Motor imagery in amyotrophic lateral Sclerosis: An fMRI study of postural control.

Background: The functional reorganization of brain networks sustaining gait is poorly characterized in amyotrophic lateral sclerosis (ALS) despite ample evidence of progressive disconnection between brain regions. The main objective of this fMRI study is to assess gait imagery-specific networks in ALS patients using dynamic causal modeling (DCM) complemented by parametric empirical Bayes (PEB) framework.

Method: Seventeen lower motor neuron predominant (LMNp) ALS patients, fourteen upper motor neuron predominant (UMNp) ALS patients and fourteen healthy controls participated in this study.

Extrapyramidal deficits in ALS: a combined biomechanical and neuroimaging study.

Introduction: Extrapyramidal deficits are poorly characterised in amyotrophic lateral sclerosis (ALS) despite their contribution to functional disability, increased fall risk and their quality-of-life implications. Given the concomitant pyramidal and cerebellar degeneration in ALS, the clinical assessment of extrapyramidal features is particularly challenging.

Objective: The comprehensive characterisation of postural instability in ALS using standardised clinical assessments, gait analyses and computational neuroimaging tools in a prospective study design.

Mechanics of standing and crouching sprint starts.

The aim of this study was to compare the kinetic and kinematic parameters of standing and crouch sprint starts. Parallel starts (PS), false starts (FS), jump starts (JS) and crouch starts (3PS) were compared. Eighteen participants performed each start on a force plate and six infrared cameras captured the three-dimensional coordinates of 36 retro-reflective markers.

Postural balance during quiet standing in patients with total hip arthroplasty with large diameter femoral head and surface replacement arthroplasty.

Objective: To compare postural balance between patients who have had either a large diameter head total hip arthroplasty or surface replacement arthroplasty.

Design: Observational study.

Setting: Outpatient biomechanical laboratory.

Gait patterns after total hip arthroplasty and surface replacement arthroplasty.

Objective: To compare gait patterns in patients with total hip arthroplasty (THA) and surface hip arthroplasty.

Design: Observational study.

Setting: Outpatient biomechanical laboratory.

Postural balance during quiet standing in patients with total hip arthroplasty and surface replacement arthroplasty.

Background: Primary total hip arthroplasty leads to better functional capacities but a general weakness of abductor muscles often persists. A larger head component may improve the postural balance in the medial-lateral direction. The aims of this study are (1) to compare postural stability in patients after total hip and surface replacement arthroplasties and (2) to evaluate the effect of the biomechanical reconstruction on postural stability.

The control of upright stance in young, elderly and persons with Parkinson's disease.

The aims of the present study are twofold: (1) to compare the postural control mechanisms of young and elderly people as well as in Parkinson's disease (PD) patients during quiet standing and (2) to assess the impact of a stooped posture on these mechanisms. All subjects were required to maintain both a side-by-side and a 45 degrees foot position. Elderly subjects performed a third condition where they were requested to mimic the stooped posture as adopted by PD subjects.

Balance control during an arm raising movement in bipedal stance: which biomechanical factor is controlled?

In order to obtain new insight into the control of balance during arm raising movements in bipedal stance, we performed a biomechanical analysis of kinematics and dynamical aspects of arm raising movements by combining experimental work, large-scale models of the body, and techniques simulating human behavior. A comparison between experimental and simulated joint kinematics showed that the minimum torque change model yielded realistic trajectories. We then performed an analysis based on computer simulations.

Assessment of postural response after a self-initiated perturbation.

The aim of this study was to assess postural response efficiency to a self-initiated perturbation using an original method based on the inverted pendulum model. Eight young subjects were asked to perform bilateral arm raising and lowering at 3 different speeds while standing on a force plate. The time necessary to recover a steady state following the movement was computed by analyzing the time evolution of the coefficient of determination between the center of pressure and center of mass difference variable (COP-COM) and the horizontal acceleration of the COM.