Mechanical pain disorders in the thoracic spine are commonly associated with impairment of mobility. 5 Thoracic spine movement limitation in individuals with mobility impairment is frequently observed in axial rotation, as well as in the sagittal plane, particularly into extension. 6 Achieving end range motion of the shoulder girdle also depends on adequate extension of the thoracic spine. 12 Consequently, observation and measurement of thoracic spine extension mobility is an important part of the physical examination of patients with thoracic spine or shoulder girdle pain disorders. Movement impairments are typically interpreted in relation to the patient's symptoms and with consideration of the expected range of motion of the region being examined. While the mechanics of thoracic motion segments have been examined in cadaveric and modeling studies, 23,26,34 few studies have examined the global and regional mobility of the thoracic spine in vivo.Normative ranges of sagittal spinal motion have been reported for the lumbar spine 4 but not for the thoracic region. This may reflect the sentiment that "extension mobility of the thoracic region is limited and usually not measured." 10 In cross-sectional studies, extension mobility in asymptomatic individuals has been variously reported as being "almost negligible," while others have recorded motion of between 20° and 40°. 18,22,35 These differences can be attributed to age, measurement technique, and the reference position from which the movement was measured.Thoracic spine mobility has been shown to decrease with increasing age, although this decline is more evident in individuals over 60 years of age. 15,22 Though several computerized spinal T T STUDY DESIGN: Cross-sectional study. T T OBJECTIVES:To examine extension mobility of the thoracic spine in young, asymptomatic adults, with particular reference to the influence of subject position and magnitude of the thoracic kyphosis. T T BACKGROUND: Impairment of thoracic extension motion is commonly associated with mechanical pain disorders in this region of the spine. Knowledge of normal thoracic mobility and the factors that may influence this motion is important in the evaluation and management of thoracic pain disorders. T T METHODS:In 40 asymptomatic adults, the total and regional thoracic extension range of motion was measured using 2-dimensional photographic image analysis. Extension mobility was measured in standing, sitting, prone, and 4-point kneeling.The association between the magnitude of the habitual thoracic kyphosis and extension mobility was also examined. T T RESULTS:When measured from the habitual standing position, the mean range of flexion was 11.5° (3.7°) and mean extension range was 8.7° T T CONCLUSION:When measured from the habitual standing position, thoracic extension range of motion in young individuals is small and poorly correlated with the magnitude of the standing thoracic kyphosis. Unloaded positions (4-point kneeling and prone), compared to positions that load the spine (standing and s...