Parkinsonism and Related Disorders 80 (2020) 133–137 Available online 20 September 2020 1353-8020/© 2020 Elsevier Ltd. All rights reserved. Short communication Action observation improves sit-to-walk in patients with Parkinson’s disease and freezing of gait. Biomechanical analysis of performance Susanna Mezzarobba a, b, d , Michele Grassi a , Lorella Pellegrini b , Mauro Catalan b , Bj¨ orn Krüger c , Lara Stragapede b , Paolo Manganotti b, d , Paolo Bernardis a, * a Department of Life Sciences, University of Trieste, Italy b Azienda Sanitaria Universitaria Giuliano Isontina, Italy c Gokhale Method Institute, CA, USA d Department of Medical, Surgical and Health Sciences, University of Trieste, Italy A R T I C L E INFO Keywords: Freezing of gait Action observation Sit to walk Parkinson’s disease Postural instability ABSTRACT Introduction: Freezing of gait (FoG) is one of the most disabling gait disorders in Parkinson’s disease (PD), refecting motor and cognitive impairments, mainly related to dopamine defciency. Recent studies investigating kinematic and kinetic factors affecting gait in these patients showed a postural instability characterized by disturbed weight-shifting, inappropriate anticipatory postural adjustment, worse reactive postural control, and a diffculty executing complex motor tasks (i.e. sit-to-walk). These symptoms are diffcult to alleviate and not very responsive to Levodopa. For this reason, additional therapeutic actions based on specifc therapeutic protocols may help patients with their daily lives. We conducted a randomized control trial aimed to test if two clinical protocols for PD patients with FoG were effective to improve postural control. Methods: Rehabilitation protocols, conceived to improve gait, were based on learning motor exercises with the Action Observation plus Sonifcation (AOS) technique, or by the use of external sensory cues. We collected biomechanical data (Center of Mass COM, Center of Pressure COP, and moving timings), using the sit-to-walk task as a measure of motor and gait performance. Results: Kinetic and kinematic data showed that when treatment effects consolidate, patients treated with AOS protocol are more effcient in merging subsequent motor tasks (sit-to-stand and gait initiation), and diminished the total moving time and the area of the COP positions. Conclusion: We demonstrated for the frst time that PD patients with FoG treated with an AOS protocol aimed at relearning appropriate gait patterns increased balance control and re-acquired more effcient postural control. 1. Introduction Freezing of gait (FoG) is one of the most disabling gait disorders in Parkinson’s disease (PD), and because of its transient nature, assessment is based on subjective reports from patients [1]. Recent studies in pa- tients with PD and FoG [2] showed a strong postural instability char- acterized by disturbed weight-shifting, inappropriate anticipatory postural adjustment, worse reactive postural control, and increased foot step variability. Another important issue is the diffculty in executing complex motor tasks that require dynamic postural stability between different phases – such as the sit-to-walk transition – commonly prac- ticed in daily life, and highly demanding in terms of balance mainte- nance. Recently, Palmisano and colleagues [3] showed that motor tasks that involve wide ranges of joint motion (i.e. sit-to-walk) are particularly impaired in PD patients prone to falls, such as patients with FoG. The same peculiar diffculty in sit-to-walk movements has been shown by Mezzarobba and colleagues [4] in PD patients with FoG. Given that gait defcit, postural instability, and freezing episodes are diffcult to alleviate and not particularly responsive to Levodopa, additional therapeutic actions based on specifc rehabilitative pro- tocols have been proposed in the last years to help patients to alleviate symptoms. There is biomechanical evidence in the literature of the effcacy of specifc rehabilitative protocols [5,6] to improve gait in PD patients, but no similar studies have been conducted in PD patients with freezing, the most disabling gait disorders. In 2018, we [7] con- ducted a randomized control trial aimed at evaluating the effcacy of * Corresponding author. Department of Life Sciences Via E. Weiss, 21. 34127 Trieste University of Trieste, Italy. E-mail address: pbernardis@units.it (P. Bernardis). Contents lists available at ScienceDirect Parkinsonism and Related Disorders journal homepage: www.elsevier.com/locate/parkreldis https://doi.org/10.1016/j.parkreldis.2020.09.029 Received 25 May 2020; Received in revised form 14 September 2020; Accepted 19 September 2020