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Biomedical subjects

Michael Gleeson

Publications and source records attributed to Michael Gleeson.

28 records · Page 2Linked to original sources
PubMed2004

The effects of pre-exercise high carbohydrate meals with different glycemic indices on blood leukocyte redistribution, IL-6, and hormonal responses during a subsequent prolonged exercise.

The purpose of this study was to determine the effect of pre-exercise high carbohydrate meals with high glycemic index (HGI) or low glycemic index (LGI) on blood leukocyte redistribution during subsequent endurance exercise. Eight male subjects performed a 90-min run on a treadmill at 70 % VO2max 3 h after ingesting an isocaloric HGI or LGI meal with GI values of 77 and 37, respectively. Blood counts of leukocytes, and neutrophils and the neutrophil/lymphocyte ratio were significantly lower in LGI than HGI at 90 min of exercise (P < 0.05). The plasma glucose concentrations were significantly higher in LGI than HGI between 15 min and 45 min of exercise. There were, however, no differences in plasma cortisol, growth hormone, and interleukin-6 concentrations between trials. Thus, the GI of a pre-exercise meal influences leukocyte trafficking and plasma glucose but has limited effects on circulating stress hormone and cytokine responses to exercise.

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PubMed2004

Effects of acute exhaustive exercise and chronic exercise training on type 1 and type 2 T lymphocytes.

The present study examined the effects of acute exhaustive exercise and chronic exercise training on type 1 and type 2 T lymphocyte distribution and intracellular cytokine production. Seven endurance-trained male cyclists completed exercise trials to exhaustion before, immediately after, and following 2 weeks of resting recovery from a 6-day intensified training period (ITP). During each trial, resting and post-exercise blood samples were incubated with phorbol 12-myristate 13-acetate (PMA) and ionomycin and stained for T lymphocyte surface antigens (CD3). Cells were then permeabilised, stained for intracellular cytokines and analysed using flow cytometry. Acute exhaustive exercise before and following 2 weeks of recovery from the ITP, but not immediately after the ITP, significantly reduced the circulating percentage and number of lFN-gamma+ (type 1) T cells (P<0.05). In addition, the amount of IFN-gamma produced by stimulated T lymphocytes was decreased (P<0.05) post-exercise during each trial. The percentage and number of interferon (IFN)-gamma+ T lymphocytes was decreased (P<0.05) at rest immediately after the ITP compared with before and following 2 weeks of resting recovery from the ITP. However, the amount of IFN-gamma produced by stimulated T lymphocytes at rest was unaltered following the ITP. Neither acute exercise nor chronic exercise training caused an alteration in the circulating percentage or number of interleukin (IL)-4+ (type 2) T lymphocytes. These results suggest a possible mechanism for the increased incidence of infection reported during chronic exercise training via modulation of type 1/type 2 T lymphocyte distribution.

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PubMed2003

Effect of pre-exercise carbohydrate ingestion on plasma cytokine, stress hormone, and neutrophil degranulation responses to continuous, high-intensity exercise.

The purpose of the present study was to examine the effect of pre-exercise carbohydrate (CHO) ingestion on circulating leukocyte numbers, plasma interleukin (IL)-6, plasma cortisol, and lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses in moderately trained male cyclists who completed approximately 1-h of high-intensity cycling. The influence of the timing of pre-exercise CHO ingestion was investigated in 8 subjects who consumed 75 g CHO as a glucose solution at either 15 (-15 trial), or 75 (-75 trial) min before the onset of exercise. The influence of the amount of pre-exercise CHO ingestion was investigated in a further 10 subjects who consumed either 25 g or 200 g CHO as a glucose solution or a placebo 45 min before the onset of exercise. At the onset of exercise in the timing experiment, the plasma glucose concentration was significantly (p < .05) lower on the -75 trial compared with pre-drink values, and the plasma cortisol concentration and neutrophil to lymphocyte (N/L) ratio were significantly (p < .05) elevated in the post-exercise period. In the -15 trial, plasma glucose level was well maintained, and the plasma cortisol concentration and N/L ratio were not significantly elevated above resting levels. However, LPS-stimulated neutrophil degranulation was similar in the -15 and -75 trials. The amount of CHO ingested had no effect on the magnitude of the rise in the N/L ratio compared with placebo when consumed 45 min pre-exercise. Finally, although an exercise-induced increase in the plasma IL-6 concentration was observed, this effect was independent of pre-exercise CHO ingestion.

Adult↗
PubMed2003

Immunological responses to overreaching in cyclists.

