Visuospatial working memory and obstacle crossing in young and older people.

Obstacle crossing requires visuospatial working memory to guide the trailing leg trajectory when vision in unavailable. Visuospatial working memory, as assessed with neuropsychological tests, declines with age, however, this remains to be investigated functionally in obstacle crossing. There is also evidence that visuospatial encoding during a secondary task interferes with balance control during stepping and walking in older people. Here, we studied the interaction effects of age by delay (study 1) and age by secondary visuospatial task (study 2) conditions on obstacle clearance in a visuospatial working memory -guided obstacle crossing task. Healthy young adults aged 19 to 36 years (n = 20 in study 1 and n = 17 in study 2) and healthy older adults aged 66 to 83 years (n = 29 in study 1 and n = 21 in study 2) were instructed to step over an obstacle with their leading leg and straddle it for a delay period before completing the crossing with their trailing leg. In study 1, two obstacle height conditions (12 cm, 18 cm) and two delay durations (20 s, 60 s) were presented in random order. In study 2, participants were required to attend to either no secondary task (control), a visuospatial secondary (star movement) task, or a nonspatial secondary (arithmetic) task, while straddling the obstacle for a delay duration of 20 s, at obstacle heights of 12 cm and 18 cm, randomly presented. Trailing leg kinematics (mean and variability of maximum toe clearance over the obstacle) were determined via motion capture. There were no statistically significant age by delay or age by secondary task interactions. In study 1, toe clearance variability was significantly greater in young adults and increased with increasing delay duration in both groups. In study 2, compared with the control condition, toe clearance variability was significantly greater in the non-spatial secondary task condition but not in the visuospatial condition. Contrary to our hypotheses, these findings suggest that young and older adults alike can store an obstacle representation via visuospatial working memory for durations of at least 60 s and use this information to safely scale their trailing leg over an obstacle. However, the increase in trailing leg toe clearance variability with delay duration suggests that obstacle representation starts to deteriorate even within the first 20 s regardless of age. The finding that undertaking a concurrent arithmetic task impaired visuospatial working memory-guided obstacle clearance suggests a potential increased risk of tripping during obstacle crossing while dual-tasking in both young and older people.

Impact of ageing, fall history and exercise on postural reflexes following unpredictable perturbations: A systematic review and meta-analyses.

INTRODUCTION: This review examined the impact of ageing, fall history and exercise on postural reflexes and adaptation to unpredictable perturbations. METHODS: MEDLINE, EMBASE, Scopus, SportDiscus and Web of Science were systematically searched for cross-sectional and intervention studies that assessed muscle onset latency following unpredictable postural perturbations in adults (CRD42020170861). RESULTS: Thirty-seven articles (n = 1257) were included in this review. Older adults had slower onset latencies compared to young adults (mean difference 14 ms, 95% CI: 10, 18, P < 0.001). Regular exercisers had faster onset latencies compared to sedentary/untrained participants (mean difference 11 ms, 95%CI: -19, -4, P = 0.002). Exercise interventions delivered in randomised control trials (RCTs) led to faster onset latencies (mean difference -4 ms, 95%CI: -9, 0, P = 0.04) compared to controls. Uncontrolled clinical trials of exercise (mainly short-term) did not show changes in onset latency in pre-post tests (mean difference -2 ms, 95%CI: -5, 1, P = 0.36). CONCLUSION: This review demonstrated that in response to postural perturbation, muscle activation is significantly delayed in older compared to young adults, and that adults who regularly exercised had faster muscle activation compared to their less active counterparts. No significant changes in onset latencies were evident in uncontrolled clinical trials of short duration, but longer-term RCTs indicated postural reflexes are responsive to training.

Strength measures are better than muscle mass measures in predicting health-related outcomes in older people: time to abandon the term sarcopenia?

There is no clear consensus on definition, cut-points or standardised assessments of sarcopenia. We found a lower limb strength assessment was at least as effective in predicting balance, mobility and falls in 419 older people as muscle mass-based measures of sarcopenia. INTRODUCTION: There is currently no consensus on the definition, cut-points or standardised assessments of sarcopenia. This study aimed to investigate whether several published definitions of sarcopenia differentiate between older people with respect to important functional and health outcomes. METHODS: Four hundred nineteen community-living older adults (mean age 81.2 ± 4.5, 49 % female) completed assessments of body composition (dual-energy X-ray absorptiometry), strength, balance, mobility and disability. Falls were recorded prospectively for a year using monthly calendars. Sarcopenia was defined according to four skeletal mass-based definitions, two strength-based definitions (handgrip or knee extensor force) and a consensus algorithm (low mass and low strength or slow gait speed). Obesity was defined according to percentage fat mass or waist circumference. RESULTS: The four skeletal mass-based definitions varied considerably with respect to the percentage of participants classified as sarcopenic and their predictive accuracy for functional and health outcomes. The knee extension strength-based definition was equivalent to or better than the mass-based and consensus algorithm definitions; i.e. weaker participants performed poorly in tests of leaning balance, stepping reaction time, gait speed and mobility. They also had higher physiological fall risk scores and were 43 % more likely to fall at home than their stronger counterparts. Adding obesity to sarcopenia definitions identified participants with greater self-reported disability. CONCLUSIONS: A simple lower limb strength assessment was at least as effective in predicting balance, functional mobility and falls in older people as more expensive and time-consuming muscle mass-based measures. These findings imply that functional terms such as muscle weakness or motor impairment are preferable to sarcopenia.

