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1.  The influence of aerobic fitness on cerebral white matter integrity and cognitive function in older adults: Results of a one-year exercise intervention 
Human brain mapping  2012;34(11):2972-2985.
Cerebral white matter degeneration occurs with increasing age and is associated with declining cognitive function. Research has shown that cardiorespiratory fitness and exercise are effective as protective, even restorative, agents against cognitive and neurobiological impairments in older adults. In this study, we investigated whether the beneficial impact of aerobic fitness would extend to white matter integrity in the context of a one-year exercise intervention. Further, we examined the pattern of diffusivity changes to better understand the underlying biological mechanisms. Finally, we assessed whether training-induced changes in white matter integrity would be associated with improvements in cognitive performance independent of aerobic fitness gains. Results showed that aerobic fitness training did not affect group-level change in white matter integrity, executive function, or short-term memory, but that greater aerobic fitness derived from the walking program was associated with greater change in white matter integrity in the frontal and temporal lobes, and greater improvement in short-term memory. Increases in white matter integrity, however, were not associated with short-term memory improvement, independent of fitness improvements. Therefore, while not all findings are consistent with previous research, we provide novel evidence for correlated change in training-induced aerobic fitness, white matter integrity, and cognition among healthy older adults.
PMCID: PMC4096122  PMID: 22674729
Diffusion tensor imaging; Anisotropy; Cerebrum; Cognition; Physical fitness; Aging
2.  Physical Activity and Cardiorespiratory Fitness Are Beneficial for White Matter in Low-Fit Older Adults 
PLoS ONE  2014;9(9):e107413.
Physical activity (PA) and cardiorespiratory fitness (CRF) are associated with better cognitive function in late life, but the neural correlates for these relationships are unclear. To study these correlates, we examined the association of both PA and CRF with measures of white matter (WM) integrity in 88 healthy low-fit adults (age 60–78). Using accelerometry, we objectively measured sedentary behavior, light PA, and moderate to vigorous PA (MV-PA) over a week. We showed that greater MV-PA was related to lower volume of WM lesions. The association between PA and WM microstructural integrity (measured with diffusion tensor imaging) was region-specific: light PA was related to temporal WM, while sedentary behavior was associated with lower integrity in the parahippocampal WM. Our findings highlight that engaging in PA of various intensity in parallel with avoiding sedentariness are important in maintaining WM health in older age, supporting public health recommendations that emphasize the importance of active lifestyle.
PMCID: PMC4167864  PMID: 25229455
3.  Effects of a DVD-Delivered Exercise Intervention on Physical Function in Older Adults 
Given the rapidly increasing demographic of older adults, it is vital to implement effective behavioral strategies to improve physical function to maintain activities of daily living. However, changing physical activity in older adults remains extremely difficult. The current trial tested the efficacy of a novel, 6-month, home-based, DVD-delivered exercise program focusing on flexibility, balance, and toning on the physical function of older adults.
Older adults (N = 307) were recruited from 83 towns and cities throughout central Illinois. The trial consisted of 4 waves of recruitment and randomization from May 2010 through January 2012. Inclusion criteria included being inactive, at least 65 years of age, English speaking, providing physician’s consent, and willingness to be randomized. Eligible participants were randomly assigned to 1 of 2 treatment conditions: the exercise intervention or a healthy aging, attentional control. Functional assessments were completed at baseline and following the 6-month DVD intervention. Measures included the Short Physical Performance Battery, assessments of flexibility and strength, and self-reported functional limitations.
Participants in the DVD intervention condition demonstrated significant improvements in the Short Physical Performance Battery (p = .005), lower extremity flexibility (p = .04), and upper body strength (p = .003). There were no effects of the intervention on self-reported functional limitations.
The exercise intervention produced a clinically significant improvement in the Short Physical Performance Battery and improvements in flexibility and strength, demonstrating the effectiveness of a low-cost DVD exercise program in improving physical function in older adults.
PMCID: PMC3738028  PMID: 23401566
Clinical trial; DVD; Home-based exercise; Functional performance; Public health; Gait; Balance.
