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Prior work suggests there may be greater reliance on executive function for walking in older people. The pre-frontal cortex (PFC), which controls aspects of executive function, is known to be active during dual-task walking (DTW). However, there is debate on how PFC activity during DTW is impacted by ageing and the requirements of the cognitive task.Functional near infrared spectroscopy, was used to investigate how PFC activity during walking was affected by (i) healthy ageing; and (ii) dual-tasks that utilise inhibition or working memory aspects of executive function.Young (n = 26, 16 females, mean 20.9 years) and older (n = 26, 16 females, mean 70.3 years) adults performed five conditions: normal walking; Reciting Alternate Letters of the alphabet (RAL, requiring cognitive inhibition and working memory) during standing and walking; and serial subtraction by threes (SS3, requiring working memory alone) during standing and walking. Walking speed, cognitive performance, the PFC haemodynamic response, and fear of falling ratings were analysed using linear mixed-effects modelling.Compared to quiet standing, PFC activity increased during normal walking for older adults but decreased for young adults (p 0.01). Across both groups, fear of falling contributed to higher PFC activity levels when walking (p 0.01). PFC activity increased during DTW, and this increase was greater when performing RAL compared to the SS3 task (p 0.01). Although the rate of correct responses was higher for RAL, walking speed reduced more with RAL than SS3 in the young group (p = 0.01), and the rate of correct responses reduced more when walking with RAL than SS3 in the older group (p 0.01).Older adults have increased levels of PFC activation during walking compared to younger adults and fear of falling is a cofounding factor. The interference between gait and a concurrent cognitive task is higher when the cognitive task requires inhibition.

Essential tremor (ET) is the most common cause of tremor in older adults. However, it is increasingly recognised that 30–50% of ET cases are misdiagnosed. Late-onset ET, when tremor begins after the age of 60, is particularly likely to be misdiagnosed and there is mounting evidence that it may be a distinct clinical entity, perhaps better termed ‘ageing-related tremor’. Compared with older adults with early-onset ET, late-onset ET is associated with weak grip strength, cognitive decline, dementia and mortality. This raises questions around whether late-onset ET is a pre-cognitive biomarker of dementia and whether modification of dementia risk factors may be particularly important in this group. On the other hand, it is possible that the clinical manifestations of late-onset ET simply reflect markers of healthy ageing, or frailty, superimposed on typical ET. These issues are important to clarify, especially in the era of specialist neurosurgical treatments for ET being increasingly offered to older adults, and these may not be suitable in people at high risk of cognitive decline. There is a pressing need for clinicians to understand late-onset ET, but this is challenging when there are so few publications specifically focussed on this subject and no specific features to guide prognosis. More rigorous clinical follow-up and precise phenotyping of the clinical manifestations of late-onset ET using accessible computer technologies may help us delineate whether late-onset ET is a separate clinical entity and aid prognostication.

Recent evidence suggests increased activity of the pre-frontal cortex (PFC) is associated with sensorimotor disturbances of standing balance. Here we manipulate sensorimotor inputs and concurrently load cognitive resources in order to investigate the functional role of PFC activity during standing balance, and how this changes with healthy ageing. Healthy younger (n = 24; mean age = 20.8 years) and older (n = 25; mean age = 70.6 years) adults maintained balance while sensorimotor inputs were manipulated by removing vision, reducing the base of support, and reducing proprioceptive feedback. To load cognitive resources, each balance condition was undertaken alone or simultaneously with a cognitive task (dual-task). Functional near infrared spectroscopy (fNIRS) measured PFC activity and a force-plate measured postural sway. When comparing dual-tasks relative to single balance tasks (dual-task effect), at lower levels of balance task demand, the older adults exhibited increased PFC activity and similar levels of postural sway. However, at higher levels of balance task demand, a limit to PFC activity was observed and postural sway became more unstable in older adults. In contrast, for younger adults at higher levels of balance task demand, the dual-task effect resulted in an increase in PFC activity and postural sway was not unduly affected. These results suggest that PFC activity is compensating for sensorimotor deficits to maintain stability, and that a cognitive resource limit is reached for easier balance tasks in older people compared to younger people. These results suggest that increasing cortical capacity in older people may improve their balance.

