Muscular dystrophy is a hereditary musculoskeletal disorder caused by a mutation in the dystrophin gene. Duchenne muscular dystrophy (DMD) is one of the most common, and progresses relatively faster than other muscular dystrophies. It is characterized by progressive myofiber degeneration, muscle weakness and ultimately ambulatory loss. Since it is an X-linked recessive inheritance, DMD is mostly expressed in males and rarely expressed or less severe in females. The most effective measurement tool for DMD is magnetic resonance imaging (MRI), which allows non-invasive examination of longitudinal measurement. It can detect progressive decline of skeletal muscle size by measuring a maximal cross-sectional area of skeletal muscle. Additionally, other techniques in MRI, like T2-weighted imaging, assess muscle damage, including inflammation, by detecting changes in T2 relaxation time. Current MRI techniques even allow quantification of metabolic differences between affected and non-affected muscles in DMD. There is no current cure, but physical therapist can improve their quality of life by maintaining muscle strength and function, especially if treatment (and other forms of medical intervention) begins in the early stages of the disease.

It is important to find the effective position for cough and sputum clearance in respiratory physical therapy. The purpose of this study was to compare the changes in peak expiratory flow (PEF), forced expiratory volume in 1 second (FEV1), and peak cough flow (PCF) related to functional level and measurement position in patients with Duchenne muscular dystrophy. Twenty one subjects were classified into three functional levels, and measurements was undertaken in three different measurement positions (upright sitting, 45˚ reclining and supine). Vitalograph PEF/FEV DIARY was used to measure PEF and FEV1, and Ferraris Pocket Peak was used to measure PCF. Mixed two-way analysis of variance and Bonferroni post-hoc test were used for statistical analysis. The results of the study were as follows: 1) Significant main effects for measurement position were found. 2) PEF was the highest in upright sitting, followed by 45˚ reclining, and supine in order. 3)FEV1 in upright sitting and 45˚ reclining were significantly greater compared with that in supine. 4) PCF in upright sitting and 45˚ reclining were significantly greater compared with that in supine. 5) No significant main effects for functional level were found in PEF, FEV1, and PCF. 6) No significant functional level by measurement position interactions were found in PEF, FEV1, and PCF. Therefore, it is concluded that upright sitting and 45˚ degree reclining positions are recommended for effective cough and sputum clearance.