Does cognitive loading interfere with walking control?

Background: Cognitive-motor interference is a common method used to investigate the cognitive demands of human walking. Using this methodology, consistent effects emerge: under cognitive load, walking velocity decreases, while spatio-temporal variability of walking increases. These effects are often interpreted as indicative of an interference in the ability to control gait. However, walking velocity is highly correlated with most gait parameters; thus, the increase in variability does not necessarily reflect reduced control, but rather a constant signal-to-noise ratio. Methods: To investigate the effect of cognitive loading on gait variability, we retrospectively analysed 3721 records of healthy young adults, walking with and without a concurrent cognitive task, on a treadmill. Results: Stride duration and length increased under cognitive load, while the variability of these parameters decreased. Further, these effects were different between participants starting to walk without cognitive loading and those starting to walk with cognitive loading. Conclusions: Dual tasking is more likely to divert the focus of attention away from the walking task, causing a shift of balance between automatic and conscious control, as opposed to interference per-se.