Key points While it has been well described that prolonged rotational stepping will adapt the podokinetic sense of rotation, the mechanisms involved are not clearly understood. By studying podokinetic after-rotations following conditioning rotations not previously reported we have shown that slower rotational velocities are more readily adapted than faster velocities and adaptation occurs more quickly than previously thought. We propose a dynamic feedback model of vestibular and podokinetic adaptation that can fit rotation trajectories across multiple conditions and data sets. Two adaptation processes were identified that may reflect central and peripheral processes and the discussion unifies prior findings in the podokinetic literature under this new framework. The findings show the technique is feasible for people with locomotor turning problems. Abstract After a prolonged period stepping in circles, people walk with a curved trajectory when attempting to walk in a straight line without vision. Podokinetic adaptation shows promise in clinical populations to improve locomotor turning; however, the adaptive mechanisms involved are poorly understood. The first phase of this study asks: how does the podokinetic conditioning velocity affect the response velocity and how quickly can adaptation occur? The second phase of the study asks: can a mathematical feedback model account for the rotation trajectories across different conditioning parameters and different datasets? Twelve healthy participants stepped in place on the axis of a rotating surface ranging from 4 to 20 deg s-1 for durations of 1-10 min, while using visual cues to maintain a constant heading direction. Afterward on solid ground, participants were blindfolded and attempted to step without rotating. Participants unknowingly stepped in circles opposite to the direction of the prior platform rotation for all conditions. The angular velocity of this response peaked within 1 min and the ratio of the stimulus-to-response peak velocity fitted a decreasing power function. The response then decayed exponentially. The feedback model of podokinetic and vestibular adaptive processes had a good fit with the data and suggested that podokinetic adaptation is explained by a short (141 s) and a long (27 min) time constant. The podokinetic system adapts more quickly than previously thought and subjects adapt more readily to slower rotation than to faster rotation. These findings will have implications for clinical applications of the technique.

Key points It is unclear whether the visual input that accompanies a perturbation of a standing person can affect whether a recovery step is taken. Visual motion speeds were manipulated during unexpected forward and backward shoulder pulls. Visual motion that appeared slower than actual body motion reduced the initial in-place resistance to the perturbation. As a result of the modulation of the in-place response, less pull force was needed to trigger a step when visual velocity appeared slower than normal. The visuomotor postural response occurred earlier and was larger when the full-field visual input was paired with a mechanical perturbation. Abstract The present study aimed to determine how visual motion evoked by an upper body perturbation during standing affects compensatory postural responses. This was investigated by rotating the visual field forwards or backwards about the ankle, time-locked to a forwards or backwards shoulder pull. Kinematic, kinetic and electromyographic responses were recorded to a range of pull forces over 160 trials in 12 healthy adults (mean ± SD = 31 ± 5.8 years). Stepping threshold forces and in-place postural responses were compared between conditions. When the visual field moved in the same direction as the pull, so that the apparent velocity of the body was reduced (SLOW condition), the pull-force required to induce a step was less than when the visual field either rotated in the opposite direction (FAST) or was unaltered (NATURAL). For in-place responses, the body was displaced further in the direction of the pull in the SLOW condition. This was the result of a reduction in the resistive force from lower leg muscles 130 ms after the visual motion onset. In trials with no pull, the visual motion induced postural responses that were later (290 ms) and had smaller amplitudes compared to when visual motion is paired with an unexpected perturbation of the body. The results suggest that the apparent speed of the visual environment during a perturbation does influence whether a compensatory step is taken, not via a direct effect on the decision to step but by modulating the initial in-place response.

Across the world, Essential Tremor (ET) is the most common tremor diagnosis but up to half of these diagnoses are inaccurate. The misdiagnosis rate is particularly high in late-onset ET, when tremor begins after the age of 60 years. Currently, ET is reported to affect 5.5% of those over 65 years old and 21.7% aged over 95 but there is emerging evidence that late-onset ET has associations with dementia, mortality and more rapid progression. With ageing populations, and a range of new surgical treatments for ET, there is urgent need to clarify whether the clinical manifestations of late-onset ET are the same as for earlier-onset ET. This scoping review used MEDLINE, EMBASE and CINAHL as the information sources of published peer-reviewed research articles between 2011 and 2021. Analysis was done by narrative synthesis. 14 relevant papers were retrieved from studies conducted in Denmark, India, Italy, Germany, Spain and the US and, together, they comprised 7684 participants in total. Compared to older adults with earlier-onset ET, there is evidence that late-onset ET is associated with higher risk of cognitive impairment and dementia, higher mortality rate, faster rate of progression, lack of family history, altered cortical electrical activity, prolonged pupillary responses, and less propensity to demonstrate characteristic alcohol sensitivity. There is evidence that late-onset ET has different clinical manifestations to earlier-onset ET; in particular there is higher risk of dementia and mortality. The prognosis is important for clinicians to consider when selecting candidates for deep brain stimulation surgery and also for advanced care planning.

