Are there differences in the dual-task walking variability of minimum toe clearance in chronic low back pain patients and healthy controls?

The control of minimum toe clearance (MTC, as quantified with its stride-to-stride variability during walking) is a promising marker to evaluate motor control. The control of MTC, compared to other gait parameters, was reported to have higher priority. The relationship between the control of MTC and other gait parameters should be examined to elucidate tripping mechanisms. This study aimed at investigating the variability of MTC, stride time and stride length in normal walking and in dual-task walking in back pain sufferers. Twelve patients with chronic low back pain and twelve healthy controls walked with inertial sensors attached on their feet with and without a cognitive dual task. Standard deviations of stride time, stride length and MTC were calculated. Regarding the comparison of dual-task walking in pain patients vs. controls, we found higher variability in stride time in the back-pain group. Higher dual-task walking variability was observed in stride length and stride time only in back pain sufferers. Regarding MTC, however, neither a difference between groups nor between walking conditions were found. We observed that individuals with pain, who generally show higher gait variability, are able to control MTC in a dual-task condition indicating that their central nervous system might prioritize control of MTC over other gait parameters. Cases in which also MTC variability increase because of a dual task might characterize alarming fall risk. Dual-task MTC variability should, therefore, be estimated in individuals with severe fall risk as in old individuals with pain, frail people or neurological patients.