Title: Effects of Exercise and Lack of Exercise on Glucose Tolerance and Insulin Sensitivity
Author: Heath, G. W.; Gavin, J. R., 3rd; Hinderliter, J. M.; Hagberg, J. M.; Bloomfield, S. A.; Holloszy, J. O.; (Date: Aug, 1983)
Journal: J Appl Physiol; V. 55; Issue: 2; Pages: 512-7
Abstract: Physically trained individuals have a markedly blunted insulin response to a glucose load and yet have normal glucose tolerance. This phenomenon has generally been ascribed to long-term adaptations to training which correlate with maximal oxygen uptake (VO2max) and reduced adiposity. Our study was undertaken to test the hypothesis that residual effects of the last bouts of exercise play an important role in this phenomenon. Eight well-trained subjects stopped training for 10 days. There were no significant changes in VO2max (58.6 +/- 2.2 vs. 57.6 +/- 2.1 ml/kg), estimated percent body fat (12.5 +/- 0.7 vs. 12.5 +/- 0.8%), or body weight. The maximum rise in plasma insulin concentration in response to a 100-g oral glucose load was 100% higher after 10 days without exercise than when the subjects were exercising regularly. Despite the increased insulin levels, blood glucose concentrations were higher after 10 days without exercise. Insulin binding to monocytes also decreased with physical inactivity. One bout of exercise after 11 days without exercise returned insulin binding and the insulin and glucose responses to an oral 100-g glucose load almost to the initial “trained” value. These results support our hypothesis.
Notes: Journal Article
Title: The Asthmatic Athlete: Metabolic and Ventilatory Responses to Exercise with and without Pre-Exercise Medication
Author: Ienna, T. M.; McKenzie, D. C.; (Date: Feb, 1997)
Journal: Int J Sports Med; V. 18; Issue: 2; Pages: 142-8
Abstract: To determine whether asthmatic athletes have normal physiological responses to exercise without pre-exercise medication, we studied 17 female and male asthmatic subjects, 9 highly trained (HT) and 8 moderately trained (MT) under 2 conditions: salbutamol (S) 200 micrograms taken via inhaler 15 minutes prior to exercise or placebo (PL). The exercise task was 4 continuous 5 minute increments representing 25, 50, 75 and 90% of the subject’s VO2max.VO2, minute ventilation (VE), respiratory exchange ratio (RER), % saturation (SaO2), and HR were continuously measured during exercise. Blood lactate (LA) was measured each minute throughout exercise and recovery. Post-medication, exercise, and recovery measurements of peak expiratory flow rates (PEFR) were made using a Mini-Wright flow meter. No differences (p > 0.05) between treatment conditions were found at any stage of exercise with respect to VO2, VE, RER, HR and SaO2. However, among the HT group the mean HR for the 4 exercise conditions was significantly higher under PL (PL = 151.7;S = 147.2; p = 0.01). No difference was found in LA during exercise or in recovery. Pre-exercise PEFR was significantly higher when pretreatment was S(S = 582; PL = 545 l.sec-1; p = 0.003). During the exercise and recovery conditions mean PEFR measures were significantly higher (S = 600.1; PL = 569.6; p = 0.002) with the S treatment. Bonferroni’s test detected a difference in PEFR measures between S and PL at 25% and 50% VO2max and 3 and 15 minutes into recovery. There was no difference in the physiological response to exercise between groups based on training status. It was concluded that although S affects the PEFR these asthmatic athletes do not have altered metabolic or ventilatory responses during this incremental exercise protocol.
Notes: Clinical Trial
Randomized Controlled Trial
Author Address: School of Human Kinetics, University of British Columbia, Vancouver, Canada.
Abstract: Moderate and heavy exercise induce a multitude of changes in the neuroendocrine immune system, the net effects of which depend on various other factors including the host’s physical condition, and the intensity and duration of the exercise bout. Most investigators report that the risk of upper respiratory infection is increased following heavy exertion, but is decreased after moderate exercise. Many heavy exercise-induced changes in the host’s immune defenses are consistent with the alterations reported in classical stress studies; some consensus has been achieved in this area that heavy exertion may indeed elicit responses common to psychological forms of stress. The immunomodulation consists, most notably, of shifts in the number and function of circulating innate and adaptive immune cell populations apparently in response to the release of classical stress hormones and cytokines, and expression of selectin and adhesin molecules. Rapid trafficking of cells in and out of the blood compartment in response to exertion probably mirrors the demand for certain cell types in specific tissues, a hypothesis requiring verification in animal models and ultimately the human. Also needed are studies correlating the functional status of the circulating cells with those in the tissues.
