Exercise,nutrition and immune function

Strenuous bouts of prolonged exercise and heavy training are associated with depressed immune cell function. Furthermore, inadequate or inappropriate nutrition can compound the negative influence of heavy exertion on immunocompetence. Dietary deficiencies of protein and specific micronutrients have long been associated with immune dysfunction. An adequate intake of iron, zinc and vitamins A, E, B6 and B12 is particularly important for the maintenance of immune function, but excess intakes of some micronutrients can also impair immune function and have other adverse effects on health. Immune system depression has also been associated with an excess intake of fat. To maintain immune function, athletes should eat a well-balanced diet sufficient to meet their energy requirements. An athlete exercising in a carbohydrate-depleted state experiences larger increases in circulating stress hormones and a greater perturbation of several immune function indices. Conversely, consuming 30–60?g carbohydrate?·?h^?1 during sustained intensive exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immune depression. Convincing evidence that so-called ‘immune-boosting’ supplements, including high doses of antioxidant vitamins, glutamine, zinc, probiotics and Echinacea, prevent exercise-induced immune impairment is currently lacking.     

Nutritional strategies to counter stress to the immune system in athletes, with special reference to football

Although epidemiological data indicate that athletes are at increased risk of upper respiratory tract infection during periods of heavy training and the 1 - 2 week period following endurance race events, there is very limited information on the responses to football training and match-play. For several hours after heavy exertion, components of both the innate (e.g. natural killer cell activity and neutrophil oxidative burst activity) and adaptive (e.g. T and B cell function) immune system exhibit suppressed function. Although such responses to football training and competition do not appear to be as pronounced, variations in immune cell numbers and function are reported in professional footballers over the course of a season. Attempts have been made through nutritional means (e.g. glutamine, vitamins C and E, and carbohydrate supplementation) to attenuate immune changes following intensive exercise and thus lower the risk of upper respiratory tract infection. Carbohydrate supplementation during heavy exercise has emerged as a partial countermeasure and attenuates increases in blood neutrophil counts, stress hormones, and inflammatory cytokines, but has little effect on decrements in salivary IgA output or natural killer cell function. Animal research indicates that other nutritional components such as beta-glucan, quercetin, and curcumin warrant human investigations to determine if they are effective countermeasures to exercise-induced immune dysfunction.     

Recommendations to maintain immune health in athletes

Numerous studies over the last 35 years report an increase in upper respiratory infection (URI) symptoms in athletes during periods of heavy training and competition. Challenges athletes face such as heavy exercise and life stress influence immune function via activation of the hypothalamic–pituitary–adrenal axis and the sympathetic nervous system and the resulting immunoregulatory hormones. Both innate and acquired immunity are often reported to decrease transiently in the hours after heavy exertion, typically 15–70%: prolonged heavy training sessions in particular have been shown to decrease immune function; potentially providing an ‘open window’ for opportunistic infections. Whether the observed changes in immunity with acute strenuous exercise or periods of heavy training account for the increased susceptibility to URI symptoms remains contentious. Nevertheless, there is little doubt that URI symptoms hinder athletic training and competition; underpinning the need to identify the prominent risk factors and appropriate countermeasures. Recent studies have identified prominent risk factors, including: intensified training in the winter; long-haul travel; low energy availability; high levels of psychological stress and anxiety; and depression. Given the shared pathways and effector limbs for the body’s response to physical and psychological challenges, it is logical that psychological strain influences immunity and illness incidence in athletes under heavy training; indeed, stress and anxiety have recently been shown to modify the immune response to exercise. This mini-review provides new insights and evidence-based recommendations for coping with the various challenges that athletes encounter on immune health, including: heavy exercise; life stress; sleep disruption; environmental extremes and nutritional deficits.     

运动与免疫系统研究进展

运动对机体免疫功能有急慢性以及正负性影响。有规律的适度运动可增强免疫功能而降低感染风险。急性运动后肌源性IL-6释放增加,IL-10上升从而抑制细胞免疫功能。急性运动增强自然杀伤细胞活性但是降低白细胞的吞噬功能。长时间的高强度运动可能会通过抑制黏膜IgA分泌而增加上呼吸道感染风险。定期补充抗氧化剂如维生素C和E以及在运动过程中摄入碳水化合物有助于预防免疫抑制。平衡营养饮食匹配合理的运动计划可支持和促进免疫系统。     

