Ilan Kurz

A retrospective analysis of balance control parameters in elderly fallers and non-fallers

BACKGROUND A cross-sectional retrospective study of parameters reflecting balance function in elderly fallers and non-fallers was conducted to better understand postural control mechanisms in individuals prone to falls. METHODS Ninety-nine old adults (65-91 years, mean age 78.4 (SD 5.7)) from two self-care residential facilities participated in the study. Foot center-of-pressure (CoP) displacement data were collected during narrow base upright stance eyes closed conditions and analyzed using summary statistics and Stabilogram-Diffusion Analysis (SDA) for mediolateral (ML) and anteroposterior (AP) directions. Subjects were instructed to minimize body sway. FINDINGS Twenty-nine of the subjects reported at least one fall and 69 subjects reported no falls in the past six months. The SDA showed significantly higher short-term diffusion coefficients and critical displacements in fallers in the ML but not the AP direction. Mean sway area and ML-CoP sway range were also larger in fallers. INTERPRETATION The greater ML critical displacement seen in fallers suggests that balance corrections on average occurred at higher sway amplitudes in this population. This is consistent with an ML decrease in the sensitivity of their postural control system. A higher short-term diffusion coefficient is consistent with increased muscle stiffness, a possible compensation for lost control sensitivity. Testing balance function under narrow stance conditions provides a modest increase in task difficulty that may help reveal pre-conditions of the balance control system that could increase the risk of falls.

Regular Exercise in the Elderly Is Effective to Preserve the Speed of Voluntary Stepping under Single-Task Condition but Not under Dual-Task Condition

Background: Stepping response may be considered the most important postural reaction to prevent a fall because it is the inability to respond effectively to a loss of balance that ultimately determines whether a fall occurs. However, very little has been studied on the effect of exercising on step execution behavior in the elderly. Objectives: To explore whether older persons who exercise regularly have faster voluntary stepping times than sedentary elderly persons. Additionally, we investigated the association between step execution behavior, self-reported physical function, and balance performance. Methods: Case-control study of 48 elderly adults aged 65–91 years who live independently in retirement homes. Participants were classified as 24 exercisers (reporting >2 exercise training activities/week) and 24 age- and gender-matched inactive elderly individuals (who do not exercise regularly). The Voluntary Step Execution Test was performed as a reaction time task while standing on a force platform under single-task and dual-task conditions. Step initiation phase, foot off time, foot contact time, preparatory, and swing phases were extracted from center of pressure and ground reaction force data. Self-reported function was examined using Late-Life Function and Disability Instrument; Berg Balance Test was also performed. Results: Exercisers had significantly faster voluntary step times in single-task condition (959 vs. 1,158 ms) but not during dual-task condition (1,170 vs. 1,303 ms). Exercisers had a significantly higher Berg Balance Test (53.7 ±3.6 vs. 49.8 ±5.3), consumed less medication (3.3 ±2.3 vs. 5.6 ±2.9), and their lower extremity function scores were higher (88.61 ±2.3 vs. 73.1 ±2.7) than those of inactive subjects. Conclusion: Exercising regularly protects from physical functioning loss in older persons and against a decrease in voluntary step execution times during single-task but not during dual-task conditions. Lack of specificity (dual-task exercises) during the training may be the cause of insignificant differences in dual-task stepping performance. Thus, adding dual-task training may improve dual-task performance in the elderly.

Characteristics of balance control in older persons who fall with injury--a prospective study.

OBJECTIVE Older adults who have recently fallen demonstrate increased postural sway compared with non-fallers. However, the differences in postural control between older adults who were seriously injured (SI) as a result of a fall, compared with those who fell but were not injured (NSI) and non-fallers (NFs), has not been investigated. The objective of the present study was to investigate the underlying postural control mechanisms related to injuries resulting from a fall. METHODS Both traditional postural sway measures of foot center-of-pressure (CoP) displacements and fractal measures, the Stabilogram-Diffusion Analysis (SDA), were used to characterize the postural control. One hundred older adults aged 65-91years were tested during narrow base upright stance in eyes closed condition; falls were monitored over a 1-year period. RESULTS Forty-nine older adults fell during the 1-year follow-up, 13 were seriously injured as a result of a fall (SI), 36 were not injured (NSI), and 49 were non-fallers (NFs); two passed away. The SDA showed significantly higher short-term diffusion coefficients and critical displacements in SI in the anterior-posterior direction compared with both NSI and NF. However, in the medio-lateral direction there were no statistically significant differences between groups. For the traditional measures of sway, the average anterior-posterior CoP range was also larger in SI individuals. CONCLUSIONS This work suggests that older fallers with a deterioration of anterior-posterior postural control may be at higher risk of serious injury following fall events.

