Physical Abilities in Low Back Pain Patients: A Cross-Sectional Study with Exploratory Comparison of Patient Subgroups

Abstract

An abundance of literature has investigated the association between low back pain (LBP) and physical ability or function. It has been shown that LBP patients display reduced range of motion, decreased balance ability, impaired proprioception, and lower strength compared to asymptomatic persons. The aim of this study was to investigate the differences between LBP patients and healthy controls in terms of several physical abilities. Based on the premised that different biomechanical and physiological causes and consequences could be related to different types of LBP, a secondary exploratory attempt of the study was to examine the differences between LBP subgroups based on the pain location (local or referred) or type of pathology (discogenic or degenerative) on the level of impairment of function and ability. Participants performed range of motion tests, trunk maximal voluntary contraction force tests, a sitting balance assessment, the timed up-and-go test, the chair rise test, and the trunk reposition error test. Compared to the control group, symptomatic patients on average showed 45.7% lower trunk extension (p < 0.001, η² = 0.33) and 27.7 % lower trunk flexion force (p < 0.001, η² = 0.37) during maximal voluntary contraction. LBP patients exhibited decreased sitting balance ability and lower scores in mobility tests (all p < 0.001). There were no differences between groups in Schober's test and trunk repositioning error (p > 0.05). No differences were observed among the LBP subgroups. The exploratory analyses are limited by the sample size and uncertain validity of the diagnostic procedures within this study. Further studies with appropriate diagnostic procedures and perhaps a different subgrouping of the LBP patients are needed to elucidate if different types of LBP are related to altered biomechanics, physiology, and function.

Keywords: biomechanics; degeneration; discogenic pain; flexibility; function; low back pain; mobility; radiated pain; strength.

Figure 1

Sitting balance test (A), and measurements of strength for trunk lateral flexors (B), flexors (C), and extensors (D).

Figure 2

Differences between groups regarding sacrum inclination (left panel) and center of pressure (CoP) velocity during sitting balance test (right panel). § denotes a statistically significant main effect of one-way analysis of variance, and * indicates statistically significant post-hoc comparisons (p < 0.005).

Figure 3

Differences between groups regarding trunk extension (upper), trunk flexion (middle), and trunk lateral flexion (lower) strength. Note that only left lateral flexion is shown, as both sides showed virtually identical results. § denotes a statistically significant main effect of one-way analysis of variance, and * indicates statistically significant post-hoc comparisons (p < 0.005).