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The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing). Breathing behavior was continuously monitored, and dyspnea was rated every 10 s. The within-subject correlations between dyspnea on the one hand and end-tidal CO2 and minute ventilation on the other were used to index the degree to which perceived dyspnea was related to specific relevant respiratory changes. The results showed that perceived symptoms were less strongly related to relevant physiological parameters in MUS patients than in healthy persons, specifically when afferent physiological input was relatively weak. This suggests a stronger role for top-down psychological processes in the symptom perception of patients with MUS.

Background Most studies fail to show an association between higher levels of pain‐related fear and protective movement behaviour in patients with chronic low back pain (CLBP). This may be explained by the fact that only general measures of pain‐related fear have been used to examine the association with movement patterns. This study explored whether task‐specific, instead of general measures of pain‐related fear can predict movement behaviour. Methods Fifty‐five patients with CLBP and 54 healthy persons performed a lifting task while kinematic measurements were obtained to assess lumbar range of motion (ROM). Scores on the Photograph Daily Activities Series‐Short Electronic Version (PHODA‐SeV), Tampa Scale for Kinesiophobia and its Activity Avoidance and Somatic Focus subscales were used as general measures of pain‐related fear. The score on a picture of the PHODA‐SeV, showing a person lifting a heavy object with a bent back, was used as task‐specific measure of pain‐related fear. Results Lumbar ROM was predicted by task‐specific, but not by general measures of pain‐related fear. Only the scores on one other picture of the PHODA‐SeV, similar to the task‐specific picture regarding threat value and movement characteristics, predicted the lumbar ROM. Compared to healthy persons, patients with CLBP used significantly less ROM, except the subgroup with a low score on the task‐specific measure of pain‐related fear, who used a similar ROM. Conclusions Our results suggest to use task‐specific measures of pain‐related fear when assessing the relationship with movement. It would be of interest to investigate whether reducing task‐specific fear changes protective movement behaviour. Significance This study shows that lumbar range of motion in CLBP is predicted by task‐specific, but not by general measures of pain‐related fear. This suggests that both in clinical practice and for research purposes, it might be recommended to use task‐specific measures of pain‐related fear when assessing the relationship with movement behaviour. This may help to disentangle the complex interactions between pain‐related fear, movement and disability in patients with CLBP.