BACKGROUND: Functional near-infrared spectroscopy (fNIRS) is increasingly used in the field of posture and gait to investigate patterns of cortical brain activation while people move freely. fNIRS methods, analysis and reporting of data vary greatly across studies which in turn can limit the replication of research, interpretation of findings and comparison across works.\ud \ud RESEARCH QUESTION AND METHODS: Considering these issues, we propose a set of practical recommendations for the conduct and reporting of fNIRS studies in posture and gait, acknowledging specific challenges related to clinical groups with posture and gait disorders.\ud \ud RESULTS: Our paper is organized around three main sections: 1) hardware set up and study protocols, 2) artefact removal and data processing and, 3) outcome measures, validity and reliability; it is supplemented with a detailed checklist.\ud \ud SIGNIFICANCE: This paper was written by a core group of members of the International Society for Posture and Gait Research and posture and gait researchers, all experienced in fNIRS research, with the intent of assisting the research community to lead innovative and impactful fNIRS studies in the field of posture and gait, whilst ensuring standardization of research.

While upper limb reaches are often made in a feed-forward manner, visual feedback during the movement can be used to guide the reaching hand towards a target. In Parkinson’s disease (PD), there is evidence that the utilisation of this visual feedback is increased. However, it is unclear if this is due solely to the characteristic slowness of movements in PD providing more opportunity for incorporating visual feedback to modify reach trajectories, or whether it is due to cognitive decline impacting (feed-forward) movement planning ability. To investigate this, we compared reaction times and movement times of reaches to a target in groups of PD patients with normal cognition (PD-NC), mild cognitive impairment (PD-MCI) or dementia (PD-D), to that of controls with normal cognition (CON-NC) or mild cognitive impairment (CON-MCI). Reaches were undertaken with full visual feedback (at a ‘natural’ and ‘fast-as-possible’ pace); with reduced visual feedback of the reaching limb to an illuminated target; and without any visual feedback to a remembered target with eyes closed. The PD-D group exhibited slower reaction times than all other groups across conditions, indicative of less efficient movement planning. When reaching to a remembered target with eyes closed, all PD groups exhibited slower movement times relative to their natural pace with full visual feedback. Crucially, this relative slowing was most pronounced for the PD-D group, compared to the PD-MCI and PD-NC groups, suggesting that substantial cognitive decline in PD exacerbates dependence on visual feedback during upper limb reaches.

Objective To understand and examine the relation between postural response latencies obtained during postural perturbations and representative measures of balance during standing (sway variables) and walking (trunk motion). Design Cross-sectional. Setting University medical center. Participants Persons with multiple sclerosis (MS) (n=40) were compared with similar aged control subjects (n=20). There were 20 subjects with MS in the normal walking velocity group and 20 subjects with MS who had slow walking velocity based on a timed 25-foot walk (T25FW) of Interventions None. Main Outcome Measures Postural response latency, sway variables, trunk motion variables. Results We found that subjects with MS with both slow or normal walking velocities had significantly longer postural response latencies than the healthy control group. Postural response latency was not correlated with the T25FW. Postural response latency was significantly correlated with center of pressure sway variables during quiet standing (root mean square: ρ=.334, P =.04; range: ρ=.385, P =.017; mean velocity: ρ=.337, P =.038; total sway area: ρ=.393, P =.015). Postural response latency was also significantly correlated with motion of the trunk during walking (sagittal plane range of motion: ρ=.316, P =.05; SD of transverse plane range of motion: ρ=−.43, P =.006). Conclusions These findings clearly indicate that slow postural responses to external perturbations in patients with MS contribute to disturbances in balance control during both standing and walking.

Background: The effect of the surgical site of DBS on balance and gait in Parkinson’s Disease (PD) is uncertain. This is the first double-blind study of subjects randomized to either the STN (N 5 14) or GPi (N 5 14) who were assessed on a range of clinical balance measures. Methods: Balance testing occurred before and 6 months postsurgery. A control PD group was tested over the same period without surgery (N 5 9). All subjects were tested on and off medication and DBS subjects were also tested on and off DBS. The Postural Instability and Gait Disability items of the UPDRS and additional functional tests, which we call the Balance and Gait scale, were assessed. Activities of Balance Confidence and Activities of Daily Living questionnaires were also recorded. Results: Balance was not different between the besttreated states before and after DBS surgery for both sites. Switching DBS on improved balance scores, and scores further improved with medication, compared to the off state. The GPi group showed improved performance in the postsurgery off state and better ratings of balance confidence after surgery, compared to the STN group.