Visual Field Dependence Is Associated with Reduced Postural Sway, Dizziness and Falls in Older People Attending a Falls Clinic.

Moving visual fields can have strong destabilising effects on balance, particularly when visually perceived motion does not correspond to postural movements. This study investigated relationships between visual field dependence (VFD), as assessed using the roll vection test, and reported dizziness, falls and sway under eyes open, eyes closed and optokinetic conditions. Ninety five falls clinic attendees undertook the roll vection test (i.e. attempted to align a rod to the vertical while exposed to a rotating visual field). Sway was assessed under different visual conditions by centre of pressure movement. Participants also completed questionnaires on space and motion discomfort, fear of falling, depression and anxiety. Thirty four (35.8%) participants exhibited VFD, i.e. had an error > 6.5º in the roll vection test. Compared to participants without VFD, participants with VFD demonstrated less movement of the centre of pressure across all visual conditions, were more likely to report space and motion discomfort and to have suffered more multiple falls in the past year. VFD was independent of fear of falling, anxiety and depression. VFD in a falls clinic population is associated with reduced sway possibly due to a stiffening strategy to maintain stance, dizziness symptoms and an increased risk of falls.

Does a fall prevention educational programme improve knowledge and change exercise prescribing behaviour in health and exercise professionals? A study protocol for a randomised controlled trial.

INTRODUCTION: Falling in older age is a serious and costly problem. At least one in three older people fall annually. Although exercise is recognised as an effective fall prevention intervention, low numbers of older people engage in suitable programmes. Health and exercise professionals play a crucial role in addressing fall risk in older adults. This trial aims to evaluate the effect of participation in a fall prevention educational programme, compared with a wait-list control group, on health and exercise professionals' knowledge about fall prevention and the effect on fall prevention exercise prescription behaviour and confidence to prescribe the exercises to older people. METHODS AND ANALYSIS: A randomised controlled trial involving 220 consenting health and exercise professionals will be conducted. Participants will be individually randomised to an intervention group (n=110) to receive an educational workshop plus access to internet-based support resources, or a wait-list control group (n=110). The two primary outcomes, measured 3 months after randomisation, are: (1) knowledge about fall prevention and (2) self-perceived change in fall prevention exercise prescription behaviour. Secondary outcomes include: (1) participants' confidence to prescribe fall prevention exercises; (2) the proportion of people aged 60+ years seen by trial participants in the past month who were prescribed fall prevention exercise; and (3) the proportion of fall prevention exercises prescribed by participants to older people in the past month that comply with evidence-based guidelines. Outcomes will be measured with a self-report questionnaire designed specifically for the trial. ETHICS AND DISSEMINATION: The trial protocol was approved by the Human Research Ethics Committee, The University of Sydney, Australia. Trial results will be disseminated via peer reviewed journals, presentations at international conferences and participants' newsletters. TRIAL REGISTRATION NUMBER: Trial protocol was registered with the Australian and New Zealand Clinical Trials Registry (Number ACTRN12614000224628) on 3 March 2014.

Six minutes of walking leads to reduced lower limb strength and increased postural sway in people with Multiple Sclerosis.

BACKGROUND: Fatigue, lower limb weakness and poor balance can significantly limit safe mobility in people with Multiple Sclerosis (MS). Further research is required to elucidate relationships among these factors. OBJECTIVE: To investigate the effect of walking-induced fatigue on lower limb strength and postural sway in people with moderately disabling MS. METHODS: Thirty-four people (26 female) with moderate MS (mean Expanded Disability Status Scale of 3.7 ± 0.7) underwent assessments of acute fatigue, postural sway and lower limb strength before and after six-minute conditions of seated rest and walking. A matched sample of 10 healthy controls also undertook identical assessments before and after a six-minute walk. RESULTS: Significant time by condition effects for all assessment measures indicated the six-minute walk induced fatigue with associated increases in postural sway and reductions in lower limb strength in people with MS. Increases in sway with eyes closed correlated with increases in acute fatigue and self-reported impact of fatigue on physical and psychological functioning. No changes were observed in healthy controls. CONCLUSION: People with MS show signs of fatigue after 6 minutes of walking, including strength and balance deficits. These findings have implications for both mobility and fall risk in this group.

