4 performance, BMI, and pulmonary function. Patients with class I and II CFTR mutation had the lowest peak anaerobic power in the WAnT compared to those with classes III, IV, and V CFTR mutations, respectively [43]. Unfortunately, most training studies in CF are of short duration, and longitudinal data are lacking, especially in the paediatric population. Longitudinal and controlled studies are required to verify training eﬀects in association with disease progression in CF and decline in pulmonary function and peak V˙O2. Studies, documenting less or no eﬀects after exercise training on CPF, are most likely due to a low number of study subjects, lack of a control group or lack of training supervision, and poor compliance [25, 44]. Further research is warranted to assess the eﬀects of diﬀerent training methods longitudinally (aerobic versus anaerobic training versus a combination of both training regimes). More detailed infor- mation regarding training protocols (intensity, duration, and rest periods) would be advantageous to therapists and health care providers working with children with CF. Furthermore, when working with children the fun component needs to be emphasised, while group activities may be the preferred choice rather than isolated training (i.e., cycling or stepping), infection control permitting. Trampolining, for example, as a popular although controversial activity, has been discussed in the paediatric population and CF lung disease, especially due to the increased risk potential for injuries [45–47]. However, providing there is particular focus on safety issues and supervision, trampolining can be an eﬀective adjunct to regular airway clearance techniques or even as part of physiotherapy in CF [48]. In habitual daily life patients with CF are faced with certain barriers and challenges according to their participation in regular exercise and habitual physical activity [14]. Parents should be encouraged to exercise with their children and serve as role models (i.e., aiming to increase habitual physical activity levels). Based on the training studies available in children and adolescents with CF, there is no deﬁnitive evidence regarding the sustainability of training eﬀects in the long term (i.e., months to years). 2.2. Possible Risks Associated with Exercise Training in CF. Speciﬁc risks of exercise training in CF are presented in the table. During prolonged exercise, as a consequence of excessive sweat and sodium losses, children with CF are advised to drink repeatedly (i.e., every 15–20 min), and ideally including approximately 50 mmol·L−1 sodium chloride in their drink [49]. Especially, in hot conditions, children may underestimate their ﬂuid needs with the risk to undergo excessive dehydration [50]. Certain sports in this population should also be viewed with caution. For example, CF patients with portal hyper- tension with signiﬁcant enlargement of spleen and liver should, as a precaution, be advised against participation in contact sports. Patients participating in physical activities which take place at high altitudes (e.g., skiing) should be monitored, especially if the patient is already hypoxic. Furthermore, episodes of acute right heart failure induced by a combination of altitude and high intensity exercise have been documented [51]. During diving activities air trapping could occur in patients with lung disease, on ascent the air International Journal of Pediatrics Table 1: General exercise and training recommendations. Patients with severe CF lung disease Ergometric cycling, walking, strengthening exercises, gymnastics, and day-to-day activities Intermittent 5 times per week 20–30 minutes 60%–80% HRmax; 50%–70% peak V˙O2; LT; GET Indicated, if SaO2 drops below 90% during exercise (cave: resting hypoxia) Bungee-jumping, high diving, scuba diving, and hiking in high altitude Recommended activities Method Frequency Duration Intensity Oxygen supplementation Patients with mild to moderate CF lung disease Cycling, walking, hiking, aerobics, running, rowing, tennis, swimming, strength training, climbing, roller-skating, (trampolining) Intermittent and steady-state 3–5 times per week 30–45 minutes 70%–85% HRmax; 60%–80% peak V˙O2; LT; GET Indicated, if SaO2 drops below 90% during exercise Bungee-jumping, high Activities to avoid diving, and scuba diving Dehydration Hypoxemia Bronchoconstriction Potential risks Pneumothorax associated with Hypoglycaemia∗ exercise, and Hemoptysis training Oesophageal bleedings Cardiac arrhythmias Rupture of liver and spleen Spontaneous fractures∗∗ HRmax: maximum heart rate; peak V˙O2: peak oxygen consumption; LT: lactate threshold; GET: gas exchange threshold; SaO2: oxygen saturation. ∗Depending on the existence of an impaired glucose tolerance. ∗∗Depending on the existence of untreated CF-related bone disease. expands, with risk of development of pneumothorax [52]. Exercise-induced hypoxemia is a potential hazard for patients with CF, thus participation in high-intensity exercise needs consideration. However, soon after the termination of high intensity eﬀorts, SaO2 returns to pre-exercise levels, while there is no evidence that brief exercise-induced hypoxemia causes damage to the child with CF [53]. Cough with sputum may be observed during exercise in patients; however, this is indicative of airway clearance. General guidelines for clinical exercise testing [54, 55] and training in patients with chronic disease are beyond the scope of this paper and can be found elsewhere [49]. The table summarises a selection of recommended exercises, including training intensities for patients with CF. The