Association Between Lumbar Lordosis, Thoracic Kyphosis, and Muscle Activations During Different Low 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 and show the effects of lumbar lordosis and thoracic kyphosis angles on muscle activations during three different low back exercises. Materials and Methods: Participants were divided into hyper lordotic lumbar angle - Increased thoracic kyphosis (n=11) and normal lordotic lumbar - thoracic angle (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 hyper lordotic lumbar angle - increased thoracic kyphosis group (p<0.05). 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 low 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.