Assessing autonomic dysfunction in early diabetic neuropathy: the Survey of Autonomic Symptoms.

OBJECTIVE: Autonomic symptoms may occur frequently in diabetic and other neuropathies. There is a need to develop a simple instrument to measure autonomic symptoms in subjects with neuropathy and to test the validity of the instrument. METHODS: The Survey of Autonomic Symptoms (SAS) consists of 11 items in women and 12 in men. Each item is rated by an impact score ranging from 1 (least severe) to 5 (most severe). The SAS was tested in observational studies and compared to a previously validated autonomic scale, the Autonomic Symptom Profile (ASP), and to a series of autonomic tests. RESULTS: The SAS was tested in 30 healthy controls and 62 subjects with neuropathy and impaired glucose tolerance or newly diagnosed diabetes. An increased SAS score was associated with the previously validated ASP (rank order correlation=0.68; p<0.0001) and with quantitative measures of autonomic function: a reduced quantitative sudomotor axon reflex test sweat volume (0.31; p<0.05) and an abnormal 30:15 ratio (0.53; p<0.01). The SAS shows a high sensitivity and specificity (area under the receiver operating characteristic curve 0.828) that compares favorably with the ASP. The SAS scale domains had a good internal consistency and reliability (Cronbach α=0.76). The SAS symptom score was increased in neuropathy (95% confidence interval [CI] 2.99-4.14) compared to control (95% CI 0.58-1.69; p<0.0001) subjects. CONCLUSIONS: The SAS is a new, valid, easily administered instrument to measure autonomic symptoms in early diabetic neuropathy and would be of value in assessing neuropathic autonomic symptoms in clinical trials and epidemiologic studies.

The effect of lateral stabilization on walking in young and old adults.

We tested how lateral stability affects gait as a function of age. A simple computational model suggests that walking is laterally unstable and that age-related decreases in motor and sensory function may be treated as noise-like perturbations to the body. Step width variability may be affected by active control of foot placement subject to noise. We hypothesized that age-related deficits may lead to increased step width variability. A possible compensation would be to walk with wider steps to reduce the lateral instability. The addition of external stabilization, through elastic cords acting laterally on the body during treadmill walking, would be expected to yield reduced step width variability and/or reduced average step width. We measured step width, its variability (defined as standard deviation), and metabolic energy expenditure in eight adult human subjects aged less than 30 years (Young) and ten subjects aged at least 65 years (Old). Subjects walked with and without external stabilization, each at a self-selected step width as well as a prescribed step width of zero. In normal walking, Old subjects preferred 41% wider steps than Young, and expended 26% more net energy (P < 0.05). External stabilization caused both groups to prefer 58% narrower steps. In the prescribed zero step width condition, Old subjects walked with 52% more step width variability and at 20% higher energetic cost. External stabilization resulted in reduced step width variability and 16% decreased energetic cost. Although there was no significant statistical interaction between age group and stabilization, Old and Young subjects walked with similar energetic costs in the stabilized, prescribed step width condition. Age-related changes appear to affect lateral balance, and the resulting compensations explain much of the increased energetic cost of walking in older adults.

The effect of age and movement speed on maximum forward reach from an elevated surface: a study in healthy women.

