Noa Fogelson

Myotonometry provides a non-invasive assessment of resting muscle mechanical properties, but its reliability and functional relevance in Parkinson’s disease (PD) remain insufficiently established. This study examined the within-session intra-rater reliability of MyotonPRO measurements and explored their associations with clinical motor severity, gait, functional mobility, and manual dexterity in 24 people with PD assessed in the ON-medication state. Frequency, stiffness, logarithmic decrement, relaxation time, and creep were measured bilaterally in the biceps brachii, triceps brachii, tibialis anterior, and medial gastrocnemius. Reliability between two sets of five impulses was assessed using ICC(3,2), and associations were examined using Spearman correlations with Benjamini–Hochberg false discovery rate correction. Under the standardized same-session, same-rater protocol, all parameters showed good-to-excellent reliability point estimates (ICC = 0.823–0.988), although the precision of some estimates was limited by relatively wide confidence intervals. No significant associations were found with MDS-UPDRS III scores, Hoehn and Yahr stage, or Timed Up and Go performance. Several moderate nominal correlations were observed between lower-limb myotonometric parameters and preferred gait performance, and between triceps brachii parameters and Grooved Pegboard completion time (|r_s| = 0.410–0.488); however, none remained significant after false discovery rate correction. Thus, the reliability findings apply to the present standardized protocol, whereas the associations with motor performance remain exploratory and hypothesis-generating.

Background/Objectives: Gait impairment and reduced handgrip strength are common in Parkinson’s disease (PD), but their relationship remains unclear. This study examined whether associations between handgrip force and gait reflect PD-specific impairment or broader functional capacity. Methods: In this cross-sectional study, 45 individuals with PD and 51 healthy older adults completed unilateral maximal isometric handgrip testing and overground gait assessment at preferred and maximal speed. Handgrip variables included peak force (PF), rate-of-force development (RFD), and impulse. Gait speed, cadence, and step length were recorded. Results: PF was significantly associated with gait speed and step length in both groups, especially under maximal-speed conditions. RFD and impulse were not significantly associated with gait performance in either group. Compared to controls, participants with PD showed poorer gait performance, with lower preferred walking speed and shorter step length in both gait conditions. Within the PD group, PF was lower on the more-affected side than on the less-affected side, whereas most RFD and impulse variables showed no side differences. Conclusions: Maximal handgrip strength, but not upper-limb RFD or impulse, was associated with key gait outcomes in both PD and healthy older adults. These findings suggest that handgrip strength may reflect general functional capacity rather than a PD-specific neuromuscular mechanism and support its use as a practical clinical indicator of mobility-related function.