Effects of 24-week prebiotic intervention on self-reported upper respiratory symptoms, gastrointestinal symptoms, and markers of immunity in elite rugby union players.

OBJECTIVES: Elite rugby union players face numerous physiological and psychological stressors which can increase upper respiratory and gastrointestinal illness risk, and in turn can compromise training and competitive performance. This study aimed to investigate the effect of daily prebiotic supplementation on upper respiratory symptoms, gastrointestinal symptoms, and markers of immune function in elite rugby union players. METHODS: Thirty-three elite rugby union players were randomly assigned to consume a prebiotic (2.8 g/day galactooligosaccharide) or placebo (2.8 g/day maltodextrin), daily for 168 days under double-blind conditions. Participants completed daily and weekly questionnaires for self-reported upper respiratory and gastrointestinal symptoms respectively. Blood and saliva samples were collected at 0, 84, and 168 days for assessment of plasma TNF-α and CRP, and saliva IgA respectively. RESULTS: The prebiotic group experienced a 2-day reduction in upper respiratory symptom duration (P = 0.045). Gastrointestinal symptom severity and incidence were lower in the prebiotic group compared to the placebo group (P < 0.001, P = 0.041) respectively. Salivary immunoglobulin A secretion rate was 42% greater in the prebiotic group compared to the placebo group at day 168 (P = 0.004), no differences in CRP and TNF-α were found (P > 0.05). CONCLUSION: A 168-day dietary prebiotic intervention reduced the duration of upper respiratory symptoms and reduced the incidence and severity of gastrointestinal symptoms in elite rugby union players. These findings suggest that seasonal prebiotic interventions may be beneficial for reducing illness in elite rugby union players, improving their availability to train and compete.Key pointsElite athletes are susceptible to upper respiratory symptoms and gastrointestinal symptoms which may impact upon training availability and competition performance.For the first time, this study shows that a dietary prebiotic intervention can reduce the duration of upper respiratory symptoms by 2 days in elite rugby union players.Dietary prebiotic supplementation can improve the incidence and severity of gastrointestinal symptoms experienced by elite rugby union players.Prebiotic supplementation was able to increase salivary IgA secretion after 168 days.These findings can inform practice suggesting that seasonal prebiotic use has the potential to modulate immune function and reduce illness in elite rugby union, which may improve a player's availability to train and compete.The mechanisms by which prebiotics reduce URS and GIS require further research exploration.

The effect of trait self-control on dyspnoea and tolerance to a CO2 rebreathing challenge in healthy males and females.

BACKGROUND: High trait self-control is associated with greater tolerance of unpleasant sensations including effort and pain. Dyspnoea and pain have several commonalities and this study aimed to investigate for the first time whether trait self-control influences responses to a hypercapnic rebreathing challenge designed to induce dyspnoea. As sex also influences tolerance to dyspnoea, we also sought to investigate whether this moderated the role of trait self-control. METHODS: Participants (n = 65, 32 females) scoring high or low for trait self-control, performed a standardised rebreathing challenge, in which inspired carbon dioxide (CO2) gradually increased over a period of 6 min or until an intolerable level of dyspnoea. Air hunger (AH) intensity - a distinctive quality of dyspnoea, was measured every 30 s. The multidimensional dyspnoea profile (MDP) was completed after the rebreathing challenge for a more complete overview of breathing discomfort. RESULTS: Males high in trait self-control (SCHIGH) (302 ± 42 s), tolerated the rebreathing challenge for longer than males low in self-control (SCLOW) (252 ± 66 s, P = 0.021), experienced slower increases in AH intensity during the rebreathing challenge (0.03 ± 0.01 cm.s - 1 vs. 0.04 ± 0.01 cm.s - 1,P = 0.045) and reported lower perceived mental effort on the MDP (4.94 ± 2.46 vs. 7.06 ± 1.60, P = 0.007). There was no difference between SCHIGH and SCLOW females for challenge duration. However, SCHIGH females (9.29 ± 0.66 cm) reported greater air hunger at the end of the challenge than SCLOW females (7.75 ± 1.75 cm, P = 0.003). It is possible that SCLOW females were unwilling to tolerate the same perceptual intensity of AH as the SCHIGH females. CONCLUSIONS: These results indicate that individuals high in trait self-control are more tolerant of dyspnoea during a CO2 rebreathing challenge than low self-control individuals. Tolerance of the stimulus was moderated by the sex of the participant, presenting an interesting opportunity for future research.

Locomotor muscle fatigue is not critically regulated after prior upper body exercise.

