Whether minimizing sternocleidomastoid (SCM) activation in supine position would increase diaphragm activation during loaded inspiratory muscle tests remains to be determined. Therefore, the purpose is to exam diaphragm and SCM activation during loaded inspiratory muscle tests in sitting and supine position in healthy adults.

Inspiratory muscle training usually performed in the upright sitting position. In healthy individuals, sternocleidomastoid (SCM) is rarely recruited during tidal breathing, but previous studies have demonstrated SCM activation during loaded inspiratory muscle tests in upright sitting position. Whether minimizing SCM activation in supine position would increase diaphragm activation during loaded inspiratory muscle tests remains to be determined. Therefore, the purpose is to exam diaphragm and SCM activation during loaded inspiratory muscle tests in sitting and supine position in healthy adults.

Inclusion Criteria:

• age > 20 years old
• without exercise habit (any exercise that less than 3 days/week)
• can cooperate with the measurements of this study

Exclusion Criteria:

• any clinical diagnosis that will influence the measurement, including any history of neuromyopathy
• angina, acute myocardial infarction in the previous one month
• pregnancy
• participated in inspiratory muscle training program in the previous three months
• any psychiatric or cognitive disorders, for example: Mini-Mental State Examination (MMSE) < 24, that will disturb the communication and cooperation of the study

Healthy adults that are willing to cooperate the measurement of this study.