The use of a dual-task paradigm to identify superior sensory organisation ability in rhythmic gymnasts.

Previous study has showed superior sensory organisation ability in rhythmic gymnasts, but mostly in longitudinal data. With a cross-sectional design, this study used a dual-task paradigm to examine the above phenomenon. Fifteen female rhythmic gymnasts (15.0 ± 1.8 yr.) and matched peers (15.1 ± 2.1 yr.) were recruited. The Sensory Organization Test (SOT) was administered with a concurrent lower-demand (serial subtraction of three, serving as the baseline) or higher-demand (serial subtraction of seven, serving as the dual-task) arithmetic task. The results showed no main effect of group, but a group by level of arithmetic task (P = 0.001) interaction effect on SOT equilibrium score. The higher-demand task facilitated balance performance in the gymnasts, but it impeded performance in the controls, with the differences more pronounced in challenging SOT conditions. With the higher-demand task, the gymnasts adopted a sensory strategy with a higher visual ratio but a smaller somatosensory ratio compared to the controls. Better visual utilisation of sensory organisation ability was apparent in gymnasts, but only when the SOT test was performed with a higher-demand secondary task. We have demonstrated the efficacy of using the dual-task paradigm to identify the superior sensory organisation ability of adolescent rhythmic gymnasts.

Development of a Smartphone-Based Balance Assessment System for Subjects with Stroke.

Stroke is a cerebral artery disease that negatively affects activities of daily living (ADLs) and quality of life (QoL). Smartphones have demonstrated strong potential in assessing balance performance. However, such smartphone-based tools have thus far not been applied to stroke survivors. The purpose of this study was to develop a smartphone-based balance assessment system for subjects who have experienced strokes and evaluate the system feasibility. The smartphone-based balance assessment application was developed with Android Studio, and reliability and validity tests were conducted. The smartphone was used to record data using a built-in accelerometer and gyroscope, and increased changes represented greater instability. Six postures were tested for 30 s each. Ten healthy adults were recruited in the reliability test, and the intraclass correlation coefficient (ICC) was used to analyze the within-day and between-day reliabilities. Eight subjects with chronic stroke and eight healthy adults were recruited for the validity test, in which balance performance was compared to represent the application validity. The ICC values of the reliability tests were at least 0.76 (p = 0.00). The acceleration data exhibited no difference between individuals who have experienced stroke and healthy subjects; however, all six postures were found to differ significantly between the two groups in the gyroscope data. The study demonstrates that the smartphone application provides a convenient, reliable, and valid tool for the balance assessments of subjects who have experienced chronic stroke.

Superior short-term learning effect of visual and sensory organisation ability when sensory information is unreliable in adolescent rhythmic gymnasts.

Rhythmic gymnasts specialise in dynamic balance under sensory conditions of numerous somatosensory, visual, and vestibular stimulations. This study investigated whether adolescent rhythmic gymnasts are superior to peers in Sensory Organisation test (SOT) performance, which quantifies the ability to maintain standing balance in six sensory conditions, and explored whether they plateaued faster during familiarisation with the SOT. Three and six sessions of SOTs were administered to 15 female rhythmic gymnasts (15.0 ± 1.8 years) and matched peers (15.1 ± 2.1 years), respectively. The gymnasts were superior to their peers in terms of fitness measures, and their performance was better in the SOT equilibrium score when visual information was unreliable. The SOT learning effects were shown in more challenging sensory conditions between Sessions 1 and 2 and were equivalent in both groups; however, over time, the gymnasts gained marginally significant better visual ability and relied less on visual sense when unreliable. In conclusion, adolescent rhythmic gymnasts have generally the same sensory organisation ability and learning rates as their peers. However, when visual information is unreliable, they have superior sensory organisation ability and learn faster to rely less on visual sense.

Postural stabilization effects of light touch do not come from axis-specific cues of postural sway: a pilot study.