OBJECTIVE: To test the hypotheses (1) that the maximum distance reached by young or older women when standing on a raised platform is independent of movement speed, and (2) the maximum forward momentum generated at comfortable and fast reaching speeds is independent of age. DESIGN: Repeated measures case-control study in a university laboratory setting.Background. Maximum forward reach distance is often part of a geriatric mobility assessment. The effect of movement speed, and hence momentum, on forward reaching behavior is unknown in young or older subjects, despite the fact that excess momentum might increase the risk of fall-related injuries, especially from an elevated surface. METHODS: Ten healthy young women (mean age 23.7 years) and 10 healthy older women (mean age 70.5 years) participated. Subjects stood on an instrumented force platform and forward reach body segment kinematics were measured optoelectronically. Whole-body center of reaction and center of mass trajectories were calculated during six maximum forward reach trials: three performed "at a comfortable speed", and three performed "as fast as possible". RESULTS: Subjects reached slightly further at a comfortable speed than when reaching as fast as possible (P=0.016). Fast reaches were associated with a 25% increase in momentum (P<0.001; however, under both speed conditions, older women developed less whole-body momentum than did young controls (for example, 4.1 vs. 6.1 kgm/s at comfortable speed, P<0.05). Three young and one older women lost their balance in at least one trial. CONCLUSIONS: Independent of age, these women reached further when reaching slowly than when reaching rapidly, and older women restricted peak forward momentum under both speed conditions when standing on the elevated surface. RELEVANCE: Interventions designed to reduce falls from raised surfaces might utilize the insights gained from these women that (1) at any age, one cannot expect to reach as far when reaching fast as one can when reaching slowly; and (2) comfortable reaching speed is reduced in older individuals.

Effects of functional ability and training on chair-rise biomechanics in older adults.

BACKGROUND: Difficulty in rising from a chair is common in older adults and may be assessed by examining the biomechanics of the rise. The purposes of this study were (i) to analyze the biomechanics of rise performance during chair-rise tasks with varying task demand in older adults with varying rise ability and (ii) to determine whether a strength-training program might improve chair-rise success and alter chair-rise biomechanics, particularly under situations of increased task demand. METHODS: A training group (n = 16; mean age, 82 years) completed a 12-week strength-training regimen while a control group (n = 14; mean age, 84 years) participated in a seated flexibility program. Outcomes included the ability to complete seven chair-rise tasks, and, if the chair-rise tasks were successful, the biomechanics of these rises. Chair-rise task demand was increased by lowering the seat height, restricting the use of hands, increasing rise speed, and limiting foot support. RESULTS: At baseline, increased chair-rise task demand generally required increased task completion time, increased anterior center of pressure (COP) placement, increased momentum, increased hip flexion, and increased hip and knee torque output. Those unable to rise at 100% knee height without the use of their hands (task NH-100), compared with those able to rise during task NH-100, followed this pattern in requiring increased time, more anterior placement of the COP, and increased hip flexion to rise in the least demanding tasks allowing the use of hands. However, the unable subjects generated less momentum and knee torque in these tasks. At 12 weeks, and compared with baseline and controls, the training group demonstrated changes in chair-rise biomechanics but no significant changes in rise success. The training subjects, as compared with the controls, maintained a more posterior COP, increased their vertical and horizontal momentum, maintained their knees in greater extension, and maintained their knee-torque output. CONCLUSIONS: These data demonstrate that subtle yet significant changes can be demonstrated in chair-rise performance as a result of a controlled resistance-training program. These biomechanical changes may represent a shift away from impairment in chair-rise ability, and, although the changes are small, they represent how training may reduce rise difficulty.

How quickly can healthy adults move their hands to intercept an approaching object? Age and gender effects.

BACKGROUND: The upper extremities are often used to protect the head and torso from impact with an object or with the ground. We tested the null hypotheses that neither age nor gender would affect the time required for healthy adults to move their upper extremities into a protective posture. METHODS: Twenty young (mean age 25 years) and twenty older (mean age 70 years) volunteers, with equal gender representation, performed a seated arm-movement task under three conditions: Condition 1, in which subjects were instructed to raise the hands upon cue as quickly as possible from thigh level to a shoulder height target; Condition 2, in which subjects were instructed as in Condition 1 with the addition of intercepting a swinging pendulum at the prescribed hand target; and Condition 3, in which subjects were instructed as in Condition 2 but were asked to wait as long as possible before initiating hand movement to intercept the pendulum. Arm movements were quantified using standard kinematic techniques. RESULTS: Age (p <.01) and gender (p <.05) affected hand movement times. In Conditions 1 and 2, the older women required 20% longer movement times than the other subject groups (335 vs 279 milliseconds; p <.01). In Condition 3, shorter movement times were achieved by young men (20%; p =.002) and older women (10%; p =.056) as compared with their respective performance in Conditions 1 and 2 because they did not fully decelerate their hands. The other groups slowed their movements in Condition 3. CONCLUSIONS: Age, gender, and perceived threat significantly affected movement times. However, even the slowest movement times were well within the time available to deploy the hands in a forward fall to the ground.

