The characteristics of postural sway were assessed in quiet standing under three different postural task conditions in 14 patients with nonspecific chronic low back pain and 12 healthy subjects using linear and nonlinear center of pressure parameters. The linear parameters consisted of area, the mean total velocity, sway amplitude, the SD of velocity, and the phase plane portrait. The nonlinear parameters included the Lyapunov exponent, sample entropy, and the correlation dimension. The results showed that the amount of postural sway was higher in the patients with low back pain compared with the healthy subjects. Assessing the nonlinear parameters of the center of pressure showed a lower sample entropy and a higher correlation dimension in the patients with low back pain compared with the healthy subjects. The results of this study demonstrate the greater regularity and higher dimensionality of the center of pressure fluctuations in patients with nonspecific chronic low back pain, which suggests that these patients adopt different postural control strategies to maintain an upright stance.
Fatemeh Azadinia, Ismail Ebrahimi-Takamjani, Mojtaba Kamyab, Morteza Asgari, and Mohamad Parnianpour
Rasool Bagheri, Ismail Ebrahimi Takamjani, Mohammad R. Pourahmadi, Elham Jannati, Sayyed H. Fazeli, Rozita Hedayati, and Mahmood Akbari
The first purpose was to investigate the trunk muscle endurance, the second aim was to evaluate the trunk–pelvis kinematics during gait, and the third was to evaluate the relationship between trunk–pelvis kinematics and the trunk muscle endurance. Thirty participants (15 nonspecific chronic low back pain [NCLBP] and 15 healthy) were included. The authors first assessed trunk muscle endurance on endurance testing protocols. The authors next measured the trunk–pelvis kinematics during gait using a 3-dimensional motion capture system. Angular displacement, waveform pattern (CVp), and offset variability (CVo) were also examined. Statistical analysis revealed a significant difference in (1) the trunk muscle endurance and (2) sagittal, frontal, and transverse planes CVp between groups (P < .05). A significant moderate correlation was found between supine double straight-leg raise and frontal CVp (r = .521, P = .03) and transverse planes CVp (r = .442, P = .05). However, a significant moderate correlation was observed between prone double straight-leg raise and sagittal plane CVp (r = .528, P = .03) and transverse plane CVp (r = .678, P = .001). The relationship between (1) lower trunk extensor endurance with transverse and sagittal planes CVp and (2) lower abdominal muscle endurance with transverse and frontal planes CVp suggests that gait variability in these planes may result because of trunk muscle deconditioning accompanying NCLBP.