A light finger touch can stabilize posture despite it not providing enough force to create mechanical support. The underlying mechanism may be due to the finger touch providing information in the axis with the greatest instability. The most appropriate way to test this hypothesis is a dual-axis paradigm, i.e., to remove sway-related information from touch in either anterior-posterior (AP) or medio-lateral (ML) axis and then measure postural sway in both axes when the standing posture is equally unstable in AP and ML axes. In this study, 16 participants stood in a feet-together stance, and center of pressure in both axes was measured. Apart from No touch and Stable conditions, the touch surface was manipulated to move in close synchrony with postural sway so as to remove information regarding postural sway in one axis (AP Sway-referenced) or two axes (AP-ML Sway-referenced). The results showed that AP Sway-referenced condition stabilized posture in both axes, whereas AP-ML Sway-referenced condition did not stabilize posture in either axis. The pilot results indicated that touch effects do not come from axis-specific sensory cues of postural sway.

Effects of the direction of Kinesio taping on sensation and postural control before and after muscle fatigue in healthy athletes.

In this study, Kinesio tape (KT) was applied in two different directions to the gastrocnemius muscle, the most important muscle in stance stability, to investigate the effect of different taping directions on overall balance and sensation systems before versus after muscle fatigue. The participants, comprising 45 healthy athletes, were randomly divided into three groups: the placebo taping group (PTG), the facilitation KT group (FKTG), and the inhibition KT group (IKTG). The tests involved in this study were a balance test, a superficial sensory function test, and a combined cortical sensation test. The data from these tests were collected before taping, after taping and a 10-min rest, and immediately after continuous heel raises were performed to fatigue. The results of the balance tests showed no significant group × time interaction, whether subjects stood barefoot on one foot or stood on a soft mat with eyes open or closed (p > 0.05). Only the sway distance and sway velocity of the center of pressure (COP) when subjects stood barefoot on one foot with eyes open were significantly higher in the inhibition taping group than in the placebo taping group (p < 0.05). In addition, significant differences were noted in the sway area and sway distance of the COP before taping, after taping, and after exercise to fatigue when the participants stood on the soft mat with their eyes open (p < 0.05). When the participants stood on the soft mat on one foot with their eyes closed, no significant differences were noted among the groups. When subjects stood on a soft mat on one foot with eyes open, significant improvements were noted after fatiguing exercise versus before taping for all three groups (p < 0.05). The results of the superficial sensory test showed no significant group × time interaction and no difference among the three taping conditions or before/after taping and after fatiguing exercise. Only in the two-point discrimination test was a sensory difference observed, with the facilitation taping group having a significantly shorter discrimination distance than the placebo taping and inhibition taping groups (p < 0.05). The present study showed that KT application for a simple balance task (e.g., barefoot on a hard floor with eyes open) may slightly influence postural control, especially when the inhibition method is used. However, more difficult balance tasks (e.g., barefoot on a soft mat with eyes closed) show no effect of KT application-either the facilitation method or the inhibition method-on posture control.

Effect of age on postural performance and control strategies during changes in visual input and dual-tasking stances.

Background: With age, people begin to experience deterioration in standing balance, especially when sensory input is suddenly removed or added. Here, we sought to explore the effects of age on postural performance and postural control strategies. Methods: The convenience sample consisted of 15 young, 10 middle-aged, and 14 elderly healthy adults. They were instructed to stand with their feet together in four randomly administered conditions involving visual input removal/addition and single-/dual-tasking. Dual-tasking involved continuous subtraction by 3s. Results: Postural sway displacement in the two older groups seemed larger than that in the younger group; however, neither the main effect of group (F2, 36 = 1.152, p = .327) nor the group × time interaction effect (F4, 27 = 0.229, p = .922) was significant. Greater stiffness of the lower leg muscles was observed in the vision-addition condition than in the vision-removal condition in only the elderly group (t13 = -2.755, p = .016). The dual-tasking condition resulted in smaller sway displacement (F1, 36 = 7.690, p = .009) and greater muscle stiffness (F1, 36 = 5.495, p = .025). In the vision-removal condition, the increase in muscle stiffness due to dual-tasking was significantly larger in the middle-aged (t9 = -3.736, p = .005) and elderly groups (t13 = -2.512, p = .026). Conclusions: In healthy older individuals, age-related changes were observed in control strategies used to maintain standing balance upon changes in visual input. The dual-task paradigm induced the use of an ankle-stiffening strategy in middle-aged and elderly adults.

