Affiliations: [a] School of Kinesiology and Health Science, York University, Toronto, ON, Canada | [b] Department of Physical Therapy, University of Toronto, Toronto, ON, Canada
Correspondence:
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Corresponding author: Janessa D.M. Drake, School of Kinesiology and Health Science, York University, Toronto, ON, M3J 1P3, Canada. Tel.: +1 416 736 2100 x. 33568; Fax: +1 416 736 5772; E-mail: [email protected]
Abstract: Background:Assessment of trunk muscle co-contraction can provide insight into the behaviour of the trunk musculature, as co-contraction differs between healthy participants and those with low back pain/injury. To date, co-contraction of the trunk musculature has been examined predominately during single-plane and maximal range-of-motion movement tasks. Objective:To assess differences in co-contraction patterns of the trunk musculature as a function of movement task (maximal and combined, mid-range trunk movement tasks) and phase of the movement task. Methods:Thirteen asymptomatic males performed a series of maximal trunk range-of-motion tasks, as well as movement tasks with various combinations of lumbar and thoracic movements ('combined' movement tasks), in both sitting and standing. Co-contraction between all possible pairings of six bilateral muscles (66 in total) was determined and compared between movement tasks and phase of movement. Results:Twisting and combined movement tasks produced greater co-contraction when moving into and/or holding the position, while uncontrolled flexion movement tasks produced the greatest co-contraction when returning to a neutral upright position. Conclusions:Combined movement tasks and tasks involving twisting required greater co-contraction to actively maintain the positions, providing insight into potential mechanisms of injury if the positions were adopted with high repetition or long duration. These findings are applicable to injury prevention, job and workstation design, rehabilitation practices, and return-to-work protocols.
