Biomedical subjects

L T Mackinnon

Publications and source records attributed to L T Mackinnon.

At least 19 recordsLinked to original sources

PubMed2002

The relationship of natural killer cell counts, perforin mRNA and CD2 expression to post-exercise natural killer cell activity in humans.

The aim of this study was to further investigate the mechanism of suppression of natural killer (NK) cell cytotoxic activity in peripheral blood following strenuous exercise. Blood was collected for analysis of NK cell concentration, cytotoxic activity, CD2 surface expression and perforin gene expression from runners (RUN, n=6) and resting controls (CONTROL, n=4) pre-exercise, 0, 1.5, 5, and 24 h following a 60-min treadmill run at 80% of VO2 peak. Natural killer cytotoxic activity, measured using a whole blood chromium release assay, fluctuated minimally in the CONTROL group and increased by 63% and decreased by 43% 0 and 1.5 h post-exercise, respectively, in the RUN group (group x time, P < 0.001). Lytic index (cytotoxic activity per cell) did not change. Perforin mRNA, measured using quantitative real-time polymerase chain reaction (QRT-PCR) decreased from pre- to post-exercise and remained decreased through 24 h. The decrease from pre- to 0 h post-exercise was seen predominately in the RUN group and was inversely correlated (r=- 0.95) to pre-exercise perforin mRNA. The NK cell surface expression of CD2 (lymphocyte function-associated antigen-2) was determined using fluorescent antibodies and flow cytometry. There was no change in the proportion of NK cells expressing CD2 or CD2 density. We conclude that (1) numerical redistribution accounted for most of the change in NK cytotoxic activity following a strenuous run, (2) decrease in perforin gene expression during the run was inversely related to pre-exercise levels but did not parallel changes in cytotoxic activity, and (3) CD2 surface expression was not affected by exercise.

Adolescent↗

PubMed2001

The effects of stress management on symptoms of upper respiratory tract infection, secretory immunoglobulin A, and mood in young adults.

OBJECTIVE: To investigate the efficacy of a stress management programme on symptoms of colds and influenza in 27 university students before and after the examination period. METHOD: The incidence of symptoms, levels of negative affect, and secretion rate of secretory immunoglobulin A (sIgA) were recorded for 5 weeks before treatment, for the 4 weeks of treatment, and for 8 weeks after treatment in treated subjects and in 25 others who did not participate in stress management. RESULTS: Symptoms decreased in treated subjects but not in controls during and after the examination period. Although sIgA secretion rate increased significantly after individual sessions of relaxation, resting secretion rate of sIgA did not increase over the course of the study. Negative affect decreased after examinations in both groups, but was not affected by treatment. CONCLUSION: Stress management reduced days of illness independently of negative affect and sIgA secretion rate. Although the component of treatment responsible for this effect has yet to be identified, psychological interventions may have a role in reducing symptoms of upper respiratory tract infection.

Adolescent↗

PubMed2001

The effect of moderate aerobic exercise and relaxation on secretory immunoglobulin A.

A deficiency in secretory immunoglobulin A (sIgA) is associated with recurrent upper respiratory tract infections both in the general community and in elite athletes. The aim of this paper was to investigate the effect of aerobic exercise and relaxation on various indices of sIgA in 12 male and 8 female adults who varied in levels of recreational activity. Salivary samples were obtained before, immediately after and 30 minutes after an incremental cycle ergometer test to fatigue, after 30 minutes of cycling at 30% or 60% of maximum heart rate, and after 30 minutes of relaxation with guided imagery. Each session was run on a separate day. When expressed in relation to changes in salivary flow rate, sIgA did not change after exercise. However, both the absolute concentration and secretion rate of sIgA increased during relaxation (167 +/- 179 microg x ml(-1), p < 0.001; and 37 +/- 71 microg x min(-1), p < 0.05 respectively). Nonspecific protein increased more than sIgA during incremental exercise to fatigue (decrease in the sIgA/protein ratio 92 +/- 181 microg x mg protein(-1), p < 0.05), but sIgA relative to protein did not change during relaxation. Our findings suggest that sIgA secretion rate is a more appropriate measure of sIgA than sIgA relative to protein, both for exercise and relaxation. These data suggest the possibility of using relaxation to counteract the negative effects of intense exercise on sIgA levels.

Adult↗

PubMed2000

Chronic exercise training effects on immune function.