INTRODUCTION: Acute bouts of prolonged strenuous exercise are often associated with immune suppression and an increased risk of infection. However, few studies have examined immunological responses to intensified training that results in overreaching or overtraining. We investigated the effects of intensified training on plasma cytokines, glutamine, glutamate, and other related immunological variables in endurance-trained cyclists. METHODS: Eight male subjects (age 27.0 +/- 3.0 yr, [OV0312]O(2max) 58.0 +/- 1.7 mL.kg-1.min-1, mass 73.7 +/- 2.1 kg) completed 6 wk of training: 2 wk each of normal training (N, 7 +/- 2 h.wk-1), intensified training (ITP, 14 +/- 5 h.wk-1) and recovery training (R, 3.5 +/- 2.5 h.wk-1). During the study period, subjects completed six graded cycle ergometer tests to exhaustion (MT), six simulated time trial tests (TT), and eight 2 x 10-min maximal effort bouts (IT). Subjects also completed questionnaires to assess mood state. Plasma concentrations of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), salivary IgA, plasma glutamine, glutamate, ammonia, urea, creatine kinase activity, and routine hematological measures were determined once per week. RESULTS: ITP resulted in overreaching in all subjects identified by a significant decline in performance and disturbances of mood state. Significant increases during the ITP were observed in creatine kinase activity and glutamate, whereas the glutamine/glutamate ratio (Gln/Glu ratio), red blood cell numbers (RBC), hemoglobin concentration (Hb), and packed cell volume (PCV) declined after ITP. No significant changes were observed in TNF-alpha, IL-6, salivary IgA, glutamine, ammonia, urea and various routine hematological measures. CONCLUSION: Alterations in plasma cytokines do not appear to be related to the decline in performance and increased mood state characteristic of overreaching; however, the Gln/Glu ratio may be of use as a marker of overreaching and/or overtraining.

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PubMed2002

Determination of the exercise intensity that elicits maximal fat oxidation.

PURPOSE: The aim of this study was to develop a test protocol to determine the exercise intensity at which fat oxidation rate is maximal (Fat(max)). METHOD: Eighteen moderately trained cyclists performed a graded exercise test to exhaustion, with 5-min stages and 35-W increments (GE(35/5)). In addition, four to six continuous prolonged exercise tests (CE) at constant work rates, corresponding to the work rates of the GE test, were performed on separate days. The duration of each test was chosen so that all trials would result in an equal energy expenditure. Seven other subjects performed three different GE tests to exhaustion. The test protocols differed in stage duration and in increment size. Fat oxidation was measured using indirect calorimetry. RESULTS: No significant differences were found in Fat(max) determined with the GE(35/5), the average fat oxidation of the CE tests, or fat oxidation measured during the first 5 min of the CE tests (56 +/- 3, 64 +/- 3, 58 +/- 3%VO(2max), respectively). Results of the GE(35/5) protocol were used to construct an exercise intensity versus fat oxidation curve for each individual. Fat(max) was equivalent to 64 +/- 4%VO(2max) and 74 +/- 3%HR(max). The Fat(max) zone (range of intensities with fat oxidation rates within 10% of the peak rate) was located between 55 +/- 3 and 72 +/- 4%VO(2max). The contribution of fat oxidation to energy expenditure became negligible above 89 +/- 3%VO(2max) (92 +/- 1%HR(max)). When stage duration was reduced from 5 to 3 min or when increment size was reduced from 35 to 20 W, no significant differences were found in Fat(max), Fat(min), or the Fat(max) zone. CONCLUSION: It is concluded that a protocol with 3-min stages and 35-W increments in work rate can be used to determine Fat(max). Fat oxidation rates are high over a large range of intensities; however, at exercise intensities above Fat(max), fat oxidation rates drop markedly.

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PubMed2002

Influence of carbohydrate supplementation on plasma cytokine and neutrophil degranulation responses to high intensity intermittent exercise.

Ingesting carbohydrate (CHO) beverages during prolonged, continuous heavy exercise results in smaller changes in the plasma concentrations of several cytokines and attenuates a decline in neutrophil function. In contrast, ingesting CHO during prolonged intermittent exercise appears to have negligible influence on these responses, probably due to the overall moderate intensity of these intermittent exercise protocols. Therefore, we examine the effect of CHO ingestion on plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses to high-intensity intermittent running. Six trained male soccer players performed 2 exercise trials, 7 days apart, in a randomized, counterbalanced design. On each occasion, they completed six 15-min periods of intermittent running consisting of maximal sprinting interspersed with less intense periods of running and walking. Subjects consumed either CHO or artificially sweetened placebo (PLA) beverages immediately before and at 15-min intervals during the exercise. At 30 min post-exercise, CHO versus PLA was associated with a higher plasma glucose concentration (p < .01), a lower plasma cortisol and IL-6 concentration (p < .02), and fewer numbers of circulating neutrophils (p < .05). Following the exercise, LPS-stimulated elastase release per neutrophil fell 31% below baseline values on the PLA trial (p = .06) compared with 17% on the CHO trial (p = .30). Plasma TNF-alpha concentration increased following the exercise (main effect of time, p < .001) but was not affected by CHO. These data indicate that CHO ingestion attenuates changes in plasma IL-6 concentration, neutrophil trafficking, and LPS-stimulated neutrophil degranulation in response to intermittent exercise that involves bouts of very high intensity exercise.

