No intervention 40 years or older, clinical diagnosis of COPD (Global Initiative for Chronic Obstructive Lung Disease stages I to IV)

40 years or older, not with the clinical diagnosis of COPD

no intervention in this study

The machine analyze the breath of participants including oxygen consumption and minute ventilation volume. Oxygen consumption is reported in mL/min and minute ventilation volume is reported in L/min.

The surface EMG is performed to assess the maximum voluntary contraction and muscle activity of upper limb muscles and accessory inspiratory muscles during performing simulated ADL tasks. The maximal voluntary contraction (MVC) is used as the reference level of muscle activity to normalize the EMG data of performing simulated ADL tasks. The muscle activity is reported in percentage.

This is a self-reported questionnaire to measure the impact of COPD on participants' health status. The rating scores is a 7-point scale (0=no limitation, 6=totally limited).Higher scores mean the more severe impact of COPD on participants' daily living.

This is a self-reported scale to measure how much participants perceive dyspnea. The range from 0 which means no difficulty to breathe to 10 which means with maximal difficulty to breathe.

This is a five-point scale to assess the severity of breathlessness.

This is a self-reported questionnaire for measuring generic health status