Self-reported mobility and instrumental activities of daily living: test-retest reliability and criterion validity.

To determine the test-retest reliability and criterion validity of self-reported function in mobility and instrumental activities of daily living (IADL) in older adults, a convenience sample of 70 subjects (72.9 ± 6.6 yr, 34 male) was split into able and disabled groups based on baseline assessment and into consistently able, consistently disabled, and inconsistent based on repeat assessments over 2 weeks. The criterion validities of the self-reported measures of mobility domain and IADL-physical subdomain were assessed with concurrent baseline measures of 4 mobility performances, and that of the self-reported measure of IADL-cognitive subdomain, with the Mini-Mental State Examination. Test-retest reliability was moderate for the mobility, IADL-physical, and IADL-cognitive subdomains (κ = .51-.66). Those who reported being able at baseline also performed better on physical- and cognitive-performance tests. Those with variable performance between test occasions tended to report inconsistently on repeat measures in mobility and IADL-cognitive, suggesting fluctuations in physical and cognitive performance.

Changes in cognitive-motor interference during rehabilitation of cane walking in patients with subacute stroke: A pilot study.

No previous research has examined cognitive-motor interference (CMI) repeatedly in patients with subacute stroke. This pilot study aimed to report on the changes over time in CMI in patients with stroke who have recently learned to walk with a cane. The assessment started as soon as the participants could walk independently with a quad cane, and was repeated up to six sessions as long as the cane was still used. The dual-tasking paradigm required participants to walk and perform continuous subtractions by 3s. Data were analyzed for 9 participants 33-127 days post-stroke. All 9 participants showed CMI in walking velocity at baseline and 8 of these showed improvement over time (Z = -2.547; p = 0.011). The improvement in CMI was associated with baseline dual-tasking performance (ρ = 0.600; p = 0.044), motor control ability (ρ = -0.695; p = 0.019), walking velocity (ρ = -0.767; p = 0.008), and functional mobility (ρ = 0.817; p = 0.004). All participants showed decrements in both tasks (mutual interference) at baseline, 1 evolved to decrements in walking velocity (cognitive-related motor interference), and 3 finally evolved to decrements in cognitive performance but increments in walking velocity (motor-priority tradeoff). In conclusion, during rehabilitation with cane walking in patients with subacute stroke, the dual-tasking paradigm revealed CMI and its improvements in the majority of participants. Greater improvement in CMI was moderately to strongly associated with worse baseline performance of many variables. The evolution of the CMI pattern over time provides novel information relevant to neurological recovery.

Age-related differences in alpha and beta band activity in sensory association brain areas during challenging sensory tasks.

Sensory challenges to postural balance are daily threats for elderly individuals. This study examined electroencephalography (EEG) in alpha and beta bands in sensory association areas during the Sensory Organization Test, involving withdrawal of visual or presenting misleading somatosensory inputs, in twelve young and twelve elderly participants. The results showed stepwise deterioration in behavioral performance in four conditions, with group effects that were amplified with combined sensory challenges. With eye closure, alpha and beta activities increased in all sensory association areas. Fast beta activity increased in the bilateral parietal-temporal-occipital areas. Misleading somatosensory information effects on EEG activity were of smaller amplitude than eye closure effects and in a different direction. Decreased alpha activity in left parietal-temporal-occipital areas and decreased beta and fast beta activities in bilateral parietal-temporal-occipital areas were significant. Elderly participants had increased fast beta activity in the left temporal-occipital and bilateral occipital areas, indicative of sustained efforts that they made in all sensory conditions. Similar to the young participants, elderly participants with eyes closed showed increased alpha activity, although to a smaller degree, in bilateral temporal-occipital and left occipital areas. This might indicate a lack of efficacy in redistributing relative sensory weights when elderly participants dealt with eye closure. In summary, EEG power changes did not match the stepwise deterioration in behavioral data, but reflected different sensory strategies adopted by young and elderly participants to cope with eye closure or misleading somatosensory information based on the efficacy of these different strategies.

Attentional demands of cane-free walking and cane walking in subacute stroke patients who have just learned to walk without a cane.

