The effect of prolonged sitting on neuromuscular and biomechanical responses of the low back in healthy individuals

Greene, Ryan (2019) The effect of prolonged sitting on neuromuscular and biomechanical responses of the low back in healthy individuals. Masters thesis, Memorial University of Newfoundland.

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Abstract

Background: Sub-maximally flexed spine postures have the potential to elicit creep (lengthening) in the posterior passive tissues of the spine leading to a delay in the normal muscle reflexes of the spine. This scenario could result in a low back injury when a sudden perturbation is experienced following a prolonged period of sitting. Methods: 17 men and 23 women were recruited to examine the effect sitting in an office chair had on the reflex onset times of muscles in the low back. Surface EMG of the low back, and lumbar spine and pelvic angles were collected continuously through all trials. Muscle reflexes were elicited immediately before and after exposure to 2 hours of sitting, and onset times were compared. Results: Low back muscle reflexes were non-significantly longer after sitting for two hours (72.89 ms ± 38.72) as compared to pre-sitting latencies (60.00 ms ± 27.77). No significant interactions or main effects of pain groups or sex were found for reflex times. Conclusion: Sitting for two-hours in an office chair does not appear to affect the ability of the low back muscles to respond to a sudden perturbation. This conclusion holds for males and females as well as those who develop transient sitting-induced pain. Future work should examine if longer periods of sitting and/or different chair conditions and spine postures induce delayed reflexes.

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