Endurance Training on Airway Cells and Bronchial Reactivity

Credit: Renata L. Riha Credit: Renata Educational aims ●● To illustrate the characteristics of endurance exercise training and its positive effects on health. ●● To provide an overview on the effects of endurance training on airway cells and bronchial reactivity. ●● To summarise the current knowledge on respiratory health problems in elite athletes. 140 Breathe | June 2016 | Volume 12 | No 2 Giuseppe Morici1,2, Claudia I. Gruttad’Auria3, Pierpaolo Baiamonte3, [email protected] Emilia Mazzuca3, Alessandra Castrogiovanni3, Maria R. Bonsignore2,3 1BioNeC Dept, University of Palermo, Palermo, Italy. 2Institute of Biomedicine and Molecular Immunology (IBIM), CNR, Palermo, Italy. 3DiBiMIS, University of Palermo, Palermo, Italy. Endurance training: is it bad for you? Cite as: Morici G, Endurance exercise training exerts many positive effects on health, including improved metabol Gruttad’Auria CI, ism, reduction of cardiovascular risk, and reduced allcause and cardiovascular mortality. Intense Baiamonte P, et al. Endurance endurance exercise causes mild epithelial injury and inflammation in the airways, but does not training: is it bad for you? appear to exert detrimental effects on respiratory health or bronchial reactivity in recreational/ Breathe 2016; 12: 140–147. nonelite athletes. Conversely, elite athletes of both summer and winter sports show increased susceptibility to development of asthma, possibly related to environmental exposures to allergens or poor conditioning of inspired air, so that a distinct phenotype of “sports asthma” has been proposed to characterise such athletes, who more often practise aquatic and winter sports. Over all, endurance training is good for health but may become deleterious when performed at high intensity or volume. @ERSpublications Endurance training is good for health but may become deleterious when performed at high intensity or volume http://ow.ly/4n9jR4 Introduction Endurance exercise: physiology Physical activity is increasingly recognised as a major factor of health of the general population Among the different types of exercise training, worldwide. A sedentary lifestyle and overcon predominantly aerobic activities appear best sumption of processed carbohydrates and other suited to attain favourable metabolic and cardio unhealthy foods are considered major culprits of vascular effects. Endurance sports are character the obesity epidemics. Recent analyses showed ised by repeated isotonic contractions of large that, despite increased knowledge about obesity skeletal muscle groups. Classical examples include and public health efforts against it, no trend inver running, swimming and cycling among summer sion towards decreased body mass index (BMI) sports, and crosscountry skiing or speed skating can be foreseen in the next 10 years [1]. How among winter sports. ever, studies comparing the detrimental effects of From a physiological point of view, endurance physical inactivity and increased body weight con exercise is typically performed at submaximal sistently found a larger positive effect of habitual intensity, with the main purpose of progressively exercise compared with the effects of body weight moving the anaerobic threshold, i.e. the begin on mortality, indicating that being fit is more pro ning of anaerobic metabolism and lactate pro tective than being lean [2]. duction, towards higher exercise intensity. This http://doi.org/10.1183/20734735.007016 Breathe | June 2016 | Volume 12 | No 2 141 Endurance training occurs through complex modifications in muscle Habitual exercise is a potent factor in body metabolism, with increased mitochondrial density weight control at all ages, and also exerts many and oxidative enzymes (i.e. the machinery neces other positive effects, including prevention of sary for energy production), shifts in fibre type, and metabolic and cardiovascular disease and promo increased capillarisation of muscle fibres. tion of psychological wellbeing. A recent meta- Aerobic training requires the perfect match analysis including studies on the effects of running ing of the respiratory and cardiovascular sys in sedentary healthy adults confirmed that BMI, tems, in order to provide the muscles with the body fat, resting heart rate and triglycerides necessary supply of energy to be transformed decreased, while maximal oxygen uptake and into mechanical work. On the part of the car highdensity lipoprotein cholesterol increased, diovascular system, increased supply of arterial especially when regular training was prolonged blood (and oxygen) to the involved skeletal mus over time [11]. Similar results were reported by cles and constant removal of metabolic waste studies on the effects of endurance training in (such as carbon dioxide or