This study compared the attentional demands between cane-free walking and cane walking in patients with stroke during the transitional period of cane weaning. Patients with stroke who had just learned to walk cane-free were recruited. Cross-sectional measurement was scheduled within 30 days since the patients were able to walk independently without a quad cane. The dual-tasking paradigm required participants to walk with and without a cane, as well as perform continuous subtractions by 1 s (low-demand) or 3 s (high-demand). The cognitive-motor interference (CMI) of walking velocity was calculated as [(low-demand - high-demand)/low-demand] × 100%. Nine participants (average age, 53.4 ± 6.4 years; stroke onset, 38-131 days) were recruited, and eight showed positive CMI. The paired t-test confirmed a significantly smaller CMI during cane-free walking than during cane walking [t (8) = -3.168; P = 0.013]. The Pearson correlation tests revealed associations between age and CMI of cane walking (r = 0.751; P = 0.010) and CMI of cane-free walking (r = 0.584; P = 0.050). The time since independent cane-free walking was associated with CMI of cane walking (r = 0.699; P = 0.018). In conclusion, experience with cane-free walking leads to increased attentional demand for cane walking. In subacute stroke patients weaning use of a cane, the attentional demand for cane-free walking decreases to less than that of cane walking. During both cane and cane-free walking, the older the participant, the more the walking performance deteriorated due to dual-tasking.

Feasibility of a smartphone-based balance assessment system for subjects with chronic stroke.

BACKGROUND: Stroke is a cerebral artery disease that may lead to long-term disabilities or death. Patients that survive a stroke usually suffer balance impairments, which affect their performance in activities of daily living (ADLs) and quality of life (QoL). In recent years, smartphones have become very popular and have many capabilities. Smartphone built-in sensors have shown their ability and potential in balance performance assessment. However, the feasibility of smartphones on subjects with chronic strokes remains to be proved. Therefore, the purpose of this study is to evaluate the feasibility of a smartphone-based balance assessment system for subjects with chronic stroke. METHODS: Ten subjects with chronic stroke and thirteen healthy adults were recruited in the study. The smartphone HTC 10 (HTC Corporation, Taiwan) was used to perform the balance assessment, and its built-in accelerometer and gyroscope were used to record data from the subjects. Six postures were tested for thirty seconds each: shoulder-width stance (SWS) with eyes opened (E/O) and eyes closed (E/C), feet-together stance (FTS) with E/O and E/C, and semi-tandem stance (STS) with E/O and E/C. The smartphone was fixed to the back of subjects at the second sacral spine (S2) level. The changes registered in the accelerometer and gyroscope data were used to represent the balance performance, in which higher values indicate more instability. Data was analyzed using the independent t-test with the software SPSS 20, and the statistical significance level was set to α < 0.05. RESULTS AND DISCUSSION: Significant difference in the acceleration data was found among subjects with chronic stroke and healthy adults under four assessment postures: SWS with E/C (p = 0.048), FTS with E/O (p = 0.027), FTS with E/C (p = 0.000), and STS with E/C (p = 0.048). Furthermore, according to the gyroscope data, there were significant differences in how the two groups performed the postures. The results demonstrate that a smartphone with a built-in accelerometer and gyroscope can be used to classify balance performances between healthy adults and subjects with chronic stroke. CONCLUSION: This study shows that smartphones are feasible to assess balance for subjects with chronic stroke.

The synchronisation of lower limb responses with a variable metronome: the effect of biomechanical constraints on timing.

Stepping in time with a metronome has been reported to improve pathological gait. Although there have been many studies of finger tapping synchronisation tasks with a metronome, the specific details of the influences of metronome timing on walking remain unknown. As a preliminary to studying pathological control of gait timing, we designed an experiment with four synchronisation tasks, unilateral heel tapping in sitting, bilateral heel tapping in sitting, bilateral heel tapping in standing, and stepping on the spot, in order to examine the influence of biomechanical constraints on metronome timing. These four conditions allow study of the effects of bilateral co-ordination and maintenance of balance on timing. Eight neurologically normal participants made heel tapping and stepping responses in synchrony with a metronome producing 500 ms interpulse intervals. In each trial comprising 40 intervals, one interval, selected at random between intervals 15 and 30, was lengthened or shortened, which resulted in a shift in phase of all subsequent metronome pulses. Performance measures were the speed of compensation for the phase shift, in terms of the temporal difference between the response and the metronome pulse, i.e. asynchrony, and the standard deviation of the asynchronies and interresponse intervals of steady state synchronisation. The speed of compensation decreased with increase in the demands of maintaining balance. The standard deviation varied across conditions but was not related to the compensation speed. The implications of these findings for metronome assisted gait are discussed in terms of a first-order linear correction account of synchronisation.