4.  Influence of allowable interruption period on estimates of accelerometer wear time and sedentary time in older adults 
The criteria one uses to reduce accelerometer data can profoundly influence the interpretation of research outcomes. The purpose of this study was to examine the influence of three different interruption periods (i.e., 20, 30, and 60 minutes) on the amount of data retained for analyses and estimates of sedentary time among older adults. Older adults (N=311; Mage=71.1) wore an accelerometer for seven days and reported wear time on an accelerometer log. Accelerometer data were downloaded and scored using 20, 30, and 60-minute interruption periods. Estimates of wear time derived using each interruption period were compared to self-reported wear time, and descriptive statistics were used to compare estimates of sedentary time. Results showed a longer interruption period (i.e., 60 minutes) yields the largest sample size and the closest approximation of self-reported wear time. A short interruption period (i.e., 20 minutes) is likely to underestimate sedentary time among older adults.
PMCID: PMC3875619  PMID: 23752299
5.  Neurobiological markers of exercise-related brain plasticity in older adults 
The current study examined how a randomized one-year aerobic exercise program for healthy older adults would affect serum levels of brain-derived neurotrophic factor (BDNF), insulin-like growth factor type 1 (IGF-1), and vascular endothelial growth factor (VEGF) - putative markers of exercise-induced benefits on brain function. The study also examined whether (a) change in the concentration of these growth factors was associated with alterations in functional connectivity following exercise, and (b) the extent to which pre-intervention growth factor levels were associated with training-related changes in functional connectivity. In 65 participants (mean age = 66.4), we found that although there were no group-level changes in growth factors as a function of the intervention, increased temporal lobe connectivity between the bilateral parahippocampus and the bilateral middle temporal gyrus was associated with increased BDNF, IGF-1, and VEGF for an aerobic walking group but not for a non-aerobic control group, and greater pre-intervention VEGF was associated with greater training-related increases in this functional connection. Results are consistent with animal models of exercise and the brain, but are the first to show in humans that exercise-induced increases in temporal lobe functional connectivity are associated with changes in growth factors and may be augmented by greater baseline VEGF.
PMCID: PMC3544982  PMID: 23123199
exercise; aging; functional connectivity; fMRI; default mode network; aerobic fitness; growth factors
6.  Evaluation of the Factor Structure of the Rosenberg Self-Esteem Scale in Older Adults 
The Rosenberg Self-Esteem Scale is the most utilized measure of global self-esteem. Although psychometric studies have generally supported the uni-dimensionality of this 10-item scale, more recently, a stable, response-bias has been associated with the wording of the items (Marsh, Scalas, & Nagengast, 2010). The purpose of this report was to replicate Marsh et al.’s findings in a sample of older adults and to test for invariance across time, gender and levels of education. Our results indicated that indeed a response-bias does exist in esteem responses. Researchers should investigate ways to meaningfully examine and practically overcome the methodological challenges associated with the RSE scale.
PMCID: PMC3505083  PMID: 23185099
global self-esteem; psychometrics; aging
7.  BDNF mediates improvements in executive function following a 1-year exercise intervention 
Executive function declines with age, but engaging in aerobic exercise may attenuate decline. One mechanism by which aerobic exercise may preserve executive function is through the up-regulation of brain-derived neurotropic factor (BDNF), which also declines with age. The present study examined BDNF as a mediator of the effects of a 1-year walking intervention on executive function in 90 older adults (mean age = 66.82). Participants were randomized to a stretching and toning control group or a moderate intensity walking intervention group. BDNF serum levels and performance on a task-switching paradigm were collected at baseline and follow-up. We found that age moderated the effect of intervention group on changes in BDNF levels, with those in the highest age quartile showing the greatest increase in BDNF after 1-year of moderate intensity walking exercise (p = 0.036). The mediation analyses revealed that BDNF mediated the effect of the intervention on task-switch accuracy, but did so as a function of age, such that exercise-induced changes in BDNF mediated the effect of exercise on task-switch performance only for individuals over the age of 71. These results demonstrate that both age and BDNF serum levels are important factors to consider when investigating the mechanisms by which exercise interventions influence cognitive outcomes, particularly in elderly populations.
PMCID: PMC4263078  PMID: 25566019
BDNF; executive function; aging; exercise; physical activity; cognition; mediation analysis
8.  Self-efficacy: Implications for Physical Activity, Function, and Functional Limitations in Older Adults 
American journal of lifestyle medicine  2011;5(4):10.1177/1559827610392704.
