Rigidity is one of the cardinal symptoms of Parkinson’s disease (PD). Present in up 89% of cases, it is typically assessed with clinical scales. However, these instruments show limitations due to their subjectivity and poor intra- and inter-rater reliability. To compile all of the objective quantitative methods used to assess rigidity in PD and to study their validity and reliability, a systematic review was conducted using the Web of Science, PubMed, and Scopus databases. Studies from January 1975 to June 2019 were included, all of which were written in English. The Strengthening the Reporting of observational studies in Epidemiology Statement (STROBE) checklist for observational studies was used to assess the methodological rigor of the included studies. Thirty-six studies were included. Rigidity was quantitatively assessed in three ways, using servomotors, inertial sensors, and biomechanical and neurophysiological study of muscles. All methods showed good validity and reliability, good correlation with clinical scales, and were useful for detecting rigidity and studying its evolution. People with PD exhibit higher values in terms of objective muscle stiffness than healthy controls. Rigidity depends on the angular velocity and articular amplitude of the mobilization applied. There are objective, valid, and reliable methods that can be used to quantitatively assess rigidity in people with PD.

Background: People with Parkinson’s disease (PD) present deficits of the active range of motion (ROM), prominently in their trunk. However, if these deficits are associated with axial rigidity, the functional mobility or health related quality of life (HRQoL), remains unknown. The aim of this paper is to study the relationship between axial ROM and axial rigidity, the functional mobility and HRQoL in patients with mild to moderate PD. Methods: An exploratory study was conducted. Non-probabilistic sampling of consecutive cases was used. Active trunk ROM was assessed by a universal goniometer. A Biodex System isokinetic dynamometer was used to measure the rigidity of the trunk. Functional mobility was determined by the Get Up and Go (GUG) test, and HRQoL was assessed with the PDQ-39 and EuroQol-5D questionnaires. Results: Thirty-six mild to moderate patients with PD were evaluated. Significant correlations were observed between trunk extensors rigidity and trunk flexion and extension ROM. Significant correlations were observed between trunk flexion, extension and rotation ROM and GUG. Moreover, significant correlations were observed between trunk ROM for flexion, extension and rotations (both sides) and PDQ-39 total score. However, these correlations were considered poor. Conclusions: Trunk ROM for flexion and extension movements, measured by a universal goniometer, were correlated with axial extensors rigidity, evaluated by a technological device at 30°/s and 45°/s, and functional mobility. Moreover, trunk ROM for trunk flexion, extension and rotations were correlated with HRQoL in patients with mild to moderate PD.

Background and purpose: The Kinesthetic and Visual Imagery Questionnaire (KVIQ) and the Movement Imagery Questionnaire-Revised Second Version (MIQ-RS) are measurement instruments that assess motor imagery vividness. The aim of this study was to examine the validity and reliability of the Spanish KVIQ and MIQ-RS in people with Parkinson disease (PD). Methods: A longitudinal descriptive study was conducted following the COSMIN standards. Thirty-five people with idiopathic PD were evaluated twice (7-15 days apart) with the Spanish KVIQ and MIQ-RS. Structural validity, internal consistency, test-retest reliability (ICC), standard error of measurement (SEM), smallest detectable change (SDC), and criterion validity of the MIQ-RS and KVIQ long (KVIQ-20), short (KVIQ-10), and extended (KVIQ-34) versions and their subscales (if pertinent) were tested. Results: Factor analysis was satisfactory for the MIQ-RS, KVIQ-20, and KVIQ-10, providing evidence of their 2-dimensional structure. Evidence of the structural validity of the KVIQ-34 was not confirmed and thus was analyzed as an overall score. Revelle's ω > 0.9 showed excellent internal consistency. Test-retest reliability was moderate (ICC = 0.58-0.75) and higher for all visual subscales. SEM and SDC were up to 14.39% and 39.89% of the scores, respectively. Criterion validity between questionnaires and subscales was strong (Spearman's r > 0.7). Discussion and Conclusions: The results provide evidence for the validity and reliability of the Spanish MIQ-RS, KVIQ-20, and KVIQ-10 to assess motor imagery vividness in people with PD, whereas the KVIQ-34 should only be interpreted as an overall score. Psychometric, procedural, and practical features of the questionnaires should be considered when applying into clinical practice. Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A401).

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