PURPOSE: This paper reviews the recent literature on the chronic effects of exercise training on immune function in humans. There is a general perception by athletes and other physically active individuals that regular moderate activity enhances, whereas intense exercise suppresses, resistance to minor illnesses such as upper respiratory tract infection (URTI). This perception is supported by epidemiological data in endurance athletes and limited data from intervention studies using moderate exercise in previously untrained individuals. The apparently high incidence of URTI among endurance athletes has prompted interest the relationship between chronic exercise training and immune function. Whereas immune cell number is generally normal during intense exercise training, recent evidence suggests that prolonged periods of intense training may lead to slight impairment in immune parameters such as neutrophil function, serum and mucosal immunoglobulin levels, plasma glutamine concentration, and possibly natural killer cell cytotoxic activity. In contrast. moderate exercise training has either no effect on, or may stimulate, these immune parameters. CONCLUSION: Whereas athletes are not clinically immune deficient, it is possible that the combined effects of small changes in several immune parameters may compromise resistance to minor illnesses such as URTI. Strategies to prevent URTI in athletes include avoiding overtraining, providing adequate rest and recovery during the training cycle and after competition, limiting exposure to sources of infection, ensuring adequate nutrition, and possibly vitamin C supplementation. It is uncertain at present whether moderate exercise training is helpful in preventing infectious illness among the wider population.

Antibody Formation↗

PubMed1999

The effects of strength training on endurance performance and muscle characteristics.

PURPOSE: The purpose of this study was to determine the effects of resistance training on endurance performance and selected muscle characteristics of female cyclists. METHODS: Twenty-one endurance-trained, female cyclists, aged 18-42 yr, were randomly assigned to either a resistance training (RT; N = 14) or a control group (CON; N = 7). Resistance training (2X x wk(-1)) consisted of five sets to failure (2-8 RM) of parallel squats for 12 wk. Before and immediately after the resistance-training period, all subjects completed an incremental cycle test to allow determination of both their lactate threshold (LT) and peak oxygen consumption VO2). In addition, endurance performance was assessed by average power output during a 1-h cycle test (OHT), and leg strength was measured by recording the subject's one repetition maximum (1 RM) concentric squat. Before and after the 12-wk training program, resting muscle was sampled by needle biopsy from m. vastus lateralis and analyzed for fiber type diameter, fiber type percentage, and the activities of 2-oxoglutarate dehydrogenase and phosphofructokinase. RESULTS: After the resistance training program, there was a significant increase in 1 RM concentric squat strength for RT (35.9%) but not for CON (3.7%) (P < 0.05). However, there were no significant changes in OHT performance, LT, VO2, muscle fiber characteristics, or enzyme activities in either group (P > 0.05). CONCLUSION: The present data suggest that increased leg strength does not improve cycle endurance performance in endurance-trained, female cyclists.

Adolescent↗

PubMed1999

Physiological and psychometric variables for monitoring recovery during tapering for major competition.

PURPOSE: This study attempted to identify variables that are useful in monitoring recovery during tapering. METHODS: Changes in physiological variables, tethered swimming force, mood states, and self-ratings of well-being were measured in 10 elite swimmers from before to after 2 wk of tapering for national championships. Physiological measures included resting heart rate (HR); blood pressure (BP); blood lactate concentration; red blood cell, white blood cell, and differential counts; and plasma cortisol, free testosterone, and catecholamine concentrations. Measures taken after 100-m maximal and 200-m standardized submaximal swims included HR, BP, and blood lactate concentration. RESULTS: Step-down regression analysis showed that changes in plasma norepinephrine concentration, heart rate after maximal effort swimming and confusion as measured by the Profile of Mood States (POMS) predicted the change in swimming time with tapering (r2 = 0.98); the change in plasma norepinephrine concentration predicted the change in swim time with tapering (r2 = 0.82) by itself. CONCLUSION: These data suggest that recovery after intense training can be monitored during tapering and that an accurate prediction of performance changes may be possible if the changes in a range of physiological and psychological variables are measured.

Adolescent↗

PubMed1999

Effects of exercise on lipoprotein(a).

