Although physical exercise is recommended for asthmatics, evidence on the effects of exercise on clinical key factors is still missing. We performed a systematic review and meta-analysis to determine the effect of exercise training (EXT) on quality of life (QoL), bronchial hyperresponsiveness (BHR), exercise-induced bronchoconstriction (EIB), lung function and exercise capacity, plus the factors affecting changes in QoL and exercise capacity in asthmatics after a period of EXT. A computerized search was conducted in MEDLINE, EMBASE, and CINAHL (last search on 15 November 2012), without language restriction, and references of original studies and reviews were searched for further relevant studies. Two independent investigators screened full-text studies with asthmatic subjects undertaking EXT (defined as training for ≥7 days, ≥2 times per week, ≥5 training sessions in total) that assessed at least one of the following outcomes: QoL, airway hyperreactivity, forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), inflammatory parameters, exercise capacity, or exercise endurance. Potentially relevant studies were excluded if only respiratory muscle training, breathing exercises or yoga was performed, if asthmatic subjects with co-morbidities were investigated, if only data of mixed patient groups without separate results for asthmatics were presented, if training regimens were not sufficiently specified, if no numerical outcome data were presented, and if new long-term medication was introduced in addition to physical training. Of 500 potentially relevant articles, 13.4 % (67 studies including 2,059 subjects) met the eligibility criteria and were included for further analyses. Data extraction and risk of bias assessment was performed according to the Cochrane Handbook for Systematic Reviews of Interventions. A meta-analysis of all randomized controlled trials (RCTs) was performed to determine the effect of EXT on asthma symptoms, BHR, EIB, FEV1, exercise capacity and exercise endurance compared with control training. In addition, relative pre/post changes were analysed in all RCTs and controlled trials. Finally, multiple linear regression models were used to identify effects of relative changes in airway hyperreactivity (BHR or EIB), lung function (FEV1 or PEF) and training hours on QoL and exercise performance. In a total of 17 studies including 599 subjects, meta-analyses showed a significant improvement in days without asthma symptoms, FEV1 and exercise capacity while BHR only tended to improve. The analysis of relative within-group changes after EXT showed, however, significant improvements in QoL (17 %), BHR (53 %), EIB (9 %), and FEV1 (3 %) compared with control conditions. Multiple linear regression models revealed that changes in airway hyperreactivity and lung function significantly contributed to the change in QoL, while mainly the changes in airway hyperreactivity contributed to the change in exercise capacity. EXT was shown to improve asthma symptoms, QoL, exercise capacity, BHR, EIB, and FEV1 in asthmatics and improvements in BHR explained part of the improvement in QoL and exercise capacity. Thus, physical activity should be recommended as a supplementary therapy to medication. However, more well controlled studies should be performed assessing the relationship of physical activity, QoL, airway hyperreactivity, lung function and especially airway inflammation as well as medication intake.

Effects of Exercise Training on Airway Hyperreactivity in Asthma: A Systematic Review and Meta-Analysis

More than 40 years ago, the effects of exertional dyspnoea and the associated fear of an asthma attack usually lead to an avoidance of physical activity amongst asthmatic children. This issue still exists today, particularly in children with severe asthma. This article presents a comprehensive review of published information concerning the effects of training programmes on children and adolescents with asthma. The primary focus of these investigations was to examine the effects of physical conditioning on aerobic fitness, the severity and incidence of exercise-induced asthma (EIA) and asthma symptoms. The large majority of training studies of asthmatic children and adolescents demonstrate significant increases in aerobic fitness post-training or the achievement of normal levels of aerobic fitness. While there are a few reports of a reduced severity in EIA symptoms post-training, the majority of studies demonstrate no change in the occurrence or degree of EIA. However, a number of these studies have reported some reductions in hospitalisations, wheeze frequency, school absenteeism, doctor consultations and medication usage. It is, therefore, recommended that children and adolescents with asthma should participate in regular physical activity. This may improve asthma management and associated general health benefits, whilst minimising inactivity-related health risks.