Variability of movement reflects important information for the maintenance of the health of the system. For pathological populations, changes in variability during gait signal the presence of abnormal motor control strategies. For persons with multiple sclerosis (PwMS), extensive gait problems have been reported including changes in gait variability. While previous studies have focused on footfall variability, the present study used accelerometers on the trunk to measure variability during walking. Thus, the purpose of this study was to examine the variability of the acceleration pattern of the upper and lower trunk in PwMS compared to healthy controls. We extracted linear and nonlinear measures of gait variability from 30 s of steady state walking for 15 PwMS and 15 age-matched healthy controls. PwMS had altered variability compared to controls with greater Lyapunov exponent in the ML (p < 0.001) and AP (p < 0.001) directions, and greater frequency dispersion in the ML direction (p = 0.034). PwMS also demonstrated greater mean velocity in the ML direction (p = 0.045) and lower root mean square of acceleration in the AP direction (p = 0.040). These findings indicate that PwMS have altered structure of variability of the trunk during gait compared to healthy controls and agree with previous findings related to changes in gait variability in PwMS.

Object The effect of deep brain stimulation (DBS) for Parkinson disease (PD) on balance is unclear. The goal of this study was to investigate how automatic postural responses (APRs) were affected in patients randomized to either subthalamic nucleus (STN) or globus pallidus internus (GPi) surgery. Methods The authors tested 24 patients with PD who underwent bilateral DBS, 9 control patients with PD who did not undergo DBS, and 17 age-matched control volunteers. The electrode placement site was randomized and blinded to the patients and to the experimenters. Kinematic, kinetic, and electromyographic recordings of postural responses to backward disequilibrium via forward translations of the standing surface were recorded in the week prior to surgery while the patients were off (OFF) and on (ON) antiparkinsonian medication (levodopa), and then 6 months after surgery in 4 conditions: 1) off medication with DBS switched off (OFF/OFF); 2) off medication with DBS on (DBS); 3) on medication with DBS off (DOPA); and 4) with both medication and DBS on (DBS+DOPA). Stability of the automatic postural response (APR) was measured as the difference between the displacement of the center of pressure and the projected location of the center of body mass. Results Patients with PD had worse APR stability than controls. Turning the DBS on at either site improved APR stability compared with the postoperative OFF condition by lengthening the tibialis response, whereas medication did not show an appreciable effect. The STN group had worse APR stability in their best functional state (DBS+DOPA) 6 months after the DBS procedure compared with their best functional state (ON levodopa) before the DBS procedure. In contrast, the GPi group and the PD control group showed no change over 6 months. The APR stability impairment in the STN group was associated with smaller tibialis response amplitudes, but there was no change in response latency or coactivation with gastrocnemius. Conclusions Turning the DBS current on improved APR stability for both STN and GPi sites. However, there was a detrimental DBS procedural effect for the STN group, and this effect was greater than the benefit of the stimulating current, making overall APR stability functionally worse after surgery for the STN group.

Object While deep brain stimulation (DBS) has proven to be an effective treatment for many symptoms of Parkinson disease (PD), a deterioration of axial symptoms frequently occurs, particularly for speech and swallowing. These unfavorable effects of DBS may depend on the site of stimulation. The authors made quantitative measures of jaw velocity to compare the relative effectiveness of DBS in the globus pallidus internus (GPi) or the subthalamic nucleus (STN). This was a randomized, double-blind, and longitudinal study, with matched healthy controls. Methods The peak velocities of self-scaled and externally scaled jaw movements were studied in 27 patients with PD before and after 6 months of bilateral DBS in the GPi or the STN. A mixed-effects model was used to identify differences in jaw velocity before DBS surgery (baseline) while off and on levodopa therapy, and after 6 months of DBS (postoperative) during 4 treatment conditions (off- and on-levodopa states with and without DBS). Results Self-scaled jaw velocity was impaired by the DBS procedure in the STN; velocity was significantly decreased across all postoperative conditions compared with either the off- or on-levodopa baseline conditions. In contrast, the postoperative velocity in the GPi group was generally faster than the baseline off-levodopa state. Turning the DBS off and on had no effect on jaw velocity in either group. Unlike baseline, levodopa therapy postoperatively no longer increased jaw velocity in either group, and this lack of effect was not related to postoperative changes in dose. The externally scaled jaw velocity was little affected by PD, but DBS still slightly affected performance, with the STN group significantly slower than the GPi group for most conditions. Conclusions The authors' results suggest that either the electrode implant in STN or the subsequent period of continuous STN stimulation negatively affected voluntary jaw velocity, including the loss of the preoperative levodopa-induced improvement. While the GPi group showed some improvement in voluntary jaw velocity postoperatively, their performance during the combination of DBS and levodopa was not different from their best medical management presurgery. The results have implications for DBS target selection, particularly for those patients with oromotor dysfunctions.