Attenuating the physical decline and increases in disability associated with the aging process is an important public health priority. Evidence suggests that regular physical activity participation improves functional performance, such as walking, standing balance, flexibility, and getting up out of a chair, and also plays an important role in the disablement process by providing a protective effect against functional limitations. Whether these effects are direct or indirect has yet to be reliably established. In this review, the authors take the perspective that such relationships are indirect and operate through self-efficacy expectations. They first provide an introduction to social cognitive theory followed by an overview of self-efficacy's reciprocal relationship with physical activity. They then consider the literature that documents the effects of physical activity on functional performance and functional limitations in older adults and the extent to which self-efficacy might mediate these relationships. Furthermore, they also present evidence that suggests that self-efficacy plays a pivotal role in a model in which the protective effects conferred by physical activity on functional limitations operate through functional performance. The article concludes with a brief section making recommendations for the development of strategies within physical activity and rehabilitative programs for maximizing the major sources of efficacy information.
PMCID: PMC3864698  PMID: 24353482
physical activity; aging; self-efficacy; function; limitations; social cognitive theory
9.  A Profile for Predicting Attrition from Exercise in Older Adults 
The purpose of this study was to determine a profile for predicting attrition among older adults involved in a 12-month exercise program.
The parent study was a single-blinded randomized controlled trial. The study took place between 2006 and 2009 within a university setting. Older adults (N = 179) completed baseline assessments of functional performance and psychosocial measures. Participants who relinquished their consent to participate were considered “dropouts” and those remaining were classified as “completers.”
A discriminant function analysis differentiated dropouts (n = 35) from completers (n = 144) at likelihood much better than chance (72% accurate overall) across four measures: frequency of forgetting, barriers self-efficacy scale, balance, and stair performance. Study dropouts exhibited a higher frequency of forgetting, lower efficacy for overcoming barriers to exercise, poorer single leg balance, and longer times to walk down stairs.
The results provide an initial validation of a profile for discriminating between “dropouts” and “completers,” one that may have considerable utility for screening older adults prior to study entry.
PMCID: PMC3806454  PMID: 23412942
exercise; attrition; dropout; older adults
10.  Longitudinal Invariance and Construct Validity of the Abbreviated Late-Life Function and Disability Instrument in Healthy Older Adults 
To cross-validate the psychometric properties of the abbreviated Late-Life Function and Disability Instrument (LL-FDI), a measure of perceived functional limitations and disability.
Baseline and 12-month follow-up assessments conducted across the course of a 12-month exercise program.
University research community.
Older healthy adults (N=179; mean ± SD age, 66.43±5.67y) at baseline; 145 were retained at follow-up.
Not applicable.
Main Outcome Measures
LL-FDI and functional performance measures.
Factor analyses confirmed the factor structure of the abbreviated LL-FDI, and all subscales met minimal criteria for temporal invariance. Significant correlations also were found between functional limitations subscales and an array of physical function performance measures, supporting the scale’s construct validity.
The abbreviated LL-FDI with some modifications appears to be temporally invariant in community-dwelling older adults. Additionally, moderate relationships between functional limitations and functional performance provide further support for these being conceptually distinct constructs.
PMCID: PMC3772086  PMID: 21458777
Geriatrics; Longitudinal studies; Psychometrics; Rehabilitation
11.  Physical Activity, Function, and Quality of Life: Design and Methods of the FlexToBa™ Trial 
Contemporary Clinical Trials  2011;33(1):228-236.
The Flexibility, Toning, and Balance (FlexToBa™) Trial is a two-armed randomized controlled trial which will contrast the effects of a DVD-delivered, home-based, physical activity intervention and a Healthy Aging attention control condition on physical activity, functional performance, functional limitations, and quality of life in low active, older adults. This innovative trial will recruit 300 participants across central Illinois who will be randomized into the intervention arm or control arm of the study. The intervention will last 6 months with a 6 month follow-up. Assessments at baseline, post intervention and follow-up will include physical activity (self-report and accelerometry), a battery of functional performance measures, functional limitations, quality of life, and an array of psychological health measures. In addition, measures of external validity will be included to determine public health significance of a successful outcome. Participants will engage in a progressive series of activities focusing on flexibility, strengthening, and balance exercises which are demonstrated by a trained exercise leader and age-appropriate models on a series of DVDs. Delivery of the intervention has its basis in social cognitive theory. The specific aims of the trial are (a) to determine the effects of the DVD-delivered FlexToBa™ program on physical activity, functional performance, functional limitations, and quality of life, (b) to examine the mediators of the relationships between physical activity and functional limitations and quality of life, (c) to assess external validity indicators relative to the intervention, and (d) to determine differential effects of the intervention on psychosocial health measures.