Age and gender differences in peak lower extremity joint torques and ranges of motion used during single-step balance recovery from a forward fall.

Previous studies have found substantial age and gender group differences in the ability of healthy adults to regain balance with a single step after a forward fall. It was hypothesized that differences in lower extremity joint strengths and ranges of motion (ROM) may have contributed to these observed differences. Kinematic and forceplate data were therefore used with a rigid-link biomechanical model simulating stepped leg dynamics to examine the joint torques and ROM used by subjects during successful single-step balance recoveries after release from a forward lean. The peak ROM and torques used by subjects in the study were compared to published estimates or measured values of the available maxima. No significant age or gender group differences were found in the mean ROM used by the subjects for any given initial lean angle. As initial lean angle increased, larger knee ROM and significantly larger hip ROM were used in the successful recoveries. There were substantial gender differences and some age group differences in peak lower extremity joint torques used in successful recoveries. Both young and older females often used nearly maximal joint torques to recover balance. Subjects' maximum joint strengths in plantarflexion and hip flexion were not good predictors of single-step balance recovery ability, particularly among the female subjects.

Task-specific resistance training to improve the ability of activities of daily living-impaired older adults to rise from a bed and from a chair.

OBJECTIVES: To determine the effect of a 12-week intervention to improve the ability of disabled older adults to rise from a bed and from a chair. DESIGN: Subjects were randomly allocated to either a 12-week task-specific resistance-training intervention (training in bed- and chair-rise subtasks, such as sliding forward to the edge of a chair with the addition of weights) or a control flexibility intervention. SETTING: Seven congregate housing facilities. PARTICIPANTS: Congregate housing residents age 65 and older (n = 161, mean age 82) who reported requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related activities of daily living: transferring, walking, bathing, and toileting. MEASUREMENTS: At baseline, 6 weeks, and 12 weeks, subjects performed a series of bed- and chair-rise tasks where the rise task demand varied according to height of the head of the bed, chair seat height, and use of hands. Outcomes were able or unable to rise and, if able, the time taken to rise. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. Following log transformation of rise time, a linear effects model was used to compare rise time between tasks. RESULTS: Regarding the maximum total number of bed- and chair-rise tasks that could be successfully completed, a significant training effect was seen at 12 weeks (P = .03); the training effect decreased as the total number of tasks increased. No statistically significant training effects were noted for rise ability according to individual tasks. Bed- and chair-rise time showed a significant training effect for each rise task, with analytic models suggesting a range of approximately 11% to 20% rise-time (up to 1.5 seconds) improvement in the training group over controls. Training effects were also noted in musculoskeletal capacities, particularly in trunk range of motion, strength, and balance. CONCLUSIONS: Task-specific resistance training increased the overall ability and decreased the rise time required to perform a series of bed- and chair-rise tasks. The actual rise-time improvement was clinically small but may be useful over the long term. Future studies might consider adapting this exercise program and the focus on trunk function to a frailer cohort, such as in rehabilitation settings. In these settings, the less challenging rise tasks (such as rising from an elevated chair) and the ability to perform intermediate tasks (such as hip bridging) may become important intermediate rehabilitation goals.

Body positions used by healthy and frail older adults to rise from the floor.

