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Update - January 2013

People with COPD also experience changes in the muscles that control strength and movement, as well as support the body. My research will look into these changes and why they happen.

People with COPD experience a reduction in the blood flow, the size and the thickness of their muscles. This is due to changes in the muscle fibres in the large thigh muscle, called vastus lateralis. Muscles are made up of different fibre types that make energy in different ways:

• Type I, or ‘slow twitch’ fibres, contain lots of tiny blood vessels (capillaries). They contract slowly, releasing energy at a slower rate, but can keep going for a long time.

• Type II, known as ‘fast twitch’ muscle fibres contain lots of stored energy that is easy to access for short bursts of energy. They contract quickly, but rapidly get tired.

As part of my study, I’ve analysed results from previous research on samples of tissue from the muscles of people with COPD. These studies confirm that the number and distribution of the muscle fibre types I and II changes in people with COPD. We then developed our own study with 30 participants: 10 patients with COPD and muscle wasting; 10 patients with COPD and normal muscle; and 10 people without COPD of the same age and gender as those with COPD. We asked all participants if they were current or ex-smokers, and their smoking history, how many exacerbations they had in the last year, and asked them to complete both a health related quality of life questionnaire, and a physical activity level questionnaire.

We performed spirometry tests to measure their lung function, measured the amount of body fat and muscle, thigh muscle strength, ability to walk for 6 minutes. A biopsy of the vastus lateralis muscle was also taken from all participants to be assessed for analysis, especially looking for changes in the type of muscles fibres.

When we compared the results for all these different tests we found that there was more slow twitch muscle fibre in people with low breath test results, who had smoked more cigarettes daily, and for more years, and who had experienced more exacerbations over the last year.

These results support previous studies on the muscle of patients with COPD confirming that the ability of the muscles to use and transport oxygen in patients with COPD is changed and reduced, due to changes in the muscle fibre type; and that this continues as the COPD progresses.

Next I will be looking at inflammation and oxygen transportation in people with COPD. We know that reduced oxygen and swelling are common in people with COPD, especially during exacerbations, and I will be trying to learn more about how this affects the skeletal muscle.

The image shows the different fibre types in a section of human thigh muscle in a healthy study participant. The type I fibre is stained blue and Type II stained Red.