A fundamental concern of the brain is to establish the spatial relationship between self and the world to allow purposeful action. Response adaptation to unvarying sensory stimuli is a common feature of neural processing, both peripherally and centrally. For the semicircular canals, peripheral adaptation of the canal-cupula system to constant angular-velocity stimuli dominates the picture and masks central adaptation. Here we ask whether galvanic vestibular stimulation circumvents peripheral adaptation and, if so, does it reveal central adaptive processes. Transmastoidal bipolar galvanic stimulation and platform rotation (20 deg s−1) were applied separately and held constant for 2 min while perceived rotation was measured by verbal report. During real rotation, the perception of turn decayed from the onset of constant velocity with a mean time constant of 15.8 s. During galvanic-evoked virtual rotation, the perception of rotation initially rose but then declined towards zero over a period of ∼100 s. For both stimuli, oppositely directed perceptions of similar amplitude were reported when stimulation ceased indicating signal adaptation at some level. From these data the time constants of three independent processes were estimated: (i) the peripheral canal-cupula adaptation with time constant 7.3 s, (ii) the central ‘velocity-storage' process that extends the afferent signal with time constant 7.7 s, and (iii) a long-term adaptation with time constant 75.9 s. The first two agree with previous data based on constant-velocity stimuli. The third component decayed with the profile of a real constant angular acceleration stimulus, showing that the galvanic stimulus signal bypasses the peripheral transformation so that the brainstem sees the galvanic signal as angular acceleration. An adaptive process involving both peripheral and central processes is indicated. Signals evoked by most natural movements will decay peripherally before adaptation can exert an appreciable effect, making a specific vestibular behavioural role unlikely. This adaptation appears to be a general property of the internal coding of self-motion that receives information from multiple sensory sources and filters out the unvarying components regardless of their origin. In this instance of a pure vestibular sensation, it defines the afferent signal that represents the stationary or zero-rotation state.

The sense of orientation during locomotion is derived from our spatial relationship with the external environment, sensed predominantly by sight and sound, and from internal signals of motion, generated by the vestibular sense and the pattern of efferent and afferent signals to the muscles and joints. The sensory channels operate in different reference frames and have different time-dependent adaptive properties and yet the inputs are combined by the central nervous system to create an internal representation of self-motion. In normal circumstances vestibular, visual and proprioceptive cues provide congruent information on locomotor trajectory; however, in cases of sensory discord there must be a recalibration of sensory signals to provide a unitary representation. We develop a means of studying these fusion processes by perturbing each channel in isolation about a consistent behavioural axis. This review focuses on creating the vestibular perturbation of the orientation sense by transmastoidal galvanic stimulation, a technique generally used to evoke balance reflexes. Vector summation across the population of semicircular canal afferents creates a net signal that is interpreted by the brain as a vector of angular acceleration in a craniocentric reference frame. The signal feeds perceptual processes of orientation after transformation that resolves the 3-D signal onto the terrestrial or behavioural plane. Changing head posture changes the interpretation of the galvanic vestibular signal for balance and orientation responses. With appropriate head alignments during locomotion, the galvanic stimulus can be used to either steer trajectory over the terrestrial plane or perturb balance.

Trips are the largest contributor to falls in older people, yet little is known about the underlying physiological mechanisms for safe obstacle negotiation. The aims of the study were to determine (i) the effect of a secondary visual task on obstacle contacts when older people negotiated an obstacle course and (ii) physiological factors associated with obstacle contacts.Thirty community-living adults aged 65 years and older walked along a 14.5-m walkway containing 21 obstacles with and without a secondary task. The secondary task required participants to call out a series of letters presented in front of them at head height and the suit of a playing card framed on the sidewall. Obstacle contacts, secondary task errors, eye peak-to-peak pitch amplitude and head peak-to-peak pitch amplitude (PA-H), and head angle in pitch were measured. Participants also completed assessments of sensorimotor function and balance.Compared with the obstacle-only trials, participants performed the dual-task trials more slowly (p.001), contacted more obstacles (p = .032), showed greater PA-H (p.001), and an extended head position (p.001). Most participants also made secondary task errors. Regression analysis revealed that depth perception was the only significant determinant of obstacle contacts (explaining 20.6% of the variance) in the obstacle-only task and that depth perception and PA-H were independent and significant determinants of obstacle contacts (explaining 42.3% of the variance) in the dual task.The findings demonstrate the importance of depth perception and head movement for safe negotiation of obstacles in older people and suggest that depth perception in particular should form part of fall risk assessments.