OBJECTIVE: The purpose of this study was to describe how older adults, particularly more physically impaired older adults, might differ from healthy controls in the body positions used to rise from the floor. DESIGN: Cross-sectional analysis of young, healthy older, and congregate housing older women. SETTING: University-based laboratory and congregate housing facility. PARTICIPANTS: Healthy young university student controls (n = 22, mean age 23 years); healthy old adults living independently in the community (n = 24, mean age 73 years); and congregate housing older adults (n = 29, mean age 81 years). INTERVENTION: Videotaping and timing of rising from a supine position on the floor to standing. MAIN OUTCOME MEASURES: In addition to the time taken to rise from the floor, 10 specific trunk and extremity positions used during the rise, termed Intermediate Positions (IP), were identified. RESULTS: The Young controls had the fastest rise time and used the fewest number of IP, whereas the Congregate residents had the slowest rise time and used the most IP, with the Healthy old adults intermediate in both time and IP use. Prevalence of certain IP, together with correlational and factor analyses, suggest that use of Sit and Crouch was the most preferred rise strategy for the Young controls, whereas use of Tuck, Crouch-Kneel, All Fours, and Bearwalk was the most preferred rise strategy among the Congregate residents. The Healthy old used IP common to both Young and Congregate residents, reflecting a rise strategy intermediate to the latter groups. A substantial subset of the Congregate residents (38%) were unable to rise without assistance and appeared to use certain preparatory positions (Sit, Kneel, Tuck) but were unable to get into presumably more challenging positions (Crouch-Kneel, All Fours, Bearwalk). CONCLUSIONS: With increasing age and physical impairment, body positions used during rising from the floor suggest a preference for maintaining upper and lower extremity contact with the floor, presumably minimizing the lower extremity strength requirements to rise and maximizing stability and postural control. These intermediate body positions may be useful as the basis for training older adults to rise from the floor.

Self-reported walking ability predicts functional mobility performance in frail older adults.

OBJECTIVE: To determine how self-reported physical function relates to performance in each of three mobility domains: walking, stance maintenance, and rising from chairs. DESIGN: Cross-sectional analysis of older adults. SETTING: University-based laboratory and community-based congregate housing facilities. PARTICIPANTS: Two hundred twenty-one older adults (mean age, 79.9 years; range, 60-102 years) without clinical evidence of dementia (mean Folstein Mini-Mental State score, 28; range, 24-30). INTERVENTION AND MAIN OUTCOME MEASURES: We compared the responses of these older adults on a questionnaire battery used by the Established Populations for the Epidemiologic Study of the Elderly (EPESE) project, to performance on mobility tasks of graded difficulty. Responses to the EPESE battery included: (1) whether assistance was required to perform seven Katz activities of daily living (ADL) items, specifically with walking and transferring; (2) three Rosow-Breslau items, including the ability to walk up stairs and walk a half mile; and (3) five Nagi items, including difficulty stooping, reaching, and lifting objects. The performance measures included the ability to perform, and time taken to perform, tasks in three summary score domains: (1) walking ("Walking," seven tasks, including walking with an assistive device, turning, stair climbing, tandem walking); (2) stance maintenance ("Stance," six tasks, including unipedal, bipedal, tandem, and maximum lean); and (3) chair rise ("Chair Rise," six tasks, including rising from a variety of seat heights with and without the use of hands for assistance). A total score combines scores in each Walking, Stance, and Chair Rise domain. We also analyzed how cognitive/ behavioral factors such as depression and self-efficacy related to the residuals from the self-report and performance-based ANOVA models. RESULTS: Rosow-Breslau items have the strongest relationship with the three performance domains, Walking, Stance, and Chair Rise (eta-squared ranging from 0.21 to 0.44). These three performance domains are as strongly related to one Katz ADL item, walking (eta-squared ranging from 0.15 to 0.33) as all of the Katz ADL items combined (eta-squared ranging from 0.21 to 0.35). Tests of problem solving and psychomotor speed, the Trails A and Trails B tests, are significantly correlated with the residuals from the self-report and performance-based ANOVA models. CONCLUSIONS: Compared with the rest of the EPESE self-report items, self-report items related to walking (such as Katz walking and Rosow-Breslau items) are better predictors of functional mobility performance on tasks involving walking, stance maintenance, and rising from chairs. Compared with other self-report items, self-reported walking ability may be the best predictor of overall functional mobility.

A clinical measure of maximal and rapid stepping in older women.

