Is the fear avoidance model associated with the reduced level of aerobic fitness in patients with chronic low back pain?

OBJECTIVES

To compare aerobic fitness of patients with chronic low back pain (CLBP) against healthy controls and to assess whether variables of the fear avoidance model are associated with loss of aerobic fitness.

DESIGN

A case-comparison study.

SETTING

Rehabilitation centers.

PARTICIPANTS

Patients with CLBP (n=223), and normative data from healthy subjects (n=18,082).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Maximal oxygen uptake (VO2max) was estimated on the basis of a modified submaximal Astrand bicycle test performed by patients with CLBP (observed level of aerobic fitness) and compared with the normative data of healthy controls matched for age, sex, and level of sport activity (expected level of aerobic fitness). Pain (visual analog scale); disability (Roland Disability Questionnaire); pain-related fear (Tampa Scale for Kinesiophobia); depression (Beck Depression Inventory); catastrophizing (Pain Catastrophizing Scale); and the level of activity during sport, work/household, and leisure time (Baecke Physical Activity Questionnaire) were assessed. Multiple linear regression analysis was performed with the difference of the observed and expected level of aerobic fitness as dependent variable and putative influential factors including those of the fear avoidance model as independent variables.

RESULTS

VO2max could be calculated in 175 (78%) of the patients. Both men and women with CLBP had significant lower VO2max than expected (10.3mL/kg lean body mass (LBM)xmin(-1) and 6.5mL/kg LBMxmin(-1), respectively; P<.001). The levels of activity during leisure time and work/household were significantly associated with this reduced level of aerobic fitness. However, the variables of the fear avoidance model were not.

CONCLUSIONS

Most patients with CLBP-associated disability have a lower level of aerobic fitness, but this is not associated with fear avoidance.