Objectives: To determine whether wearing multifocal glasses affects obstacle avoidance and eye and head movements during walking with and without a secondary visual task in older people. Design: Randomized order, cross-over, controlled comparison. Setting: Falls laboratory, medical research institute. Participants: Thirty community-living adults aged 65 and older. Measurements: Obstacle contacts, secondary-task errors, average head angle (HA) in pitch, and peak-to-peak pitch amplitude of the eye (PA-E) and the head (PA-H) were assessed during obstacle-only and dual-task trials that required participants to read a series of letters presented in front of them at eye level under multifocal and single-lens glasses conditions. Results: When wearing multifocal lens glasses, participants performed the obstacle-only trials more slowly ( P = 0.004) and contacted more obstacles in the dual-task trials ( P = 0.001) than when wearing single-lens glasses. For the dual task trials under the multifocal glasses condition, greater PA-E was associated with more obstacle contacts (ρ = 0.409, P = 0.02) and greater PA-H was associated with more secondary-task errors (ρ = 0.583, P = 0.002). Lower HA was associated with more secondary-task errors (ρ = 0.608, P = 0.002) and increased PA-H (ρ = 0.426, P = 0.02). Conclusion: The findings demonstrate that older adults contact more obstacles while walking with their attention divided when wearing multifocal glasses. This is probably because of a failure to adopt a compensatory increase in pitch head movement, resulting in blurred vision of obstacles viewed through the lower segments of multifocal glasses.

Background. Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people. Methods. Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test. Results. Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p

Objective: To determine whether a 22 week water exercise program can improve physical functioning in older people. Methods: The controlled study was conducted with 85 water exercise subjects (mean age 71.8 years) and 44 controls (mean age 76.5 years). The outcome measures were leaning balance, quadriceps strength, reaction time and shoulder range of motion. Results: At baseline, the groups were well-matched across most demographic, health and physical performance measures. At retest, the 48 exercise subjects who were available for retest showed significantly improved leaning balance (as measured by tests of maximal balance range and coordinated stability) and shoulder range of motion compared with the controls. The groups did not differ in tests of quadriceps strength and reaction time. Conclusions: These findings show that water exercise can produce benefits with regard to improving balance and flexibility in older people.

Menz HB, Lord SR, St George R, Fitzpatrick RC. Walking stability and sensorimotor function in older people with diabetic peripheral neuropathy. Arch Phys Med Rehabil 2004;85:245–52. Objective To evaluate, in older people with diabetic peripheral neuropathy (DPN) and in age-matched controls, acceleration patterns of the head and pelvis when walking to determine the effect of lower-limb sensory loss on walking stability. Design Case-control study. Setting Falls and balance laboratory in Australia. Participants Thirty persons with diabetes mellitus (age range, 55–91y) and 30 age-matched controls. Interventions Acceleration patterns of the head and pelvis were measured while participants walked on a level surface and an irregular walkway. Participants also underwent tests of vision, sensation, strength, reaction time, and balance. Main outcome measures Temporospatial gait parameters and variables derived from acceleration signals. Results Participants with DPN had reduced walking speed, cadence, and step length, and less rhythmic acceleration patterns at the head and pelvis compared with controls. These differences were particularly evident when participants walked on the irregular surface. Participants with DPN also had impaired peripheral sensation, reaction time, and balance. Conclusions Older people with DPN have an impaired ability to stabilize their body when walking on irregular surfaces, even if they adopt a more conservative gait pattern. These results provide further insights into the role of peripheral sensory input in the control of gait stability, and suggest possible mechanisms underlying the increased risk of falling in older people with diabetic neuropathy.

