Using Inertial Measurement Units to Assess Outdoor Walking

Effect of augmented plantarflexion power on preferred walking speed and economy in young and older adults

Background Part-list cuing impairment is the counterintuitive finding that presenting a subset of previously studied items as a retrieval cue can impair memory for the remaining items. This study examined the temporal persistence of part-list cuing impairment in younger and older adults. Methods Younger and older adults studied item lists under two encoding conditions: a single study trial versus two study-test cycles, the latter assumed to induce more associative encoding than the former. Participants then completed a critical test with part-list cues to assess the initial effect, followed by a final uncued test to assess the persistence of part-list cuing impairment. Results Part-list cuing impairment was lasting when items were encoded through a single study trial, but transient when items were encoded through two study-test cycles. This encoding-dependent dissociation was observed equally in younger and older adults. Conclusions The present findings provide evidence for two distinct, age-invariant mechanisms underlying part-list cuing impairment in younger and older adults: lasting retrieval inhibition in low associative encoding conditions, and transient strategy disruption in higher associative encoding conditions.

PurposeThe purpose of this study was to determine whether net metabolic cost of walking is affected by age per se.MethodsWe selected 10 healthy, active older adults (mean age 75 years) and 10 young adults (mean age 26 years), and determined their preferred overground walking speed. On the same day, in a morning and afternoon session, we had them walk at that speed overground and on a treadmill while we measured oxygen consumption rate. From the latter we subtracted the rate in sitting and calculated net metabolic cost.ResultsAnthropometrics were not different between the groups nor was preferred walking speed (1.27 m s−1 both groups). There was no difference in net metabolic cost of overground walking between older and young adults (e.g., in the morning 2.64 and 2.56 J kg−1 m−1, respectively, p > 0.05). In the morning session, net metabolic cost of walking was higher on the treadmill than overground in our older adults by 0.6 J kg−1 m−1 (p < 0.05), but not in young adults.ConclusionFirst, there is no effect of age per se on metabolic cost of overground walking. Second, older adults tend to have higher metabolic cost of walking on a treadmill than walking overground at preferred speed, and adaptation may take a long time. The commonly reported age-related elevation of metabolic cost of walking may be due to confounding factors causing preferred walking speed to be lower in older adults, and/or due to older adults reacting differently to treadmill walking than young adults.

The Metabolic Cost of Walking (MCoW) is typically expressed either in terms of Gross Cost of Walking (GCoW) or Net Cost of Walking (NCoW). MCoW is defined as the metabolic energy expended per meter travelled and is an important variable in daily life. From the literature we can see that increased MCoW for elderly compared to young might lead to elderly becoming fatigued and sedentary. Increased fatigue and sedentarism limits their functional possibilities, thereby affecting the overall quality of life. The motivation for this doctoral project was that we wanted to know the reasons why elderly have a higher MCoW compared to young, especially during overground walking. We were interested in overground walking since it is the ecologically relevant mode of walking. However, before trying to know why elderly have a higher MCoW than young we wanted to see whether this finding of elevated MCoW for elderly was valid in the first place and if so, specifically for overground walking. To answer our research questions, we conducted three studies in this thesis. We started with a systematic review and meta-analysis and reported on this study in Chapter 1 of this thesis. Then we followed it up with two experimental studies and then reported on them in Chapters 2 and 3 of this thesis. To summarise, from the studies conducted in this thesis, we were able to show that the commonly reported elevation in MCoW for Older Adults (OA) over Young Adults (YA) is not due to age per se but is probably due to the differential reaction to treadmills by healthy YA and OA. In Chapters 2 and 3 we have shown that OA react differently to overground and treadmill walking (elevated MCoW on treadmills compared to overground) at their overground Preferred Walking Speed (PWS), which we directly imposed on the treadmills. YA do not react differently to overground and treadmill walking at the same speed as they have similar MCoW. Due to this differential reaction to overground and treadmill walking by YA and OA walking energetics are different between the two groups. In conclusion, through this thesis we have shown how to have age as the only differentiating factor between YA and OA while trying to learn about the differences in MCoW between the cohorts. There were no differences in anthropometrics, physical activity and fitness levels and overground PWS between our YA and OA. Our main finding is that we have shown there are no differences in overground MCoW between them. As overground walking is the ecologically relevant mode of walking, overground MCoW should be considered important. Due to the differential reaction of YA and OA to treadmills, treadmills are not suitable for comparison of MCoW between the two populations. The results of similar overground MCoW of YA and OA could have some clinical implications. For example, these results could be interpreted in the way that if people adopt a healthy and active lifestyle from an early age, when they grow old, they can have similar levels of PWS and MCoW like a young person. Comparable levels of PWS would generally mean that mobility and daily life gait will not be affected and similar levels of MCoW will mean that elderly will expend the same amount of energy after walking the same distance as a young person. Overall this will imply that elderly will be able to lead a normal healthy lifestyle, not become fatigued and sedentary, and we can achieve the goals of healthy aging in our society.