BACKGROUND: In older adults, clinical measures have been used to assess fall risk based on the ability to maintain stance or to complete a functional task. However, in an impending fall situation, a stepping response is often used when strategies to maintain stance are inadequate. We examined how maximal and rapid stepping performance might differ among healthy young, healthy older, and balance-impaired older adults, and how this stepping performance related to other measures of balance and fall risk. METHODS: Young (Y; n = 12; mean age, 21 years), unimpaired older (UO; n = 12; mean age, 69 years), and balance-impaired older women IO; n = 10; mean age, 77 years) were tested in their ability to take a maximal step (Maximum Step Length or MSL) and in their ability to take rapid steps in three directions (front, side, and back), termed the Rapid Step Test (RST). Time to complete the RST and stepping errors occurring during the RST were noted. RESULTS: The IO group, compared with the Y and UO groups, demonstrated significantly poorer balance and higher fall risk, based on performance on tasks such as unipedal stance. Mean MSL was significantly higher (by 16%) in the Y than in the UO group and in the UO (by 30%) than in the IO group. Mean RST time was significantly faster in the Y group versus the UO group (by 24%) and in the UO group versus the IO group (by 15%). Mean RST errors tended to be higher in the UO than in the Y group, but were significantly higher only in the UO versus the IO group. Both MSL and RST time correlated strongly (0.5 to 0.8) with other measures of balance and fall risk including unipedal stance, tandem walk, leg strength, and the Activities-Specific Balance Confidence (ABC) scale. CONCLUSION: We found substantial declines in the ability of both unimpaired and balance-impaired older adults to step maximally and to step rapidly. Stepping performance is closely related to other measures of balance and fall risk and might be considered in future studies as a predictor of falls and fall-related injuries.

Chair and bed rise performance in ADL-impaired congregate housing residents.

OBJECTIVES: To examine the ability of activity of daily living (ADL)-impaired older adults to successfully rise, and, when successful, the time taken to rise, from a bed and chair under varying rise task demands. SETTING: Seven congregate housing facilities SUBJECTS: Congregate housing residents (n = 116, mean age 82) who admitted to requiring assistance (such as from a person, equipment, or device) in performing at least one of the following mobility-related ADLs: transferring, walking, bathing, and toileting. METHODS: Subjects performed a series of bed and chair rise tasks where the rise task demand varied according to the head of bed (HOB) height, chair seat height, and use of hands. Bed rise tasks included supine to sit-to-edge, sit up in bed with hand use, and sit up in bed without hands, all performed from a bed where the HOB was adjusted to 0, 30, and 45 degrees elevations; roll to side-lying then rise (HOB 0 degrees); and supine to stand (HOB 0 degrees). Chair seat heights were adjusted according to the percent of the distance between the floor and the knee (% FK), and included rises (1) with hands and then without hands at 140, 120, 100, and 80% FK; (2) from a reclining (105 degrees at chair back) and tilting (seat tilted 10 degrees posteriorly) chair (100% FK); and (3) from a 80% FK seat height with a 4-inch cushion added, with and then without hands. Logistic regression for repeated measures was used to test for differences between tasks in the ability to rise. After log transformation of rise time, a linear effects model was used to compare rise time between tasks. RESULTS: The median total number of tasks successfully completed was 18 (range, 3-21). Nearly all subjects were able to rise from positions where the starting surface was elevated as long as hand use was unlimited. With the HOB at 30 or 45 degrees essentially all subjects could complete supine to sit-to-edge and sit up with hands. Essentially all subjects could rise from a seat height at 140, 120, and 100% FK as long as hand use was allowed. A small group (8-10%) of subjects was dependent upon hand use to perform the least challenging tasks, such as 140% FK without hands chair rise and 45 degrees sit up without hands. This dependency upon hand use increased significantly as the demand of the task increased, that is, as the HOB or seat height was lowered. Approximately three-quarters of the sample could not rise from a flat (0 degrees HOB elevation) bed or low (80% FK) chair when hand use was not allowed. Similar trends were seen in rise performance time, that is, performance times tended to increase as the HOB or chair seat elevation declined and as hand use was limited. Total self-reported ADL disability, compared to the single ADL transferring item, was a stronger predictor of rise ability and timed rise performance, particularly for chair rise tasks. CONCLUSIONS: Lowering HOB height and seat height increased bed and chair rise task difficulty, particularly when hand use was restricted. Restricting hand use in low HOB height or lowered seat height conditions may help to identify older adults with declining rise ability. Yet, many of those who could not rise under "without hands" conditions could rise under "with hands" conditions, suggesting that dependency on hand use may be a marker of progressive rise impairment but may not predict day-to-day natural milieu rise performance. Intertask differences in performance time may be statistically significant but are clinically small. Given the relationship between self-reported ADL disability and rise performance, impaired rise performance may be considered a marker for ADL disability. These bed and chair rise tasks can serve as outcomes for an intervention to improve bed and chair rise ability and might also be used in future studies to quantify improvements or declines in function over time, to refine physical therapy protocols, and to examine the effect of bed and chair design modifications on bed and chai

