The pain-related impairment, the skeletal muscle index, and the functional performance inventory of individuals with chronic low back pain: a correlation study

      Objectives were to: 1) quantify the pain-related impairments (PRI) of individuals with chronic low back pain (CLBP) using the Pain Disability Questionnaire (PDQ); spinal flexion (SFS) and extensor strength (SES) by 1-Repetition-Maximum Method (1RM); and, skeletal muscle index (SMI) using the Bioelectric Impedance Analysis (BIA); and, 2) investigate the correlation between PRI, SMI, & SFS/SES and Functional Performance Tests (FPT) scores. A retrospective study was undertaken in an outpatient rehabilitation clinic. Thirty-eight subjects with CLBP (24 women) completed the PDQ. The PDQ measured PRI stratified as: mild, moderate, severe, and extreme. The BIA measured the SMI, calculated using a BIA prediction equation. The 1RM measured the SFS and SES. FPT included: Sit-to-Stand (STS), Loaded-Reach (LR), and 50-feet-Walk-Fastest (FWF) tests. The Shapiro-Wilk test suggested that FPT scores were non-normal (all p<0.05); therefore, nonparametric tests were used. Several variables differed among PRI categories; data were separated by mild/moderate (m/m) and severe/extreme (s/e) for correlation analysis. For m/m, PRI correlated with LR (r=-.544, p=.036). For s/e, PRI correlated strongly with: SES (r=-.650, p=.009), STS (r=.461, p=.047), and FWF (r=.583, p=.009). Also for s/e, the FWF correlated with SFS (r=-.642, p=.007) and SES (r=-.784, p=.001). There were no statistical differences between genders. In both PRI groups, SMM and SMI also did not differ. Individuals with CLBP and mild/moderate PRI had low functional performance with loaded-reach activities, while those with severe/extreme PRI had poor performance due to decreased SES, poor sit/stand changing positions, and longer walking duration. In s/e, walking performance is influenced by PRI and spinal strength. These findings possibly describe the clinical pain characteristics as the long-term CLBP effects progress. The PDQ can be a valuable clinical tool in assessing PRI of individuals with CLBP. Further research on the PDQ & FPT scores, amongst other disorders such as neuropathic pain, would be beneficial.