Immune function and exercise

This review will examine the effects of exercise and training on immune func-tion and will discuss the methodological problems that limit the interpretation of many exercise immunology studies. Acute bouts of exercise cause a tempo-rary depression of various aspects of immune function, such as neutrophil oxidative burst, lymphocyte proliferation, monocyte MHC class II expression, and natural killer cell cytotoxic activity, that will usually last for approximately three to 24 hours after exercise, depending on the intensity and duration of the exercise bout. Post-exercise immune function depression is most pronounced when the exercise is continuous, prolonged (<1.5 hours), of moderate to high intensity (55-75% VO₂max), and performed without food intake. Periods of intensified training that result in overreaching have been shown to chronically depress immune function—i.e., immune cell functions measured at rest are still depressed 24 hours after the last exercise bout. Although elite athletes are not clinically immune deficient, it is possible that the combined effects of small changes in several immune parameters may compromise resistance to common minor illnesses such as upper respiratory tract infection. Protracted immune depression linked with prolonged training may determine susceptibility to infection, particularly at times of major competitions.     

The BASES expert statement on exercise, immunity, and infection

An individual's level of physical activity influences their risk of infection, most likely by affecting immune function. Regular moderate exercise reduces the risk of infection compared with a sedentary lifestyle, but very prolonged bouts of exercise and periods of intensified training are associated with an increased risk of infection. There are several lifestyle, nutritional, and training strategies that can be adopted to limit the extent of exercise-induced immunodepression and minimize the risk of infection. This expert statement provides a background summarizing the evidence together with extensive conclusions and practical guidelines.     

运动性免疫抑制形成的可能负反馈机制及缓解措施的研究进展

目前新型冠状病毒肺炎疫情形势严峻,其传染性极强,能够通过飞沫、接触等途径迅速传播。在此背景下,增强机体免疫系统功能尤为重要。长时间或大强度运动锻炼能够造成运动性免疫抑制,使机体在运动后免疫系统功能大幅下降。因此,缓解或避免运动后的免疫抑制对于防控新冠肺炎疫情具有重要意义。通过分析相关文献,对运动性免疫抑制形成的可能负反馈机制及缓解措施进行综述。研究结果:1)总体而言,中等强度运动能够增强免疫系统功能,且运动性免疫抑制出现的临界强度约为60%V.O2_max强度,而长时间大强度运动能够抑制免疫系统功能。2)运动性免疫抑制形成的负反馈机制包括TCR-P38负反馈机制、MAPK-DUSP负反馈机制、干扰素-STAT1负反馈机制、Foxp3-IL2负反馈机制、低血糖环境-Tregs负反馈机制和CTLA-4-T细胞负反馈机制等。3)缓解运动性免疫抑制值得研究的分子靶点包括DUSP、STAT1、Foxp3、CTLA-4等,且此类分子易受运动、睡眠、饮食等生活行为调节。研究结论:1)运动性免疫抑制的形成可能与免疫系统负反馈调节机制有关;2)除避免长时间大强度运动以外,提高睡眠质量、合理饮食亦能够提高免疫系统功能。     

急性运动降低感染风险的免疫调节机制

由于新型冠状病毒(2019-nCoV)感染的肺炎疫情暴发,人们将居家运动作为提高免疫力与保持健康的重要手段,运动与免疫的关系再度受到关注。一般认为,在充分恢复的前提下进行规律的中高强度运动可提高免疫功能,而急性运动(acute exercise)可能抑制免疫功能并增加感染风险。急性运动后外周血淋巴细胞计数及功能降低、免疫球蛋白A水平分泌减少被认为是运动抑制免疫的理论基础。但目前这种独立于非运动因素影响免疫功能增加感染风险的认识受到了现有研究的挑战。急性运动可通过应激反应将淋巴细胞亚群迅速动员至循环中,运动结束后,淋巴细胞亚群又会迅速迁移至外周组织。淋巴细胞的重新分布(lymphocyte redeployment)可能是一种进化保守的免疫机制,这一过程强化了外周组织的免疫监视与调节功能,有助于提升机体抵抗感染能力。因此,从这一视角就急性运动对机会性感染风险及免疫功能影响的现状进行综述。     

剧烈运动与训练诱发体内产生免疫抑制蛋白的初步研究

免疫抑制蛋白是在应激情况下体内出现的一种大分子蛋白,可抑制免疫功能,它是否参与了运动与免疫的调节?研究结果表明,持续的大运动量训练可使运动员血清出现免疫抑制蛋白,其分子量为140KD;1次急性超负荷游泳后小鼠血清内出现大分子量的免疫抑制因子,其分子量亦为140KD。说明免疫抑制蛋白在运动与免疫的调节中发挥着作用,提示在运动与免疫的调节中,存在着不同于神经内分泌调节机制的另一途径,即免疫抑制蛋白途径。     