Muscle activities used by young and old adults when stepping to regain balance during a forward fall.

The current study was undertaken to determine if age-related differences in muscle activities might relate to older adults being significantly less able than young adults to recover balance during a forward fall. Fourteen young and twelve older healthy males were released from forward leans of various magnitudes and asked to regain standing balance by taking a single forward step. Myoelectric signals were recorded from 12 lower extremity muscles and processed to compare the muscle activation patterns of young and older adults. Young adults successfully recovered from significantly larger leans than older adults using a single step (32.2 degrees vs. 23.5 degrees ). Muscular latency times, the time between release and activity onset, ranged from 73 to 114 ms with no significant age-related differences in the shortest muscular latency times. The overall response muscular activation patterns were similar for young and older adults. However older adults were slower to deactivate three stance leg muscles and also demonstrated delays in activating the step leg hip flexors and knee extensors prior to and during the swing phase. In the forward fall paradigm studied, age-differences in balance recovery performance do not seem due to slowness in response onset but may relate to differences in muscle activation timing during the stepping movement.

Bed mobility task performance in older adults.

Difficulty in transferring, the ability to rise in and out of a bed and chair, is a common problem in older adults, particularly those residing in skilled nursing facilities. Focusing on one aspect of transferring, rising from supine to sitting position, we devised a set of bed mobility tasks to test key arm, leg, and trunk movements that likely contribute to successful rising from bed. Healthy young controls (YC, n=22, mean age 23), and older adults (aged 60 and over) either residing independently in congregate housing (CH, n=29, mean age 84) or undergoing rehabilitation in a skilled nursing facility (SNF, mean age 77) were assessed in the time to rise from supine to sitting and in the ability or inability to perform 16 other bed mobility tasks. Trunk function-related tasks, specifically those requiring trunk elevation and trunk balance, were most difficult for the SNF, followed by CH, and then YC. Tasks focusing on trunk flexion strength (sit up arms crossed, bilateral heel raise) and lateral trunk strength/balance were the most difficult for both SNF and CH, although there was minimal difference in the percent unable to complete each task. The major CH-SNF differences occurred in trunk elevation tasks where the upper limb was important in facilitating trunk elevation (sit up with head of bed elevation with use of arms, sit up with the use of a trapeze, or sit up with use of arms from a flat bed position). These findings suggest that to improve frail older adult performance on bed mobility tasks, and specifically in rising from supine to sitting, training should move beyond improving trunk function (i.e., trunk strength). There should be an additional focus, either through therapy or bed design modifications, on how upper limb movements and positioning can be used to assist in trunk elevation.

Age and gender differences in single-step recovery from a forward fall.