Introduction: The use of shared automated vehicles (SAVs) should lead to several societal and individual benefits, including reduced greenhouse gas emissions, reduced traffic, and improved mobility for persons who cannot safely drive themselves. We define SAVs as on-demand, fully automated vehicles in which passengers are paired with other riders traveling along a similar route. Previous research has shown that younger adults are more likely to report using conventional ridesharing services and are more accepting of new technologies including automated vehicles (AVs). However, older adults, particularly those who may be close to retiring from driving, stand to greatly benefit from SAV services. In order for SAVs to deliver on their aforementioned benefits, they must be viewed favorably and utilized. We sought to investigate how short educational and/or experiential videos might impact younger, middle-aged, and older adult respondents’ anticipated acceptance and attitudes toward SAVs. Knowing what types of introductory experiences improve different age groups’ perceptions of SAVs will be beneficial for tailoring campaigns aiming to promote SAV usage. Methods: We deployed an online survey using the platform Prolific for middle-aged and older respondents, and our departmental participant pool for younger adults, collecting 585 total responses that resulted in 448 valid responses. Respondents answered questions regarding their demographic attributes, their ridesharing history, preconceptions of technology, as well as their anticipated acceptance attitudes towards SAVs as measured by the dimensions of the Automated Vehicle User Perception Survey (AVUPS). After this, respondents were randomly assigned to an intervention condition where they either watched 1) an educational video about how SAVs work and their potential benefits, 2) an experiential video showing a AV navigating traffic, 3) both the experiential and educational videos, or 4) a control video explaining how ridesharing works. Anticipated acceptance attitudes towards SAVs were measured again after this intervention and difference scores calculated to investigate the effect of the intervention conditions. Prolific respondents were paid at a rate of $9.50/hour and younger adults received course credit. Results: Controlling for preconceptions of technology and ridesharing experience, a MANOVA was run on the difference scores of the dimensions of the AVUPS (intention to use, trust/reliability, perceived usefulness (PU), perceived ease of use (PEOU), safety, control/driving-efficacy, cost, authority, media, and social influence). Both older and middle-aged adults expressed significantly greater increases in PEOU and PU of SAVs than younger adults. We also observed an interaction between age and condition for both PU and PEOU. For PU, older adults’ difference scores were found to be significantly greater than younger adults’ for the control video condition. With PEOU, older adults’ difference scores were significantly greater than both younger adults’ for the control video condition, and middle-aged adults had greater difference scores for the educational-only video condition than younger or older adults. Discussion: The increases in PU observed for older adults in the control condition suggests that educating them on how to use currently available ridesharing services might transfer to and/or highlight the benefits that automated ridesharing might provide. The PEOU interactions also suggest that middle-aged adults might respond more positively than younger or older adults to an educational introduction to SAVs. Conclusion: The positive findings pertaining to PU and PEOU show that exposure to information related to SAVs has a positive impact on these attitudes. PU’s and PEOU’s positive relationship to behavioral intentions (BI) in the Technology Acceptance Model, coupled with the findings from this study, bode well for higher fidelity interventions seeking to inform and/or give individuals experience with SAVs. Providing information on how currently available ridesharing services work helped our older adult respondents recognize the potential usefulness of SAVs. Knowing that different age groups may respond better to educational versus experiential interventions, for example middle-aged adults in this study responding more positively to the educational video condition than younger or older adults, may be useful for targeted promotional campaigns.