Lipoprotein(a) [Lp(a)] is a unique lipoprotein complex in the blood. At high levels (> 30 mg/dl), Lp(a) is considered an independent risk factor for cardiovascular diseases. Serum Lp(a) levels are largely genetically determined, remain relatively constant within a given individual, and do not appear to be altered by factors known to influence other lipoproteins (e.g. lipid-lowering drugs, dietary modification and change in body mass). Since regular exercise is associated with favourable changes in lipoproteins in the blood, recent attention has focused on whether serum Lp(a) levels are also influenced by physical activity. Population and cross-sectional studies consistently show a lack of association between serum Lp(a) levels and regular moderate physical activity. Moreover, exercise intervention studies extending from 12 weeks to 4 years indicate that serum Lp(a) levels do not change in response to moderate exercise training, despite improvements in fitness level and other lipoprotein levels in the blood. However, recent studies suggest the possibility that serum Lp(a) levels may increase in response to intense load-bearing exercise training, such as distance running or weight lifting, over several months to years. Cross-sectional studies have reported abnormally high serum Lp(a) levels in experienced distance runners and body builders who train for 2 to 3 hours each day. However, the possible confounding influence of racial or ethnic factors in these studies cannot be discounted. Recent intervention studies also suggest that 9 to 12 months of intense exercise training may elevate serum Lp(a) levels. However, these changes are generally modest (10 to 15%) and, in most individuals, serum Lp(a) levels remain within the recommended range. It is unclear whether increased serum Lp(a) levels after intense exercise training are of clinical relevance, and whether certain Lp(a) isoforms are more sensitive to the effects of exercise training. Since elevation of both low density lipoprotein cholesterol (LDL-C) and Lp(a) levels in the blood exerts a synergistic effect on cardiovascular disease risk, attention should focus on changing lifestyle factors to decrease LDL-C (e.g. dietary intervention) and increase high density lipoprotein cholesterol (e.g. exercise) levels in the blood.

Body Weight↗

PubMed1998

Effects of three tapering techniques on the performance, forces and psychometric measures of competitive swimmers.

The 100-m and 400-m swim time, tethered swimming forces, mood states and self-ratings of well-being of 27 competitive swimmers were measured before and after 4 weeks of intense training and after 1 week and 2 weeks of tapering for major competition. The swimmers were divided into three groups. Each group completed one of three taper regimes similar to those currently performed by swimmers in preparation for competition: (a) reduced training frequency according to each athlete's daily ratings of well-being, (b) reduced training volume, and (c) reduced training volume and intensity. Significant improvements in the Profile of Mood States measures of tension, depression and anger (P < 0.05) were observed after 1 week of tapering, with significant improvements in total mood disturbance and fatigue (P < 0.05) and peak tethered swimming force (P < 0.01) after 2 weeks. Non-significant improvements in 100-m and 400-m swim time (P > 0.05) were observed and no significant differences were revealed among the three tapering techniques. These data highlighted the importance of providing sufficient recovery before competition, since 1 week of reduced training was not long enough to maximise the benefits of tapering. However, none of the three types of tapering currently used by competitive swimmers could be shown to be more beneficial than the others.

Adolescent↗

PubMed1998

The effect of stage duration on the calculation of peak VO2 during cycle ergometry.

This study investigated the influence of stage duration on the calculation of peak oxygen consumption (peak VO2 to determine whether both the lactate threshold (LT) and peak VO2 could be measured during the same test without compromising the peak VO2 value obtained. Eight moderately-active females (mean age +/- SD = 19.6 +/- 2.5 years) performed three peak VO2 tests on an electrically-braked cycle ergometer. Power output was increased every minute for the short peak VO2 test (S) and every three minutes for the long peak VO2 tests (L). Testing took place over two weeks with all tests separated by at least 48 hours. The first peak VO2 test was a long test (L1) and served as familiarisation. The subjects then performed a short (S) and a long (L2) peak VO2 test in random, counterbalanced order. For each subject, all three tests were performed at the same time of day in controlled environmental conditions. There was no significant difference between the two exercise protocols for peak VO2 when expressed in ml x kg(-1) x min(-1) (F[1,7]=3.47, P=0.105) or in L x min(-1) (F[1,7]=3.39. P=0.108). However, the maximum heart rate (HRmax) achieved in S was significantly less than the HRmax achieved in L2 (F[1,7]=33.4, P<0.001). The power output at exhaustion (Wpeak) was significantly greater in S than in L2 (F[1,7]=56.5, P<0.001). The data from this study therefore showed that in moderately-active females, a three-minute incremental protocol, allowing for the simultaneous calculation of the LT, could be used without compromising peak VO2, but that HRmax and Wpeak were affected.

Adolescent↗

PubMed1998

Future directions in exercise and immunology: regulation and integration.

