# Exercise as it relates to Disease/Aerobic Exercise and its effects on Cystic Fibrosis
## What is Cystic Fibrosis?

Cystic fibrosis (CF) is a chronic genetic condition that is caused from the mutation of the Cystic Fibrosis Transmembrane Conductance Regulator gene and affects many systems in the body, predominately the respiratory system. This condition is characterised by a malfunction in the endocrine system which results in abnormal secretion of mucus in both the digestive and respiratory systems. This mucus increases the individuals risk of infection as the bacteria and pathogens are trapped in the respiratory or digestive tracts
At the present, there is no cure for cystic fibrosis; however, there are some promising strategies including chest physiotherapy and regular physical activity which, when implemented correctly, can provide many positive effects and can suppress the signs and symptoms of CF. The effect of aerobic exercise on CF is dependent on the disease severity and intensity and duration of exercise. Exercise intolerance is well known to be a symptom of cystic fibrosis. Some of the other signs and symptoms attributed to cystic fibrosis include:
* Some breathing difficulties including wheezing and a persistent cough which is increased during physical activity
* Suppressed appetite
* Lethargy, which may affect physical activity levels
* Loss of salt during warmer weather
* Frequent toilet visits

## What are the Effects of Aerobic Exercise on Cystic Fibrosis?

While aerobic exercise has positve effects on the musculoskeletal, cardiorespiratory and immune systems for all individuals, the following list is the effects on aerobic exercise specific to individuals with CF.

### Cardiorespiratory System

Aerobic Exercise has been shown to decrease the rate of decline in lung function, which has recorded to be at a rate of approximately 2-3% per year. It also has been shown to improve the transepithelial potential difference in the airway, which enhances the airway clearance and improves mucus removal while also increasing ventilation recruitment in the lungs.
Individuals with CF generally display lower maximums in the VO$_2$ testing compared to healthy individuals. However, regular aerobic exercise, alongside age, sex, muscle and lung function may increase VO$_{2max}$ scores. Interestingly, improved VO$_{2max}$ scores in CF have also been shown to improve quality of life measures including improved body image and physical functionality, which create more positive attitudes towards partaking in physical activity.
Ventilation with CF is less efficient than healthy individuals when partaking in physical activity, as there is an increase in respiratory dead space, a high respiratory rate and consequently low tidal volume, which results in a lower rate of gas exchange. However, higher tolerance of exercise as a result of regular aerobic activity has been suggested to improve the tidal volume in the lungs and lower respiratory rate.

### Immune System

| Effects of aerobic exercise from one session | Effects of regular aerobic exercise |
| Can begin to reap the benefits from aerobic exercise from as little as one session, through inducing an anti-inflammatory response.However, depending on intensity, duration and type of activity, session may cause an heightened inflammatory response. | Regular exercise allows the for the adaption to stimuli and produce lower amounts of pro-inflammatory modulators and increase pro inflammatory production in tissue such as visceral fat, skeletal muscles and immune cells subsequently dampening inflammation. Ones susceptibility to viral infection may also be decreased from the effects of exercise over the long term. |

### Musculoskeletal System

Muscular strength may be lesser in individuals with CF due to hyperinflation and malnutrition, which may result in the fatigue in respiratory muscles during periods of aerobic exercise. From the respiratory inflammation characterised with CF and the insufficient respiratory power and efficiency of the muscle, people with CF generally are disadvantaged compared to their non-CF “healthy” counterparts.
Aerobic exercise has been shown to increase both the strength of muscles involved in the process respiration and the competence of neuromuscular transmission. Positive correlations between walk/run distance and inspiratory muscle strength have been recorded in people with CF. Stronger inspiratory muscle may play a positive role in compensating for reduced lung function over the duration of aerobic exercise.
Aerobic exercise combined with regular cyclic breathing techniques and utilising chest physiotherapy has also conveyed not only increases in cardiovascular endurance but also increases thoracic strength.

