In health--vital capacity is maximum in supine position.

Vital capacity, frequently measured clinically as an index of pulmonary function, gives useful information about the strength of respiratory muscles and other aspects of lung functions. It is generally noted in sitting position. As in the supine position, respiratory excursions of diaphragm is highest in normal breathing, this study was planned to note whether there occurred any alteration in vital capacity in supine position in comparison to that noted in sitting position. Young sedentary non smoker healthy medial students (n = 100, age 19-22 years) of Nepal Medical College participated as volunteers in this study. Body mass index (BMI) of each of them was calculated. Vital capacity was noted in sitting position and in supine position with the help of a spirometer, following the standard procedure. Result exhibited greater vital capacity in supine posture than in sitting position in the same individual. Diaphragm is the major muscle of inspiration, responsible for some two-thirds of the vital capacity. Naturally, in supine posture the scope of diaphragmatic movements increased and as a result, vital capacity exhibited greater value in comparison to that recorded in sitting posture.