The effects of carbohydrate supplementation during repeated bouts of prolonged exercise on saliva flow rate and immunoglobulin A

Effects of different exercise intensities or durations on salivary IgA secretion

PURPOSE

This study aimed to examine changes in salivary immunoglobulin A (s-IgA) secretion at different intensities or durations of acute exercise.

METHODS

Twelve healthy untrained young males were included in randomized crossover trials in Experiment 1 (cycling exercise for 30 min at a work rate equivalent to 35%, 55%, and 75% maximal oxygen uptake [ V ˙ O2max]) and Experiment 2 (cycling exercise at 55% V ˙ O2max intensity for 30, 60, and 90 min). Saliva samples were collected at baseline, immediately after, and 60 min after each exercise.

RESULTS

Experiment 1: The percentage change in the s-IgA secretion rate in the 75% V ˙ O2max trial was significantly lower than that in the 55% V ˙ O2max trial immediately after exercise (- 45.7%). The percentage change in the salivary concentration of cortisol, an s-IgA regulating factor, immediately after exercise significantly increased compared to that at baseline in the 75% V ˙ O2max trial (+ 107.6%). A significant negative correlation was observed between the percentage changes in saliva flow rate and salivary cortisol concentration (r = - 0.52, P < 0.01). Experiment 2: The percentage change in the s-IgA secretion rate in the 90-min trial was significantly lower than that in the 30-min trial immediately after exercise (-37.0%). However, the percentage change in salivary cortisol concentration remained the same.

CONCLUSION

Our findings suggest that a reduction in s-IgA secretion is induced by exercise intensity of greater than or equal to 75% V ˙ O2max for 30 min or exercise duration of greater than or equal to 90 min at 55% V ˙ O2max in healthy untrained young men.

The Effects of Physical Exercise on Saliva Composition: A Comprehensive Review

Saliva consists of organic and inorganic constituents. During exercise, analysis of the saliva can provide valuable information regarding training stress, adaptation and exercise performance. The objective of the present article was to review the effect of physical exercise on saliva composition. The shift in the composition of the saliva, during and after a workout, reflects the benefits of exercise, its potential risks and the capability of the saliva to serve as a health indicator. The type and the frequency of training, the physical condition and the athletes’ general health influence the hormones, immunoglobulins and saliva enzymes. The correlation between saliva and physical exercise has to be further investigated and the available knowledge to be applied for the benefit of the athletes during sports activities.

Recovery of the immune system after exercise

The notion that prolonged, intense exercise causes an "open window" of immunodepression during recovery after exercise is well accepted. Repeated exercise bouts or intensified training without sufficient recovery may increase the risk of illness. However, except for salivary IgA, clear and consistent markers of this immunodepression remain elusive. Exercise increases circulating neutrophil and monocyte counts and reduces circulating lymphocyte count during recovery. This lymphopenia results from preferential egress of lymphocyte subtypes with potent effector functions [e.g., natural killer (NK) cells, γδ T cells, and CD8⁺ T cells]. These lymphocytes most likely translocate to peripheral sites of potential antigen encounter (e.g., lungs and gut). This redeployment of effector lymphocytes is an integral part of the physiological stress response to exercise. Current knowledge about changes in immune function during recovery from exercise is derived from assessment at the cell population level of isolated cells ex vivo or in blood. This assessment can be biased by large changes in the distribution of immune cells between blood and peripheral tissues during and after exercise. Some evidence suggests that reduced immune cell function in vitro may coincide with changes in vivo and rates of illness after exercise, but more work is required to substantiate this notion. Among the various nutritional strategies and physical therapies that athletes use to recover from exercise, carbohydrate supplementation is the most effective for minimizing immune disturbances during exercise recovery. Sleep is an important aspect of recovery, but more research is needed to determine how sleep disruption influences the immune system of athletes.

The influence of hydration status during prolonged endurance exercise on salivary antimicrobial proteins

PURPOSE

Antimicrobial proteins (AMPs) in saliva including secretory immunoglobulin A (SIgA), lactoferrin (SLac) and lysozyme (SLys) are important in host defence against oral and respiratory infections. This study investigated the effects of hydration status on saliva AMP responses to endurance exercise.

METHODS

Using a randomized design, 10 healthy male participants (age 23 ± 4 years, [Formula: see text] 56.8 ± 6.5 ml/kg/min) completed 2 h cycling at 60 % [Formula: see text] in states of euhydration (EH) or dehydration (DH) induced by 24 h fluid restriction. Unstimulated saliva samples were collected before, during, immediately post-exercise and each hour for 3 h recovery.