Notes: Journal Article
Author Address: Immunology Center, Loma Linda University Medical Center, CA 92354-2870, USA. firstname.lastname@example.org
Title: The Effects of Moderate Exercise Training on Natural Killer Cells and Acute Upper Respiratory Tract Infections
Author: Nieman, D. C.; Nehlsen-Cannarella, S. L.; Markoff, P. A.; Balk-Lamberton, A. J.; Yang, H.; Chritton, D. B.; Lee, J. W.; Arabatzis, K.; (Date: Dec, 1990)
Journal: Int J Sports Med; V. 11; Issue: 6; Pages: 467-73
Abstract: A randomly controlled 15-wk exercise training (ET) study (five 45-min sessions/wk, brisk walking at 60% heart rate reserve) with a group of 36 mildly obese, sedentary women was conducted to investigate the relationship between improvement in cardiorespiratory fitness, changes in natural killer (NK) cell number and activity, and acute upper respiratory tract infection (URI) symptomatology. The study was conducted using a 2 (exercise and nonexercise groups) x 3 (baseline, 6-, and 15-wk testing sessions) factorial design, with data analyzed using repeated measures ANOVA. No significant change in NK cell number occurred as a result of ET as measured by the CD16 and Leu-19 monoclonal antibodies. ET did have a significant effect on NK cell activity (E:T 50:1) especially during the initial 6-wk period [F(2.68) = 12.34, p less than 0.001]. Using data from daily logs kept by each subject, the exercise group was found to have significantly fewer URI symptom days/incident than the nonexercise group (3.6 +/- 0.7 vs 7.0 +/- 1.4 days, respectively, p = 0.049). Improvement in cardiorespiratory fitness was correlated significantly with a reduction in URI symptom days/incident (r = 0.37, p = 0.025) and a change in NK cell activity from baseline to six but not 15 wks (r = 0.35, p = 0.036). In summary, moderate ET is associated with elevated NK cell activity after six but not 15 weeks, and reduced URI symptomatology in comparison to a randomized, sedentary control group.
Notes: Clinical Trial
Randomized Controlled Trial
Author Address: Department of Health Science, School of Public Health, Loma Linda University.
Abstract: During the last 95 years, 629 papers (60% in the 1990s) dealing specifically with exercise and immunology have been published. Major findings of practical importance in terms of public health and athletic endeavor include: (a) In response to acute exercise (the most frequently studied area of exercise immunology), a rapid interchange of immune cells between peripheral lymphoid tissues and the circulation occurs. The response depends on many factors, including the intensity, duration, and mode of exercise, concentrations of hormones and cytokines, change in body temperature, blood flow, hydration status, and body position. Of all immune cells, natural killer (NK) cells, neutrophils, and macrophages (of the innate immune system) appear to be most responsive to the effects of acute exercise, both in terms of numbers and function. In general, acute exercise bouts of moderate duration (< 60 min) and intensity (< 60% VO2max) are associated with fewer perturbations and less stress to the immune system than are prolonged, high-intensity sessions. (b) In response to long-term exercise training, the only finding to date reported with some congruity between investigators is a significant elevation in NK cell activity. Changes in the function of neutrophils, macrophages, and T and B cells in response to training have been reported inconsistently, but there is some indication that neutrophil function is suppressed during periods of heavy training. (c) Limited data suggest that unusually heavy acute or chronic exercise may increase the risk of upper respiratory tract infection (URTI), while regular moderate physical activity may reduce URTI symptomatology. (d) Work performance tends to diminish with most systemic infectious, and clinical case studies and animal data suggest that infection severity, relapse, and myocarditis may result when patients exercise vigorously. (e) Although regular exercise has many benefits for HIV-infected individuals, helper T cell counts and other immune measures are not enhanced significantly. (f) Data suggest that the incidence and mortality rates for certain types of cancer are lower among active subjects. The role of the immune system may be limited, however, depending on the sensitivity of the specific tumor to cytolysis, the stage of cancer, the type of exercise program, and many other complex factors. (g) As individuals age, they experience a decline in most cell- mediated and humoral immune responses. Two human studies suggest that immune function is superior in highly conditioned versus sedentary elderly subjects. (h) Mental stress, undernourishment, quick weight loss, and improper hygiene have each been associated with impaired immunity. Athletes who are undergoing heavy training regimens should realize that each of these factors has the potential to compound the effect that exercise stress is having on their immune systems.
