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Background. Impaired vision, cognition, and divided attention performance predict falls. Requiring both visual and cognitive input, the ability to step accurately is necessary to safely traverse challenging terrain conditions such as uneven or slippery surfaces. We compared healthy young and older adults in the time taken to step accurately under conditions of increasing cognitive and visual demand. Methods. Healthy Young (n = 42, mean age 21) and Older (n = 37, mean age 70) participants were required to step accurately on an instrumented walkway under conditions of increasing visual and cognitive demand. Based on the paper-and-pencil neuropsychological test, the Trail Making Test (P-TMT) A and B, participants stepped on instrumented targets with increasing sequential numbers (Walking Trail Making Test A [W-TMT A]) and increasing sequential numbers and letters (Walking Trail Making Test B [W-TMT B]), under conditions of Low as well as Normal lighting. Results. W-TMT performance time increased with increased age (Older vs Young), decreased light (Low vs Normal), and increased cognitive demand (Trails B vs Trails A). W-TMT performance time was disproportionately increased in Low light and in the Older group under the highest cognitive demand (W-TMT B) conditions. Paired W-TMT A-B differences were three times higher in the Older group than in the Young group. In the Older group, the correlation between W-TMT results and P-TMT B was particularly strong (p < .001). Conclusions. The time to perform a stepping accuracy task, such as may be required to avoid environmental hazards, increases under reduced lighting and with increased cognitive demand, the latter disproportionately so in older adults.

Fall-related wrist fractures are among the most common fractures at any age. In order to learn more about the biomechanical factors influencing the impact response of the upper extremities, we studied peak hand reaction force during the bimanual arrest of a 3.4 kg ballistic pendulum moving toward the subject in the sagittal plane at shoulder height. Twenty healthy young and 20 older adults, with equal gender representation, arrested the pendulum after impact at one of three initial speeds: 1.8, 2.3, or 3.0 m/sec. Subjects were asked to employ one of three initial elbow angles: 130, 1.50, or 170 deg. An analysis of variance showed that hand impact force decreased significantly as impact velocity decreased (50 percent/m/s) and as elbow angle decreased (0.9 percent/degree). A two segment sagittally-symmetric biomechanical model demonstrated that two additional factors affected impact forces: hand-impactor surface stiffness and damping properties, and arm segment mass. We conclude that hand impact force can be reduced by more than 40 percent by decreasing the amount of initial elbow extension and by decreasing the velocity of the hands and arms relative to the impacting surface. [DOI: 10.1115/1.1427702]

A new ion mobility/time-of-flight mass spectrometer employing a high-pressure MALDI source has been designed and tested. The prototype instrument operates at a source/drift cell pressure of 1-10 Torr helium, resulting in a mobility resolution of approximately 25. A small time-of-flight mass spectrometer (20 cm) with a mass resolution of up to 200 has been attached to the drift cell to identify (in terms of mass-to-charge ratio) the separated ions. A simple tripeptide mixture has been separated in the drift tube and mass identified as singly protonated species. The ability to separate peptide mixtures, e.g., tryptic digest of a protein, is illustrated and compared to results obtained on a high-vacuum time-of-flight instrument.

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.

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.

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.

Background. When balance is disturbed, often only fractions of a second are available in which to make the initial responses needed for its restoration. Abilities to develop joint torques rapidly may be critical to such responses. We undertook this study to quantify age effects among healthy adults in abilities to develop ankle joint torques rapidly. Methods. Ankle dorsiflexion (DF) and plantarflexion (PF) torque development during rapid isometric and during isokinetic (30, 60, 120, 180, and 240 deg/sec) exertions was assessed in 24 healthy young (mean age 23 years) and 24 healthy old adults (mean age 72 years). The effects of age, gender, and torque direction on the times needed to reach given torque magnitudes, maximum rates of isometric torque development (MRTD), and maximum isokinetic torques were examined. Results. The old adults required substantially more time to reach given torque magnitudes than the young adults. For example, the young and old females needed approximately 236 and 337 msec to develop 15 Nm of DF torque, of which 141 and 164 msec were reaction times. Isometric MRTD were 25 to 36% lower in the old than in the young adults. The age declines in isometric torque development time were associated with losses in maximum isometric strength. Maximum isokinetic torques developed by the old were 20 to 40% lower than those of young adults. The percent losses in isokinetic torques with age were independent of joint angular velocity for PF, but increased with velocity for DF. Conclusions. We found substantial age declines in abilities of healthy old adults to rapidly develop ankle joint torques. The capacities of even healthy old adults to recover balance or to carry out other time-critical actions that require moderate-to-substantial strengths may be considerably degraded by these declines.