PMCID: PMC3253879  PMID: 22024470
Physical activity; older adults; functional limitations; functional performance; quality of life
12.  Growth Trajectories of Exercise Self-Efficacy in Older Adults: Influence of Measures and Initial Status 
This study examines differential trajectories of exercise-related self-efficacy beliefs across a 12-month randomized controlled exercise trial.
Previously inactive older adults (N = 144; M age = 66.5) were randomly assigned to one of two exercise conditions (walking, flexibility-toning-balance) and completed measures of barriers self-efficacy (BARSE), exercise self-efficacy (EXSE), and self-efficacy for walking (SEW) across a 12-month period. Changes in efficacy were examined according to efficacy type and inter-individual differences. Latent growth curve modeling was employed to (a) examine average levels and change in each type of efficacy for the collapsed sample and by intervention condition, and (b) explore subpopulations (i.e., latent classes) within the sample that differ in their baseline efficacy and trajectory.
Analyses revealed two negative trends in BARSE and EXSE at predicted transition points, in addition to a positive linear trend in SEW. Two subgroups with unique baseline efficacy and trajectory profiles were also identified.
These results shed new light on the relationship between exercise and self-efficacy in older adults, and highlight the need for strategies for increasing and maintaining efficacy within interventions, namely targeting participants who start with a disadvantage (lower efficacy) and integrating efficacy-boosting strategies for all participants prior to program end.
PMCID: PMC3521039  PMID: 21038962
exercise; self-efficacy; trajectories of change; aging
13.  Cardiorespiratory Fitness, Hippocampal Volume and Frequency of Forgetting in Older Adults 
Neuropsychology  2011;25(5):545-553.
The purpose of this study was to extend our earlier work to determine the extent to which cardiorespiratory fitness is associated with the frequency of memory problems via its effects on the hippocampus and spatial working memory. We hypothesized that age, sex, education, body composition, and physical activity were direct determinants of fitness which, in turn, influenced frequency of forgetting indirectly through hippocampal volume and spatial working memory.
We conducted assessments of hippocampal volume, spatial working memory, frequency of forgetting, BMI, physical activity, demographic characteristics, and cardiorespiratory fitness in 158 older adults (M age = 66.49). Path analyses within a covariance modeling framework were used to examine relationships among these constructs.
Sex, age, BMI, and education were all significant determinants of cardiorespiratory fitness. The hypothesized path models testing the effects of fitness on frequency of forgetting through hippocampal volume and accuracy and speed of spatial working memory all fit the data well.
Our findings suggest that older adults with higher levels of fitness show greater preservation of hippocampal volume which, in turn, is associated with more accurate and faster spatial memory and fewer episodes of forgetting. Given the proportion of older adults reporting memory problems, it is necessary to determine whether improvements in fitness brought about by physical activity interventions can result in subsequent attenuation of memory problems or potentially improvements in memory.
PMCID: PMC3140615  PMID: 21500917
Frequency of Forgetting; Hippocampus Volume; Cardiorespiratory Fitness; Spatial Memory; Older Adults
14.  Self-Regulatory Processes and Exercise Adherence in Older Adults 
Self-efficacy and the use of self-regulatory strategies are consistently associated with physical activity behavior. Similarly, behavioral inhibition and cognitive resource allocation, indices of executive control function, have also been associated with this health behavior.
The purpose of this study was to examine the hypothesis that self-efficacy mediates the relationship between self-regulatory processes, such as executive function, and sustained exercise behavior.
Older adults (N = 177, mean age = 66.44 years) completed measures of executive function, self-reported use of self-regulatory strategies and self-efficacy prior to and during the first month of a 12-month exercise intervention. Percentage of exercise classes attended over the following 11 months was used to represent adherence. Data were collected from 2007 to 2010 and analyzed in 2010–2011. Structural equation models were tested examining the effect of executive function and strategy use on adherence via efficacy.
As hypothesized, results showed significant direct effects of two elements of executive function and of strategy use on self-efficacy and of efficacy on adherence. In addition, there were significant indirect effects of strategy use and executive function on adherence via self-efficacy.
Higher levels of executive function and use of self-regulatory strategies at the start of an exercise program enhance beliefs in exercise capabilities, which in turn leads to greater adherence.
PMCID: PMC3160622  PMID: 21855742
15.  Trajectories of change in self-esteem in older adults: exercise intervention effects 
Journal of behavioral medicine  2011;34(4):298-306.
