This study’s goal was to compare the effect of dual tasking on postural and cognitive performance between participants with and without nonspecific chronic low back pain. In this 3-factor mixed-design study, dynamic postural stability was assessed in 15 patients with chronic nonspecific low back pain and 15 age-, sex-, and size-matched asymptomatic participants. Bilateral stance on a Biodex Balance System was investigated at 3 levels of postural task difficulty (different platform stabilities levels with eyes open and closed) and 2 levels of cognitive task difficulty (with or without auditory Stroop test). We measured anterior-posterior, medial-lateral, and overall indices for postural performance. Average reaction time and error ratio of a modified auditory Stroop test were calculated as measures of the cognitive task performance. Mixed-design 3-way analyses of variance revealed significant interactions. Post hoc 2-way analyses of variance showed significant group by cognitive task difficulty for anterior-posterior (P < .001), medial-lateral (P = .003), and overall stability indices (P < .001) on a stiffness level of 5 with eyes closed. At this level, significant differences between single- and dual-task conditions for anterior-posterior (P < .001), medial-lateral (P = .02), and overall stability indices (P < .001) were found only in the chronic low back pain group. Also, at the most difficult postural conditions, participants with chronic low back pain increased their error ratio (P = .002), whereas matched asymptomatic individuals’ reaction time increased (P < .01) of the auditory Stroop test.
The study found that postural task performance is attenuated by cognitive loading at a moderate level of postural task difficulty. Due to this, to observe the effect of attentional demands of postural control, task difficulty ought to be considered.