The Effect of Prolonged Sitting on Trunk Muscle and Kinematics Responses to Suddenly Applied Loads

Prolonged sitting facilitates individuals to adopt detrimental postures that may lead to the development of low back discomfort. Interestingly, subjecting individuals to unexpected trunk perturbations can reveal altered trunk muscle activation, kinematics, and kinetics. In this research participants were exposed to two-1hr prolonged sitting exposures. Prior to, between, and post sitting exposures a 6.78 kg load was unexpectedly applied to the participants hands to perturb them. Trunk muscle electromyography, trunk kinematics, and centre of pressure (of the feet) were recorded during these unexpected perturbations. Participants who developed low back discomfort displayed increased muscle activation and longer muscle latency times in response to the unexpected perturbations. Likewise, these participants also displayed decrease centre of pressure and trunk angle displacement. Therefore, the responses to the unexpected perturbations displayed innate neuromuscular actions of the trunk that appear to increase the likelihood of an individual developing low back discomfort during prolonged sitting.