Notes: Journal Article
Author Address: Department of Health and Exercise Science, Appalachian State University, USA.
Abstract: Comparison of immune function in athletes and nonathletes reveals that the adaptive immune system is largely unaffected by athletic endeavour. The innate immune system appears to respond differentially to the chronic stress of intensive exercise, with natural killer cell activity tending to be enhanced while neutrophil function is suppressed. However, even when significant changes in the level and functional activity of immune parameters have been observed in athletes, investigators have had little success in linking these to a higher incidence of infection and illness. Many components of the immune system exhibit change after prolonged heavy exertion. During this ‘open window’ of altered immunity (which may last between 3 and 72 hours, depending on the parameter measured), viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection. However, no serious attempt has been made by investigators to demonstrate that athletes showing the most extreme post-exercise immunosuppression are those that contract an infection during the ensuing 1 to 2 weeks. This link must be established before the ‘open window’ theory can be wholly accepted. The influence of nutritional supplements, primarily zinc, vitamin C, glutamin and carbohydrate, on the acute immune response to prolonged exercise has been measured in endurance athletes. Vitamin C and glutamine have received much attention, but the data thus far are inconclusive. The most impressive results have been reported in the carbohydrate supplementation studies. Carbohydrate beverage ingestion has been associated with higher plasma glucose levels, an attenuated cortisol and growth hormone response, fewer perturbations in blood immune cell counts, lower granulocyte and monocyte phagocytosis and oxidative burst activity, and a diminished pro- and anti-inflammatory cytokine response. It remains to be shown whether carbohydrate supplementation diminishes the frequency of infections in the recovery period after strenuous exercise. Studies on the influence of moderate exercise training on host protection and immune function have shown that near-daily brisk walking compared with inactivity reduced the number of sickness days by half over a 12- to 15-week period without change in resting immune function. Positive effects on immunosurveillance and host protection that come with moderate exercise training are probably related to a summation effect from acute positive changes that occur during each exercise bout. No convincing data exist that moderate exercise training is linked with improved T helper cell counts in patients with HIV, or enhanced immunity in elderly participants.
Notes: Journal Article
Author Address: Department of Health and Exercise Science, Appalachian State University, Boone, North Carolina, USA. email@example.com
Title: Low Physical Fitness in Childhood Is Associated with the Development of Asthma in Young Adulthood: The Odense Schoolchild Study
Author: Rasmussen, F.; Lambrechtsen, J.; Siersted, H. C.; Hansen, H. S.; Hansen, N. C.; (Date: Nov, 2000)
Journal: Eur Respir J; V. 16; Issue: 5; Pages: 866-70
Abstract: Intense physical activity in children may either improve fitness and protect against asthma, or may trigger symptoms. The aim of this study was to determine whether physical fitness in childhood has an impact on the development of asthma. In this prospective, community-based study, 757 (84%) asymptomatic children with an average age at inclusion of 9.7 yrs were followed for 10.5 yrs. In both surveys a maximal progressive exercise test on a bicycle ergometer was used to measure physical fitness (maximal workload) and to induce airway narrowing. A methacholine provocation test was performed in the subjects at follow-up. During the 10-yr study period, 51 (6.7%) of the previously asymptomatic children developed asthma. These subjects had a lower mean physical fitness in 1985 than their peers: (3.63 versus 3.89 W x kg(-1); p=0.02) in boys and (3.17 versus 3.33 W x kg(-1); p=0.02) in girls. A weak correlation was found between physical fitness in childhood and airway responsiveness to methacholine at follow-up when adjusted for body mass index, age and sex (r=0.11; p<0.01). In a multiple regression analysis, physical fitness was inversely related to the development of physician diagnosed asthma, odds ratio=0.93 (0.87-0.99). Thus, the risk for the development of asthma during adolescence is reduced 7% by increasing the maximal workload 1 W x kg(-1). In conclusion, this study showed that physical fitness in childhood is weakly correlated with the development of asthma during adolescence and that high physical fitness seems to be associated with a reduced risk for the development of asthma.
Notes: Journal Article
Author Address: Dept of Respiratory Diseases, Odense University Hospital, Denmark.