The study will recruit subject of healthy adult, COPD-like patient and patient with COPD to investigate the difference of respiratory performance. We will measure the body composition, respiratory muscle force, pulmonary function and performance of voluntary cough. The muscle thickness of abdominal muscle and diaphragm, assessment of diaphragm during different breathing pattern and the muscle activation during voluntary cough will also being determined. We hypothesized that there will be a significantly different between three group on the performance of voluntary cough, and the correlation between each variable will be further investigated.

The specific aims of the study are:

1. difference of respiratory muscle performance between three groups
2. the correlation between respiratory symptom and pulmonary functional test
3. difference of functional respiratory performance (peak cough flow of voluntary cough) between three groups
4. muscle activation of abdominal muscle and diaphragm during performing voluntary force
5. performance of diaphragm under different breathing load

1. Health subject

   Inclusion Criteria:

   • aged 20 years or above
   • currently not being diagnosis as COPD
   • less than 4 times/week of aerobic exercise

2. COPD-like subject

   Inclusion Criteria:

   • aged 20 years or above
   • currently not being diagnosis as COPD
   • presented of COPD symptoms (coughing, sputum production and dyspnea), last for 3 months and more than 2 years
   • score more than 1 on modified Medical Research Council (mMRC) or COPD Assessment Test (CAT)

3. COPD subject

Inclusion Criteria:

• aged 20 years or above
• currently being diagnosis as COPD
• haven't participated in any pulmonary rehabilitation program in the past three months

Exclusion Criteria:

• Untreated comorbidities for COPD
• Postural asymmetries (Scoliosis, length discrepancy of the lower limbs or other previous surgical history of spine)
• Chronic nonspecific lumbopelvic pain
• Gynecological or abdominal surgery in the previous year
• Pregnancy or post-delivery in the previous 6 months
• Neurological or inflammatory disorders
• Any conditions that may interfere with the data collection

1. Health subject: healthy adults with no existed respiratory condition
2. COPD-like subject: subjects with COPD-like symptoms but not reach the diagnosis criteria
3. COPD subject: subjects with diagnosed COPD