or putting a textured one in there...or maybe putting a some sand or dirt in their shoe...
Textured insoles change (we like to think for the better) proprioceptive input and can improve balance and gait performance, both statically and dynamically. We have seen this in folks with parkinsons (1) as well as stroke (2), though it can be used in the elderly (3), in diabetes and neuropathy (4), as well as healthy individuals (5,6). Changes from postural stability, to changes in anterior/posterior sway, to medial/lateral sway, to step length and height, the research is there.
These results support the hypothesis that enhanced somatosensory feedback to the sensory system, both through the spinocerebellar and dorsal column pathways, as well as the vestibular system, results in an improved motor output (and most likely coordination) of gait.
Qiu F, Cole MH, Davids KW, et al. Effects of textured insoles on balance in people with Parkinson's disease. PLoS One. 2013;8(12):e83309. Published 2013 Dec 12. doi:10.1371/journal.pone.00833
Ma CC1, Rao N2, Muthukrishnan S3, Aruin AS4. A textured insole improves gait symmetry in individuals with stroke. Disabil Rehabil. 2017 Aug 7:1-5. doi: 10.1080/09638288.2017.1362477. [Epub ahead of print]
Annino G1,2,3, Palazzo F2, Alwardat MS4, Manzi V5, Lebone P2, Tancredi V1,2,3, Sinibaldi Salimei P2,6,7, Caronti A2, Panzarino M2,3, Padua E2,3. Effects of long-term stimulation of textured insoles on postural control in health elderly. J Sports Med Phys Fitness. 2018 Apr;58(4):377-384. doi: 10.23736/S0022-4707.16.06705-0. Epub 2016 Sep 15.
Paton J, Glasser S, Collings R, Marsden J. Getting the right balance: insole design alters the static balance of people with diabetes and neuropathy. J Foot Ankle Res. 2016;9:40. Published 2016 Oct 5. doi:10.1186/s13047-016-0172-3
Steinberg N1, Tirosh O, Adams R, Karin J, Waddington G. Influence of Textured Insoles on Dynamic Postural Balance of Young Dancers. Med Probl Perform Art. 2017 Jun;32(2):63-70. doi: 10.21091/mppa.2017.2012.
Collings R1, Paton J2, Chockalingam N3, Gorst T2, Marsden J2. Effects of the site and extent of plantar cutaneous stimulation on dynamic balance and muscle activity while walking. Foot (Edinb). 2015 Sep;25(3):159-63. doi: 10.1016/j.foot.2015.05.003. Epub 2015 May 11.