Association Between Lumbar Lordosis, Thoracic Kyphosis, and Muscle Activations During Different Lower Back Exercises: An Observational Study

Background and Objectives: Angular modifications in the physiological curvatures of the spine have been associated with spinal dysfunction and altered biomechanics, which may contribute to musculoskeletal complaints. The main objective of this experimental study was to investigate the association between lumbar lordosis and thoracic kyphosis angles and muscle activations during three different lower back exercises. Materials and Methods: Participants were divided into a hyperlordotic lumbar angle group—with increased thoracic kyphosis (n = 11)—and a normal lordotic lumbar thoracic angle group (n = 11). Thoracolumbar muscular activities during three different exercises were measured by surface electromyography. Results: Muscular activity was less in almost all exercises (except iliocostalis lumborum-pars lumborum) in the hyperlordotic lumbar angle/increased thoracic kyphosis group (p < 0.05). The unstable superman exercise was the exercise that produced the most muscular activity in both groups (p < 0.05). Conclusions: The study analyzed the association between lumbar lordosis, increased thoracic kyphosis, and muscle activations during specific lower back exercises. These findings highlight the relationship between spinal alignment and muscular responses during functional tasks, which may inform future biomechanical research or rehabilitation strategies.