Do voluntary step reactions in dual task conditions have an added value over single task for fall prediction? A prospective study

Background and aims: Stepping reactions play a critical role in responding to balance perturbations, whether they are a consequence of external perturbation or self-induced in nature. The aim of the present study was to determine prospectively the capacity of voluntary stepping performance in singleand dual-task conditions, to predict future falls among older community-dwelling persons. We also aimed to assess whether dual task conditions have an added value over single tasks for fall prediction. Methods: A total of 100 healthy old volunteers (mean age 78.4±5.7 yrs), from two self-care protected retirement homes for older adults, performed the Voluntary Step Execution Test in single- and dual-task conditions as a reaction time task while standing on a single force platform. Step initiation, preparatory and swing phases, and foot-contact time were extracted from data on center of pressure and ground reaction force. One-year fall incidences were monitored. Results: Ninety-eight subjects completed the one-year follow-up, 49 non-fallers, 32 one-time fallers, and 17 recurrent fallers (two or more falls). Recurrent fallers had significantly slower voluntary step execution times in both single- and dual-task conditions, especially due to a slower preparation phase. Two stepwise (backward) logistic regression models showed that longer step execution times have strong predictive value for falls in both single- and dual-task conditions (odds ratio (OR) 8.7 and 5.4, respectively, p<0.05). Conclusions: Voluntary Step Execution Test in both single- and dual-task conditions is a simple and safe examination which can potentially and effectively predict future falls, with no added value to dual- over single-task condition.

Self reported function and disability in late life: a comparison between recurrent fallers and non-fallers

Purpose. To compare self-reported function and disability between fallers and non-fallers. Method. Self-reported late life function and disability (LLFDI) were evaluated among 100 elderly persons who live independently in the community in a cross sectional study. The function component evaluates difficulty in performing physical activities in upper and lower extremity and the disability component evaluates limitations in life activities and frequency in taking part in life tasks. Falls, cognitive function, berg balance test (BBS), and timed up and go (TUG) were also evaluated. Results. Eighteen subjects reported one fall (F), 11 fell twice or more (RF) and 71 did not report retrospective fall (NF). There were significant differences in overall function of LLFDI between RF and NF (56.8 ± 5.7 vs. 63.7 ± 11.4, P = 0.04), mainly due to decreased basic lower extremity function scores (66.2 ± 8.6 vs. 75.3 ± 13.5, P = 0.03); no significant differences were found in disability component scores. RF subjects showed high to moderate correlations between overall function of LLFDI, BBS and TUG (r = 0.77, P = 0.006 and r = −0.62, P = 0.04, respectively), moderate correlation between disability limitation and BBS (r = 0.60, P = 0.05) but weaker with TUG (r = −0.38, P = 0.28). Both BBS and TUG were not correlated with disability frequency (r = −0.18, P = 0.61 and r = 0.14, P = 0.68, respectively) in RF. RF demonstrated high correlation between overall function and disability limitation (r = 0.76, P = 0.007) and low with disability frequency (r = 0.39, P = 0.23). Conclusions. Balance function, self-reported function and disability limitation are strongly associated in RF but not related to the disability frequency, suggesting that the frequency of performing life tasks was not influenced only by functional capabilities.

Age-related differences in pelvic and trunk motion and gait adaptability at different walking speeds

This study aimed at investigating age-related changes in gait kinematics and in kinematic adaptations over a wide range of walking velocities. Thirty-four older adults and 14 younger adults walked on a treadmill; the treadmill velocity was gradually increased in increments of 0.2miles/hour (mph) (1.1-1.9mph) and then decreased in the same increments. Pelvic, trunk, upper limbs and lower limbs angular total ranges of motion (tROM), stride time, stride length, and step width were measured. The older adults had lower pelvic, trunk tROM and shorter strides and stride time compared with the younger adults. As the treadmill speed was gradually increased, the older adults showed an inability to change the pelvic list angular motions (3.1±1.3° to 3.2±1.4°) between different walking velocities, while the younger adults showed changes (5.1±1.8° to 6.3±1.7°) as a function of the walking velocity. As the walking velocity increased, the older adults increased their stride length (from 57.0±10cm to 90.2±0.1cm) yet stride times remained constant (from 1.17±0.3sec to 1.08±0.1sec), while the younger adults increased stride length and reduced stride times (from 71.4±10cm to 103.0±7.9m and from 1.45±0.2sec to 1.22±0.1sec, respectively). In conclusion, the older adults were unable to make adaptations in pelvic and trunk kinematics between different walking speeds (rigid behavior), while the younger adults showed more flexible behavior. Pelvic and trunk kinematics in different walking speeds can be used as variables in the assessment of gait in older adults.

