Key pointsr Individuals with freezing of gait (FoG) due to Parkinson's disease (PD) have small and long anticipatory postural adjustments (APAs) associated with delayed step initiation.r Individuals with FoG ('freezers') may require functional reorganization of spinal mechanisms to perform APAs due to supraspinal dysfunction. As presynaptic inhibition (PSI) is centrally modulated to allow execution of supraspinal motor commands, it may be deficient in freezers during APAs.r We show that freezers presented PSI in quiet stance (control task), but they presented loss of PSI (i.e. higher ratio of the conditioned H-reflex relative to the test H-reflex) during APAs before step initiation (functional task), whereas non-freezers and healthy control individuals presented PSI in both the tasks.r The loss of PSI in freezers was associated with both small APA amplitudes and FoG severity. r We hypothesize that loss of PSI during APAs for step initiation in freezers may be due to FoG.Abstract Freezing of gait (FoG) in Parkinson's disease involves deficient anticipatory postural adjustments (APAs), resulting in a cessation of step initiation due to supraspinal dysfunction. Individuals with FoG ('freezers') may require functional reorganization of spinal mechanisms to perform APAs. As presynaptic inhibition (PSI) is centrally modulated to allow execution of supraspinal motor commands, here we hypothesized a loss of PSI in freezers during APA for Jumes Lira is a Master's researcher of the Exercise Neuroscience Research Group, School of Arts, Sciences and Humanities, University of São Paulo, Brazil. His work has focused on understanding the spinal inhibitory mechanisms in Parkinson's disease using neurophysiological approaches. More specifically, he is interested in identifying alterations in spinal pathways related to freezing of gait of Parkinson's disease during functional tasks, leading to the development of mechanistic-based interventions for physical therapy. others J Physiol 598.8step initiation, which would be associated with FoG severity. Seventy individuals [27 freezers, 22 non-freezers, and 21 age-matched healthy controls (HC)] performed a 'GO'-commanded step initiation task on a force platform under three conditions: (1) without electrical stimulation, (2) test Hoffman reflex (H-reflex) and (3) conditioned H-reflex. They also performed a control task (quiet stance). In the step initiation task, the H-reflexes were evoked on the soleus muscle when the amplitude of the APA exceeded 10-20% of the mean baseline mediolateral force. PSI was quantified by the ratio of the conditioned H-reflex relative to the test H-reflex in both the tasks. Objective assessment of FoG severity (FoG-ratio) was performed. Freezers presented lower PSI levels during quiet stance than non-freezers and HC (P < 0.05). During step initiation, freezers presented loss of PSI and lower APA amplitudes than non-freezers and HC (P < 0.05). Significant correlations were only found for freezers between loss of PSI and FoG-ratio (r = 0.59, P = 0.0005) and los...

Background Deficits in the cerebellar locomotor region (CLR) have been associated with loss of gait automaticity in individuals with freezing of gait in Parkinson's disease (freezers); however, exercise interventions that restore gait automaticity in freezers are lacking. We evaluated the effects of the adapted resistance training with instability ([ARTI] complex exercises) compared with traditional motor rehabilitation (without complex exercises) on gait automaticity and attentional set‐shifting. We also verified associations between gait automaticity change and CLR activation change previously published. Methods Freezers were randomized either to the experimental group (ARTI, n = 17) or to the active control group (traditional motor rehabilitation, n = 15). Both training groups performed exercises 3 times a week for 12 weeks. Gait automaticity (dual‐task and dual‐task cost [DTC] on gait speed and stride length), single‐task gait speed and stride length, attentional set‐shifting (time between Trail Making Test parts B and A), and CLR activation during a functional magnetic resonance imaging protocol of simulated step initiation task were evaluated before and after interventions. Results Both training groups improved gait parameters in single task (P < 0.05), but ARTI was more effective than traditional motor rehabilitation in improving DTC on gait speed, DTC on stride length, dual‐task stride length, and CLR activation (P < 0.05). Changes in CLR activation were associated with changes in DTC on stride length (r = 0.68, P = 0.002) following ARTI. Only ARTI improved attentional set‐shifting at posttraining (P < 0.05). Conclusions ARTI restores gait automaticity and improves attentional set‐shifting in freezers attributed to the usage of exercises with high motor complexity. © 2020 International Parkinson and Movement Disorder Society