BACKGROUND: Previous work has found that healthy older men were significantly less able than young male adults to recover balance by taking a single rapid step upon sudden release from forward leans. In light of the higher rates of falls and fall-related injuries among older women compared to older men, we hypothesized that healthy older women would perform more poorly than either female young adults or older men in this test of abilities to recover balance rapidly. METHODS: Ten young (mean age 25.0 years) and 10 older (73.7 years) healthy women were released from forward leans and instructed to regain standing balance by taking a single step forward. The lean angle was incrementally increased from its smallest value, approximately 14 degrees, until the subject failed to regain balance as instructed. Lower extremity kinematics were measured, and findings were compared with those of the earlier study of healthy young and old men. RESULTS: Five of the 10 older women could not recover balance with a single step after release from the smallest of the imposed forward leans. For the 5 older women who succeeded in recovering as instructed from at least one lean, the mean maximum lean angle was significantly smaller than that for young women (16.2 degrees vs 30.7 degrees, p < .001) or older men (16.2 degrees vs 23.9 degrees, p = .014). In contrast, there was no significant difference in mean maximum lean angle between female and male young adults. CONCLUSIONS: Healthy older women, compared to either young women or older men, were significantly less able to recover balance by taking a single rapid step during a forward fall. The decreased abilities of older women appeared to result from limitations in the maximum speeds at which they moved their swing foot during recovery.

Thresholds for sensing foot dorsi- and plantarflexion during upright stance: effects of age and velocity.

BACKGROUND: The objective of this study was to determine in healthy young and old adult females the influence of age, rotation direction, angle, and speed on the threshold for sensing foot dorsi- and plantarflexion when standing and bearing weight on the limb. METHODS: Twelve young (YF, mean age 22 years) and 12 old (OF, 70 years) healthy adult females stood with their dominant foot on a servo-controlled platform and the other foot on a fixed platform. The platform induced either dorsi- or plantarflexion rotations at angular velocities of 0.1, 0.5, or 2.5 degrees/s to angles of 0.05, 0.1, 0.2, 0.4 or 0.8 degree. Subjects performed five trials at each velocity-angle combination and 30 dummy trials in which no platform rotation occurred, for a total of 180 trials. Success rates were determined for detecting both rotation (SRR) and rotation direction (SRD) for each test condition. The angular thresholds required to achieve an SRD of 75% were estimated using logistic regression. RESULTS: Age, rotation angle, and rotation speed significantly affected SRD (repeated measures ANOVA: p < .001). For the YF, DF thresholds were 0.04, 0.09, and 0.41 degree at the fast, moderate, and slow velocities, respectively. Threshold angles were three to four times larger in the OF than in the YF. A 10-fold reduction in the angular threshold was observed upon increasing the speed of rotation from 0.1 to 2.5 degrees/s. CONCLUSIONS: Both age and speed significantly affected the thresholds for sensing foot dorsiflexion and plantarflexion in women.

Rising from the floor in older adults.

OBJECTIVE: The primary goal was to determine the ability of older adults to rise from the floor. A secondary goal was to explore how rise ability might differ based on initial body positions and with or without the use of an assistive device. DESIGN: Cross-sectional analysis of young, healthy older, and congregate housing older adults. SETTING: University-based laboratory and congregate housing facility. PARTICIPANTS: Young adult controls (12 men and 12 women, mean age 23 years), healthy older adults (12 men and 12 women, mean age 73 years), and congregate housing older adults (32 women and 6 men, mean age 80 years). The healthy older adult women (n = 12, mean age 75 years) and a subset of the congregate housing women (n = 27, mean age 81 years) were identified for further analyses. INTERVENTION: Videotaping and timing of rising from the floor from controlled initial body positions (supine, on side, prone, all fours, and sitting) and with or without the use of a furniture support. MAIN OUTCOME MEASURES: Whether subjects were successful in rising, and if they were, the time taken to rise. Subjects also rated their perceived difficulty of the task as compared to the reference task, rising from a supine position. RESULTS: Older adults have more difficulty rising from the floor than younger adults. The healthy old took twice as long as the young to rise, whereas the congregate old took two to three times as long as the healthy old to rise. Although all young and healthy old rose from every position, a subset of the congregate housing residents was unable to rise from any position, 24% when attempting to rise without a support and 13% when attempting to rise with a support. Congregate old were most likely to be successful when rising from a side-lying position while using the furniture for support. The more able congregate old, as well as the young and healthy old, rose more quickly and admitted to the least difficulty when rising from the all fours position. CONCLUSIONS: The inability to rise from the floor is relatively common in congregate housing older adults. Based on the differences between groups in time to complete the rise, determining the differences in rise strategies, and the underlying biomechanical requirements of rising from different positions with or without a support would appear to be useful. These data may serve as the foundation for future interventions to improve the ability to rise from the floor.

