Treatment of patients with chronic low back pain and its evolving disability primarily tries to improve the patients' levels of activities and participation. Mostly, self-reported questionnaires have been used for clinical as well as research purposes to assess daily functioning (1, 2), of which the most commonly used will be discussed below. However, this information may not necessarily reflect the real capacity of a patient's performance. A recent review showed that the correlation of self-reported disability and physical activity level was at best moderate for patients with chronic low back pain (3). In order to improve objectivity, measures of body function, e.g., spinal mobility and lumbar extensor muscle strength, have been used, although the correlation with the level of disability is very weak (4, 5). Furthermore, there are major concerns about reliability and validity (6–8).
Besides the self-reported disability measures, many have urged to use more objective and direct measures of low back pain–specific functional capacity (5, 9, 10). Capacity is defined as the highest probable level of functioning that a person may reach in an activity domain at any given moment in a standardized environment. Although there is still no consensus for the definition of functional capacity evaluation (FCE), in the past decades, several FCE measures have been developed, of which the Isernhagen Work Systems Functional Capacity Evaluation (IWS-FCE) is among the most frequently used (11, 12). However, recently published psychometric data have shown that some of the tasks included in the IWS-FCE are not reliable (13, 14). Unfortunately, the entire sequence of tasks in, for example, the IWS-FCE, is time consuming and expensive, as is the training of the test observer. Therefore, we have decided not to include these measures in this review.
Nevertheless, in order to keep up with, for example, the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials recommendations to evaluate several core outcome domains, including physical functioning (9), we wanted to include easy to use performance tasks. Several tasks have been described (8, 15–17), but most of them are not low back pain specific, and some, such as the Back Performance Scale, show insufficient factor structure, as in this measure the quality of the performance is also scored (1, 18). Therefore, we decided only to include a performance task that assesses lifting, an activity that specifically might be hampered by low back pain.
For the selection of the self-reported disability questionnaires and lifting performance tasks, we only selected questionnaires/tests that are low back pain specific and of which all psychometric, including responsiveness, properties have been studied in relevant low back pain populations and published in peer-reviewed journals.
Other criteria for selection were: being available in at least English and for performance task measures, easy to administer, inexpensive, and not time consuming when used in clinical practice.