Effects of the posterior pelvic tilt sitting posture on thoracic morphology and respiratory function.
Yoshihiro Aramaki, Fujiyasu Kakizaki, Shinichi Kawata and 2 others
PMID 33642685WHAT IT FOUND
Sitting with a 30-degree posterior pelvic tilt significantly reduced lung function measures (FVC, FEV1, PFR) in healthy young men.
Milder tilts up to 20 degrees did not impair these respiratory outcomes. The 30-degree posture also restricted lower thoracic expansion.
Key findings
01Forced vital capacity, forced expiratory volume in 1 second, and peak flow rate were significantly lower at 30° posterior pelvic tilt compared to 0°.
02Thoracic expansion volume ratio decreased progressively, with significant reductions at 20° and 30° compared to 0° and 10°.
03The 30° posture caused a significant posterior tilt of the lower thoracic spine and reduced expansion at the lowest thoracic level (D-level), which correlated with reduced respiratory function.
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What it does not show
The study included only 18 healthy young men, so results may not apply to women, older adults, or individuals with existing respiratory or musculoskeletal conditions. Respiratory muscle activity was not measured, so the specific muscular mechanisms behind the reduced expansion were inferred rather than directly observed. The postures were held statically during measurement, which may not reflect dynamic changes during functional tasks or prolonged sitting.
Declared interests
The authors declare no conflicts of interest.
The easy way to misread this
Do not assume that any amount of posterior pelvic tilt impairs breathing. Significant reductions in lung function and thoracic expansion were only observed at the 30-degree tilt; tilts of 10 and 20 degrees did not significantly lower spirometry values compared to neutral.