The effect of the surgical site of DBS on balance and gait in Parkinson's Disease (PD) is uncertain. This is the first double-blind study of subjects randomized to either the STN (N = 14) or GPi (N = 14) who were assessed on a range of clinical balance measures.Balance testing occurred before and 6 months postsurgery. A control PD group was tested over the same period without surgery (N = 9). All subjects were tested on and off medication and DBS subjects were also tested on and off DBS. The Postural Instability and Gait Disability items of the UPDRS and additional functional tests, which we call the Balance and Gait scale, were assessed. Activities of Balance Confidence and Activities of Daily Living questionnaires were also recorded.Balance was not different between the best-treated states before and after DBS surgery for both sites. Switching DBS on improved balance scores, and scores further improved with medication, compared to the off state. The GPi group showed improved performance in the postsurgery off state and better ratings of balance confidence after surgery, compared to the STN group.Clinical measures of balance function for both the STN and GPi sites showed that balance did not improve beyond the best medically treated state before surgery. Both clinical balance testing in the off/off state and self-reported balance confidence after surgery showed better performance in the GPi than the STN group.

Background: Research on the relationship between vestibular function and falls in older people is sparse. The perception of the postural vertical (PPV) provides an indicator measure of vestibular (otolith) function in the absence of visual input and diminished somatosensory feedback. Objective: This study examined whether impaired PPV is associated with falls in this group. Methods: One hundred and ninety-five people aged 70 plus years stood blindfolded on a motorised platform that could be tilted in the roll plane and attempted to adjust it so that their bodies were aligned to the vertical. Somatosensory feedback was minimised as the base and vertical support surfaces on the tilting platform were covered in thick soft foam rubber. PPV error from true vertical and PPV variability (°) were calculated. Participants also underwent an assessment of distal tactile sensitivity and the physiological profile assessment (PPA); fallers were defined as those who had one or more falls during a prospective 12-month follow-up period. Results: Eighty-eight participants (45%) reported falling in the follow-up year. Increased PPV error and variability were correlated with increased lateral sway in a condition of absent visual input and reduced foot somatosensory feedback (eyes closed/foam; r range = 0.16–0.20, p < 0.05) and with composite PPA fall risk scores (r range = 0.22–0.26, p < 0.05). PPV variability was a significant and independent predictor of falls after adjusting for the composite PPA scores, age and gender [adjusted RR = 1.42 (1.01–1.98)]. Conclusions: Older people with increased PPV variability are at increased risk of falls. These findings indicate that assessment of PPV may augment fall risk assessments in older people.

The sense of orientation during locomotion is derived from our spatial relationship with the external environment, sensed predominantly by sight and sound, and from internal signals of motion, generated by the vestibular sense and the pattern of efferent and afferent signals to the muscles and joints. The sensory channels operate in different reference frames and have different time-dependent adaptive properties and yet the inputs are combined by the central nervous system to create an internal representation of self-motion. In normal circumstances vestibular, visual and proprioceptive cues provide congruent information on locomotor trajectory; however, in cases of sensory discord there must be a recalibration of sensory signals to provide a unitary representation. We develop a means of studying these fusion processes by perturbing each channel in isolation about a consistent behavioural axis. This review focuses on creating the vestibular perturbation of the orientation sense by transmastoidal galvanic stimulation, a technique generally used to evoke balance reflexes. Vector summation across the population of semicircular canal afferents creates a net signal that is interpreted by the brain as a vector of angular acceleration in a craniocentric reference frame. The signal feeds perceptual processes of orientation after transformation that resolves the 3-D signal onto the terrestrial or behavioural plane. Changing head posture changes the interpretation of the galvanic vestibular signal for balance and orientation responses. With appropriate head alignments during locomotion, the galvanic stimulus can be used to either steer trajectory over the terrestrial plane or perturb balance.

King LA, St George RJ, Carlson-Kuhta P, Nutt JG, Horak FB. Preparation for compensatory forward stepping in Parkinson's disease. Objective To characterize preparation for compensatory stepping in people with Parkinson's disease (PD) compared with healthy control subjects, and to determine whether levodopa medication improves preparation or the execution phases of the step. Design Observational study. Setting Outpatient neuroscience laboratory. Participants Nineteen participants with idiopathic PD tested both in the on and off levodopa states and 17 healthy subjects. Intervention Moveable platform with posterior translations of 24cm at 56cm/s. Main Outcome Measures Compensatory steps forward, in response to a backward surface translation (24cm amplitude at 56cm/s), were categorized according to the presence of an anticipatory postural adjustment (APA) before stepping: no APA, single APA, or multiple APAs. The following step parameters were calculated: step latency, step length, center of mass (CoM) average velocity, and CoM displacement at the step initiation. Results Lateral APAs were evident in 57% and 42% of trials for people with PD in the off and on medication states, respectively, compared with only 10% of trials for control subjects. Compared with subjects with PD who did not have APAs, those subjects with PD who did make an APA prior to stepping had significantly later (mean ± SEM, 356±16ms vs 305±8ms) and shorter (mean ± SEM, 251±27mm vs 300±16mm) steps, their CoM was significantly farther forward (185±7mm vs 171±5mm) at foot-off, and they took significantly more steps to regain equilibrium. Levodopa did not affect the preparation or execution phase of compensatory stepping. Poor axial scores and reports of freezing in the United Parkinson's Disease Rating Scale were associated with use of 1 or more APAs before compensatory stepping. Conclusions Lateral postural preparation prior to compensatory stepping in subjects with PD was associated with inefficient balance recovery from external perturbations.