The Effect of Helping Behavior and Physical Activity on Mood States and Depressive Symptoms of Elderly People

The current study examines the effects of helping behavior and physical activity on mood states and depressive symptoms of older adults. Participants (n = 102) reported their chronic conditions, volunteering, supporting behavior, and physical activity. Helping behavior, as well as physical activity, was practiced by more than half of the participants. Physical activity was positively associated with cheerfulness and vigor and explained 4% of the variance in both moods. No links were detected between the level of physical activity and depressive symptoms. Helping behavior was positively correlated with cheerfulness and vigor and explained 6% and 22% of these moods, respectively. It was negatively correlated with depressive symptoms and explained 6% of the variance in their occurrence. The positive link between helping behavior and physical exercise can be explained by adaptation theories of aging which regard the psychological benefits of multiple forms of activity in late life.

Frontal Plane Instability Following Rapid Voluntary Stepping: Effects of Age and a Concurrent Cognitive Task

BACKGROUND Quick step execution may prevent falls when balance is lost. Lateral steps often emerge as a consequence of frontal plane instability arising after the first rapid step. In this study, we suggest a new analysis, focusing on the variability of the frontal plane fluctuations of center of pressure (CoP), that is, mediolateral instability, and their changes over time during and immediately following rapid voluntary stepping in older and younger adults in single- and dual-task conditions. This may be useful in understanding age-related alterations in the locomotor control system. METHODS Seventeen older adults, who live independently in the community, and 16 younger adults performed rapid forward voluntary stepping under single- and dual-task conditions. The average mediolateral CoP fluctuations, that is, the average distance the CoP travels from side to side in the frontal plane over time, standard deviation, and the coefficient of variation of mediolateral CoP fluctuation were extracted and calculated from CoP data during and immediately following rapid voluntary stepping using a force plate. RESULTS We found an age-related increase in the coefficient of variation that represents the variability of frontal plane fluctuations and no significant differences in the average and standard deviations of frontal plane fluctuations. Cognitive task had no influence on measures of frontal plane fluctuations in both age groups. CONCLUSION The study showed frontal plane instability during and immediately following rapid stepping in older persons. This may be a factor contributing to lateral balance loss and the large number of lateral falls seen in the older population.

Age-associated changes in obstacle negotiation strategies: Does size and timing matter?

INTRODUCTION Tripping over an obstacle is one of the most common causes of falls among older adults. However, the effects of aging, obstacle height and anticipation time on negotiation strategies have not been systematically evaluated. METHODS Twenty older adults (ages: 77.7±3.4years; 50% women) and twenty young adults (age: 29.3±3.8years; 50% women) walked through an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 25mm and 75mm. Kinect cameras captured the: (1) distance of the subjects trailing foot before the obstacles, (2) distance of the leading foot after the obstacles, (3) clearance of the leading foot above the obstacles, and (4) clearance of the trailing foot above the obstacles. Linear-mix models assessed changes between groups and conditions. RESULTS Older adults placed their leading foot closer to the obstacle after landing, compared to young adults (p<0.001). This pattern was enhanced in high obstacles (group*height interaction, p=0.033). Older adults had lower clearance over the obstacles, compared to young adults (p=0.007). This was more pronounced during unanticipated obstacles (group*ART interaction, p=0.003). The distance of the leading foot and clearance of the trailing foot after the obstacles were correlated with motor, cognitive, and functional abilities. CONCLUSIONS These findings suggest that there are age-related changes in obstacle crossing strategies that are dependent on the specific characteristics of the obstacle. The results have important implications for clinical practice, suggesting that functional exercise should include obstacle negotiation training with variable practice of height and available response times. Further studies are needed to better understand the effects of motor and cognitive abilities.