Although it is difficult to predict future directions in a rapidly expanding field such as exercise immunology, recently published research along with that presented at this Symposium allow us to ask some key questions which may point to new directions: 1) Are athletes immunocompromised? Athletes are not clinically immunodeficient, yet endurance athletes are at increased risk of illness. Long-term prospective studies are needed to understand the relationship between infection, training variables and immune parameters. 2) Is downregulation of nonspecific immunity beneficial or harmful? In athletes, neutrophils appear to be downregulated, and this may alter resistance to illness. Alternatively, neutrophils are mediators of tissue damage during inflammation. Downregulation of neutrophil function may be protective by limiting chronic inflammation. In athletes, mild immunosuppression may reflect a compromise between the body's attempts to limit inflammation while maintaining immune function. 3) What mediates communication between events in skeletal muscle and the immune system? Leukocyte mobility is affected by metabolic and mechanical factors during exercise. Exercise increases cytokine levels in damaged skeletal muscle and expression of adhesion molecules. Future work is likely to focus on the role of cytokines and adhesion molecules in mediating exercise-induced changes in leukocyte mobility. 4) Can exercise training provide a "countermeasure" against immunosuppressive events? Moderate exercise training may have a role in stimulating the immune system during certain diseases (e.g., HIV-infection), immune dysfunction (e.g., chronic fatigue syndrome) or reduced responsiveness (e.g. aging, spaceflight). It is also likely that future study will apply molecular biology techniques to further identify mechanisms by which exercise influences immune function.

Animals↗

PubMed1998

The relationship between plasma lactate parameters, Wpeak and 1-h cycling performance in women.

PURPOSE: The relationship between six descriptors of lactate increase, peak VO2, Wpeak, and 1-h cycling performance were compared in 24 trained, female cyclists (peak VO(2) = 48.11 +/- 6.32 mLxkg(-1)xmin(-1). METHODS: The six descriptors of lactate increase were: 1) lactate threshold (LT; the power output at which plasma lactate concentration begins to increase above the resting level during an incremental exercise test), 2) LT(1) the power output at which plasma lactate increases by 1 mM or more), 3) LT(D) (the lactate threshold calculated by the D-max method), 4) LT(MOD) (the lactate threshold calculated by a modified D-max method), 5) L4 (the power output at which plasma lactate reaches a concentration of 4 mmolxL(-1), and 6) LT(LOG) (the power output at which plasma lactate concentration begins to increase when the log ([La(-1]) is plotted against the log (power output). Subjects first completed a peak VO(2) test on a cycle ergometer. Finger-tip capillary blood was sampled within 30 s of the end of each 3-min stage for analysis of plasma lactate. Endurance performance was assessed 7 d later using a 1-h cycle test (OHT) in which subjects were directed to achieve the highest possible average power output. RESULTS: The mean power output (W) for the OHT (+/- SD) was 183.01 +/- 18.88, and for each lactate variable was:LT (138.54 +/- 46.61), LT(1) (179.17 +/- 27.25), LT(log) (143.97 +/- 45.74), L4 (198.09 +/- 33.84), LT(D) (178.79 +/- 24.07), LT(MOD)(212.28 +/- 31.75). Average power output during the OHT was more strongly correlated with all plasma lactate parameters (0.61<r<0.84) and W(peak) (r = 0.81) than with peak VO(2) (r = 0.55). The six lactate parameters were strongly correlated with each other (0.54<r<0.91) and of six lactate parameters, LT(D) correlated best with endurance performance (r = 0.84). CONCLUSIONS: It was concluded that plasma lactate parameters and W(peak) provide better indices of endurance performance than peak VO(2) and that, of the six descriptors of lactate increase measured in this study, LT(D) is most strongly related to 1-h cycling performance in trained, female cyclists.

Adult↗

PubMed1998

A comparison of plasma glutamine concentration in athletes from different sports.

PURPOSES: The purposes of the current investigation were to compare resting plasma glutamine concentration in athletes from different sports and to determine the relationship between resting plasma glutamine concentration and dietary protein intake. METHODS: Resting plasma glutamine concentration was measured in five groups of eight distance runners, competitive swimmers, cyclists, powerlifters, and nonathletes. Dietary protein intake of each subject was measured (g.d-1 and g.kg-1.d-1). RESULTS: Plasma glutamine concentration was significantly different between sports (P = 0.000, ANOVA) with mean plasma glutamine concentration of cyclists significantly higher than in all other groups, and mean plasma glutamine concentration of powerlifters and swimmers significantly lower than in cyclists and nonathletes (P < 0.05, post hoc analysis). There was no significant relationship between plasma glutamine concentration and total dietary protein intake when expressed as g.d-1 (r = 0.11, P > 0.05); however, plasma glutamine concentration and dietary protein relative to body mass (g.kg-1.d-1) were significantly inversely correlated (r = -0.37, P = 0.007). CONCLUSIONS: These data suggest that resting plasma glutamine concentration may vary between sports, possibly due to metabolic demands of the different sports; dietary factors may also affect plasma glutamine concentration.

