Arm swing and Gait Stability

"When discussing the effects of arm swing on gait stability, it is
necessary to start with a definition of gait stability. In steady-state gait, infinitesimally small perturbations are ever present, and the system’s response to such perturbations may be called local stability. When gait is externally perturbed, global stability can be assessed by quantifying the response to such a perturbation. Following Bruijn et al. [12], in human gait, this response may be divided into two phases: an initial phase, which is dependent upon both the steady state of the system (as it was before the perturbation) and the system’s intrinsic mechanical properties (e.g. inertia, stiffness), and a second, reactive phase (‘recovery’), which is mainly dependent on active control and reflexes." - P. Meyns et al. / Gait & Posture 38 (2013) 555–562

*The how and why of arm swing during human walking
Pieter Meyns a,1 , Sjoerd M. Bruijn a,b,1, Jacques Duysens a,c,

Does slowing gait increase gait stability ?

As this study suggests, it has been difficult to find studies that establish a clear connection between gait stability and gait speed. One can easily assume that slowing down increases stability, we do it on slippery surfaces, we do it when a joint is painful, even the elderly do it naturally everyday. Walking speed, step length, step frequency, step width, local dynamic stability , and margins of stability were measured in this study below. It was found that the subjects did not change walking speed in response to the balance perturbations rather they made shorter, faster, and wider steps with increasing perturbation intensity. They became locally less stable in response to the perturbations but increased their margins of stability in medio-lateral and backward direction. 

So what did they conclude ?  Here are their words,“In conclusion, not a lower walking speed, but a combination of decreased step length and increased step frequency and step width seems to be the strategy of choice to cope with medio-lateral balance perturbations, which increases Margins of Stability (MoS) and thus decreases the risk of falling.”

It is my assumption, and this just seems logical, that if the perturbations were to continue constantly, that one would slow the gait speed to reduce the need for these shorter, faster and wider steps. 

Dr. Shawn Allen

http://www.ncbi.nlm.nih.gov/pubmed/22464635

Gait Posture. 2012 Jun;36(2):260-4. doi: 10.1016/j.gaitpost.2012.03.005. Epub 2012 Mar 29.Speeding up or slowing down?: Gait adaptations to preserve gait stability in response to balance perturbations.Hak L¹, Houdijk H, Steenbrink F, Mert A, van der Wurff P, Beek PJ, van Dieën JH.