Acute effect of Prone Trunk-Extension on the biomechanical properties of lumbar and dorsal lower limb muscles

Abstract Background: Fascia attaches to and wraps around muscles throughout the body to expand the range of action and redistribute force transmission. However, specific data on the myofascial tensegrity network of the lumbar and lower limbs are lacking. Objective: This study investigated the effect of the prone trunk extension test (PTE) on muscle stiffness in the lower limbs, explored the optimal angle for lumbar muscle training, and analyzed the mechanical conduction patterns of the lumbar and lower limb muscles in the myofascial tension network. Design: This was a laboratory-based experimental study. Method: Twenty healthy young females were recruited for this study, and the stiffness of the erector spinae (ES), semitendinosus (ST), biceps femoris (BF), the medial head of the gastrocnemius (MG), and lateral head of the gastrocnemius (LG) was measured by MyotonPRO under four angular PTE conditions (0° horizontal position, 10°, 20°, and 30°). Results: With the increasing angle, the stiffness of ES decreased gradually, while ST and BF increased first and then decreased. The stiffness of MG and LG increased first and then decreased and then increased. There was a negative correlation between ES stiffness variation and ST (r=-0.819 to -0.728, p<0.001), BF (r=-0.620 to -0.527, p<0.05), MG (r=-788 to -0.611, p<0.01), and LG (r=-0.616 to -0.450, p<0.05). Conclusions: Horizontal PTE maximizes activation of ES. There is a tension transfer between ES, hamstrings, and gastrocnemius, mainly between ST and LG. The study provides data to explore the myofascial tensegrity network between the lumbar and lower limb muscles.