## Exercise Recommendations

The following are recommendations for individuals with CF partaking in aerobic exercise.
* Individuals with CF should consult with their GP for a screening to determine what intensity, duration, type of aerobic exercise that is most applicable to their specific condition
* Aerobic Exercise should generally be of moderate intensity and duration
* Implementing regular breathing techniques during exercise alongside chest physiotherapy has also shown to increase the clearance of mucus in the brochi, increase exercise tolerance, reduce the feeling of breathlessness and improve quality of life.
* Depending upon severity, aerobic exercise should be undertaken:
| Intensity | Duration | Frequency | Examples |
| intensity of 60-85% HR$_{max}$ | 20–45 minutes | 3-5 times a week | Walking Jogging Bike riding Swimming |
HR$_{max}$= maximum heart rate
It should also be noted that not all individuals with CF experience the same benefits or effects of aerobic exercise. While symptoms may be suppressed for some individuals from participating in phyical activity, for other they may be heightened and may experience greater breathing diffculties ,inflamation and mucus secretion. Individual responses may vary depending on a multitude of factors including severity of CF, overall health status and physical actvity levels.

## Further reading

To learn more about the condition Cystic Fibrosis:
* American Foundation for Cystic Fibrosis
* Australian Foundation for Cystic Fibrosis

## References

* ↑ Farrell P et. al Guidelines for diagnosis of cystic fibrosis in newborns through older adults: cystic fibrosis foundation consensus report. J Pediatr. 2008; 153:4-14.
* ↑ Cystic Fibrosis Australia. About Cystic Fibrosis [internet]. Available from: http://www.cysticfibrosis.org.au/all/learn/
* ↑ Elbasan B, Tunali N, Duzgan I & Ozcelik U. "Effects of chest physiotherapy and aerobic exercise training on physical fitness in young children with cystic fibrosis". Italian Journal of Pediatrics. 2012; 38(2): 1-5.
* 1 2 3 Van de Weert-van Leeuwen P, Arets H, van der End C, Beekman J. Infection inflammation and exercise in cystic fibrosis. Respiratory Research. 2013;14(32):1-10.
* ↑ Troosters, T, Langer D, Vrijsen B, Wouters K, Janssens W, Gosselink R, Decramer M, Dupont L. Skeletal muscle weakness exercise tolerance and physical activity in adults with cystic fibrosis. Eur Respir J. 2009; 33: 99-106.
* ↑ Symptoms of CF. Cystic Fibrosis Victoria.
* 1 2 3 Orenstein D, Higgins L. Update on the role of exercise in cystic fibrosis. Curr Opin Pulm Med. 2005; 11:519-523
* 1 2 3 4 5 Dassios T, Katelari A, Doudounakis S, Dimitriou G. Aerobic exercise and respiratory muscle sterngth in patients with cystic fibrosis.Respiratory Medicine. 2013;107:684-690
* ↑ Moser C, Tirakitsoontorn P, Nussbaum E, Newcomb R, Cooper D. Muscle size and cardiorespiratory response to exercise in cystic fibrosis.Am J Respir Crit Care Med. June 2000; 162: 1823-1827.
* 1 2 Hebestreit H, Kieser S, Rudiger S, Schenk T, Junge S, Hebestreit A, Ballmann M, Posselt H, Kriemler. Physical activity is independently related to aerobic capacity in cystic fibrosis.Eur Respir J.2006; 28:734-739.
* 1 2 Dunnink M, Doeleman W, Trappenburg J, de Vries W. Respiratory muscle strength in stable adolescent and adult patients with cystic fibrosis. Journal of Cystic Fibrosis. 2009; 8:31-36.
* 1 2 3 Elbasan B, Tunali N, Duzgun I, Ozcelik U. Effects of chest physiotherapy and aerobic exercise training on physical fitness in young children with cystic fibrosis. Italian Journal of Pediatrics. 2012; 38(2):1-5.