O objetivo deste estudo foi verificar dentre os sintomas motores, sintomas não motores e o medo de cair quais seriam os principais preditores de qualidade de vida em indivíduos nos estágios 2 e 3 da doença de Parkinson (DP). Trinta e nove indivíduos com DP (64,1±9,1 anos, 10,3±4,7 duração da DP) avaliados no estado on da medicação participaram do estudo. A disfunção motora foi avaliada por meio dos seguintes testes: parte III da Escala Unificada de Avaliação da Doença de Parkinson (UPDRS-III), teste Timed up and Go (TUG), Teste de Sistema de Avaliação do Equilíbrio (BESTest) e uma repetição máxima dos membros inferiores (1RM no leg press). A disfunção não motora foi avaliada por meio dos seguintes testes: Avaliação Cognitiva de Montreal (MoCA), Inventário de Depressão de Beck (IDB) e o Índice de Qualidade do Sono de Pittsburgh (PSQI). O medo de cair foi avaliado por meio da Escala Internacional de Eficácia de Quedas (FES-I). A qualidade de vida foi avaliada por meio do teste Questionário da Doença de Parkinson (PDQ-39). Uma regressão múltipla linear, método stepwise foi empregada para verificar o principal preditor do escore da PDQ-39. A única variável independente que entrou no modelo de regressão múltipla linear (stepwise) e mostrou uma alta capacidade para explicar o escore de qualidade de vida de indivíduos com DP foi a FES-I (R2 ajustado = 0,73, P<0,0001). Assim, como implicação clínica, é possível sugerir que estratégias de treinamento físico que promovam diminuição no medo de cair podem impactar positivamente na qualidade de vida de indivíduos com DP moderada.

Background Minimal detectable change (MDC) when assessing balance using the Biodex Balance System (BBS) in patients with Parkinson disease (PD) is currently unknown, limiting the interpretability of the scores. Objective To determine the MDC on the Anterior/Posterior Stability Index (APSI), Medial/Lateral Stability Index (MLSI), and Overall Stability Index (OSI) from postural stability and fall risk protocols of the BBS in patients with PD. Design This was a repeated‐measures design (at a 1‐week interval). Setting Strength training laboratory of a public university. Patients 46 patients with PD (men and women) at stages 2 and 3 (67.9 ± 7.4 years old) were assessed in the “on” state (fully medicated). Methods Patients performed three trials of 20 s for each protocol. Main Outcome Measurements Absolute and relative MDC (MDC%) calculated for APSI, MLSI, and OSI from the postural stability (stable condition) and fall risk protocols (unstable condition). Results For the postural stability, the MDC and MDC% were 0.26° and 17% for APSI, 0.41° and 21% for MLSI, and 0.22° and 12% for OSI, respectively. For the fall risk, the MDC and MDC% were 0.51° and 18% for APSI, 0.21° and 15% for MLSI, and 0.41° and 20% for OSI, respectively. These results were considered acceptable, despite indices with high MDC for MLSI (postural stability) and APSI (fall risk). Conclusions Patients with PD have more mediolateral and anteroposterior changes in the stable and unstable conditions, respectively. These abnormal balance strategies can occur principally due to postural instability of PD. However, our results demonstrated acceptable MDCs in both conditions in all of the assessed axes. Thus, BBS should be incorporated into the clinical evaluation to help therapists to determine if intervention‐induced changes in balance are clinically significant or due to measurement error. Level of Evidence II

This study had two objectives: 1) to compare the effects of 3 wk of resistance training (RT) and resistance training with instability (RTI) on evoked reflex responses at rest and during maximal voluntary isometric contraction (MVIC) of individuals with Parkinson’s disease (PD) and 2) to determine the effectiveness of RT and RTI in moving values of evoked reflex responses of individuals with PD toward values of age-matched healthy control subjects (HCs) ( z-score analysis). Ten individuals in the RT group and 10 in the RTI group performed resistance exercises twice a week for 3 wk, but only the RTI group included unstable devices. The HC group ( n = 10) were assessed at pretest only. Evoked reflex responses at rest (H reflex and M wave) and during MVIC [supramaximal M-wave amplitude (Msup) and supramaximal V-wave amplitude (Vsup)] of the plantar flexors were assessed before and after the experimental protocol. From pretraining to posttraining, only RTI increased ratio of maximal H-reflex amplitude to maximal M-wave amplitude at rest (Hmax/Mmax), Msup, Vsup/Msup, and peak torque of the plantar flexors ( P < 0.05). At posttraining, RTI was more effective than RT in increasing resting Hmax and Vsup and in moving these values to those observed in HCs ( P < 0.05). We conclude that short-term RTI is more effective than short-term RT in modulating H-reflex excitability and in increasing efferent neural drive, approaching average values of HCs. Thus short-term RTI may cause positive changes at the spinal and supraspinal levels in individuals with PD. NEW & NOTEWORTHY Maximal H-reflex amplitude (Hmax) at rest and efferent neural drive [i.e., supramaximal V-wave amplitude (Vsup)] to skeletal muscles during maximal contraction are impaired in individuals with Parkinson’s disease. Short-term resistance training with instability was more effective than short-term resistance training alone in increasing Hmax and Vsup of individuals with Parkinson’s disease, reaching the average values of healthy control subjects.