Factors Contributing to Single- and Dual-Task Timed "Up & Go" Test Performance in Middle-Aged and Older Adults Who Are Active and Dwell in the Community.

BACKGROUND: Dual-task Timed "Up & Go" (TUG) tests are likely to have applications different from those of a single-task TUG test and may have different contributing factors. OBJECTIVE: The purpose of this study was to compare factors contributing to performance on single- and dual-task TUG tests. DESIGN: This investigation was a cross-sectional study. METHODS: Sixty-four adults who were more than 50 years of age and dwelled in the community were recruited. Interviews and physical examinations were performed to identify potential contributors to TUG test performance. The time to complete the single-task TUG test (TUGsingle) or the dual-task TUG test, which consisted of completing the TUG test while performing a serial subtraction task (TUGcognitive) or while carrying water (TUGmanual), was measured. RESULTS: Age, hip extensor strength, walking speed, general mental function, and Stroop scores for word and color were significantly associated with performance on all TUG tests. Hierarchical multiple regression models, without the input of walking speed, revealed different independent factors contributing to TUGsingle performance (Mini-Mental Status Examination score, ß=-0.32), TUGmanual performance (age, ß=0.35), and TUGcognitive performance (Stroop word score, ß=-0.40; Mini-Mental Status Examination score, ß=-0.31). LIMITATIONS: At least 40% of the variance in the performance on the 3 TUG tests was not explained by common clinical measures, even when the factor of walking speed was considered. However, this study successfully identified some important factors contributing to performance on different TUG tests, and other studies have reported similar findings for single-task TUG test and dual-task gait performance. CONCLUSIONS: Although the TUGsingle and the TUGcognitive shared general mental function as a common factor, the TUGmanual was uniquely influenced by age and the TUGcognitive was uniquely influenced by focused attention. These results suggest that both common and unique factors contribute to performance on single- and dual-task TUG tests and suggest important applications of the combined use of the 3 TUG tests.

Motor dual-task Timed Up & Go test better identifies prefrailty individuals than single-task Timed Up & Go test.

AIM: The present study investigated whether dual-task Timed Up & Go tests (TUG) could identify prefrail individuals more sensitively than the single-task TUG (TUGsingle ) in community-dwelling middle-aged and older adults. METHODS: This cross-sectional study recruited adults aged 50 years and older who actively participated in local community programs. Time taken to complete single-task TUG and dual-task TUG, carrying a cup of water (TUGmanual ) or carrying out serial-3 subtraction (TUGcognitive ) while executing TUG, was measured. Prefrailty status was defined based on Fried's phenotypic definition. RESULTS: Of the 65 participants (mean age 71.5±8.1 years), 33.3% of the 12 middle-aged (50-64 years) and 62.3% of the 53 older (≥65 years) adults were prefrail, mainly as a result of weak grip strength. The receiver operating characteristic curve analyses for differentiating prefrailty from non-frailty showed that the area under the curve (AUC) for TUGmanual (0.73, 95% CI 0.60-0.86) was better than that for TUGsingle (0.67, 95% CI 0.54-0.80), whereas the AUC value was not significant for TUGcognitive (0.60, 95% CI 0.46-0.74). The optimal cut-off points for detecting prefrailty using TUGsingle , TUGmanual and TUGcognitive were 7.7 s (sensitivity 68%), 8.2 s (sensitivity 83%), and 14.3 s (sensitivity 29%), respectively. After adjusting for age, logistic regression analyses showed that individuals with TUGmanual 8.2 s or slower were 7.2-fold more likely to have prefrailty than those with TUGmanual faster than 8.2 s. CONCLUSION: TUGmanual is more valid and sensitive than TUGsingle in identifying prefrail individuals. The TUGmanual thus could serve as a screening tool for early detection of individuals with prefrailty in community-dwelling middle-aged and older adults.