Background. Tripping over an obstacle is a common cause of falls in the elderly. An earlier study of abilities to avoid stepping on suddenly appearing obstacles found that, although healthy old adults had a lower rate-of-success than young adults, the magnitude of that difference was not large. The present study inquired whether dividing attention during such a task would differentially affect young and old healthy adults. Methods. Rates-of-success were observed in 16 young and 16 old healthy adults (mean ages 24 and 72 years) in avoiding stepping on a band of light that was suddenly projected across their gait path while they walked at their comfortable gait speed. This virtual obstacle was placed at predicted next-footfall locations to give 350 or 450 msec available response times before footfall. During most of the trials the subjects were asked, in addition to trying not to step on the obstacle, simultaneously to respond vocally as quickly as possible when red lights near the end of the walkway turned on. These attention-dividing reaction time tests were of two types: synchronized, when only red lights lit at intervals synchronized with the appearance of the obstacle. and unsynchronized, when green or yellow lights lit in addition to the red lights, with lighting intervals not synchronized with the appearance of the obstacle. Results. When synchronized and unsynchronized reaction time tests were conducted concurrently with the obstacle avoidance tasks, mean rates-of-success in avoidance decreased significantly in both young and old adults. With available response times of 350 msec, mean success rates decreased from their no-division values in the young adults by 14.7% for synchronized reaction and by 19.9% for unsynchronized reaction, attention-dividing tests. Corresponding mean decreases for the old adults were 32.0 and 35.7%. This age difference in the effects of dividing attention was significant. Conclusion. Both young and old adults had a significantly increased risk of obstacle contact while negotiating obstacles when their attention was divided, but dividing attention degraded obstacle avoidance abilities of the old significantly more than it did in the young. Diminished abilities to respond to physical hazards present in the environment when attention is directed elsewhere may partially account for high rates of falls among the elderly.

Global cognitive impairment in older adults has been associated with a greater risk of falling, and tripping has been implicated a, an important factor in a large percentage of these falls. In order to evaluate the role of specific cognitive domains in tripping and falling, 23 healthy older adults completed basic and complex obstacle avoidance tasks, as well as a battery of neuropsychological tests. Using multiple regression analysis, a select pattern of neuropsychological measures was found to predict the decrement in performanee evident as avoidance task complexity increased. Whereas measures of problem solving, response inhibition, general anxiety, and variability in attention were found to be significant predictors (in that order) of the relative decline in successful obstack avoidance, measures of visuo-spatial discrimination and memory did not.

A study of 24 old and 24 young adults for their ability to avoid an obstacle during walking reveals that younger people have higher mean rates-of-success (RS) than older people whose RS decreases with decreasing available response time (ART). Lower extremity simple reaction time (SRT) tests reveal an 80 ms delay in the SRT of older people compared to that of younger people. A 50 or 100 ms delay in responding to the presence of obstacle reduces the RS of people of any age, indicating that age-related variations in SRT do not predict variations in the ability to avoid obstacles.

Falls associated with tripping over an obstacle can be devastating to elderly individuals, yet little is known about the strategies used for stepping over obstacles by either old or young adults. The gait of gender-matched groups of 24 young and 24 old healthy adults (means ages 22 and 71 years) was studied during a 4 m approach to and while stepping over obstacles of 0,25,51, or 152 mm height and in level obstacle-free walking. Optoelectronic cameras and recorders were used to record approach and obstacle crossing speeds as well as bilateral lower extremity kinematic parameters that described foot placement and movement trajectories relative to the obstacle. The esults showed that age had no effect on minimum swing foot clearance (FC) over an obstacle. For the 25 mm obstacle, mean FC was 64 mm, or approximately three times that used in level gait; FC increased nonlinearly with obstacle height for all subjects. Although no age differences were found in obstacle-free gait, old adults exhibited a significantly more conservative strategy when crossing obstacles, with slower crossing speed, shorter step length, and shorter obstacle-heel strike distance. In addition, the old adults crossed the obstacle so that it was 10% further forward in their obstacle-crossing step. Although all subjects successfully avoided the riskiest form of obstancle contact, tripping, 4/24 healthy old adults stepped on an obstacle, demonstrating an increased risk for obstacle contact with age., The way older and younger people walk and move over obstacles may have a bearing on why older people are more likely to fall, and how to prevent the problem. Gait patterns of healthy young men and women and healthy old men and women were studied as they approached and stepped over obstacles of various heights. A total of 48 volunteers were monitored electronically as they walked along a path with obstacles ranging in height from that of standard door thresholds up to the average curbstone. Each of the volunteers walked the course 42 times. The distance from the foot the person was standing on to the obstacle and the clearance of the foot was the same for all groups. Old adults were more conservative when crossing obstacles than young adults, approaching more slowly and taking more care to have the toes clear the obstacle. Although this increases the risk that the heel will catch on the object, the result would be a less serious stumble instead of a trip. Foot clearance is the most important measure of whether tripping will occur, and all subjects avoided tripping on or kicking the obstacle. Attention and cognition were not measured in this study, and the artificial setting may not reflect what happens when people walk in everyday settings. The results of the study indicate that old adults are more careful when stepping over obstacles than young adults, and are more likely to step on the obstacle, as four of the 24 old adults did. (Consumer Summary produced by Reliance Medical Information, Inc.)

