Passive trunk loading influences muscle activation during dynamic activity

Introduction: Repetitive loading of the low back tissues induces tension relaxation with a corresponding variation in the myoelectric response of the neuromuscular system, which may influence low back health. The purpose of this study was to observe trunk muscle activities before and after a passive cyclic trunk flexion–extension exercise. Methods: Nineteen participants were subjected to sagittal plane loading of the low back tissues. These individuals performed toe‐touching before and over 1 hour after load termination. Results: Lumbar paraspinal activity cessation occurred significantly sooner over time during lumbar and pelvic flexion post‐loading, as compared with pre‐loading. Lumbar paraspinal activity then re‐initiated later in lumbar extension. There was no change in peak or average muscle activity during the procedures. Conclusions: It is apparent that passive loading of the viscoelastic lumbar tissues results in a prolonged neuromuscular adaptation, followed by possible neuromuscular compensation sustained within 1 hour of load termination. Muscle Nerve, 2011