Effects and after-effects of voluntary intermittent light finger touch on body sway.

Effects of light touch on body sway have usually been investigated with some form of constant contact. Only two studies investigated transient sway dynamics following the addition or withdrawal of light touch. This study adopted a paradigm of intermittent touch and assessed body sway during as well as following short periods of touch of varying durations to investigate whether effects and after-effects of touch differ as a function of touch duration. In a modified heel-to-toe posture, 15 blindfolded participants alternated their index finger position between no-touching and touching on a strain gauge in response to low- and high-pitched auditory cues. Five trials of 46 s duration were segmented into 11 sections: a 6-s no-touching period was followed by five pseudo-randomly ordered touching periods of 0.5-, 1-, 1.5-, 2-, and 5-s duration, each of which was followed by another 6-s no-touching interval. Consistent with previous research, compared to no-touching intervals sway was reduced during touch periods with touch durations greater than 2 s. Progressive reductions in sway were evident after touch onset. After touch withdrawal in the 2-s touch condition, postural sway increased and returned to baseline level nearly immediately. Interestingly, in the 5-s touch condition, reductions in sway persisted even after touch withdrawal in the medio-lateral and antero-posterior plane for around 2.5 s and 5.5 s, respectively. Our intermittent touch paradigm resulted in duration-dependent touch effects and after-effects; the latter is a novel finding and may result from a more persistent postural set involved in proactive sway control.

Meta-analysis of type and complexity of a secondary task during walking on the prediction of elderly falls.

AIM: Dual-tasking probes divided attention and causes performance changes that are associated with an increased risk for falls in the elderly. There is no systematic review investigating the effect of task type and complexity on the prediction of elderly falls. This article synthesizes research evidence regarding this issue on the contents of dual-tasking walking. METHODS: Relevant studies were systematically identified from electronic databases of Medline, PubMed, CINAHL, Cochrane CENTRAL and PsycINFO, and the reference lists of identified articles. The selection criteria were defined a priori. Two independent reviewers classified task types based on properties for cognitive demand, assessed the methodological quality with a customized checklist, and calculated the odds ratio of fall prediction. RESULTS: There was one study of reaction time, one of discrimination and decision-making, 10 of mental tracking, three of verbal fluency and five of manual tasks. The methodological heterogeneity was manifested in the selection criteria, faller classification, tasks and measures, resulting in substantial heterogeneity (I(2) 87-92%). Meta-analyses resulted in a significant pooled odds ratio 1.33 (95% CI 1.18-1.50). The mental tracking task was the only type that yielded a significant odds ratio 3.30 (95% CI 2.00-5.44). Running meta-analyses separately for simple and difficult mental tracking task showed similar odds ratios. CONCLUSION: The mental tracking task yielded significant dual-task-related changes for fall prediction. Most studies successively used an appropriate level of task complexity specific to the specified population of interest. More research is required for definite conclusions regarding the effect of task type and complexity.

Independent control of force and timing symmetry in dynamic standing balance: implications for rehabilitation of hemiparetic stroke patients.

The extent to which force and timing are independently controlled has aroused research interest. The present study aims to examine the relationship between force and timing symmetrical performances during repetitive body weight shifting. Eight hemiparetic stroke patients and eight age- and gender-matched controls were required to repetitively shift weight from one leg to the other while standing with each foot on a separate force plate. Instructions emphasised symmetry of weight transfer in each direction. No knowledge of result feedback was given. The ratio of the vertical ground reaction forces between the legs (force symmetry) was contrasted with the ratio of the intervals between leftward and rightward movements (timing symmetry). The patients showed more asymmetric and variable performances than the controls. Timing symmetry was more variable than force symmetry. In both groups, force and timing symmetry were uncorrelated. Autocovariance estimates revealed persistent alternation of large and small ground reaction forces, whereas a tendency for alternation between short and long intervals rapidly damped to zero. In conclusion, both healthy and stroke participants exhibit independent control of the force and timing symmetry under the task of natural weight shifting. This may explain the weakness of current balance retraining paradigms based on visual biofeedback, in which an emphasis on force symmetry fails to help timing performance in dynamic tasks.

