The Spine Lengthens During Walking in Healthy Participants, with Age-Related Changes in Kinematic Parameters

Background: While the importance of the upper and lower limbs in locomotion is well understood, the kinematics of the trunk during walking remains largely unexplored. Two decades ago, a casual observation was reported indicating spine lengthening in a small sample of mostly children during walking, but this observation was never replicated. Objectives: This study aims to verify the preliminary observation that spine lengthening occurs during walking and to explore changes in spine kinematics across three different age groups. Methods: A convenience sample of 45 healthy participants was divided into three groups of 15 individuals each: children (ages 5 to 13), young adults (ages 18 to 30), and older adults (ages 50 to 70). The spinal length, defined as the distance between C7 and the coccyx, and other kinematic parameters were analyzed using a motion analysis system while participants stood and walked standing and walking at their natural cadence. Results: In all groups, the length of the spine increased while walking compared to standing. This change was primarily due to a reduction in the inferior spinal angle, which is associated with lumbar lordosis, rather than a change in the superior spinal angle, which is related to thoracic kyphosis. The average change in spinal length during the walking cycle was approximately 7% in children, while it was only about 1% in adults. We also found a reduction in the range of motion for almost all the variables in adults. Conclusions: The increase in the spinal length during walking is related to a reduction in the physiological spine curve. This occurs due to muscle contractions which are needed to stabilize the locomotor system. As people age, the reduction in spinal length changes is associated with decreased spinal mobility and to a natural tendency toward anterior trunk flexion.