Research paper summary – Amazing-Grace Lawal

Effect of endurance exercise on respiratory muscle function in patients with cystic fibrosis

Charles C. Reilly, Katie Ward, Caroline J. Jolley, Lucy Anne Frank, Caroline Elston, John Moxham, Gerrard F. Rafferty

Published in the journal Respiratory Physiology & Neurobiology, January 2012

Cystic Fibrosis (CF) is a genetic disorder in which the genes that control the movement of salt and water in and out of cells are affected, this leads to a build up of mucus mostly in the lungs but also in the liver, pancreas and intestine. The aim of the study was to determine whether high intensity exercise tasks lead to fatigue (where the muscles become briefly less able to generate force) in the abdominal muscles or the diaphragm in patients with CF.

Two groups of people were tested, one group with 10 patients with CF and the other group with 10 healthy subjects. On two different occasions the test subjects went to the lab to carry out tests. On the first occasion the subjects performed an exercise test to characterise the subjects in terms of their exercise performance and to also calculate a work rate, which was used in the second test. The second occasion involved a cycling endurance test, lung function and respiratory muscle strength testing taken on all subjects. Before and after the exercise tests, subjects underwent magnetic stimulation of their diaphragm and abdominal muscles to assess how much force the muscles could generate.

Average exercise time was similar in the healthy subjects and those with cystic fibrosis, as was the intensity of exercise they performed during the test. The measurements taken show that there were not any significant changes in the responses to magnetic stimulation after exercise in both the healthy subjects and those with CF. A decrease the response to magnetic stimulation of greater than 15% is thought to be indicative of fatigue in respiratory muscles, however, none of the subjects saw a decrease larger than 15%, thus leading to the conclusion that fatigue did not occur in any of the subjects.

The fact that that fatigue did not occur in the diaphragm or abdominal muscles after exercise in the patients with CF suggests that feelings of breathlessness and weakness in leg muscles may be more important in limiting exercise performance in those with CF. Further studies are needed in order to exactly understand the factors that hinder exercise performance of those with CF such as muscle function in non-respiratory muscles.

This summary was produced by Amazing-Grace Lawal, Year 13 student from Harris Academy South Norwood, London as part of our departmental educational outreach programme.