Biomedical subjects

Robin Callister

Publications and source records attributed to Robin Callister.

6 recordsLinked to original sources

PubMed2005

Antioxidant-restricted diet reduces plasma nonesterified fatty acids in trained athletes.

Nonesterified FA (NEFA) are a major fuel source for humans at rest and during moderate exercise. The effect of dietary antioxidant restriction on plasma NEFA levels and exercise performance in trained athletes was examined. Seventeen athletes followed a 2-wk restricted-antioxidant (R-AO) diet, which resulted in a threefold reduction in antioxidant intake (ascorbic acid, 139 to 49 mg; beta-carotene, 5093 to 1142 microg) and a significant (P = 0.001) reduction in the plasma NEFA. The amount and types of fat consumed were not different between the R-AO and habitual diets. Exercise time to exhaustion was not affected by the R-AO diet, but rating of perceived exertion (RPE) was significantly (P = 0.03) elevated. The increase in RPE may have occurred as a result of the R-AO diet and subsequent reduction in plasma NEFA; however, further research is required to confirm this conclusion.

Adolescent↗

PubMed2005

Antioxidant restriction and oxidative stress in short-duration exhaustive exercise.

PURPOSE: To determine the effect of dietary antioxidant restriction on oxidative stress, antioxidant defenses, and exercise performance in athletes. Oxidative stress has been shown to increase during exercise. To alleviate oxidative stress, a high intake of antioxidant rich foods or supplements may be required in trained athletes. METHODS: Plasma oxidative stress and antioxidant defenses were examined in 17 trained athletes who underwent two separate exercise tests. Before the initial exercise test participants followed their habitual (high) antioxidant (H-AO) diets. Then they followed a 2-wk restricted-antioxidant (R-AO) diet before the second exercise test. Blood was taken at rest, after submaximal and high-intensity exhaustive exercise, and after 1 h of recovery. RESULTS: The R-AO diet induced a threefold reduction in antioxidant intake when compared with habitual-antioxidant (H-AO) diets. F(2)-isoprostane concentration (marker of oxidative stress) was significantly higher after submaximal exercise (38%), exhaustion (45%), and 1 h of recovery (31%) when following the R-AO diet compared with the H-AO diet. Rate of perceived exertion was increased on the R-AO diet whilst exercise time to exhaustion was not affected. Total antioxidant capacity and circulating antioxidant concentrations, although not significantly different, tended to be lower when following the R-AO diet. CONCLUSION: Athletes regularly participating in up to 40 min of acute high-intensity exercise may require higher intakes of exogenous antioxidants to defend against increased oxidative stress during exercise, which can be met through an adequate intake of high-antioxidant foods. Thus, there seems no valid reason to recommend antioxidant supplements to athletes participating in acute high-intensity exercise events up to 40 min in duration, except in those known to be consuming a low-antioxidant diet for prolonged periods.

Adolescent↗

PubMed2005

Variation of salivary immunoglobulins in exercising and sedentary populations.

PURPOSE: This study examined the nature of the variability in salivary immunoglobulin and albumin concentrations within an individual, between individuals, and between populations with differing levels of habitual physical activity. METHODS: Fourteen elite swimmers, and 21 active and 18 sedentary individuals provided 12 saliva samples over a 30-d period. Group classifications were based on interviews, anthropometric measurements, and physical activity records. Symptoms of illness and physical activity data were recorded daily. Salivary IgA, IgG, and IgM were measured by ELISA, and albumin concentrations were measured by nephelometry. Variability was assessed using ANOVA procedures. RESULTS: Elite swimmers, compared with active and sedentary individuals, had higher concentrations of salivary IgA (geometric mean=65 vs 32 and 40 mg.L, P=0.002) and greater variability in salivary IgA concentrations as individuals (P=0.007) and as a group (P=0.03). Salivary IgG variability in swimmers was also twofold greater than the other two groups (P=0.008). Salivary IgM and albumin variability were not significantly different between groups, but individual variability differed for swimmers and active individuals. The intraclass correlations for salivary IgA and IgG (but not for IgM or albumin) were 50% lower for swimmers than the other two groups (ICC for IgA: 20% swimmers vs 54% active and 46% sedentary individuals; ICC for IgG: 36 vs 59 and 57%). CONCLUSION: The variability and fluctuation of salivary immunoglobulin concentrations were consistently greater in the elite swimmers, but multiple samples from individual swimmers were less correlated compared with participants with lower physical activity levels. These findings have implications for monitoring mucosal immune status within individuals and when comparing salivary immunoglobulin concentrations between groups with differing levels of physical fitness and activity.