Though some studies suggest that older adults are not differentially impacted by foreign-accented speech relative to younger adults, other studies indicate that older adults are poorer at perceiving foreign-accented speech than younger adults. The present study sought, first, to clarify the extent to which older and younger adults differed in their perception of foreign-accented speech. The secondary aim was to elucidate the extent to which the cognitive mechanisms supporting accented speech perception differ for older and younger adults. The data indicated that older adults were poorer at perceiving accented speech than younger adults. Older adults' speech perception accuracy was associated with a significant main effect of working memory as well as significant interactions between hearing acuity and cognitive flexibility and between hearing acuity and inhibitory control. Younger adults' speech perception accuracy, in contrast, was associated with a significant interaction between hearing acuity and processing speed. It therefore appears that the differences in performance between younger and older adults observed here may be attributable to differences in the cognitive mechanisms that support accented speech perception.

Changes in gait and postural control after 10-day bed rest and 30-day recovery: A comparison of young vs. older adults.

The scope and emphasis of a public health program are necessarily influenced by the changing characteristics of the population it serves. The rate of population growth affects long-range planning of community health and medical facilities. Alterations in age composition, internal migration of racial or industrial groups, changes in population density and urban-rural movement require current adaptation of the health program to solve the new problems thus created. Among the various characteristics of recent population trends, aging of the population is one of the most fundamental in its bearing on national health. The social and economic effects of an aging population have long been recognized. Dr. Louis I. Dublin appraised the problem of old age in some detail in 1926, when the provision of economic security for the aged was the dominant theme of contemporary discussion.1 The passage of the Social Security Act in 1935 represented the fruits of the efforts of this early period. Adjustment of national policy with respect to the health problems associated with aging of the population has been slower in development. Under the terms of the Social Security Act, a limited expansion of activities designed to promote the health of older adults—control of cancer and pneumonia, and industrial hygiene services—has been made possible in the cooperating States. However, the Act makes no provision for the solution of such fundamental problems as invalidity insurance and medical care of the aged. During the past five years, the health aspects of old age have received increasing attention in the discussions of public health administrators. It therefore seems appropriate to resurvey this general problem, and to consider, in particular, the nature of future trends in mortality, morbidity, and the receipt of medical care which may be expected solely as a result of changing age structure of the population.

Texting while walking (TeWW) has become common among people of all ages, and mobile phone use during gait is increasingly associated with pedestrian injury. Although dual-task walking performance is known to decline with age, data regarding the effect of age on dual-task performance in ecological settings are limited. The objective of this study was to evaluate the effect of age, environment (indoors/outdoors), and mixed reality (merging of real and virtual environments) on TeWW performance. A cross-sectional design was used. Young (n=30; 27.8±4.4 years) and older (n=20; 68.9±3.9 years) adults performed single- and dual-task texting and walking indoors and outdoors, with and without a mixed reality display. Participants also completed evaluations of visual scanning and cognitive flexibility (Trail Making Test) and functional mobility (Timed "Up & Go" Test). Indoors, similar interference to walking and texting occurred for both groups, but only older adults' gait variability increased under dual task conditions. Outdoors, TeWW was associated with larger age-related differences in gait variability, texting accuracy, and gait dual-task costs. Young adults with better visual scanning and cognitive flexibility performed TeWW with lower gait costs (r=0.52-0.65). The mixed reality display was unhelpful and did not modify walking or texting. Older adults tested in this study were relatively high functioning. Gaze of participants was not directly monitored. Although young and older adults possess the resources necessary for TeWW, older adults pay an additional "price" when dual-tasking, especially outdoors. TeWW may have potential as an ecologically valid assessment and/or an intervention paradigm for dual-task performance among older adults as well as for clinical populations.