Background: Older people often experience unusual sleeping patterns and a poor quality of night-time sleep. Insufficient sleep has potential effects on cognition and physical functioning and therefore may increase the incidence of falls in older people. Objectives: To determine the extent to which a range of physiological, psychological and health-related factors predict night-time sleep quality of older people living in self-care and assisted-care, and whether poor sleep quality is a risk factor for falls. Methods: 572 people, 81 men and 491 women (mean age 79.7 years, SD 6.4), recruited from self-care retirement villages and assisted-care hostels participated in the cross-sectional study with a subgroup of 169 followed up for falls for 1 year. The main outcome measures were sleep quality and prospective falls. Results: Approximately half of the sample rated their sleep quality as poor or fair. Many measures of health, medication use and mood were significantly associated with ratings of poor night-time sleep quality. Multiple regression analyses revealed poor circulation, use of psychotropic and diuretic medications, negative affect, pain, not having a friend in the village, lower fitness levels and daytime napping were significant and independent predictors of night-time sleep quality in both residential care groups. Napping daily was reported by 28% of the self-care group and 37% of the assisted-care group. Residents across both care levels who napped >30 min during the day, or reported Conclusions: Sleep disturbances were common and associated with a variety of psychological, physiological, health and lifestyle factors. Long daytime naps and short night-time sleep periods were associated with an increased risk of falls.

OBJECTIVE: to compare the effects of two different exercise programmes after hip fracture. DESIGN: assessor-blinded randomised controlled trial. SETTING: hospital rehabilitation units, with continued intervention at home. SUBJECTS: 160 people with surgical fixation for hip fracture transferred to inpatient rehabilitation. METHOD: in addition to other rehabilitation strategies, the intervention group received a higher dose (60 min/day) exercise programme conducted whilst standing and the control group received a lower dose exercise programme (30 min/day) primarily conducted whilst seated/supine. The primary outcome measures were knee extensor muscle strength in the fractured leg and walking speed, measured at 4 and 16 weeks. RESULTS: 150 participants (94% of those recruited) completed the trial. There were no differences between the groups for the two primary outcome measures. Post hoc analyses revealed increased walking speed among those in the higher dose, weight-bearing exercise group with cognitive impairment at 4 and 16 weeks. CONCLUSIONS: there was no benefit (or harm) due to the higher dose, weight-bearing exercise programme with respect to the primary outcome measures. However, people with hip fracture and cognitive impairment gained greater benefit from the higher dose programme than from the lower dose programme.

BACKGROUND Studies comparing the effects of spatial and nonspatial secondary tasks on balance have produced conflicting results. However, in most of these studies the difficulty levels of the secondary tasks have not been matched. In this study, we compared the effects of carefully matched visuospatial (VS) and nonspatial (NS) secondary tasks on choice stepping reaction time (CSRT). METHODS Forty-one older people (mean age 78.8 years) completed a CSRT test under five conditions: (i) no secondary task; (ii) an easy NS counting backward task; (iii) a difficult NS counting back task; (iv) an easy VS memory task; and (v) a difficult VS memory task. Response times and secondary task errors were measured for each condition. Participants also gave difficulty ratings for each secondary task. RESULTS The difficult tasks were rated significantly more difficult than the easy tasks in both VS and NS conditions, and cognitive task errors were moderately correlated with perceived difficulty. A repeated-measure analysis of variance with planned contrasts revealed a significant effect of task type, with the VS condition slowing CSRT more than the NS condition. There was also a significant task difficulty effect with the more difficult tasks increasing CSRT. CONCLUSIONS The findings suggest that VS cognitive tasks affect CSRT more so than do NS tasks. The visuospatial sketchpad appears to be specifically utilized for carrying out motor tasks necessary for preserving balance. Practical implications are that tasks that require visuospatial attention and memory may adversely influence balance control in older people.