Spasm and electromyography intensity of bilateral extensor during relaxation period in trunk anterior flexion–extension performance response to sustained asymmetry spinal loading

During sustained asymmetry spinal loading, the NEMG in bilateral HAM has significant increase and the NEMG in bilateral erect spinea has a decrease tendency. After loading, the NEMG has a significant increase, in parallel with spasms elicited in multiple extensors in relation period in flexion-extension performance, with no significant difference between bilateral sides. It may indicate that sustained asymmetry spinal loading could lead to a weakness for tension ability, and/or a micro-damage in spinal bilateral passive tissues in low back area, the risk of developing low back disorder.