Functional lifting assessment for determining impairment in low back pain patients compared with asymptomatic controls.

BACKGROUND

People with low back pain (LBP) commonly report functional impairment in activities of daily living, such as bending and lifting. A standardized, performance-based lifting assessment that can be applied in a clinical setting may provide a quantifiable measure for this impairment.

OBJECTIVE

This study investigates the usability and reliability of a lifting assessment for detecting functional impairment in individuals with LBP compared with asymptomatic controls (CTRLs).

METHODS

Forty-eight LBP patients [29 women/19 men, age 39 ± 11 years, height 175 ± 9 cm, weight 77 ± 16 kg, pain intensity ≥3 on the numerical rating scale (NRS; 0-10)] and 37 age- and sex-matched controls (27 women/10 men, age 39 ± 12 years, height 172 ± 10 cm, weight 73 ± 15 kg) performed four box-lifting tasks: squat and stoop lifting, each without (0%) and with additional weight (20% body weight) in a standardized sequence (squat 0%, stoop 0%, squat 20%, stoop 20%). Each lifting task was performed twice consecutively (T1 and T2). Time to task completion (TTC, s) was defined as the main outcome measure. Descriptive statistics are presented as mean ± SD. Group comparisons were analyzed pairwise and using two-way repeated-measures ANOVA with Bonferroni correction (mean of T1 and T2; α=0.0125). Test-retest reliability (T1 vs. T2) was assessed using the ICC, TRV%, and Bland-Altman analysis. Test performance and cut-off values were analyzed using receiver operating characteristics (ROC) curve, including the area under the curve (AUC) and Youden's index.

RESULTS

LBP patients revealed higher TTC values across all lifting conditions (4.0 ± 0.9 to 5.0 ± 1.8 s) compared with asymptomatic controls (difference of 2.8 ± 0.4 to 3.2 ± 0.4s; p < 0.001; interaction effect p = 0.005). Reliability analysis revealed ICC value ranging from 0.85 to 0.95 s, TRV values from 6% to 8%, and bias values from 0.05 to 0.34 s. ROC analysis showed an AUC ranging from 0.915 to 0.923 and threshold values from 3.5 to 3.7s.

DISCUSSION: TTC of a simple lifting task is a reliable measure that effectively differentiates people with functional limitations due to LBP from their asymptomatic counterparts, who complete the tasks more quickly and with less variability in completion time. Nevertheless, the responsiveness of this assessment remains to be clarified before its applicability in a clinical setting can be fully determined.