Objective: To assess the role of muscle strength, muscle tone and reflexes on the movement timings and inhibitory control in the subjects of Parkinson’s disease (PD).

Background: The muscle functions are associated with cognitive functions. Increased muscle strength and high muscle tone has been found to have better inhibitory control and vice versa. While the movement timings assessments such as finger tapping have long been used to evaluate and track rehabilitation progress, studies have also claimed movement timings to be a predictor of cognitive functions. These muscle functions are often affected in PD. The inhibitory control is also found to be impaired in PD. But the role and relationship these muscle functions have on the movement timings and in the inhibitory control is not well understood. This study explores how muscle strength, muscle tone and tendon reflexes affect the movement timings and inhibitory control in PD.

Method: A total population 46 mixed subjects of movement disorders were recruited for study. Muscle strength (MRC), muscle tone (MAS) and  Deep tendon reflexes (DTR) of both the upper extremities were assessed. Later, a Finger Tapping Task, a Go-NoGo task and Flanker task was performed on all the subjects and the mean Reaction Time (RT) were evaluated. For the final analysis Kruskal Wallis test and ​​Jonckheere-Terpstra tests were performed to evaluate the relationship.

Results: The movement timings of finger tapping was found to be significantly associated with all the three muscle strength, muscle tone and tendon reflexes overall. The reaction timings were found to be higher with the decreased muscle strength score and increased muscle tone score. While the tendon reflexes were found to be significantly associated with the dominant (right) side. Furthermore the muscle strength, muscle tone and tendon reflexes also had an significant impact on the movement timings of inhibition in PD.

Conclusion: Each decreasing muscle strength score and each increasing muscle tone score is distributed differently with RTs of finger tapping in PD. Whereas for the DTR score were found to be significantly associated with the RTs of finger tapping of dominant hand. The movement timings of response inhibition was also found to be associated with muscle strength, muscle tone and tendon reflexes overall. These results show that muscle functions may affect the movement timings in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/muscle-functions-on-the-movement-timings-and-inhibition-in-parkinsons-disease/