Reliability of postural stability in male subjects with and without non specific low back pain during holding dynamic load

Low back pain after load- holding and carrying can result in significant functional disability and financial disadvantage. Dynamic load-holding imposes varying torque on intervertebral joints and endangers the balance. The goal of the present study was to study the reliability of the postural stability during holding dynamic load for more accurate evaluation of lumbar spine injury.

Participants in this study were 12 healthy men and 12 male patients with low back pain (LBP), subjects were assessed 3 times in 8 conditions while they held dynamic loads in neutral and flexed trunk positions. Center of pressure (COP) data including displacement, velocity, path length and their respective standard deviations (SD) in anterior-posterior (AP) and medial-lateral (ML) directions were assessed. Relative reliability was measured using intra class correlation coefficient (ICC) while absolute reliability was obtained via standard error measurement (SEM) and minimal metrically detectable change (MMDC).

Healthy subjects’ velocity in ML direction (0.8-0.9), LBP patients’ velocity and its SD in AP direction (0.7-0.9) had the highest reliability among the parameters of interest. Reliability of displacement in ML direction and its respective SD yielded similar results in both groups (0.6-0.9). Reliability of displacement and its SD in ML direction and path length in healthy subjects were more than those of LBP patients.

Velocity of center of pressure in both AP and ML directions are suggested as appropriate parameters for evaluation postural stability during dynamic load- holding in subjects with and without non specific low back pain.