This study investigated the effect of a high and low dose of caffeine on antigen-stimulated natural killer (NK) cell (CD3−CD56+) activation after prolonged, strenuous cycling, as assessed by the early-activation molecule CD69. In a randomized crossover design, 12 healthy male endurance-trained cyclists cycled for 90 min at 70% VO2peak 60 min after ingesting either 0 (PLA), 2 (2CAF), or 6 (6CAF) mg/kg body mass of caffeine. Whole blood was stimulated with Pediacel (5 in 1) vaccine. A high dose of caffeine (6CAF) increased the number of CD3−CD56+ cells in the circulation immediately postexercise compared with PLA (p < .05). For both 2CAF and 6CAF, the geometric mean fluorescence intensity (GMFI) of CD69+ expression on unstimulated CD3−CD56+ cells was significantly higher than with PLA (both p < .05). When cells were stimulated with antigen, the GMFI of CD69 expression remained significantly higher with 2CAF than with PLA 1 hr postexercise (p < .05). Although not achieving statistical significance, 6CAF also followed a similar trend when stimulated (p = .09). There were no differences in GMFI of CD69 expression between 2CAF and 6CAF. These results suggest that a high (6 mg/kg) dose of caffeine was associated with the recruitment of NK cells into the circulation and that both a high and low (2 mg/kg) dose of caffeine increased unstimulated and antigen-stimulated NK-cell activation 1 hr after high-intensity exercise. Furthermore, there does not appear to be a dose-dependent effect of caffeine on NK-cell activation 1 hr after prolonged intensive cycling.
Deborah K. Fletcher and Nicolette C. Bishop
Nicolette C. Bishop, Michael Gleeson, Ceri W. Nicholas, and Ajmol Ali
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 examined the effect of CHO ingestion on plasma interIeukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and lipopolysaccharide (LPS)-stimuIated 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 11% on the CHO trial (p = .30). Plasma TNF-α 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.
Michael Gleeson, Nicolette C. Bishop, Marta Oliveira, and Pedro Tauler
The purpose of this study was to examine the effects of a probiotic supplement during 4 mo of winter training in men and women engaged in endurance-based physical activities on incidence of upper respiratory-tract infections (URTIs) and immune markers. Eighty-four highly active individuals were randomized to probiotic (n = 42) or placebo (n = 42) groups and, under double-blind procedures, received probiotic (PRO: Lactobacillus casei Shirota [LcS]) or placebo (PLA) daily for 16 wk. Resting blood and saliva samples were collected at baseline and after 8 and 16 wk. Weekly training and illness logs were kept. Fifty-eight subjects completed the study (n = 32 PRO, n = 26 PLA). The proportion of subjects on PLA who experienced 1 or more weeks with URTI symptoms was 36% higher than those on PRO (PLA 0.90, PRO 0.66; p = .021). The number of URTI episodes was significantly higher (p < .01) in the PLA group (2.1 ± 1.2) than in the PRO group (1.2 ± 1.0). Severity and duration of symptoms were not significantly different between treatments. Saliva IgA concentration was higher on PRO than PLA, significant treatment effect F(1, 54) = 5.1, p = .03; this difference was not evident at baseline but was significant after 8 and 16 wk of supplementation. Regular ingestion of LcS appears to be beneficial in reducing the frequency of URTI in an athletic cohort, which may be related to better maintenance of saliva IgA levels during a winter period of training and competition.
Gary J. Walker, Phillipa Caudwell, Natalie Dixon, and Nicolette C. Bishop
This study investigated the effect of caffeine ingestion on neutrophil oxidative burst responses to prolonged cycling. In a two part study, 19 endurance trained male cyclists (Part A – 11; Part B – 8) performed 90 min of exercise at 70% VO2max 1 h after ingesting 6 mg/kg body mass of caffeine (CAF) or placebo (PLA). CAF ingestion had no effect on the PMA-stimulated oxidative burst response (Part A), yet it attenuated the exercise-induced decline in f-MLP stimulated response that occurred with PLA (Part B). CAF ingestion significantly increased serum caffeine concentration and plasma adrenaline concentration following exercise. In addition, circulating lymphocyte count was increased following CAF ingestion whereas there was no effect on neutrophil number. Therefore, although CAF ingestion was associated with an increase in adrenaline, this was not associated with an expected decrease in neutrophil function. This suggests that in the present study, CAF ingestion influenced neutrophil function via alternative mechanisms.
Nicolette C. Bishop, Neil P. Walsh, Donna L. Haines, Emily E. Richards, and Michael Gleeson
Ingesting carbohydrate (CHO) beverages during heavy exercise is associated with smaller shifts in numbers of circulating neutrophils and attenuated changes in neutrophil functional responses. The influence of dietary CHO availability on these responses has not been determined. Therefore, the present study investigated the influence of pre-exercise CHO status on circulating neutrophil and lipopolysaccharide (LPS)-stimulated neutrophil degranulation responses to prolonged cycling. Twelve trained male cyclists performed a glycogen-lowering bout of cycling and were randomly assigned to follow a diet ensuring either greater than 70% (HIGH) or less than 10% (LOW) of daily energy intake from CHO for the next 3 days. On day 4, subjects performed an exercise test that comprised cycling for 1 hour at 60% Wmax immediately followed by a time-trial (TT) ensuring an energy expenditure equivalent to cycling for 30 min at 80% Wmax. Subjects repeated the protocol after 7 days, this time following the second diet. The order of the trials was counterbalanced. At TT completion, the HIGH compared with the LOW trial was associated with higher plasma glucose concentration, lower plasma cortisol concentration, and lower circulating neutrophil count. LPS-stimulated neutrophil degranulation per cell fell similarly on both trials. These findings suggest that pre-exercise CHO status influences neutrophil trafficking but not function in response to prolonged cycling.
