components can have a substantial impact on immune function and may further exacerbate the immunosuppression associated with heavy training loads. This review examines the role of nutrition in exercise-induced immunosuppression and the effect of both excessive and insufficient nutrient intake on immunocompetence. As much of the present literature concerning nutrition and immune function is based on studies with sedentary participants, the need for future research which directly investigates the relationship between exercise, training, immunity and nutrition is highlighted.

Diet↗
PubMed1998

Effect of exercise-induced muscle damage on the blood lactate response to incremental exercise in humans.

Eccentric muscle actions are known to induce temporary muscle damage, delayed onset muscle soreness (DOMS) and muscle weakness that may persist for several days. The purpose of the present study was to determine whether DOMS-inducing exercise affects blood lactate responses to subsequent incremental dynamic exercise. Physiological and metabolic responses to a standardised incremental exercise task were measured two days after the performance of an eccentric exercise bout or in a control (no prior exercise) condition. Ten healthy recreationally active subjects (9 male, 1 female), aged 20 (SD 1) years performed repeated eccentric muscle actions during 40 min of bench stepping (knee high step; 15 steps x min[-1]). Two days after the eccentric exercise, while the subjects experienced DOMS, they cycled on a basket loaded cycle ergometer at a starting work rate of 150 W, with increments of 50 W every 2 min until fatigue. The order of the preceding treatments (eccentric exercise or control) was randomised and the treatments were carried out 2 weeks apart. Two days after the eccentric exercise, all subjects reported leg muscle soreness and exhibited elevated levels of plasma creatine kinase activity (P < 0.05). Endurance time and peak VO2 during cycling were unaffected by the prior eccentric exercise. Minute volume, respiratory exchange ratio and heart rate responses were similar but venous blood lactate concentration was higher (P < 0.05) during cycling after eccentric exercise compared with the control condition. Peak blood lactate concentration, observed at 2 min post-exercise was also higher [12.6 (SD 1.4) vs 10.9 SD (1.3) mM; P < 0.01]. The higher blood lactate concentration during cycling exercise after prior eccentric exercise may be attributable to an increased rate of glycogenolysis possibly arising from an increased recruitment of Type II muscle fibres. It follows that determination of lactate thresholds for the purpose of fitness assessment in subjects experiencing DOMS is not appropriate.

Adult↗