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 44: 749-756, 2011