Joo-Eun Song

Treadmill exercise elevates striatal dopamine D2 receptor binding potential in patients with early Parkinson's disease.

We have previously demonstrated changes in dopaminergic neurotransmission after intensive exercise in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mouse model of Parkinson’s disease (PD), including an increase in the dopamine D2 receptor (DA-D2R), using noninvasive PET imaging with the radioligand [18F]fallypride. The purpose of this feasibility and translational study was to examine whether intensive exercise leads to similar alterations in DA-D2R expression using PET imaging with [18F]fallypride in individuals with early-stage PD. In this pilot study, four patients with early-stage PD were randomized to receive intensive exercise (treadmill training sessions three times/week for 8 weeks) or no exercise. Two healthy age-matched individuals participated in treadmill training. Alterations in the DA-D2R binding potential (BP) as a marker for receptor expression were determined using PET imaging with [18F]fallypride. Turning performance in the patients with PD as a measure of postural control and the Unified Parkinson’s Disease Rating Scale scores pre-exercise and postexercise were determined. Our data showed an exercise-induced increase in [18F]fallypride BP as well as improved postural control in patients with PD who exercised. Changes in DA-D2R BP were not observed in patients with PD who did not exercise. These results suggest that exercise can lead to neuroplasticity in dopaminergic signaling and contribute to improved function that may be task specific (postural control) in early-stage PD.

Lower-extremity biomechanics during forward and lateral stepping activities in older adults.

OBJECTIVEnTo characterize the lower-extremity biomechanics associated with stepping activities in older adults.nnnDESIGNnRepeated-measures comparison of kinematics and kinetics associated with forward step-up and lateral step-up activities.nnnBACKGROUNDnBiomechanical analysis may be used to assess the effectiveness of various in-home activities in targeting appropriate muscle groups and preserving functional strength and power in elders.nnnMETHODSnData were analyzed from 21 participants (mean 74.7 yr (standard deviation, 4.4 yr)) who performed the forward and lateral step-up activities while instrumented for biomechanical analysis. Motion analysis equipment, inverse dynamics equations, and repeated measures ANOVAs were used to contrast the maximum joint angles, peak net joint moments, angular impulse, work, and power associated with the activities.nnnRESULTSnThe lateral step-up resulted in greater maximum knee flexion (P<0.001) and ankle dorsiflexion angles (P<0.01). Peak joint moments were similar between exercises. The forward step-up generated greater peak hip power (P<0.05) and total work (P<0.001); whereas, the lateral step-up generated greater impulse (P<0.05), work (P<0.01), and power (P<0.05) at the knee and ankle.nnnCONCLUSIONSnIn older adults, the forward step-up places greater demand on the hip extensors, while lateral step-up places greater demand on the knee extensors and ankle plantar flexors.nnnRELEVANCEnClinicians may use data from biomechanical analyses of in-home exercises to more effectively target specific lower-extremity muscle groups when prescribing exercise activities for older adults. The forward step-up is recommended for maintaining or improving hip extensor performance; whereas, the lateral step-up is recommended when targeting the knee extensors and ankle plantar flexors.

The Relationships Between the Unified Parkinson’s Disease Rating Scale and Lower Extremity Functional Performance in Persons With Early-Stage Parkinson’s Disease

Background. The Unified Parkinson’s Disease Rating Scale (UPDRS) is the “gold standard” assessment tool for characterizing impairments in persons with Parkinson’s disease (PD); however, this scale’s ability to predict functional capabilities across different functional tasks has not been adequately assessed in persons with early-stage PD. Methods. Thirty persons with PD within 3 years of diagnosis and without motor fluctuation performed self-selected walking, fast walking, and sit-to-stand and stair-climbing tasks. Pearson’s correlation coefficients were used to calculate correlations with a standard UPDRS examination (P < .05). Simple linear regression models were used to fit each functional performance outcome measure with the UPDRS total predictor scores. Results. The correlations between the UPDRS motor (section III), UPDRS total scores, and all timed functional performance measures were fair to good (range, 0.45-0.57). Conversely, only greater self-selected time to walk 50 ft correlated with a higher UPDRS activities of daily living (II) score ( r = .386; P < .05). Conclusions. The UPDRS motor (III) and total scores may be good predictors of overall lower extremity function in persons with early-stage PD. Understanding the relationships between UPDRS scores and functional capabilities may allow clinicians to better quantify early physical functioning, longitudinally assess disease progression, and assess the efficacy of interventions.

Altered Dynamic Postural Control during Step Turning in Persons with Early-Stage Parkinson’s Disease

Persons with early-stage Parkinsons disease (EPD) do not typically experience marked functional deficits but may have difficulty with turning tasks. Studies evaluating turning have focused on individuals in advanced stages of the disease. The purpose of this study was to compare postural control strategies adopted during turning in persons with EPD to those used by healthy control (HC) subjects. Fifteen persons with EPD, diagnosed within 3 years, and 10 HC participated. Participants walked 4 meters and then turned 90°. Dynamic postural control was quantified as the distance between the center of pressure (COP) and the extrapolated center of mass (eCOM). Individuals with EPD demonstrated significantly shorter COP-eCOM distances compared to HC. These findings suggest that dynamic postural control during turning is altered even in the early stages of PD.