Despite well-documented declines in most cognitive domains, some emotional processes appear to be preserved or even enhanced in late adulthood. A good example of this is the information processing bias older adults show towards positive relative to negative emotional stimuli, often referred to as the age-related positivity effect. The present thesis presents a series of experiments that were designed to better understand the mechanisms that contribute to age-related changes in emotional processing, focusing in particular on the role of cognitive mechanisms and neural networks. In Study 1 aimed to identify the underlying cognitive mechanisms of the positivity effect. The primary focus of this study was to explore the role of distractors during the early attention allocation stage, and to also measure how selective attentional processes during encoding influence later memory outcomes for emotional items. The results showed that consistent with prior literature, a memory positivity effect was found among older relative to younger adults. However, of particular interest was the finding that, participants’ memory for negative targets was not influenced by the presence of positive distractors. This finding suggests that positive distractors did not automatically capture older adults’ attention during encoding for negative items. Importantly, we found that participants’ pupillary responses to negative items mediated the relationship between age and the memory positivity effect, indicating that older adults use their cognitive control resources when encoding negative information, perhaps to down regulate the impact of negative emotions on their memory. Collectively, these two findings provide converging support for the cognitive control account of the positivity effect. Study 2 used a similar paradigm to Study 1 to examine the underlying neural networks involved in processing emotional items during working memory encoding among older and younger adults. Results indicated that a cognitive control network that included fronto-parietal regions, was functionally connected to the left ventrolateral prefrontal cortex during the encoding of negative items among older adults. This network contributed to performance, both accuracy and response times, in older adults’ group. A less distributed network was found for encoding of positive items among older and both items among younger adults. Although older adults recruited a same network that was functionally connected to the amygdala for encoding positive and negative items, younger adults recruited this particular network specifically for encoding negative items. This network facilitated older adults’ higher accuracy and faster response times during retrieval. Taken together, the results from these functional connectivity analyses suggest that there is differential engagement of brain networks connected to these two regions, which are modulated by the emotional valence. While two separate brain networks underlying the encoding of emotionally valence targets are connected to the vlPFC region, one distinct network is functionally connected to the amygdala and subserves the processing of both positive and negative targets. In Study 3 age-related differences in neural substrates involved when processing happy and angry expressions presented with direct versus averted gaze were investigated. This research was motivated by studies that show older adults not only have difficulties processing emotional cues such as facial expression and eye gaze cues, but also have problems integrating these cues. Study 3 provides the first empirical examination of the underlying neural correlates of age-related difficulties in integrating communicative cues. The results showed that for angry facial expressions, younger adults recruited distinct networks while processing direct versus averted eye-gaze cues, however, older adults showed a lack of neural sensitivity to these cues, recruiting a single network for both types of stimuli. In contrast, for happy facial expressions, only older adults showed neural sensitivity to eye gaze cues. Participants’ performance on the scanner task was then correlated with a measure of theory of mind (TOM). Younger (but not older) adults’ performance on a measure of TOM and recognition of angry expressions was differentially correlated with activation in two sets of brain regions as a function of eye gaze. Unlike younger adults, older adults’ performance on TOM was also differentially correlated with the key node of mentalizing brain network during happy expressions as a function of eye gaze. The findings from Study 3 suggest that the age-related difficulties in integrating facial cues could be associated with the recruitment of the mentalizing network when the task imposes high demand on social-cognitive processing. Taken together, the three Studies reported in this thesis provide novel insights into our understanding of age-related differences in the processing of emotionally valenced items, particularly with respect to initial encoding of this information, and how this relates to later memory outcomes. Moreover, for the first time the neural correlates of integrating two important types of facial cue has been identified, and potentially linked to broader social cognitive difficulties. Overall, the findings of this thesis have broad implications for understanding the underlying cognitive mechanisms and neural networks that contribute to age-related differences in the processing of emotional stimuli.

Updating prior information with new information in accordance with Bayesian principles is a difficult task. Younger adult decision makers deviate from Bayes’ theorem by either overweighting prior information (i.e., using a conservatism heuristic) or overweighting new information (i.e., using a representativeness heuristic) on decision tasks without feedback. Similar to younger adults, older adults make decisions that require belief updating. Given agerelated decrements in cognitive control, older adults may be at a disadvantage compared with younger adults when updating beliefs. Prior research shows no age differences when making decisions under risk, however older adults perform worse than younger adults when making decisions under ambiguity. Currently it is unknown how older adults use heuristics when updating beliefs about risk and ambiguous information compared with younger adults. The primary aim of this dissertation was to examine age-related differences in the use of heuristics during belief updating, as well as the cognitive processes and neural correlates that underpin behaviour. In three experiments, younger and older adults completed a belief updating task with and without feedback using an urn-ball paradigm. The main results showed that both younger and older adults committed the representativeness error more than the conservatism error, with no age differences observed when updating beliefs without feedback but with younger adults updating beliefs more accurately than older adults with feedback. Further, age differences in the neural correlates that underlie belief updating showed evidence that older adults recruit additional resources in frontal regions of the brain to facilitate performance compared with younger adults. Event-related potentials showed evidence of cognitive control in response to conflicting information in both age groups, but a diminished neural response to feedback in older compared with younger adults. Additionally, while younger adults were not influenced by ambiguous information, older adults avoided committing the representativeness error only when new information was ambiguous. Last, individual differences in numeracy and cognitive reflection, but not thinking disposition, modulated belief updating performance. Together, the results show that younger and older adults can learn to update beliefs with feedback but with younger adults learning to a greater degree than older adults, especially when information is ambiguous.