多巴胺与运动能力的关系

多巴胺主要生理功能是调节躯体运动、神经活动等。脑中的多巴胺合成和分解与运动能力有密切的关系,其含量的增加可以提高运动能力,尤其是耐力运动能力,多巴胺还可以通过调节其他激素以及影响心血管来影响运动能力;多巴胺也与运动性中枢疲劳有联系;多巴胺合成和分泌异常与帕金森综合征并伴有迟发型运动障碍有关。本文对多巴胺与运动能力之间的关系做一综述。     

复方红景天口服液提高运动能力及消除疲劳的实验研究

采用实验对比的方法,探讨复方红景天口服液对提高运动能力及消除疲劳的影响。结果表明。该口服液能明显提高实验对象大运动量训练期间及不同负荷量时的Hb,对运动期间的BUN有显著的降低作用：能提高实验对象的抗缺氧能力及力竭游泳时间;降低定量负荷时的BLA。提示,复方红景天口服液具有一定的提高运动能力及消除疲劳之功效。     

Oxidants,antioxidant nutrients and the athlete

Strenuous physical exercise induces oxidative stress. There may be a number of sources of this oxidative stress, including mitochondrial superoxide production, ischaemia-reperfusion mechanisms and auto-oxidation of catecholamines. Severe or prolonged exercise can overwhelm antioxidant defences, which include vitamins E and C and thiol antioxidants, which are interlinked in an antioxidant network, as well as antioxidant enzymes. Evidence for oxidative stress and damage during exercise comes from direct measurement of free radicals, from measurement of damage to lipids and DNA, and from measurement of antioxidant redox status, especially glutathione. There is little evidence that antioxidant supplementation can improve performance, but a large body of work suggests that bolstering antioxidant defences may ameliorate exercise-induced damage, suggesting that the benefits of antioxidant intervention may be for the long term rather than the short term.     

运动应激性胃溃疡动物模型的建立及其行为学评价

目的：探讨运动应激性胃溃疡动物模型建立的可行性和行为学评价方法。方法：雌性SD大鼠随机分组,实验测试指标有：旷场实验、暗盒实验、内脏疼痛指数行为学指标变化,动物摄食量和体重变化,以及溃疡指数,血清皮质醇含量。结果：1）力竭组大鼠溃疡指数显著升高（P〈0.01）,运动应激动物体重、摄食量显著下降;2）力竭组大鼠矿场实验中的水平运动、垂直运动得分显著下降（P〈0.01）,表明大鼠的活动能力水平和活动兴趣均下降;理毛次数显著减少（P〈0.01）,表明大鼠的清洁行为明显减少;暗环境适应能力下降（P〈0.01）,内脏疼痛行为表现显著增加（P〈0.01）。3）力竭组大鼠血清皮质醇含量显著性升高（P〈0.01）。结论：旷场、暗盒和内脏疼痛指数实验可以作为评价雌性大鼠力竭性跑台训练导致运动应激性胃溃疡模型的行为学测试方法。     

The Governor has a sweet tooth – Mouth sensing of nutrients to enhance sports performance

Abstract

The oral–pharyngeal cavity and the gastrointestinal tract are richly endowed with receptors that respond to taste, temperature and to a wide range of specific nutrient and non-nutritive food components. Ingestion of carbohydrate-containing drinks has been shown to enhance endurance exercise performance, and these responses have been attributed to post-absorptive effects. It is increasingly recognised, though, that the response to ingested carbohydrate begins in the mouth via specific carbohydrate receptors and continues in the gut via the release of a range of hormones that influence substrate metabolism. Cold drinks can also enhance performance, especially in conditions of thermal stress, and part of the mechanism underlying this effect may be the response to cold fluids in the mouth. There is also some, albeit not entirely consistent, evidence for effects of caffeine, quinine, menthol and acetic acid on performance or other relevant effects. This review summarises current knowledge of responses to mouth sensing of temperature, carbohydrate and other food components, with the goal of assisting athletes to implement practical strategies that make best use of its effects. It also examines the evidence that oral intake of other nutrients or characteristics associated with food/fluid intake during exercise can enhance performance via communication between the mouth/gut and the brain.     

Exercise-induced oxidative stress: Friend or foe?

The first report demonstrating that prolonged endurance exercise promotes oxidative stress in humans was published more than 4 decades ago. Since this discovery, many ensuing investigations have corroborated the fact that muscular exercise increases the production of reactive oxygen species (ROS) and results in oxidative stress in numerous tissues including blood and skeletal muscles. Although several tissues may contribute to exercise-induced ROS production, it is predicted that muscular contractions stimulate ROS production in active muscle fibers and that skeletal muscle is a primary source of ROS production during exercise. This contraction-induced ROS generation is associated with (1) oxidant damage in several tissues (e.g., increased protein oxidation and lipid peroxidation), (2) accelerated muscle fatigue, and (3) activation of biochemical signaling pathways that contribute to exercise-induced adaptation in the contracting muscle fibers. While our understanding of exercise and oxidative stress has advanced rapidly during the last decades, questions remain about whether exercise-induced increases in ROS production are beneficial or harmful to health. This review addresses this issue by discussing the site(s) of oxidant production during exercise and detailing the health consequences of exercise-induced ROS production.     

