Laryngeal view of the patient and anesthesiologist's discomfort level during endotracheal intubation in relation to the various heights of operating table has not been investigated. The investigators hypothesis is higher table height will improve the laryngeal exposure.

Eight anesthesiologists will be participated. For each anesthesiologist, 20 patients will be enrolled and they will be randomly allocated into one of 4 groups; T10, T8, T6 or T4. The height of operating table will be adjusted prior to commencement of anesthesia induction to place the patient's forehead at one of four anesthesiologist's dermatome levels (T10, T8, T6 or T4) depending on the group. The best laryngeal views will be graded before and after the anesthesiologist's postural change to improve laryngeal visualization of the patient during intubation. Subjective and objective measurement of anesthesiologists' joint flexion during intubation and discomfort ratings for the mask ventilation or intubation will be recorded.

Inclusion Criteria:

• have experiences of more than 100 cases of endotracheal intubation

Exclusion Criteria:

• have acute or chronic musculoskeletal disease or pain

certificated anesthesiologists