Acute resistance exercise and pressure pain sensitivity in knee osteoarthritis: a randomised crossover trial.

OBJECTIVE: To determine whether a single bout of resistance exercise produces an analgesic effect in individuals with knee osteoarthritis (OA). DESIGN: Eleven participants with knee OA (65.9 ± 10.4 yrs), and 11 old (61.3 ± 8.2 yrs) and 11 young (25.0 ± 4.9 yrs) healthy adults performed separate bouts of upper and lower body resistance exercise. Baseline and post-exercise pressure pain thresholds were measured at eight sites across the body and pressure pain tolerance was measured at the knee. RESULTS: Pressure pain thresholds increased following exercise for all three groups, indicating reduced pain sensitivity. For the young and old healthy groups this exercise-induced analgesia (EIA) occurred following upper or lower body resistance exercise. In contrast, only upper body exercise significantly raised pain thresholds in the knee OA group, with variable non-significant effects following lower body exercise. Pressure pain tolerance was unchanged in all groups following either upper or lower body exercise. CONCLUSION: An acute bout of upper or lower body exercise evoked a systemic decrease in pain sensitivity in healthy individuals irrespective of age. The decreased pain sensitivity following resistance exercise can be attributed to changes in pain thresholds, not pain tolerance. While individuals with knee OA experienced EIA, a systemic decrease in pain sensitivity was only evident following upper body exercise.

Relationships between serum vitamin D levels, neuromuscular and neuropsychological function and falls in older men and women.

UNLABELLED: Among 463 community dwellers aged 70-90 years, those with vitamin D insufficiency showed reduced neuromuscular function, balance control and stepping ability and performed worse in tests of cognitive function. In men, vitamin D insufficiency was associated with an increased risk of falling. INTRODUCTION: The purpose of this study was to investigate the relationship between serum 25-hydroxy vitamin D (serum 25OHD) levels, physiological and neuropsychological function in older people, and to examine the relationship between serum 25OHD and prospective falls. METHODS: Four hundred sixty-three community-dwelling people aged 70-90 years underwent an assessment of physiological and neuropsychological performance and structured interviews relating to comorbidity and disability. Fall frequency during the 12 months follow-up was monitored with monthly falls diaries. RESULTS: Twenty-one percent of the men and 44% of the women were vitamin D insufficient (serum 25OHD ≤ 50 nmol/L). Participants with vitamin D insufficiency had weaker upper and lower limb strength, slower simple finger press and choice stepping reaction time, poorer leaning balance and slower gait speed, after controlling for age and body mass index, and, poorer executive function and visuospatial ability, after controlling for age and education. Vitamin D insufficiency significantly increased the rate of falls in men (IRR = 1.94, 95% CI = 1.19-3.15, p = 0.008) but not in women. CONCLUSIONS: These findings highlight the associations between vitamin D insufficiency and impairments in physiological and neuropsychological function that predispose older people to fall. The significant relationship between vitamin D insufficiency and falls found in the men may relate to the stronger association found between serum 25OHD levels and dynamic balance measures evident in this male population.

Balance disorders in the elderly.

Good balance is an imperative skill for daily life that requires the complex integration of sensory information regarding the position of the body relative to the surroundings and the ability to generate appropriate motor responses to control body movement. Balance calls upon contributions from vision, vestibular sense, proprioception, muscle strength and reaction time. With increased age, there is a progressive loss of functioning of these systems which can contribute to balance deficits. Balance disorders represent a growing public health concern due to the association with falls and fall-related injuries, particularly in regions of the world in which high proportions of the population are elderly. Falls present one of the most serious and costly problems associated with older adulthood. Falls can mark the beginning of a decline in function and independence and are the leading cause of injury-related hospitalisation in older people. One in three people over the age of 65 years who are living in the community experience at least one fall each year and 10-15% of these falls are associated with serious injury. In economic terms, the direct and indirect costs associated with falls are large and will grow as the proportion of older people increases. Consequently, understanding age-related changes in the physiological systems imperative to balance is of utmost importance to prevent falls in older people and reduce the injury-related burden on individuals and society.

The physiology of falling: assessment and prevention strategies for older people.

Balance calls upon contributions from vision, peripheral sensation, vestibular sense, muscle strength, neuromuscular control and reaction time. With increased age, there is a progressive loss of functioning of these systems and an increased likelihood of falls. Falls can mark the beginning of a decline in function and independence and are the leading cause of injury-related hospitalisation in older people. By using simple tests of vision, leg sensation, muscle strength, reaction time and standing balance, it is possible to identify accurately older people at risk of falls and assess intervention outcomes. This approach overcomes the limitations associated with traditional methods of assessing falls risk via medical diagnoses, including varied severity between individuals. Using a physiological approach provides information at the impairment and functional capacity levels to assist in understanding falls and developing and evaluating optimal falls prevention strategies for older people.