Adult↗

PubMed1997

Immunity in athletes.

There is a general perception among athletes, coaches and sports physicians that athletes are susceptible to infectious illness, such as upper respiratory tract infection (URTI), during intensive training and major competition; recent epidemiological evidence is consistent with this perception. Recent studies have focused on the effects of exercise on immune parameters in order to better understand mechanisms by which exercise training may influence resistance to infection. Intensive exercise has been shown to transiently alter a number of immune parameters including circulating leukocyte and subset numbers, plasma cytokine concentrations, natural killer cell activity, secretory immunoglobulin A secretion rate, and neutrophil and macrophage phagocytic activity. Many of these changes persist for several hours or even days after intensive exercise. Some athletes have been shown to exhibit low resting or postexercise values on some nonspecific immune parameters compared with clinical norms, such as complement, acute phase proteins, and neutrophil activation. In addition, extended periods of intensive exercise training have been associated with progressive decreases in some immune parameters such as neutrophil function and certain subclasses of serum and secretory immunoglobulin. These data suggest the possibility of clinically relevant immune suppression in well-trained athletes. Psychological stress associated with training and competition at the elite level may be an additive factor to the effects of intensive exercise on immune function.

Cytokines↗

PubMed1997

Acute effects of treadmill running on lipoprotein(a) levels in males and females.

This investigation examined the acute response of serum lipoprotein(a) (Lp(a)) concentration immediately after, and during several days following, level and downhill motorized treadmill running. Eight males ran for 1 h on a level motorized treadmill at an intensity producing 90% maximum heart rate (MHR). On a separate occasion, three males and three females performed downhill (negative 13.4% incline) treadmill running at an intensity producing 75-80% MHR. For both protocols, serial blood samples were taken pre- and post-exercise and at the same time of day 1, 3, 5, and 7 days following exercise. Levels of Lp(a), creatine kinase (CK), C-reactive protein (CRP), and ferritin were measured. Repeated measures statistical analysis (Friedman ANOVA) showed no significant change in the median level of Lp(a) (level run, 5.0 mg.dl-1; downhill run, 7.45 mg.dl-1) across time following either protocol. After level running, ferritin levels 5 and 7 d post-exercise were significantly (P < 0.05) lower compared with immediately and 1 d post-exercise measures (Friedman ANOVA). Following level running, the Wilcoxon signed rank test showed significant (P < 0.05) elevations in CK levels immediately, 1 and 5 d post-exercise compared with pre-exercise values. Following downhill running. CK level was significantly elevated up to 3 d post-exercise (Wilcoxon signed rank). Calculated plasma volume did not change significantly following either protocol. These data suggest that Lp(a) does not change acutely in response to level or downhill treadmill running up to 60 min duration.

Acute-Phase Proteins↗

PubMed1997

Effects of physical activity and diet on lipoprotein(a).

Lipoprotein(a) [Lp(a)] represents a class of lipoproteins with some structural similarity to low density lipoprotein (LDL), but containing a unique apoprotein, apoprotein(a). First reported in 1963, Lp(a) is now considered to have an independent role in the development of atherosclerotic lesions. The level of Lp(a) in the blood is under strong genetic influence and does not appear to be alterable by lifestyle factors known to influence other lipoproteins. Regular moderate exercise has been shown to favorably alter other lipoproteins, and recent attention has focused on whether Lp(a) level can be influenced by physical activity. Current data from cross-sectional and intervention studies show little effect of moderate exercise on serum Lp(a) concentration. One possible exception may be an elevation of serum Lp(a) concentration in adult endurance and power athletes who exercise intensely on a daily basis. However, not all studies have taken into account possible racial or ethnic differences in Lp(a) concentrations and the skewed distribution observed within most populations. Standard dietary intervention such as a low fat diet recommended for weight loss and control of other blood lipids has little effect on serum Lp(a) level. At present, serum Lp(a) concentration does not appear to be significantly altered by realistic dietary changes and moderate physical activity as recommended for health. The synergistic effect on cardiovascular disease risk when both LDL-cholesterol and Lp(a) are elevated highlight the importance of attending to those risk factors that can be modified by exercise and other lifestyle changes.