Adult↗
PubMed2002

Time course of performance changes and fatigue markers during intensified training in trained cyclists.

To study the cumulative effects of exercise stress and subsequent recovery on performance changes and fatigue indicators, the training of eight endurance cyclists was systematically controlled and monitored for a 6-wk period. Subjects completed 2 wk of normal (N), intensified (ITP), and recovery training. A significant decline in maximal power output (N = 338 +/- 17 W, ITP = 319 +/- 17 W) and a significant increase in time to complete a simulated time trial (N = 59.4 +/- 1.9 min, ITP = 65.3 +/- 2.6 min) occurred after ITP in conjunction with a 29% increase in global mood disturbance. The decline in performance was associated with a 9.3% reduction in maximal heart rate, a 5% reduction in maximal oxygen uptake, and an 8.6% increase in perception of effort. Despite the large reductions in performance, no changes were observed in substrate utilization, cycling efficiency, and lactate, plasma urea, ammonia, and catecholamine concentrations. These findings indicate that a state of overreaching can already be induced after 7 days of intensified training with limited recovery.

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PubMed2002

Degeneration pattern of human first-order cochlear neurons.

In the present study, quantitative analysis of the cochlear neurons in the osseous spiral lamina, the modiolus and the internal auditory canal of the same cochlea was performed. Forty-five temporal bones were obtained from 25 patients and prepared by means of microdissection. Ten patients had age-related normal hearing (ARNH) assuming that the 5 children without audiogram had normal hearing. Fifteen patients had sensorineural hearing loss due to various causes. The present study has shown that in young individuals the numbers of cochlear neurons are almost identical at all 3 sites. In patients over 60 years with ARNH, the loss of peripheral nerve processes is always severer than the loss of central nerve processes. This finding suggests that the central processes degenerate at a much slower rate or not at all. Furthermore, 4 different peripheral degeneration patterns were described. The factors responsible for the different degeneration behaviors are still not understood and need further investigation.

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PubMedDate not supplied

The effect of single and repeated bouts of prolonged cycling and circadian variation on saliva flow rate, immunoglobulin A and alpha-amylase responses.

The purpose of this study was to establish the effect of exercise at different times of day on saliva flow rate, immunoglobulin A (sIgA) concentration and secretion rate, and alpha-amylase activity, and to establish how these parameters change following a second exercise bout performed on the same day. In a counterbalanced design, eight male volunteers participated in three experimental trials separated by at least 4 days. On the trial with afternoon exercise only, the participants cycled for 2 h at 60% VO2max starting at 14:00 h. On the other two trials, participants performed either two bouts of exercise at 60% VO2max for 2 h (the first started at 09:00 h and the second started at 14:00 h) or a separate resting trial. Unstimulated saliva samples were obtained 10 min before exercise, after 58 - 60 min and during the last 2 min of exercise, and at 1 h and 2 h after exercise. Venous blood samples were taken 5 min before exercise and immediately after exercise for both bouts. Participants remained fasted between 23:00 h on the day before the trials and 18:00 h on the day of the trial. Circadian variations were found in sIgA concentration, which decreased with time from its highest value in the early morning to its lowest value in the evening, and salivary alpha-amylase secretion rate, which increased from its lowest value in the morning to its highest value in the late afternoon. Cycling at 60% VO2max for 2 h significantly decreased saliva flow rate, increased sIgA concentration and alpha-amylase activity, but did not influence sIgA secretion rate. Performing prolonged cycling at different times of day did not differentially affect the salivary and plasma hormonal responses in the short term. Performance of a second prolonged exercise bout elicited a greater plasma stress hormone response but did not appear to compromise oral immunity acutely. These findings also suggest that, in terms of saliva secretion, sIgA and alpha-amylase responses, a 3 h rest is enough to recover from previous strenuous exercise. During such exercise, sympathetic stimulation appears to be strong enough to inhibit saliva flow rate; however, it appears that it does not increase sIgA output via transcytosis.

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