A large number of aged persons need assistance getting in and out of chairs and beds; estimates are that nearly 8 percent of those aged 65 and over who are not living in institutions have such difficulty. These people may be at increased risk for immobility-related diseases and for institutionalization. Though there may be more overt causes for the difficulties that the elderly have in rising, biomechanics are always involved. To gain an understanding of the biomechanics involved in rising from a chair and the difficulties that might occur, 51 adults were classified as either young, old able, or old unable based upon their age and whether they could rise from a chair without the use of the hand-rests. The young group consisted of 17 subjects with an average age of 23 years, the old able group had 23 subjects whose average age was 72 years, and the old unable group consisted of 11 subjects with an average age of 84 years. Subjects were asked to rise from a chair, during which the timing, body segment angles, and hand forces were measured. Compared with the young subjects, the old able subjects spent a greater amount of time in the first of two phases of rising, and they rotated their body segments by a different amount. This was despite the fact that there was no difference in functional ability between the two groups. The old unable group took more time to rise than the old able group, they used different rotations, and they used the force of their hands more as compared with the force of their bodies. These data show that the mechanics of rising from a chair can be quantified in such a way that further analyses of joint strengths and postural stability can be made to determine their contributions to problems in rising. (Consumer Summary produced by Reliance Medical Information, Inc.)

Peptide sequencing by surface-induced dissociation (SID) on a MAIDI-ion mobility-orthogonal TOF mass spectrometer is demonstrated. SID of ~100-fmol amounts of model peptides HLGLAR (m/z 666.8), gramicidin S (m/z 1142,5), and bovine insulin b chain (m/z 3495.5) was accomplished using hydrocarbon-coated gold grids and ~20-eV collision energies. The current version of the instrument achieves a mobility resolution of ~20 and TOF mass resolution better than 200. Peptide sequences of four peptides from a tryptic digest of cytochrome c (~1 pmol deposited) were obtained. The advantage of IM-SID-o-TOF-MS is that a single experiment can be used to simultaneously measure the molecular weights of the tryptic peptide fragments (e.g., peptide mass mapping) and partial sequence analysis, (e.g., real-time tandem mass spectrometry.)

The King Penguin ( Aptenodytes patagonicus) is a pelagic seabird that breeds on Subantarctic islands and is considered a rare vagrant in South Africa. From 2001 to 2017, six King Penguins were rescued along the South African coast and admitted into rehabilitation centers. These and previous records of King Penguins were obtained near the country's major ports, which suggests that some of these birds may have been ship-assisted. One of the King Penguins evaluated in this study died shortly after being admitted to the rehabilitation center due to extensive hemorrhage caused by a long-line fishing hook, and another had a beak wound consistent with fishing hook injury. Three King Penguins were infected with the tick-borne protozoan Babesia peircei and two died as a result of babesiosis. One King Penguin was diagnosed with an infection by Rickettsia-like organisms. Pox-like lesions, presumably mosquito-borne, developed on the eyelid skin of one penguin. Additionally, one of two King Penguins permanently captive in Cape Town during the same period also presented a lethal case of spirochetosis, which was possibly tick-borne. These novel records of vector-borne pathogens in King Penguins highlight the risk of seabird rehabilitation centers to serve as potential sources of pathogens to vagrant species, while also illustrating the opportunities that these centers provide for pathogen research and surveillance. [ABSTRACT FROM AUTHOR]