lactate) released by subjects with the metabolic syndrome [12]. the exercising muscles require an increase in cardiac output. The left ventricle undergoes hypertrophy and dilatation, and sympathetic stimulation during exercise increases myocar Endurance exercise and the dial contractility, contributing to the increase airways in stroke volume to match demand. Similar changes occur in the right ventricle. At the Our group has been particularly interested in microvascular level, increased production of nitric studying the biological aspects of endurance exer oxide is associated with enhanced endothelium cise and training in the large airways of amateur dependent vasodilation and decreased arterial athletes, including runners, swimmers and row stiffness. In the elite athlete, cardiac output can ers. To study airway cells, we analysed induced increase up to 40 L⋅min−1, while in healthy sub sputum samples collected at rest and shortly after jects the response to exercise training is lower exercise to assess cell apoptosis and regeneration, but still considerable (cardiac output from 5 up and inflammatory markers. The interested reader to 20 L⋅min−1). Endurance training forms the basis is referred to a comprehensive review summaris of exercisebased rehabilitation programmes in ing our results [13]. patients with cardiovascular disease, and exerts The main finding of our studies in marathon positive effects on autonomic balance 3[ ] and and halfmarathon runners was that induced cardiovascular outcomes [4, 5]. sputum showed increased neutrophil counts, In contrast to the cardiovascular system, which especially in postrace samples, compared with can be “trained”, the respiratory system is over induced sputum composition of healthy sedentary sized for the ventilation required at rest, may subjects. Interestingly, influx of inflammatory cells increase ventilation more than 20 times over into the airways was not associated with any clear baseline during exercise, but cannot improve its evidence of activation or respiratory symptoms performance beyond its natural limits [6], i.e. the [14]. Subsequent studies showed that bronchial structural and functional properties of the lung epithelial cells (BECs) were damaged after endur and airways remain essentially unchanged after ance exercise and released interleukin (IL)8, a training. In healthy and fit individuals, hypoxaemia known chemoattractant of neutrophils (figure 1). can develop at very high workloads. Several factors However, this response appeared selflimiting, contribute to occurrence of hypoxaemia during since a large proportion of BECs in the airways exercise: inefficient gas exchange, vocal cord dys were shown to be apoptotic (figure 2) [15]. Other function, flow limitation in intrathoracic airways studies in young competitive rowers suggested and high energy requirements by the respiratory that increased BEC counts were positively associ muscles during heavy exercise [6, 7]. This latter ated with very high ventilation rates [16]. Environ effect could be at least partly counteracted by spe mental pollutants also appear to affect airway cell cific training of the respiratory muscles, which was apoptosis, whereas exercise intensity seems the shown to improve exercise performance in both main factor in the pathogenesis of apoptosis of athletes and nonathletes [8]. The central ner BECs [17]. vous system exerts a complex and fine tuning of Therefore, we hypothesised that epithelial ventilation during exercise and is involved in the cell injury caused by insufficient conditioning perception of fatigue [9]. of inspired air at high ventilation might be the Adaptations in other systems also occur. For main cause of neutrophil influx into the airways example, training increases oxygen transport ( figure 3) [18]. Such changes are probably of little through haematological adaptations such as relevance in the amateur athlete, but may cause increased red cell mass and increased plasma symptoms and limit performance in elite athletes. volume. Mobilisation of endothelial progenitors We also assessed whether airway inflamma during exercise may contribute to the positive tion might be associated with bronchoconstriction microvascular effects of endurance training [10]. in nonasthmatic subjects. Acute exercise exerts 142 Breathe | June 2016 | Volume 12 | No 2 Endurance training ** a) 90 b) 3.5 80 3.0 70 –1 2.5 60 ** ** 50 2.0 -8 ng·mL per mL 4 40 1.5 30 ×10 1.0 20 ost-race IL P 0.5 Bronchial epithelial cells 10 0 0 0 2 4 6 8 Bronchial epithelial cells ×104 per mL ost-race ost-race ost-race Baseline Baseline Baseline P P P Oct May Nov Figure 1 a) Bronchial epithelial cell counts in induced sputum significantly increased post-race. **: p<0.01. b) IL-8 con- centration

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