Back extensor muscle oxygenation and fatigability in healthy subjects and low back pain patients during dynamic back extension exertion

Abstract

The purpose of this study was to assess if chronic low back pain patients have impaired paraspinal muscle O 2 turnover and endurance capacity as compared to healthy control subjects during dynamic exercise. Middle-aged healthy male subjects ( n = 12, control) and male patients with chronic low back pain ( n = 17, CLBP) participated in the study. L4–L5 level paraspinal muscle fatigue was objectively assessed during earlier validated 90 s dynamic back endurance test (spectral EMG, MPF slope). Also EMG amplitude (EMG amplitude) and initial MPF (MPF initial) were assessed from the initial 5 s of the endurance contraction. Simultaneously near infrared spectroscopy (NIRS) was used for quantitative measurement of local L4–L5 paraspinal muscle O 2 consumption. Subcutaneous tissue thickness (ATT) was measured from the EMG and NIRS recording sites. The results indicated that control and CLBP groups were compatible as regarding anthropometric variables, paraspinal muscle activation levels (EMG amplitude), initial MPF (MPF initial) and ATT. When the ATT was used as a covariate in the ANOVA analysis, CLBP group did not show significantly greater paraspinal muscle fatigability (right MPF slope – 12.2 ± 10.7%/min, left right MPF slope – 12.6 ± 13.3%/min) or O 2 consumption (right NIRS slope – 52.8 ± 79.6 μM/l/s) as compared to healthy controls (right MPF slope – 11.9 ± 7.6%/min, left MPF slope – 12.7 ± 8.6%/min, right NIRS slope – 53.7 ± 95.2 μM/l/s). As a conclusion, these CLBP male patients did not show any impaired rate of paraspinal muscle oxygen consumption or excessive paraspinal muscle fatigability during dynamic exercise as compared with healthy controls. Subcutaneous tissue thickness has a strong influence on the NIRS and EMG amplitude measurements and, if unchecked, it could result in the false interpretation of the results.