Adolescent↗

PubMed1997

Hormonal, immunological, and hematological responses to intensified training in elite swimmers.

The purpose of this study was to compare the responses of selected hormonal, immunological, and hematological variables in athletes showing symptoms of overreaching with these variables in well-trained athletes during intensified training. Training volume was progressively increased over 4 wk in 24 elite swimmers (8 male, 16 female); symptoms of overreaching were identified in eight swimmers based on decrements in swim performance, persistent high ratings of fatigue, and comments in log books indicating poor adaptation to the increased training. Urinary excretion of norepinephrine was significantly lower (P < 0.05, post hoc analysis) in overreached (OR) compared with well-trained (WT) swimmers throughout the 4 wk. There were no significant differences between OR and WT swimmers for other variables including: concentrations of plasma norepinephrine, cortisol, and testosterone, and the testosterone/cortisol ratio; peripheral blood leukocyte and differential counts, neutrophil/lymphocyte ratio, and CD4/CD8 cell ratio; serum ferritin and blood hemoglobin concentrations, erythrocyte number, hematocrit, and mean red cell volume (MCV). MCV increased significantly over the 4 wk in both groups, suggesting increased red blood cell turnover. These data show that, of the 16 hormonal, immunological, and hematological variables measured, urinary norepinephrine excretion appears to be the only one to distinguish OR from WT swimmers during short-term intensified training. Low urinary norepinephrine excretion was observed 2 to 4 wk before the appearance of symptoms of overreaching, suggesting the possibility that neuroendocrine changes may precede, and possibly contribute to, development of the overreaching/overtraining syndromes.

Adolescent↗

PubMed1996

Relationship between gear ratio and 10-s sprint cycling on an air-braked ergometer.

This investigation examined the relationship between gear ratio and peak and mean power outputs (PPO and MPO) and peak cadence (PC) during a 10-s all-out sprint on a multi-geared air-braked cycle ergometer. Ten physically active men [mean age 21.0 years (SEM 0.7)] performed in random order six 10-s sprints (15-min rest between each sprint) on two occasions (48 h apart) in six different gear ratios; flywheel revolutions per pedal crank revolution (FR/PCR) ranged between 5.22 and 11.61. The PPO, MPO, and PC were recorded from each sprint. Of the six gear ratios tested, a gear ratio eliciting 8.87 FR/PCR elicited the highest PPO for the initial test session; the PPO output of 1274 W was significantly greater (P < 0.01) than that produced in the other five gears. Analysis of data from the second test session revealed no statistically significant difference in PPO between gear ratios eliciting 8.00, 8.87, and 10.06 FR/PCR. The PPO from these three ratios were significantly greater (P < 0.05) than those produced using the ratios resulting in 6.32, 7.06, and 10.78 FR/PCR. The PC in the gear ratio maximising PPO was 120 rpm. Analysis of PC data revealed a significant decrease (P < 0.05) as the number of FR/PCR increased.

Adult↗

PubMed1996

Plasma glutamine and upper respiratory tract infection during intensified training in swimmers.

The purposes of this study were to determine the effects of 4 wk of intensified training on resting plasma glutamine concentration, and to determine whether changes in plasma glutamine concentration relate to the appearance of upper respiratory tract infection (URTI) in swimmers during intensified training. Resting plasma glutamine concentration was measured by high performance liquid chromatography in 24 elite swimmers (8 male, 16 female, ages 15-26 yr) during 4 wk of intensified training (increased volume). Symptoms of overtraining syndrome (OT) were identified in eight swimmers (2 male, 6 female) based on decrements in swim performance and persistent high fatigue ratings; non-overtrained subjects were considered well-trained (WT). Ten of 24 swimmers (42%, 1 OT and 9 WT) exhibited URTI during the study. Plasma glutamine concentration increased significantly (P = 0.04, ANOVA) over the 4 wk, but the increase was significant only in WT swimmers (P < 0.05, post-hoc analysis). Compared with WT, plasma glutamine was significantly lower in OT at the mid-way timepoint only (P < 0.025, t-test with Bonferroni correction). There was no significant difference in glutamine levels between athletes who developed URTI and those who did not. These data suggest that plasma glutamine levels may not necessarily decrease during periods of intensified training, and that the appearance of URTI is not related to changes in plasma glutamine concentration in overtrained swimmers.

Adolescent↗