Objective: Investigate whether people with Parkinson’s disease (PD) have deficient balance mechanisms following visual perturbations during walking.

Background: We recently showed that maintaining upright balance during walking requires the use of multiple mechanisms that are temporally coordinated to regain upright stability [1,2]. These balance mechanisms are: 1) the lateral ankle roll, altering the ankle inversion/eversion during single stance; 2) foot placement, the location of the foot after swing phase; and 3) the push off mechanism, alteration of the trailing leg ankle plantarflexion angle during double stance. Considering that poor upright stability is a major concern with the progression of PD [3], we investigated how people with PD used these mechanisms in response to visual fall stimuli during walking.

Method: Eleven adults diagnosed with Parkinson’s disease underwent an experimental session walking on an instrumented treadmill for ten two-minute trials in a 3D virtual reality cave. At randomized heel strikes, the visual field was briefly rotated (600 ms), resulting in a perceived fall to the side. Kinematic and muscular responses were measured to determine how people with PD control upright balance in response to a perturbation.

Results: Following a visual perturbation, participants shifted their center of mass (CoM) in the opposite direction of the perceived fall. The CoM displacement during perturbed steps was 0.081 ± 0.053 m larger than during unperturbed steps. Participants showed a diminished ankle roll and push off response in the first post-stimulus step, compared to what was previously seen in healthy young adults[1]. The foot placement mechanism occurred in the second and third steps following a perceived fall, which is later than in healthy young adults.

Conclusion: The larger excursion of the CoM is likely due to deficits in the balance mechanisms. The primary use of the step placement mechanism, while delayed, suggests people with PD rely on proximal balance mechanisms rather than distal ones. Such a shift from distal to proximal control may be related to the well-established proprioceptive deficit in people with PD. Further research will investigate if this difference is due to the pathology of the disease or an aging effect.

References: 1. H. Reimann, T. Fettrow, E. D. Thompson, and J. J. Jeka, “Neural Control of Balance During Walking,” Frontiers in Physiology, vol. 9, no. September, p. 1271, 2018. [Online]. Available: https://www.frontiersin.org/article/10.3389/fphys.2018.01271/full 2. Fettrow T, Reimann H, Grenet D, Thompson E, Crenshaw J, Higginson J, et al. (2019) Interdependence of balance mechanisms during bipedal locomotion. PLoS ONE 14(12): e0225902. https://doi.org/10.1371/journal.pone.0225902 3. Koller, W. C., Glatt, S., Vetere-Overfield, B., & Hassanein, R. (1989). Falls and Parkinson’s disease. Clin.Neuropharmacol., Vol. 12, pp. 98–105.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deficient-balance-mechanisms-during-walking-in-people-with-parkinsons-disease/