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Effects of Physical Conditioning on Children and Adolescents with Asthma

Fifty children with exercise-induced asthma (EIA) volunteered to take part in a study of the influence of training on EIA. 1) Ten children did not change physical activity. 2) Twelve children trained after premedication with salbutamol inhalations. 3) Thirteen children trained after premedication with disodium chromoglicate (DSCG) and used that drug for treatment. 4) Fifteen children trained in their own regimen, commonly after premedication with salbutamol. Their training programme (groups 2-3) consisted of high load exercise periods of two minutes interrupted by intervals of rest for two minutes during 30 minutes followed by interval swimming for another 30 minutes, twice a week for 3-4 months. Before the training period the degree of EIA was tested with a battery of lung function tests before and after running for 6 minutes on a treadmill at heart rate 170. EIA after training was measured applying the same procedure. Cardiocirculatory performance was evaluated before and after training with work on a cycle ergometer and expressed as W/kg body weight at heart rate 170. The children in groups 2, 3 and 4 improved their physical working capacity by 11% (p less than 0.01), 21% and 11%, respectively, but no improvement was found in group 1. Significant improvements in EIA after the training periods were found in all training groups, but basal asthma improved most in group 3, probably due to the basal treatment with DSCG.

Improvement after training of children with exercise‐induced asthma

Twenty-seven children (age 7–17 years) with varying degrees of blindness but with no other known disorder were assessed for physical fitness. Twenty-seven randomly selected children with normal eyesight were also assessed. Maximum oxygen uptake (\(\dot V_{{\text{O}}_{{\text{2 max}}} } \)) was measured directly during a progressive exercise test on a treadmill. There was a significant and substantial reduction in\(\dot V_{{\text{O}}_{{\text{2 max}}} } \) in totally blind children (mean ± standard deviation 35.0±7.5 ml · min−1 · kg−1) compared with normal children (45.9±6.6 ml · min−1 · kg−1). Partially sighted children had a significant but smaller reduction in\(\dot V_{{\text{O}}_{{\text{2 max}}} } \). Fitness assessed by a step-test was significantly reduced in the visually impaired children, and skin-fold thickness was also significantly greater in totally blind children.

Physical fitness of blind and sighted children

Physical exercise is not hazardous to asthmatics Some asthmatics may benefit from physical training, and almost all asthmatics can perform any kind of physical exercise Free running was earlier thought to induce more asthma than swimming, for example; however, when ventilation is identical during running and swimming, the exercise-induced asthma will also be the same Hyperventilation alone is as good as physical exercise to induce exercise-induced asthma If the physical exercise provokes an asthmatic attack, this is most often easily reversed by inhaled β2-agonists Pretreatment of exercise-induced asthma is most efficient by inhaled β2-agonist; orally dosed β2-agonist is not as efficient as inhaled β2-agonist in the pretreatment of exercise-induced asthma Inhaled sodium cromoglycate diminishes exercise-induced asthma, and the effect seems to be better in children than in adults Inhaled steroids have no immediate effect on exercise-induced asthma, but long term treatment with steroids diminishes exercise-induced asthma

Exercise and the Asthmatic

Plasma citrate was determined in seven asthmatic children exposed to 6 min treadmill running before and after 6 weeks of physical training. Resting plasma citrate concentration increased from 116 ± 9 μmol/l (mean ± SE) before to 158± 11 μmol/l after training (P<0.02). Plasma lactate increase during exercise was lowered by training (P<0.02); the individual change correlated inversely with the training-induced rise in resting plasma citrate concentration (r = -0.77, P<0.05). The postexercise percentage fall in peak expiratory flow rate decreased from 32 ± 13 % before to 15 ± 8 % after training (P<0.05).The results agree with the hypothesis that an increased citrate concentration of tissues, by inducing an inhibition of phosphofructokinase, may be of regulatory importance for the decreased lactate accumulation following endurance training in man. In addition, a beneficial effect of training on exercise-induced asthma is demonstrated.

R. Dahl

Papers

Effects of physical training on plasma citrate and exercise-induced asthma