Sagittal imbalance such as flattened lumbar spine and reduction in lumbar lordosis is an essential clinical sign of back health problems. This study investigated the difference in upper body (thoracic) acceleration during gait in young individuals with lumbar flat back posture. A total of 22 younger, asymptomatic volunteers were divided into two groups: those with reduced lumbar lordosis (RLL, lumbar lordosis <20°) and those with normal lumbar lordosis (NLL, 20° ≤ lumbar lordosis < 30°). Participants walked 7 m at a self-determined speed with an accelerometer attached over the T7 spinous process. The T7- normalized medial–lateral (ML) acceleration was higher in the NLL group, whereas the T7 anterior–posterior (AP) acceleration was higher in the RLL group. These findings suggest that lumbar posture affected thoracic acceleration, and that the AP thoracic velocity changed more frequently in individuals with RLL than in subjects with normal lordosis during walking. Therefore, the RLL group required AP directional movement control during walking to improve walking efficiency.