RESULTS

Fluid restriction resulted in a 1.5 ± 0.5 % loss of body mass from baseline and a 4.3 ± 0.7 % loss immediately post-exercise. Pre-exercise urine osmolality was higher in DH than EH and overall, saliva flow rate was reduced in DH compared with EH (p < 0.05). Baseline SIgA secretion rates were not different between conditions; however, exercise induced a significant increase in SIgA concentration in DH (161 ± 134 to 309 ± 271 mg/L) which remained elevated throughout 3 h recovery. SLac secretion rates increased from pre- to post-exercise in both conditions which remained elevated in DH only. Overall, SLac concentrations were higher in DH than EH. Pre-exercise SLys concentrations were lower in DH compared with EH (1.6 ± 2.0 vs. 5.5 ± 6.7 mg/L). Post-exercise SLys concentrations remained elevated in DH but returned to pre-exercise levels by 1 h post-exercise in EH.

CONCLUSIONS

Exercise in DH caused a reduction in saliva flow rate yet induced greater secretion rates of SLac and higher concentrations of SIgA and SLys. Thus, DH does not impair saliva AMP responses to endurance exercise.

Exercise-induced immunodepression in endurance athletes and nutritional intervention with carbohydrate, protein and fat-what is possible, what is not?

Heavily exercising endurance athletes experience extreme physiologic stress, which is associated with temporary immunodepression and higher risk of infection, particularly upper respiratory tract infections (URTI). The aim of this review is to provide a critical up-to-date review of existing evidence on the immunomodulatory potential of selected macronutrients and to evaluate their efficacy. The results of 66 placebo-controlled and/or crossover trials were compared and analysed. Among macronutrients, the most effective approach to maintain immune function in athletes is to consume ≥6% carbohydrate during prolonged exercise. Because inadequate nutrition affects almost all aspects of the immune system, a well-balanced diet is also important. Evidence of beneficial effects from other macronutrients is scarce and results are often inconsistent. Using a single nutrient may not be as effective as a mixture of several nutritional supplements. Due to limited research evidence, with the exception of carbohydrate, no explicit recommendations to reduce post-exercise URTI symptoms with single macronutrients can be derived.

Lecturing to 200 students and its effects on cytokine concentration and salivary markers of adrenal activation

Stress not only activates the SAM system and the hypothalamic-pituitary-adrenal axes, but also the immune system. The aims of this study are to assess the physiological variations in saliva (cytokines, cortisol and alpha-amylase) and perceived stress in professors when they had to lecture to 200 students. A total of eight unstimulated saliva samples were collected from nine professors: four on a working day that included the lecture and four controls on a working day without a lecture. The professors also rated subjective stress on a seven-point scale 5 min before the lecture, immediately after the lecture and at the same times on the control day. The lecture elicited substantial increases in subjective stress ratings, with the values on the lecture day significantly higher than those on the control day. Lecturing resulted in significant increases in Tumor Necrosis Factor (TNF)-α, Interleukin (IL)-2 and IL-4 concentrations, but did not affect the IL-10 values. These changes appeared to be concomitant with changes in the concentrations of the stress markers, alpha-amylase and cortisol. The mechanisms by which psychosocial stress can induce cytokine changes and modify the activity of salivary alpha-amylase are not entirely understood, and further research is thus warranted.

Imunoglobulina A salivar (IgA-s) e exercício: relevância do controle em atletas e implicações metodológicas

O objetivo do presente estudo é realizar uma análise e discussão dos principais achados envolvendo o comportamento da imunoglobulina A salivar (IgA-s) em relação ao estímulo do exercício e evidenciar a importância de seu controle em atletas. O exercício físico é um importante modulador das características do sistema imune, sobretudo do comportamento da IgA-s, componente fundamental na proteção de infecções do trato respiratório superior (ITRS). No entanto, a relação direta entre baixas concentrações de IgA-s e ITRS precisa de mais evidências para ser confirmada. As concentrações de IgA-s durante e logo após um exercício intenso diminuem, deixando o indivíduo mais suscetível à infecção, porém, atletas envolvidos em atividades extenuantes não são clinicamente imunodeficientes, comparados com indivíduos sedentários. Essas modificações são transitórias, com retorno aos valores normais após aproximadamente 48 horas de repouso. A razão dessas alterações não é clara, mas se apresenta multifatorial: elevação de hormônios estressores; fatores nutricionais; ação de espécies reativas de oxigênio; e estresse psicológico. Apesar do efeito transitório das alterações provocadas nos elementos do sistema imune frente ao exercício, observa-se diferença na variabilidade da IgA-s em populações com diferentes níveis de condicionamento. Diferenças metodológicas - como o protocolo de exercício, o método de coleta, armazenamento e manipulação da saliva, a forma de expressão da IgA-s, o nível de hidratação, o controle da dieta, a sazonalidade do período de competição, a aclimatação entre outros fatores - devem ser levadas em consideração para comparação entre os estudos. Além disso, ajudam a explicar, em parte, os resultados adversos envolvendo exercício moderado e os intermitentes, em que se encontram aumento, redução e até ausência de alteração nos níveis de IgA-s. Investigações de elementos inovadores, como os toll-like receptors, e o avanço tecnológico podem colaborar para aumentar as evidências sobre o tema.