Effect of dual tasking on anticipatory and compensatory postural adjustments in response to external perturbations in individuals with nonspecific chronic low back pain: Electromyographic analysis

BACKGROUND: In patients with chronic low back pain (CLBP), postural control is a demanding task in terms of attention. Although the attentional demands of postural control have been investigated in these patients, the attentional demands of postural recovery during dual task performance have not been evaluated in patients with nonspecific CLBP. OBJECTIVE: To investigate the effect of dual tasking on anticipatory and compensatory postural adjustments in response to an external perturbation in patients with nonspecific CLBP. METHODS: Twenty-five patients with nonspecific CLBP of at least 3 months' duration and 25 healthy persons were exposed to predictable and unpredictable external perturbations. The attentional demands of postural adjustments were evaluated while participants simultaneously performed a cognitive task. Onset latency and integrated electromyographic activity of the trunk and leg muscles were compared between dual task (postural recovery and backward digit span memory) and single task conditions (postural recovery only). RESULTS: The results showed delayed activation of the tibialis anterior (agonist) and early activation of the gastrocnemius (antagonist) muscles during the dual task in patients with nonspecific CLBP compared to healthy participants. Integrated electromyographic activity was significantly greater in the dual task than the single task condition in the gastrocnemius (antagonist) muscle in patients with nonspecific CLBP compared to healthy persons during unpredictable perturbations. CONCLUSION: The impaired ankle muscle activities during a cognitive task suggest that postural control recovery following external perturbation requires attentional resources in patients with nonspecific CLBP. This may increase the risk of re-injury in people with nonspecific CLBP while they perform an attentionally demanding task in more difficult circumstances.