Abilities to turn suddenly while walking: effects of age, gender, and available response time.

BACKGROUND: Falls may occur when an unexpected turn must be made quickly, in order to avoid colliding with an object in the gait path. Little is known about abilities, particularly about abilities of old adults, to turn suddenly. METHODS: Twenty young and 20 old (mean age 73.8) healthy and physically active adults, while walking straight ahead, were cued to make approximately a 90 degrees turn without advance knowledge of where the turn was to be made or whether it would be to the right or left. Subjects were given available response times (ART), the times between the cue to turn, and potential crossing of a specified forward limit line, of 375, 450, 600, and 750 ms. The rate of success (RS) in completing the turns as prescribed was determined. Regression analyses were used to estimate the additional ART that would be needed for other groups to achieve the same RS as did the young male subject group. RESULTS: For all ART, old subjects had a lower rate of success in completing the turns as prescribed than the young. At an ART of 375 ms, mean RS was 36% for the young and 6% for the old. The regression analyses suggested that, for RS from 30 to 95%, old adults needed 112 ms longer than young of corresponding gender to succeed as well. Females needed on the order of 50 ms longer ART than males of corresponding age. CONCLUSIONS: There are significant age and gender differences among healthy and physically active adults in the available response times they need when walking for successfully making sudden turns.

Age differences in using a rapid step to regain balance during a forward fall.

BACKGROUND: Earlier studies showed that healthy old adults have substantially reduced abilities to develop joint torques rapidly. We hypothesized that this age decline would reduce abilities to regain balance once a forward fall is underway. The present study examined whether aging in fact reduces ability to regain balance by taking a single, rapid step upon release from a forward lean. METHODS: Ten young (mean age 24.3 yr) and ten old (72.8 yr) healthy males were released from a forward-leaning position and instructed to regain standing balance by taking a single step forward. Lean angle was successively increased until a subject failed to regain balance as instructed. Lower extremity motions and foot-floor reactions were measured during the responses. Total response time was divided into reaction, weight transfer, and step times. RESULTS: At small lean angles, responses of old subjects were similar to those of the young. However, the mean maximum lean angle from which old could regain balance as instructed was significantly smaller than that for young (23.9 vs 32.5 deg, p < .0005). Within each age group, maximum lean angle correlated strongly with weight transfer time and step velocity. CONCLUSIONS: Substantial age-related declines in the ability to regain balance by taking a rapid step exist among healthy adults when the time available for recovery is short. The source of the decline seems largely to lie in the decrease with age of maximum response execution speed rather than in the sensory or motor programming processes involved in response initiation.

What leads to age and gender differences in balance maintenance and recovery?

OA compared to YA have high rates of falls and fall-related injuries. OF have notably higher rates of falls and fall-related injuries than OM. Healthy OA compared to YA, and females compared to males of any adult age, have lower strengths and have development rates for at least some strengths that are lower. The results of the obstacle avoidance and balance recovery studies described suggest that OA are not notably more at risk than YA, nor are females notably more at risk than males, in avoidance and recovery tasks that are time-critical (TC), but do not have high strength (HS) requirements. The results suggest that for TC/HS avoidance and recovery tasks, OA compared to YA and females compared to males are substantially more at risk for injury. The source of these age and gender differences seems to lie primarily in differences in muscle strengths and speeds of muscle contraction once contraction is initiated, rather than in neural factors underlying the sensory processing or motor planning that leads to the initiation of muscle contraction. Perhaps these findings help to explain the high rates of falls and fall injuries among OA compared to YA, and among OF compared to OM.