★Assistant professor Sado and Ph.D. student Tominaga article was published in International Journal of Sports Medicine.
The psoas major originates from the lumbar spine and inserts onto the femur, passing anterior to the pelvis. It is a key muscle for forward leg swing during running. However, due to its lower force-generating capacity when lengthened, excessive hip extension during high-speed running has been considered disadvantageous for force generation. Previous discussions on psoas major length, however, have neglected lumbar spine motion, to which the psoas major attaches. Recent work by Assistant Professor Sado and colleagues (Tominaga et al., J Biomech, 2025) demonstrated that the lumbar spine becomes increasingly lordotic as running speed increases. Based on this, they hypothesised that lumbar spine motion may affect psoas major length during running.
In this study, they aimed to examine the effect of lumbar spine motion on psoas major length across a wide range of running speeds. To do so, they established three-dimensional lumbar spine–pelvis–femur musculoskeletal models and estimated psoas major length during running. The results revealed that lumbar spine motion mitigates the elongation of the psoas major even when hip extension becomes greater at higher running speeds. This finding suggests that lumbar spine motion may help preserve the force-generating capacity of the psoas major during high-speed running. By quantitatively demonstrating the effect of spinal motion on muscle behaviour, this study provides a novel functional perspective on lumbar spine motion during running.
【Title】Effect of lumbar spine motion on psoas major length during running at different speeds
【Author】Tempei Tominaga, Natsuki Sado
【Journal】International Journal of Sports Medicine
【Date】18 October 2025
【DOI】10.1055/a-2726-4968
International Journal of Sports Medicine
