Objective Quantify the effects of increased amplitude and rate of muscle stretch on parkinsonian rigidity. Methods Eighteen subjects with Parkinson’s disease participated in this study. Subjects’ tested hand was passively displaced through 60° and 90° ranges of wrist flexion and extension at velocities of 50°/s and 280°/s in both treated and untreated conditions. Joint angular position, resistance torque, and surface electromyography (EMG) of the wrist flexors and extensors were recorded. Rigidity was quantified by normalized work scores and normalized angular impulses for flexion and extension, separately. Reflex responses of stretched and shortened muscles were quantified by mean EMG and EMG ratio. A series of ANOVAs was performed to determine the effect of amplitude, velocity and medication on selected variables. Results Both work scores and angular impulses revealed that the larger displacement amplitude and the higher velocity were associated with significantly greater rigidity, increased EMG ratio and mean EMG of stretched muscles. Dopaminergic medication was not associated with a reduction in rigidity. Conclusions Parkinsonian rigidity is modulated by the amplitude and rate of muscle stretch. Significance These findings shed light on the biomechanical underpinnings and physiological characteristics of rigidity and may inform clinical rigidity assessment in Parkinson’s disease.

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Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by rigidity, bradykinesia, resting tremor, and postural instability. Rigidity, defined as an increased resistance to passive movement of a joint, progresses faster than other motor signs in PD. Rigidity is attributable to both exaggerated neural reflex and altered muscle mechanical properties. However, little is known about the contributions of individual components to rigidity. Further, there is no evidence regarding the effects of dopaminergic medication on individual components. Objectives of this study were to quantify the contributions of neural reflexes and intrinsic muscle properties to rigidity and investigate the effects of medication on each contributing component. Joint torque and muscle activities of the wrist in 14 patients and 14 controls were measured during externally induced movements. Each subject with PD was tested in Off- and On-medication states. A system identification technique was applied to differentiate and quantify the neural reflex and intrinsic mechanical components. A mixed model of ANOVA was performed to compare the differences between the two components of rigidity for both groups, and to compare between the Off- and On-medication states for patients. The results showed that reflex and intrinsic components are comparable (p > 0.05), and both are enhanced in subjects with PD than in the controls (p < 0.05). Medication decreased the reflex component of rigidity (p < 0.01). It is concluded that both reflex and intrinsic factors are responsible for rigidity. Present findings are clinically significant as they may provide guidance in development of effective therapeutic interventions.

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Agro-based products and complex chlorides/minerals (CCM) based products are increasingly employed in snow and ice control operations, either used alone or more commonly as additives for chloride-based products. Recent studies have shown that agro-based or CCM based products have the potential to improve the overall deicing and/or anti-icing performance and reduce the corrosion and environmental impacts. However, the effectiveness of such products has been limited to qualitative field observations and their specific role in snow and ice control is poorly understood. This work consists of a systematic laboratory investigation, with a focus on the thermal properties, ice melting behavior, and corrosivity of four agro-based deicers and two CCM based deicers. First, CCM based deicers do not exhibit significantly better ability to lower the freezing point of water when compared with NaCl, but they feature slightly better ice melting capacity at 15 o F than NaCl. Second, agro-based additives seem to significantly lowered the freezing point of 23 wt.% NaCl brine but did not significantly improve the ice melting capacity at 15 o F or 25 o F, implying their role as 'cryoprotectants'. Third, CCM and agro-based deicers do not exhibit significantly lower characteristic temperature than reagent-grade NaCl. A very strong positive linear relationship exists between the eutectic temperature (T e ) and the characteristic temperature (T c ) of the tested liquids, indirectly confirming the validity of using DSC thermograms to assess liquid deicers. The gravimetric method reveals that CCM based deicers exhibit slightly lower corrosivity to carbon steel than NaCl and agro-based additives exhibit significant benefits in reducing the corrosivity of 23 wt.% NaCl brine. The electrochemical method reveals that while the beet-based additives do not significantly alter the corrosion potential of carbon steel, the other type of additives moved the corrosion potential to a much more positive level, implying anodic type inhibitor at work.