Hazaki K1, Okada K2
1Osaka Electro-Communication University, Department of Physical Therapy, Shijounawate, Osaka, Japan, 2Yamanobe Hospital, Department of Physical Therapy, Sakurai, Nara, Japan
Background: It is well known that vital capacity decreases with kyphosis-like postures, as in the elderly. The decrease in vital capacity generally results from reduction in rib cage expansion and decrease in diaphragmatic excursion, although it is not clear whether the decrease caused by kyphosis-like postures is due to the former or the latter.
Purpose: The present study aimed to examine the effect of upright and slumped sitting postures on dilatation of the rib cage and diaphragmatic excursion.
Methods: The study included 17 healthy male college students (mean age: 20.8±1.2 y, mean BMI: 21.2±1.5 kg/m2) who were free from cardiopulmonary disease, had no history of smoking and no postural abnormalities. The participants were asked to sit upright with their heads upright, thoraco-lumber spines extended and pelvis rotated anteriorly, followed by sitting in a slumped posture with heads facing forward, thoraco-lumber spines bent and posterior rotation of the pelvis. The participants were asked to perform tidal and deep breathing in each posture. Rib cage dilatation was measured as the change in the horizontal chest circumference at the xiphoid process level from maximal expiration to maximal inspiration using a thoracic excursion measuring device (TKK 3345, Takei Instrumentation Co.). Diaphragmatic excursion distance was measured using B-mode ultrasonography (MyLab 25, Hitachi Medical Co.) with a 3.5-MHz convex probe placed at the intersection of the right midclavicular line and the arcus costalis with a longitudinal orientation. Then, the left branch of the portal vein was identified using the inferior vena cava as a landmark, and displacement of the portal vein branch during maximal inspiration and maximal exhalation was measured as the diaphragmatic excursion distance. Analyses were performed using ImageJ image analysis software. Paired t-test were used for statistical comparisons.
Results: Rib cage expansions were 4.2±1.5 cm in upright sitting and 3.6±1.1 cm in slumped sitting positions, indicating a significant difference in expansion between the two postures (p 0.05). Diaphragmatic excursions were 5.9±1.6 cm in upright sitting and 4.9±1.7 cm in slumped sitting positions, again indicating a significant difference in diaphragmatic excursion between the two postures (p 0.05).
Conclusion(s): The mechanism of the decrease in vital capacity in the slumped sitting position is reduction in both rib cage expansion and diaphragmatic excursion. The reduction in rib cage expansion is probably due to limited rib elevation when the ribs rotate anteriorly during forward bending of the thoracic vertebrae. Decrease in diaphragmatic excursion is probably due to sagging of the diaphragm due to decrease in the anterior-posterior diameter of the chest wall in the slumped position, and due to limitation in diaphragmatic descent due to narrowing of the abdominal cavity.
Implications: The decrease in vital capacity in elderly people with kyphosis-like postures may not be related to age, because slumped sitting affects respiratory movement even in young people. It is necessary to evaluate and improve posture in patients with respiratory diseases.
Keywords: upright sitting position, slumped sitting position, ultrasonography
Funding acknowledgements: Nothing
Purpose: The present study aimed to examine the effect of upright and slumped sitting postures on dilatation of the rib cage and diaphragmatic excursion.
Methods: The study included 17 healthy male college students (mean age: 20.8±1.2 y, mean BMI: 21.2±1.5 kg/m2) who were free from cardiopulmonary disease, had no history of smoking and no postural abnormalities. The participants were asked to sit upright with their heads upright, thoraco-lumber spines extended and pelvis rotated anteriorly, followed by sitting in a slumped posture with heads facing forward, thoraco-lumber spines bent and posterior rotation of the pelvis. The participants were asked to perform tidal and deep breathing in each posture. Rib cage dilatation was measured as the change in the horizontal chest circumference at the xiphoid process level from maximal expiration to maximal inspiration using a thoracic excursion measuring device (TKK 3345, Takei Instrumentation Co.). Diaphragmatic excursion distance was measured using B-mode ultrasonography (MyLab 25, Hitachi Medical Co.) with a 3.5-MHz convex probe placed at the intersection of the right midclavicular line and the arcus costalis with a longitudinal orientation. Then, the left branch of the portal vein was identified using the inferior vena cava as a landmark, and displacement of the portal vein branch during maximal inspiration and maximal exhalation was measured as the diaphragmatic excursion distance. Analyses were performed using ImageJ image analysis software. Paired t-test were used for statistical comparisons.
Results: Rib cage expansions were 4.2±1.5 cm in upright sitting and 3.6±1.1 cm in slumped sitting positions, indicating a significant difference in expansion between the two postures (p 0.05). Diaphragmatic excursions were 5.9±1.6 cm in upright sitting and 4.9±1.7 cm in slumped sitting positions, again indicating a significant difference in diaphragmatic excursion between the two postures (p 0.05).
Conclusion(s): The mechanism of the decrease in vital capacity in the slumped sitting position is reduction in both rib cage expansion and diaphragmatic excursion. The reduction in rib cage expansion is probably due to limited rib elevation when the ribs rotate anteriorly during forward bending of the thoracic vertebrae. Decrease in diaphragmatic excursion is probably due to sagging of the diaphragm due to decrease in the anterior-posterior diameter of the chest wall in the slumped position, and due to limitation in diaphragmatic descent due to narrowing of the abdominal cavity.
Implications: The decrease in vital capacity in elderly people with kyphosis-like postures may not be related to age, because slumped sitting affects respiratory movement even in young people. It is necessary to evaluate and improve posture in patients with respiratory diseases.
Keywords: upright sitting position, slumped sitting position, ultrasonography
Funding acknowledgements: Nothing
Topic: Human movement analysis; Musculoskeletal: spine; Older people
Ethics approval required: Yes
Institution: Osaka Electro-Communication University
Ethics committee: The ethics review board for studies involving living persons
Ethics number: 14-007
All authors, affiliations and abstracts have been published as submitted.