Nicolette C. Bishop, Neil P. Walsh, Donna L. Haines, Emily E. Richards, and Michael Gleeson
Ingesting carbohydrate (CHO) beverages during heavy exercise is associated with smaller changes in the plasma concentrations of several cytokines. The influence of dietary CHO availability on these responses has not been determined. Therefore, the present study investigated the influence of pre-exercise CHO status on plasma interleukin (IL)-6, IL-10, and IL-1 receptor antagonist (IL-1ra) responses to prolonged cycling. Seven trained male cyclists performed a glycogen-lowering bout of cycling and were randomly assigned to follow a diet ensuring either greater than 70% (HIGH) or less than 10% (LOW) of daily energy intake from CHO for the next 3 days. On day 4 subjects performed an exercise test that comprised cycling for 1 hour at 60% Wmax immediately followed by a time-trial (TT) ensuring an energy expenditure equivalent to cycling for 30 min at 80% Wmax. Subjects repeated the protocol after 7 days, this time following the second diet. The order of the trials was counterbalanced. At 1 and 2 hours post-TT, plasma concentrations of IL-6 and IL-10 were 2-fold greater on the LOW trial than on the HIGH trial, and peak plasma concentrations of TL-1ra were 9-fold greater on the LOW trial than on the HIGH trial. These findings suggest that pre-exercise CHO status can influence the plasma cytokine response to prolonged cycling.
Michael Gleeson, Nicolette C. Bishop, Marta Oliveira, Tracey McCauley, Pedro Tauler, and Claire Lawrence
The purpose of this study was to examine the effects of a probiotic supplement during 4 mo of spring training in men and women engaged in endurance-based physical activities on incidence of upper respiratory tract infections (URTI) and mucosal immune markers. Sixty-six highly active individuals were randomized to probiotic (n = 33) or placebo (n = 33) groups and, under double-blind procedures, received probiotic (PRO: Lactobacillus salivarius, 2 × 1010 bacterium colony-forming units) or placebo (PLA) daily for 16 wk. Resting blood and saliva samples were collected at baseline and after 8 and 16 wk. Weekly training and illness logs were kept. Fifty-four subjects completed the study (n = 27 PRO, n = 27 PLA). The proportion of subjects on PRO who experienced 1 or more wk with URTI symptoms was not different from that of those on PLA (PRO .58, PLA .59; p = .947). The number of URTI episodes was similar in the 2 groups (PRO 1.6 ± 0.3, PLA 1.4 ± 0.3; p = .710). Severity and duration of symptoms were not significantly different between treatments. Blood leukocyte, neutrophil, monocyte, and lymphocyte counts; saliva IgA; and lysozyme concentrations did not change over the course of the study and were not different on PRO compared with PLA. Regular ingestion of L. salivarius does not appear to be beneficial in reducing the frequency of URTI in an athletic cohort and does not affect blood leukocyte counts or levels of salivary antimicrobial proteins during a spring period of training and competition.
Neil P. Walsh, Andrew K. Blannin, Nicolette C. Bishop, Paula J. Robson, and Michael Gleeson
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%
Michael Gleeson, Andrew K. Blannin, Neil P. Walsh, Nicolette C. Bishop, and Anya M. Clark
We examined the effects of a low-carbohydrate (CHO) diet on the plasma glutamine and circulating leukocyte responses to prolonged strenuous exercise. Twelve untrained male subjects cycled for 60 min at 70% of maximal oxygen uptake on two separate occasions, 3 days apart. All subjects performed the first exercise task after a normal diet: they completed the second exercise task after 3 days on either a high-CHO diet (75±8% CHO, n = 6) or a low-CHO diet (7±4% CHO, n = 6). The low-CHO diet was associated with a larger rise in plasma cortisol during exercise, a greater fall in the plasma glutamine concentration during recovery, and a larger neutrophilia during the postexercise period. Exercise on the high-CHO diet did not affect levels of plasma glutamine and circulating leukocytes. We conclude that CHO availability can influence the plasma glutamine andcirculaling leukocyte responses during recovery from intense prolonged exercise.
Christof A. Leicht, Nicolette C. Bishop, Thomas A.W. Paulson, Katy E. Griggs, and Victoria L. Goosey-Tolfrey
Altered autonomic innervation in tetraplegic individuals has been shown to depress certain immune parameters at rest and alter exercise-related salivary immunoglobulin A (sIgA) responses. The purpose of this study was to examine resting sIgA responses as a function of training load and episodes of upper respiratory symptoms (URS) in elite tetraplegic athletes.
Resting saliva samples were obtained from 14 tetraplegic athletes at 12 predefined time points over 5 months and analyzed for sIgA. Occurrence of self-reported URS and training load was recorded throughout the study’s duration. Regression analyses were performed to investigate the relationship between sIgA responses and training load. Furthermore, the relationships between sIgA responses and URS occurrence were examined.
sIgA secretion rate was negatively correlated with training load (P = .04), which only accounted for 8% of the variance. No significant relationships were found between sIgA responses and subsequent URS occurrence. Finally, sIgA responses did not differ between athletes with and without recorded URS during the study period.
In line with findings in ablebodied athletes, negative relationships between sIgA secretion rate and training load were found in tetraplegic athletes. This may explain some of the higher infection risk in wheelchair athletes with a high training load, which has been previously observed in paraplegic athletes. However, the nonsignificant relationship between sIgA responses and URS occurrence brings into question the use of sIgA as a prognostic tool for the early detection of URS episodes in the studied population.