Gait and attentional performance in freezers under methylphenidate.

BACKGROUND: Attentional resources appear to be involved in the occurrence of FoG. The Parkgait study recently reported that methylphenidate reduces gait hypokinesia and freezing of gait (FoG) in advanced PD patients receiving STN-DBS in the off-dopaminergic drug condition. Methylphenidate is considered to improve attention. The primary objective of the present ancillary study was to determine whether methylphenidate reduced the interference between a cognitive task and gait in patients with FoG. The study's secondary objective was to compare attentional performance in methylphenidate-treated and placebo-treated patients. METHODS: A total of 24 patients (from two centers) were included in the study. Patients were randomly assigned 1:1 to a three-month course of methylphenidate (1mg/kg/day) or placebo. Patients were assessed after an acute L-dopa challenge. The primary outcome criterion was the stride length ratio ((dual-task stride length minus free gait stride length)/free gait stride length). Trials with FoG episodes were excluded from the analysis. Secondary outcomes included changes in reaction times for computerized attention tasks and FoG severity. RESULTS: When comparing patients receiving methylphenidate with those receiving placebo, we did not observe any significant differences in the interaction between the dual task and gait or in attentional performance. CONCLUSION: As in the main Parkgait study, methylphenidate did not reduce gait hypokinesia in patients receiving dopaminergic treatment. Our present results suggest that the reduction in the number of FoG episodes previously observed in patients on methylphenidate was neither due to interaction between a dual-task and gait nor an increase in attentional performance.

Center of pressure path during Sit-to-walk tasks in young and elderly humans.

OBJECTIVE: This study aimed to investigate differences in total center of pressure (TCOP) paths during a Sit-to-Walk task in young and elderly subjects. METHOD: Nine young and 19 elderly subjects were asked to repeat five Sit-to-Walk tasks. The COP paths were computed during the rising from vertical forces. RESULTS: For 4 young and 17 elderly subjects, the TCOP moved on the anterior-posterior axis during the 1st period (from the beginning of the rising to maximal force under the swing leg) and then joined the stance foot during the 2nd period (from maximal force to the toe off). For the two other paths observed in young subjects, the duration of the 2nd period was increased (33% of total duration vs. 18%, P = 0.02) or the area of TCOP displacement during the 1st period was decreased. CONCLUSION: During the Sit-to-Walk task, different TCOP paths can be described in relation to age. These profiles are influenced by the level of postural stability required before initiating the first step. After further validation, the analysis of TCOP paths could be used to estimate the level of postural ability, especially in the elderly.

Kinematic and electromyographic analysis of rising from a chair during a "Sit-to-Walk" task in elderly subjects: role of strength.

BACKGROUND: With aging, the deterioration of the ability to rise from a chair constitutes a major source of disability and a factor contributing to the loss of autonomy. The aim of this study was to describe kinematic and electromyographic characteristics of rising from a chair during a Sit-to-Walk task and to investigate the relationships between lower limb muscle strength and Sit-to-Walk characteristics. METHODS: Twenty-four healthy elderly subjects (mean age: 73.8 (6.4) years) were included. The task analyzed consisted in standing up and taking a step. Kinematic data were obtained using a 3D motion analysis software. Surface electromyography of eight lower limb muscles was recorded. Isokinetic strength of ankle plantar flexor and knee flexors and extensors was evaluated. FINDINGS: The Sit-to-Walk was divided into four phases. For 19 subjects, this task can be considered as a continuum with an overlap of the phases. In comparison with the Sit-to-Stand description, the Sit-to-Walk transition phase, which combined trunk flexion and knee extension, appeared longer in order to increase the body forward transfer for gait initiation. In most cases, the tibialis anterior and peroneus longus muscles were first activated. The isokinetic strength of the knee extensors was negatively correlated with the amplitude of trunk flexion and the knee flexors/extensors torque ratio was correlated with the length of this phase. INTERPRETATION: Characterization of Sit-to-Walk movement provides information about the ability to rise from a chair. In the elderly, a better knowledge of its determinants could lead to improve strategies for rehabilitation of this critical task.