Frances Huxham

Three‐dimensional gait biomechanics in Parkinson's disease: Evidence for a centrally mediated amplitude regulation disorder

We examined whether people with Parkinsons disease (PD) have a central amplitude regulation disorder using three‐dimensional (3‐D) gait analyses to compare the effects of medication and attentional strategies on gait in 12 PD subjects and 12 matched comparison subjects. Subjects with PD first performed several 10‐m gait trials at preferred speed while off levodopa. They then walked at preferred speed on levodopa; off levodopa with cues; and on levodopa with cues. Control subjects walked at preferred speed and then with visual cues to match their stride length to PD values. As well as spatiotemporal footstep data, pelvic and lower limb kinematic profiles and angle–angle diagrams were produced for sagittal, coronal, and transverse plane movements using a 3‐D motion analysis system. In people with PD, decreased step length was accompanied by reduced movement amplitude across all lower limb joints, in all movement planes. When control subjects were required to walk with short steps matched to the size of PD comparisons, they displayed a similar multijoint reduction in amplitude. For PD subjects, both levodopa and visual cues increased movement amplitude across all lower limb joints. Amplitude increased further when levodopa and visual cues were combined, resulting in normalization of step length. This finding suggested that reduced step length is due to a mismatch between cortically selected movement amplitude and basal ganglia maintenance mechanisms. Levodopa and cues normalized amplitude across all joints by altering motor set and bypassing defective basal ganglia mechanisms.

Theoretical considerations in balance assessment

Although balance control is an integral component of all daily activities, its complex and flexible nature makes it difficult to assess adequately. This paper discusses balance by examining it in relation to function and the physical environment. Balance is affected by both the task being undertaken and the surroundings in which it is performed. Different tasks and environments alter the biomechanical and information processing needs for balance control. These issues are discussed and a modification of Gentile s Taxonomy of Tasks is suggested for analysis of clinical balance tests, some of which are used as examples.

Postural instability in Parkinson's disease: a comparison with and without a concurrent task

The purpose of this investigation was to determine the effects of dual task performance on postural instability in subjects with idiopathic Parkinsons disease (PD) compared with healthy elderly people. In particular, we aimed to divert attention to a secondary task so the full extent of balance disturbance could be revealed without compensation by attentional mechanisms. Forty-five subjects were tested: 15 PD subjects with a past history of falls; 15 PD subjects with no history of falls; and 15 unimpaired individuals. Groups were matched for age and sex and subjects with PD were tested at peak dose in the levodopa medication cycle. Each subject was tested on their ability to maintain stability in three conditions: (1) steady standing (feet apart, feet together, step stance, tandem stance, single leg stance); (2) in response to perturbations generated by self-initiated movements (arm raise test, step test); and (3) in response to an unexpected external perturbation in upright stance, the shoulder tug test. The concurrent task was verbal-cognitive and required subjects to recite the days of the week backwards. The concurrent task produced a significant deterioration in performance for the arm raise test in all groups, the step test for the PD fallers and controls and for tandem stance in the PD fallers. Ceiling effects were evident for timed tests with feet apart and feet together resulting in poor discriminative validity for these tests. The external perturbation test showed differences between the three groups for both unitask and concurrent task conditions, yet similar rates of change from unitask to dual task conditions. Because PD fallers had a more severe initial deficit than controls, deterioration placed them in that part of the balance continuum at high risk of losing equilibrium.

The sequence effect and gait festination in Parkinson disease: contributors to freezing of gait?

Festination and freezing of gait (FOG) are poorly understood gait disorders that cause disability and falls in people with Parkinson disease (PD). In PD, basal ganglia malfunction leads to motor set deficits (hypokinesia), while altered motor cue production leads to a sequence effect, whereby movements becomes progressively smaller as in festination. We suggest both factors may contribute to FOG. Disturbance of set maintenance by the basal ganglia in PD has previously been examined in gait, but limited systematic evaluation of the sequence effect exists. In this study, we investigated the step‐to‐step amplitude relationship in 10 PD subjects with clinical evidence of festination and FOG. Four conditions were examined: off levodopa, off with attentional strategies, off with visual cues, and on levodopa. Participants demonstrated a sequence effect (F = 6.24; P = 0.001), which was reversed only by use of visual cues. In contrast, medication, attentional strategies, and visual cues all improved hypokinesia. Variability was marked both within and between participants in all conditions. The variability of FOG is suggested to relate to a combination of factors, including the sequence effect and its variability, as well as the severity of hypokinesia and its response to medications.

Constraints on the kinetic, kinematic and spatiotemporal parameters of gait in Parkinson's disease

Abstract The characteristic slow, short stepped, shuffling walking pattern in Parkinsons disease (PD) results from a combination of constraints on locomotor control imposed by neurotransmitter imbalance. Previous research on the pathogenesis of gait disorders in PD has been confined to descriptions of changes in spatiotemporal parameters of the footstep pattern in response to antiparkinsonian medication and attentional strategies. By analysing the changes that occur in kinematics and kinetics with systematic manipulations of dopaminergic status and attention, a fuller understanding of the primary determinants of gait dysfunction in PD can be obtained. We illustrate this point with a case history on a 71 year old hypokinetic woman with PD who demonstrated normalisation of key kinematic and spatiotemporal variables of gait when provided with visual cues at peak-dose of the medication cycle, despite persistent abnormalities in gait kinetics. PsycINFO classification : 2330; 3297; 2520

Head and trunk rotation during walking turns in Parkinson's Disease.