Hierarchy of higher-level physical functions: a longitudinal investigation on a nationally representative population of community-dwelling middle-aged and elderly persons.

PURPOSE: Understanding the hierarchy of higher-level physical functions to infer disability level (mild, moderate or severe) is essential for the precise targeting of preventive interventions and has been examined previously in a cross-sectional study. Based on longitudinal data, this study evaluated the hierarchy of higher-level physical functions. METHODS: Data from a cohort of 2729 community-dwelling persons aged over 50 with no initial disability were drawn from the "Survey of Health and Living Status of the Elderly in Taiwan" from 1996 through 2007. The three-level hierarchy of eight chosen activities was examined by the median ages to disability onset with survival analyses and by Cox regressions, which examined the effects of sex and age on the development of this hierarchy. RESULTS: The progression of incident disability was as follows: mild level-running, carrying weight, and squatting; moderate level-climbing stairs, walking, and standing; and severe level-grasping and raising arms up. Women and older persons were at greater risk of developing more severe levels of disability. Another Cox regression with one index activity from each hierarchical level revealed similar results. CONCLUSIONS: The three-level hierarchy of higher-level physical functions has been validated longitudinally, suggesting rich research and clinical implications.

A hierarchical categorisation of tasks in mobility disability.

PURPOSE: In the field of long-term care, disability usually refers to difficulties in instrumental activities of daily living (IADL) or basic activities of daily living (BADL); this term may also refer to difficulties in mobility for those more interested in preventive intervention or general health promotion. The aims of this study were to (1) categorise a complete set of mobility tasks according to a revealed hierarchy, and (2) examine the relationship between this mobility hierarchy and IADL/BADL disabilities. METHODS: We categorised nine mobility tasks according to appearance order in self-reported difficulties data obtained from a Taiwanese national database of community-dwelling elders aged over 65. We also performed correlation tests to explore the relationships of these mobility tasks with six tasks each of IADL and BADL. RESULTS: The results revealed a three-level hierarchy of mobility disability: (1) mild disability indicated by difficulties in four mobility tasks, which correlated with difficulty in one IADL task; (2) moderate disability indicated by difficulties in three mobility tasks, which correlated with difficulties in most IADL tasks; and (3) severe disability indicated by difficulties in two mobility tasks, which correlated with difficulties in all BADL tasks. The same hierarchy was observed for males and females. CONCLUSIONS: There is a clear hierarchical structure of mobility disability that correlates differently with IADL and BADL disabilities. These results suggest that different mobility tasks should be included in disability assessments to suit specific purposes.

Altered muscle activation characteristics associated with single volitional forward stepping in middle-aged adults.

BACKGROUND: Middle-aged adults show a higher incidence of falls compared to young adults when performing outdoor physical activities. This study investigated whether or not the patterns and quantitative characteristics of the trunk and lower extremity muscle activations associated with stepping, which represents an important movement for arresting falls, differ between middle-aged adults and young adults. METHODS: Nine healthy young adults (age=22[3] years) and nine healthy middle-aged adults (age=52[8] years), performed a single-step, volitional, fast forward stepping movement with each leg. The stepping movement was divided into the step-initiation, single-leg-support, and landing phases based on foot-switch signals. The activation sequence, occurrence rate, onset latency, burst duration, and normalized co-contraction duration of the tibialis anterior, medial gastrocnemius, rectus femoris, biceps femoris, and gluteus medius of the stance and swing legs and that of bilateral erector spinae muscles were analyzed using surface electromyography. We defined the essential muscle activation as exhibiting an occurrence rate of 90% or more in all of these trials. FINDINGS: As compared to young adults, the middle-aged adults demonstrated several additional essential bursts throughout the stepping movement. Middle-aged adults also displayed significantly longer burst durations of the biceps femoris and medial gastrocnemius of the swing leg after landing, as well as longer co-contraction of the rectus femoris and biceps femoris of the stance leg in the single-leg-support phase (P<0.05). INTERPRETATION: Age-related changes in step-related neuromuscular control exist in healthy middle-aged adults. We propose that training focused on improving or maintaining neuromuscular control associated with volitional leg movements may benefit middle-aged individuals.