Papers of the Week

Chronic low back pain (CLBP) is associated with postural control impairments and is highly prevalent in elderly people. The objective of this study is to verify whether anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) are affected by CLBP in elderly people by assessing their postural control during a self-initiated perturbation paradigm induced by rapid upper arm movement when pointing to a target. The participants' lower limb muscle onset and center of pressure (COP) displacements were assessed prior to perturbation and throughout the entire movement. T moment (i.e., the beginning of the movement) was defined as the anterior deltoid (DEL) onset, and all parameters were calculated with respect to it. The rectus femoris (RT), semitendinosus (ST), and soleous (SOL) showed delayed onset in the CLBP group compared with the control group: RF (control: - 0.094 ± 0.017 s; CLBP: - 0.026 ± 0.012 s, t = 12, p < 0.0001); ST (control: - 0.093 ± 0.013 s; CLBP: - 0.018 ± 0.019 s, t = 12, p < 0.0001); and SOL (control: - 0.086 ± 0.018 s; CLBP: - 0.029 ± 0.015 s, t = 8.98, p < 0.0001). In addition, COP displacement was delayed in the CLBP group (control: - 0.035 ± 0.021 s; CLBP: - 0.015 ± 0.009 s, t = 3; p = 0.003) and presented a smaller amplitude during APA COP [control: 0.444 cm (0.187; 0.648); CLBP: 0.228 cm (0.096; 0.310), U = 53, p = 0.012]. The CLBP group required a longer time to reach the maximum displacement after the perturbation (control: 0.211 ± 0.047 s; CLBP 0.296 ± 0.078 s, t = 3.582, p = 0.0013). This indicates that CLBP elderly patients have impairments to recover their postural control and less efficient anticipatory adjustments during the compensatory phase. Our results suggest that people with CLBP have altered feedforward hip and ankle muscle control, as shown from the SOL, ST, and RT muscle onset. This study is the first study in the field of aging that investigates the postural adjustments of an elderly population with CLBP. Clinical assessment of this population should consider postural stability as part of a rehabilitation program.