Head and trunk axial rotation during walking to align with a new path are integral components of direction change (turning). Turning is problematic in people with Parkinsons disease (PD), who appear to move en‐bloc when turning and when walking straight. Axial rotation has been little investigated in this group. Accordingly, head, thorax, and pelvis rotation relative to the laboratory axes (global rotation) was investigated in 10 patients with PD and 10 matched comparison subjects when walking straight and when turning 60 and 120°. Data were selected at three footfalls before and three after a pole denoting the corner. Although rotation was reduced overall in patients with PD, final differences were minimized by rotation commencing at an earlier step in the patient group. When rotation was measured at various distances relative to the corner, the patient group demonstrated greater rotation than their peers. In support of clinical observations, patients constrained thorax and pelvis closely together around the corner, while control subjects maintained a pattern of reciprocal oscillation when turning. Stride length reduction appears to contribute more to inefficient turning in PD than under‐scaled amplitude of rotation.

Feasibility, safety, and compliance in a randomized controlled trial of physical therapy for Parkinson's disease.

Both efficacy and clinical feasibility deserve consideration in translation of research outcomes. This study evaluated the feasibility of rehabilitation programs within the context of a large randomized controlled trial of physical therapy. Ambulant participants with Parkinsons disease (PD) (n = 210) were randomized into three groups: (1) progressive strength training (PST); (2) movement strategy training (MST); or (3) control (“life skills”). PST and MST included fall prevention education. Feasibility was evaluated in terms of safety, retention, adherence, and compliance measures. Time to first fall during the intervention phase did not differ across groups, and adverse effects were minimal. Retention was high; only eight participants withdrew during or after the intervention phase. Strong adherence (attendance >80%) did not differ between groups (P = .435). Compliance in the therapy groups was high. All three programs proved feasible, suggesting they may be safely implemented for people with PD in community-based clinical practice.

Footstep adjustments used to turn during walking in Parkinson's disease

Turning during walking is frequently problematic in Parkinsons disease (PD). The spatiotemporal characteristics of footstep adjustments used to turn 60 and 120 degrees were examined in 10 people with PD and 10 age, gender‐ and height‐matched control subjects, using three‐dimensional motion analysis. Control subjects used a recognizable pattern of spatial and temporal footstep modulations to turn. Participants with PD demonstrated significant differences in almost all variables. They (1) failed to turn as far as their peers; (2) showed a similar but scaled‐down pattern of spatial adjustments to turn; (3) used shorter strides when walking, with exaggerated reductions when turning; and (4) demonstrated small but significant temporal differences in step time adjustments. Group differences were more marked for the larger turn. Spatial results, interpreted in light of hypothesized basal ganglia dysfunction, are consistent with a normal motor command but impaired ability to maintain movement amplitude. Differences in adjustment of step time to turn may reflect impaired locomotor timing control in subjects with PD during challenging gait tasks.

Central gait control mechanisms and the stride length – cadence relationship

The stride length - cadence relationship (SLCrel) was investigated to explore a theory of two alternate but inter-related pathways for gait control. Sixty-three healthy people in three age groups walked along a computerized walkway (GAITRite(®)) at five self-selected speeds from very slow to very fast, five cadences from 70 to 150 steps/min and five stride lengths from 0.8 to 1.6m. The data points from two walks in each level of each condition were examined for linear and quadratic relationships. In the self-selected speed condition 97% of participants had a positive linear or quadratic relationship of R(2)≥0.90. The quadratic relationships showed stride length decreased with very high cadences. When walks with cadences above 150 steps/min were removed, 95% of participants had a positive linear relationship of R(2)≥0.90. No age-related differences were found in slope or intercept of linear relationships or in maximum, minimum or range of stride length or cadence in the self-selected speed condition. In the cadence and stride length conditions, only 32% and 14% of positive linear or quadratic relationships were R(2)≥0.90. The near-invariant SLCrel, unaffected by ageing that exists for nearly all individuals when walking at self-selected speeds, indicates that the SLCrel may be used to simplify central control of automatic gait in healthy individuals. The current investigation also provides SLCrel data for healthy people which can be compared with patient populations.

A Randomized Controlled Trial to Reduce Falls in People With Parkinson’s Disease

Background. Falls are common and disabling in people with Parkinson’s disease (PD). There is a need to quantify the effects of movement rehabilitation on falls in PD. Objective. To evaluate 2 physical therapy interventions in reducing falls in PD. Methods. We randomized 210 people with PD to 3 groups: progressive resistance strength training coupled with falls prevention education, movement strategy training combined with falls prevention education, and life-skills information (control). All received 8 weeks of out-patient therapy once per week and a structured home program. The primary end point was the falls rate, recorded prospectively over a 12 month period, starting from the completion of the intervention. Secondary outcomes were walking speed, disability, and quality of life. Results. A total of 1547 falls were reported for the trial. The falls rate was higher in the control group compared with the groups that received strength training or strategy training. There were 193 falls for the progressive resistance strength training group, 441 for the movement strategy group and 913 for the control group. The strength training group had 84.9% fewer falls than controls (incidence rate ratio [IRR] = 0.151, 95% CI 0.071-0.322, P < .001). The movement strategy training group had 61.5% fewer falls than controls (IRR = 0.385, 95% CI 0.184-0.808, P = .012). Disability scores improved in the intervention groups following therapy while deteriorating in the control group. Conclusions. Rehabilitation combining falls prevention education with strength training or movement strategy training reduces the rate of falls in people with mild to moderately severe PD and is feasible.