The role of current mood and stop rules on physical task performance: an experimental investigation in patients with work-related upper extremity pain.

Patients with work-related upper extremity pain (WRUED) experience disability in daily life activities. The factors that influence levels of disability are still unclear. Both excessive avoidance and persistence have been suggested, but the affective and motivational processes that underlie these behaviours have not been scrutinized. This study was aimed at examining the role of current mood and stop rules on physical task performance, controlling for gender, pain severity, pain catastrophizing, and pain-related fear. An additional focus was the role of the interaction between current mood and stop rules as predicted by the novel Mood-as-Input (MAI) model. Following MAI, it is the informational value of current mood within a goal context (stop rule), rather than mood per se that predicts behaviour. A 2 (mood) x 2 (stop rule) x 2 (physical task order) factorial design was used in which 62 WRUED patients performed an upper and lower extremity physical task. A stress interview was used to induce positive and negative mood. Patients received either an "as-much-as-can (AMAC)" stop rule instruction, or a "feel-like-discontinuing (FLDC)" stop rule instruction. Results showed that physical task performance was predicted by pain-related fear, current mood, stop rule. However, the predicted mood x stop rule interaction was not found, and there was no influence of gender, pain severity, and pain catastrophizing on task performance. The findings suggest that not only pain-related fear, but current mood and goal context factors independently affect physical performance in patients with WRUED.