Adolescent↗

PubMed2004

Effect of ingested fluid composition on exercise-related transient abdominal pain.

The present study investigated the effect of ingested fluid composition on the experience of exercise-related transient abdominal pain (ETAP). Forty subjects, susceptible to ETAP, completed 4 treadmill exercise trials: a no-fluid trial and flavored water (FW, no carbohydrate, osmolality = 48 mosmol/L, pH = 3.3), sports drink (SD, freshly mixed Gatorade, 6% total carbohydrate, 295 mosmol/L, pH = 3.3), and reconstituted fruit juice (FJ, BERRI trade mark orange, 10.4 % total carbohydrate, 489 mosmol/L, pH= 3.2) trials. Measures of the experience of ETAP and gastrointestinal disturbances, particularly bloating, were quantified. The FJ was significantly (p =.01) more provocative of both ETAP and bloating than all other trials. There was no difference among the no-fluid, FW, and SD in the severity of ETAP experienced, although the difference between the no-fluid and SD approached significance at the.05 level (p =.056). There was a significant relationship between both the mean (r = 0.40, p =.01) and peak (r= 0.44, p=.01) levels of ETAP and bloating. When the level of bloating was controlled for, the FJ remained significantly (p =.01) more provocative of ETAP than the other conditions, with no difference between the FW and SD (p =.37). The results indicate that in order to avoid ETAP, susceptible individuals should refrain from consuming reconstituted fruit juices and beverages similarly high in carbohydrate content and osmolality, shortly before and during exercise. Further, the mechanism responsible for the heightened experience of ETAP in the FJ trial extends beyond a gastric mass explanation.

Abdominal Pain↗

PubMed2004

The missing links in exercise effects on mucosal immunity.

This review highlights research limitations within the existing exercise immunology literature and summarises unanswered questions to assist researchers and clinicians interested in exploring relationships between exercise, training and mucosal immunity. The primary limitations of the existing literature include: inadequate descriptions of training stimuli, age, gender and physical activity of subjects; failing to account for the influence of these factors and the underlying fitness and health status of subjects; methodological differences in assessments of mucosal immunity; limited understanding of the sources of biological variability in mucosal immunity; limited clinical and laboratory diagnosis of respiratory illness; and neglect of psychological, environmental, nutritional and pharmacological influences. Despite a considerable volume of research on mucosal immunity the unanswered research questions include: whether athletes are really more prone to illness; whether illness impacts on athletic performance; identifying subject or training characteristics that influence the mucosal immune responses to exercise; defining how exercise influences the acute mucosal immune response; assessing whether moderate exercise can enhance mucosal immune status; defining more clearly the treatment and management strategies for the athlete suffering recurrent illness, overtraining or long-term fatigue; and the effectiveness of dietary and therapeutic interventions. Answers to these questions should define future research strategies and assist clinicians seeking guidance on the assessment, treatment and management of athletes suffering from respiratory illness, particularly those with recurrent illness, long-term post-viral fatigue or suspected of being overtrained.

Aging↗

PubMed2002

Factors influencing exercise-related transient abdominal pain.

PURPOSE: Exercise-related transient abdominal pain (ETAP) is a widely experienced but poorly understood problem. This study examined the influence of age, gender, body mass index (BMI), training status, and sporting activity on the experience of ETAP and shoulder tip pain (STP). STP may occur as a result of referred pain from tissues innervated by the phrenic nerve; these tissues are implicated in theories proposed to explain ETAP. METHODS: A total of 965 regular sporting participants were surveyed from six sporting activities: running, swimming, cycling, aerobics, basketball, and horse riding. RESULTS: The prevalence (r = -0.28, P < 0.01) and severity (r = -0.17, P < 0.01) of ETAP decreased with age. Gender, BMI, and training status had no affect on the prevalence or severity of ETAP, but respondents who trained more frequently reported experiencing ETAP less often. Younger respondents were more inclined than the older respondents to report ETAP on the left side of the abdomen (P < 0.05). The prevalence (r = -0.11, P < 0.01) and severity (r = -0.37, P < 0.01) of STP decreased with age. STP was described as more severe (r = 0.23, P < 0.05) by respondents with high BMI values. Gender and training status had no influence on the experience of STP. Controlling for all other factors, ETAP was respectively 10.5 and 9 times more common (P < 0.01) in running and horse riding than cycling. STP was 13 times more common in running than cycling. CONCLUSION: Training status alters the frequency of occurrence of ETAP but has little effect on the incidence or severity of the pain. Further, ETAP and STP decrease with age but are not related to gender or BMI.

Abdominal Pain↗