This study examined the effects of prior upper body exercise on subsequent high-intensity cycling exercise tolerance and associated changes in neuromuscular function and perceptual responses. Eight men performed three fixed work-rate (85% peak power) cycling tests: 1) to the limit of tolerance (CYC); 2) to the limit of tolerance after prior high-intensity arm-cranking exercise (ARM-CYC); and 3) without prior exercise and for an equal duration as ARM-CYC (ISOTIME). Peripheral fatigue was assessed via changes in potentiated quadriceps twitch force during supramaximal electrical femoral nerve stimulation. Voluntary activation was assessed using twitch interpolation during maximal voluntary contractions. Cycling time during ARM-CYC and ISOTIME (4.33 ± 1.10 min) was 38% shorter than during CYC (7.46 ± 2.79 min) (P < 0.001). Twitch force decreased more after CYC (-38 ± 13%) than ARM-CYC (-26 ± 10%) (P = 0.004) and ISOTIME (-24 ± 10%) (P = 0.003). Voluntary activation was 94 ± 5% at rest and decreased after CYC (89 ± 9%, P = 0.012) and ARM-CYC (91 ± 8%, P = 0.047). Rating of perceived exertion for limb discomfort increased more quickly during cycling in ARM-CYC [1.83 ± 0.46 arbitrary units (AU)/min] than CYC (1.10 ± 0.38 AU/min, P = 0.003) and ISOTIME (1.05 ± 0.43 AU/min, P = 0.002), and this was correlated with the reduced cycling time in ARM-CYC (r = -0.72, P = 0.045). In conclusion, cycling exercise tolerance after prior upper body exercise is potentially mediated by central fatigue and intolerable levels of sensory perception rather than a critical peripheral fatigue limit.

Reproducibility of the bronchoconstrictive response to eucapnic voluntary hyperpnoea.

BACKGROUND: Eucapnic voluntary hyperpnoea (EVH) is considered an effective bronchoprovocation challenge for identifying exercise-induced bronchoconstriction (EIB). However, the reproducibility of the hyperpnoea-induced bronchoconstriction (HIB) response elicited by EVH remains unknown and was therefore the focus of this study. METHODS: Two cohorts of 16 physically active males (each cohort comprised 8 controls and 8 with physician diagnosis of asthma) participated in two studies of the short- and long-term reproducibility of the bronchoconstrictive response to an EVH test with dry air. EVH was performed on days 0, 7, 14, and 21 (short-term study), and 0, 35, and 70 (long-term study). HIB was diagnosed by a ≥10% fall in forced expiratory volume in 1 s (FEV1) after EVH. RESULTS: On day 0 of the short-term study, FEV1 fell by 2 ± 1% (P < 0.05) and 27 ± 18% (P < 0.01) from pre-to post-EVH in control and HIB-positive groups respectively. The post-EVH fall in FEV1 did not differ across the short-term study test days. In the HIB-positive group, the day-to-day coefficient of variation, reproducibility, and smallest meaningful change for the fall in FEV1 were 12%, 328 mL, and 164 mL, respectively. On day 0 of the long-term study, FEV1 fell by 2 ± 2% and 25 ± 18% (P < 0.01) after EVH in control and HIB-positive groups respectively. The post-EVH fall in FEV1 did not differ across the long-term study test days. In the HIB-positive group, the day-to-day coefficient of variation, reproducibility, and smallest meaningful change for the fall in FEV1 were 10%, 196 mL, and 98 mL respectively. CONCLUSION: The EVH test elicits a reproducible bronchoconstrictive response in physically active males with physician diagnosed asthma. These data thus support the clinical utility of the EVH test for EIB screening and monitoring.

Thermotolerance of Escherichia coli O157:H7 ATCC 43,894, Escherichia coli B, and an rpoS-deficient mutant of Escherichia coli O157:H7 ATCC 43,895 following exposure to 1.5% acetic acid.

On a beef carcass, Escherichia coli may sequentially encounter acid- and heat-intervention steps. This study tested whether acid stress (1.5% [vol/vol] acetic acid, pH 4.0, 37 degrees C, 15 min) would enhance subsequent heat resistance of E. coli. Initially, cells (E. coli O157:H7 ATCC 43894, nonpathogenic E. coli B [strain FRIK-124], and rpoS-deficient mutant 813-6 [derived from E. coli O157:H7 ATCC 43895]) were acid stressed and transferred to 54 degrees C trypticase soy broth (TSB), and survivors were immediately enumerated after at least three intervals of 12, 2, and 6 min, respectively, by plating. The ATCC 43894 and 813-6 strains survived the acid stress but strain FRIK-124 did not. Acid-stressed ATCC 43894 had significantly lower D values than the non-acid-stressed controls. Strain 813-6 had significantly lower D values than strain ATCC 43894, with no significant difference between acid-stressed and non-acid-stressed cells. In a second experiment, cooling of cells prior to plating resulted in an increased D value for acid-stressed ATCC 43894 cells, such that it was not significantly different from the D value for non-acid-stressed controls. Using this protocol, there was no significant difference in D values between acid-stressed and non-acid-stressed ATCC 43894 cells in prewarmed TSB (54, 58, and 62 degrees C), in prewarmed ground beef slurry (GBS; 58 degrees C), or in TSB and GBS inoculated at 5 degrees C and heated to 58 degrees C. The acid stress tested does not enhance subsequent heat resistance of E. coli.