Objective To investigate older and younger adults’ perceptions of older and younger adults who wear hearing aids. Design Participants completed two Implicit Association Tests: One with images of older adults (OA-IAT) and one with images of younger adults (YA-IAT), either wearing or not wearing hearing aids. Participants also rated age, attractiveness, and intelligence of younger and older adults pictured with or without a hearing aid. Study sample Thirty older adults (M age = 70 years, SD = 4.38) and 30 younger adults (M age = 23 years, SD = 3.01) who reported not having hearing aids or a diagnosed hearing impairment. Results For both IATs, older and younger participants responded faster and more accurately when images of individuals wearing hearing aids were paired with negative words in comparison to positive words. Photo ratings did not vary in relation to the presence or absence of hearing aids for either age group. Conclusion Although the photo rating tasks indicate neutral explicit attitudes towards individuals who wear hearing aids, our interpretation of the IAT results indicates that younger and older adults may hold negative implicit attitudes towards both older and younger hearing aid users.

Synergic control of the minimum toe clearance in young and older adults during foot swing on treadmill walking in different speeds

Intraexaminer and interexaminer, within- and between-day reliability study. To compare the intraexaminer and interexaminer procedural reliability of ultrasound imaging (USI) thickness measurements of the lumbar multifidus muscle at rest and during a contralateral lower-limb lift (CLL) between older (60-85 years of age) and younger (18-40 years of age) adults. Among younger adults, USI has been shown to be reliable and valid for assessing multifidus thickness. Older adults present with age-related changes that may impact assessment. To our knowledge, no USI studies have focused on establishing reliability for multifidus thickness assessments in older adults. Two examiners performed assessments of lumbar multifidus thickness at rest and during a CLL in 30 older and 31 younger adults. Intraclass correlation coefficient (ICC) with 95% confidence interval, standard error of measurement, 95% minimal detectable change for resting and during the CLL, and percent thickness change were calculated. Within-day interexaminer procedural reliability for multifidus thickness measurements was similar among younger (ICC = 0.90-0.92) and older adults (ICC = 0.86-0.90), as was between-day intraexaminer and interexaminer reliability (younger adults, ICC = 0.84-0.94; older adults, ICC = 0.86-0.93). Throughout, estimates of percent thickness change were inconsistent (ICC = 0.31-0.86), and standard errors of measurement and minimal detectable changes were larger for older adults. Ultrasound imaging reliability for measurements of multifidus thickness at rest and during a CLL among older adults is consistent with previously published findings for younger adults. Among older adults, it may be preferable to have a single examiner conduct USI assessments.

Background and ObjectivesAugmented reality (AR) telepresence is a novel interactive communication modality that maps a user’s 3D photorealistic avatar to another user’s physical environment. However, AR’s application with older adult populations is understudied. As such, we examined young and older adults’ perceptions of utilizing this modality for social communication. Additionally, we tested the participants’ ability to recognize 6 common emotions displayed by 3D photorealistic avatars compared to video clips of real people, examining whether age differences existed in communication perceptions and emotion recognition accuracy.Research Design and MethodsTo assess participants’ perceptions, older (n = 31) and younger (n = 31) adults interacted with a volunteer’s 3D photorealistic avatar using a structured conversational activity through a head-mounted display (HMD). Participants rated the quality of the HMD-AR communication based on physical and human realism, comfort while talking to the avatar, and the degree of social presence offered by the HMD-AR. Participants then identified 6 basic emotions exhibited by (1) video clips of a real person and (2) an animation of their 3D photorealistic avatars via an HMD. Each participant viewed a total of 36 video and avatar stimuli. Subgroup analyses were conducted by age group.ResultsParticipants reported a positive communication experience with the 3D photorealistic avatar, with older adults rating the quality higher. Ratings were generally lowest for how life-like the model appeared (68% younger adults; 61% older adults). Most younger participants (93%) were able to accurately identify nonverbal emotions displayed by the avatar; older adults had less overall accuracy (80%).Discussion and ImplicationsParticipants, including older adults, were enthusiastic regarding AR telepresence for interpersonal communication. Most were able to accurately identify emotions displayed by the 3D photorealistic avatars, although younger adults outperformed older adults. Further technology development will likely enhance the quality of AR communication for everyday use.