Patients with cystic fibrosis (CF) are living longer and better than ever. Current projections suggest that young CF patients have an even brighter future. Along with increases in longevity, CF patients are busy accomplishing more than ever before. In the realm of sports, there are now CF patients performing at, or close to, national and world class levels. When you consider that there are only 70,000 CF patients worldwide, having several elite athletes amongst the CF population is truly a significant accomplishment. Their feats attest to the heights that CF patients can achieve.
So, who should be physically active? If we look at the general population, everyone can benefit from a healthy, active lifestyle, even people with chronic heart or lung conditions. This also holds true for patients with CF. So everyone can be active and can profit from increases in regular physical activity.
Factors Limiting Exercise Ability
There are several factors which can impose limitations on maximal exercise ability. It should be remembered that it is rare for anyone to exercise for any prolonged period at maximal levels. However, maximal ability is a good marker of what people can readily tolerate on a daily basis.
In people without heart or lung disease, exercise ability is generally limited by muscular ability. Muscular ability depends on both the amount of muscle available and the level of physical conditioning. In other words, the more muscle we have and the more exercise we do, the more we can do, and the less active we are or the less muscle we have, the less we can do.
Respiratory Factors
In CF patients with moderate or more advanced disease, ventilatory or breathing capacity can also potentially limit exercise ability. When lung disease progresses in CF, there is difficulty exhaling air fast enough (expiratory flow limitation). This is because the airways become narrowed from secretions and inflammation. In patients with bronchiectasis, the airways lose their stiffness, and may narrow even more when breathing heavily. If air does not come out quickly enough when exhaling, there can be a build up of air in the lungs (air trapping). Patients with air trapping often look barrel-chested. When there is air trapping, the muscles used to inhale must work harder. Patients often sense this increased work of breathing, and it is not unusual for patients with advanced disease to complain of difficulty breathing during exercise.
Muscular Factors
Muscular ability is also often limiting in CF patients. In CF, besides the amount of muscle and physical conditioning, other factors can influence muscular ability. The mutation in the CF gene appears to impact upon the mitochondria (the body’s power house, present in virtually every cell), and its ability to generate energy. The mitochondria is where the fats and sugars derived from our diet are turned into energy to allow our muscle to contract or shorten, allowing us to move. Generally, not much of the protein we eat is used for energy production. Instead, it is used for building and renewing the body’s tissues. Other energy- generating processes may also be limited in CF patients for unknown reasons. Some of these aspects are being currently explored in a research project being done in Montreal and Toronto.
It is well recognized that CF patients have a lot of inflammation in their lungs. However, the inflammatory response is not solely confined to the lungs, and there is a spill-over effect, with increases in certain markers of inflammation in the blood. These markers (cytokines) can lead to loss of muscle tissue and decreased muscular function.
Finally, another factor influencing muscular ability is medical therapy. Some CF patients receive oral corticosteroids over prolonged periods of time. While corticosteroids can help decrease inflammation, they can also sometimes cause significant muscular weakness. Patients and their medical team must be on the look-out for this and try to limit the dose of corticosteroids.
The Benefits of Physical Activity in CF
The most important benefit to be gained from an active lifestyle is quality of life; you’ll feel better. Increased exercise ability seems to have a bigger impact on quality of life than changes in lung function.
We found that in children, patients who were more physically active on a daily basis had a better maintenance of lung function, regardless of their initial lung function. This may be partially due to the enhanced removal of secretions that accompanies physical activity. So, being active can really help, in addition to regular chest physical therapy, although exercise does not replace regular chest physical therapy.
Exercise can also have a positive influence of growth hormone, which helps maintain muscle bulk and function. The changes seen with exercise are similar to what is seen with growth hormone injections.
Exercise is safe and can be well tolerated by all patients, provided it is geared to the appropriate level. Often the clinic physiotherapist can give guidance on exercise and training programs. The most successful programs are those that get people doing the types of physical activities that they want to do. Treadmills, stationary bikes or free weights can get really boring so it’s important to mix up and combine fun activities, such as group sports. It’s also important that patients replenish the salt and water they lose through sweat.
Exercise is particularly important for patients with respiratory limitations. Exercise training reduces the amount of carbon dioxide and lactate that is produced in our body. Carbon dioxide and the acid produced from lactate force us to do more ventilatory (breathing) work. So if we get fit through more regular exercise, we can decrease the production of carbon dioxide and lactate for the same amount of work, and we’ll breathe easier. As mentioned earlier, it is quite common for people to stop exercising because they feel that they are breathing too hard and they are short of breath. If people become more physically active, activities become better tolerated and even enjoyable.
Other Factors That Can Enhance Exercise Ability
As mentioned, there are several modifiable factors, aside from muscle bulk and conditioning, that can have an impact on exercise ability. Decreasing the systemic inflammatory response with antibiotics or high dose ibuprofen may enhance weight gain and muscle performance, in addition to improving lung function. Nutritional supplements that can increase antioxidant defences may also be of some help. These therapies should be discussed with the CF treatment team, as they require specific dosing and monitoring on a regular basis.
Conclusions
Everyone feels better being more active. CF patients can particularly benefit from a more active lifestyle. Physical activity is a lifestyle choice, and not another treatment. Put down this article and get out there!
Larry C. Lands, MD, PhD Director
Cystic Fibrosis Clinic Montreal Children’s Hospital-McGill University Health Centre