大鼠运动应激性溃疡模型的建立

对大鼠力竭性游泳和跑台跑运动后即刻的胃溃疡分数和运动时间进行了比较研究 ,以筛选运动应激性溃疡的建模方法。结果 :力竭性游泳运动和力竭性跑台跑运动都可导致大鼠胃粘膜呈点状或条索状的出血或溃烂 ,产生运动应激性溃疡 ;但游泳运动组动物运动时间显著延长 (p <0 .0 5) ,溃疡分数显著升高 (P <0 .0 5)。提示 :二者均可作为复制运动应激性溃疡模型的方法 ,但力竭性游泳运动较跑台跑运动更易成功复制运动应激性溃疡模型。     

运动训练中补充抗氧化剂：有益还是有害？

运动过程中骨骼肌产生的高水平反应物会导致肌肉损伤和肌肉功能受损，一般认为补充抗氧化剂可以保护肌肉不受损伤。无论对于运动爱好者还是专业运动员，抗氧化剂都是最常用的运动补剂之一。目前备受关注的是用额外口服抗氧化剂的方法来支持内源性防御系统，从而实现预防或减轻氧化应激、减少肌肉损伤并改善运动表现。目前有大量已发表的研究对该主题进行了讨论，大多数研究表明，抗氧化剂可以减轻运动引起的氧化应激，但大多数研究都未发现其对肌肉损伤和肌肉功能有任何影响。此外，越来越多的证据表明，抗氧化剂对健康和训练适应有消极作用。本文深入分析总结了关于活性物质（Reactive Species）在体内的作用以及服用抗氧化剂对维持健康和提高身体性能的功效的文献。     

5周递增负荷训练对内分泌免疫机能影响的研究

目的：探讨递增负荷训练对机体内分泌免疫机能的影响。方法：实验对象进行为期5周的递增负荷训练，于集合训练开始前一天和第2周、第3周、第4周及第5周训练结束末36h后上午7：30-8：00取安静时肘静脉血，测定训练前及每一负荷训练阶段后外周血液中内分泌激素指标和免疫指标的变化。结果：T第3周比训练前显著升高（P〈0．05），C第3、第5周比训练前显著升高（P〈0．05），T／C比值第4周比训练前显著下降（P〈0．05）。CD4第2周比训练前显著下降（P〈0．05），而第3周比训练前显著升高（P〈0．05）；CDB第4周比训练前、第2周、第3周显著下降（P〈0．05），CD4／CDB比值第3、第4周均比训练前、第2周显著升高（P〈0．05）。结论：训练负荷是影响机体内分泌免疫机能的一个重要因素，中等负荷训练促进机体内分泌免疫机能，大负荷训练会降低机体的内分泌免疫机能，但随着对递增负荷应激的适应，机体的内分泌免疫机能又会得到加强。     

穴位离子导入对皮艇运动员心肺功能的影响

采用RPE评分、运动成绩测试、心肺功能测试及心脏内分泌激素放射免疫法检测等方法对运动员心脏功能进行跟踪观察。结果表明：(1)穴位离子导入能明显改善运动员的主观感觉，提高专项成绩，改善心肺功能，降低无氧闲心率，提高有氧耐力，推迟心源性运动性疲劳的发生；(2)穴位离子导入可改善运动员心脏神经肽ET和CGRP的分泌，使之向更有利于适应运动负荷的方向发展。结论是：(1)心源性运动性疲劳的发生与多因素相关；(2)穴位离子导入能多环节、多层面地保护心肌和改善心脏功能，从而延缓疲劳产生和促进疲劳消除。     

运动时糖皮质激素分泌增多对大鼠心、肾糖皮质激素受体及 Na~+-K~+-ATP 酶的影响和机制分析

本文研究急性运动后糖皮质激素(GC)分泌增多对大鼠心、肾细胞糖皮质激素受体(GR)及Na~+-K~+-ATP 酶的影响,结果表明,无负荷游泳后造成 GR 的适度减少,伴有对 Na~+-K~+-ATP 酶的诱导加强,其发生可分别被 Trilostane 和 RU_(A86)抑制;6%体重负荷游泳1h 后,出现 GR 过度减少并伴有血浆 GC 对靶细胞 Na~+-K~+-ATP 酶诱导抑制,提示靶细胞对 GC 抵抗。本文提出运动时 GR 过度下降是限制机体运动能力的一个重要因素。