This 12-month, 2 arm, single blind randomized controlled exercise trial examined relationships among changes in multidimensional self-esteem as a function of intervention mode (i.e., walking vs. flexibility-toning-balance). Data were collected on three equidistant occasions (baseline, 6 and 12 months). One-hundred seventy-nine older adults (Mage = 66.38) began the study and 145 completed assessments at all time points. Participants completed measures of physical and global self-esteem as well as demographic information. There were no significant group differences at baseline on these demographic indicators or esteem variables. Data were analyzed using linear and parallel process growth modeling procedures. Results supported the position that across both groups, domain-level (i.e., physical self-worth) was dependent upon sub-domain-level (i.e., perceived attractiveness, strength, and condition) esteem change. Furthermore, greater improvements were observed in the flexibility-toning-balance group, in terms of perceived strength and attractiveness esteem, compared to the walking group. Our findings support theoretically-based predictions and extend the literature showing unique psychological responses conditional on specific types of physical activities.
PMCID: PMC3118401  PMID: 21222223
Self perceptions; Physical activity; Growth models; Modes of exercise
16.  Caudate Nucleus Volume Mediates the Link between Cardiorespiratory Fitness and Cognitive Flexibility in Older Adults 
Journal of Aging Research  2012;2012:939285.
The basal ganglia play a central role in regulating the response selection abilities that are critical for mental flexibility. In neocortical areas, higher cardiorespiratory fitness levels are associated with increased gray matter volume, and these volumetric differences mediate enhanced cognitive performance in a variety of tasks. Here we examine whether cardiorespiratory fitness correlates with the volume of the subcortical nuclei that make up the basal ganglia and whether this relationship predicts cognitive flexibility in older adults. Structural MRI was used to determine the volume of the basal ganglia nuclei in a group of older, neurologically healthy individuals (mean age 66 years, N = 179). Measures of cardiorespiratory fitness (VO2max), cognitive flexibility (task switching), and attentional control (flanker task) were also collected. Higher fitness levels were correlated with higher accuracy rates in the Task Switching paradigm. In addition, the volume of the caudate nucleus, putamen, and globus pallidus positively correlated with Task Switching accuracy. Nested regression modeling revealed that caudate nucleus volume was a significant mediator of the relationship between cardiorespiratory fitness, and task switching performance. These findings indicate that higher cardiorespiratory fitness predicts better cognitive flexibility in older adults through greater grey matter volume in the dorsal striatum.
PMCID: PMC3415086  PMID: 22900181
17.  Non-Exercise Estimated Cardiorespiratory Fitness: Associations with Brain Structure, Cognition, and Memory Complaints in Older Adults 
There is increasing evidence that cardiorespiratory fitness (CRF) is associated with brain structure and function, and improvements in CRF through exercise training have been associated with neural and cognitive functioning in older adults. The objectives of this study were to validate the use of a non-exercise estimate of CRF, and to examine its association with cognitive function, brain structure and subjective memory complaints. Low active, older adults (N = 86; M age= 65.14) completed a physician-supervised maximal exercise test, a 1-mile timed walk, several measures of cognitive function, and a 3 Tesla structural MRI. Fitness was also calculated from an equation derived by (Jurca et al., 2005) based on age, sex, body mass index, resting heart rate, and self-reported physical activity level. Analyses indicated that all three measures of CRF were significantly correlated with one another. In addition, measures of cognitive function, hippocampus volume, and memory complaints were significantly correlated with each measure of fitness. These findings have implications for using a low-risk, low-cost, non-exercise estimate of CRF in determining fitness associations with brain structure and cognitive function in older adults. As such, this measure may have utility for larger population based studies. Further validation is required, as is determination of whether such relationships hold over the course of exercise interventions.
PMCID: PMC3146052  PMID: 21808657
Equation-derived CRF; cognitive function; hippocampus; older adults
18.  Measuring enjoyment of physical activity in older adults: invariance of the physical activity enjoyment scale (paces) across groups and time 
The purpose of this study was to validate the Physical Activity Enjoyment Scale (PACES) in a sample of older adults. Participants within two different exercise groups were assessed at two time points, 6 months apart. Group and longitudinal invariance was established for a novel, 8-item version of the PACES. The shortened, psychometrically sound measure provides researchers and practitioners an expedited and reliable instrument for assessing the enjoyment of physical activity.
PMCID: PMC3206413  PMID: 21951520
19.  Plasticity of Brain Networks in a Randomized Intervention Trial of Exercise Training in Older Adults 
Research has shown the human brain is organized into separable functional networks during rest and varied states of cognition, and that aging is associated with specific network dysfunctions. The present study used functional magnetic resonance imaging (fMRI) to examine low-frequency (0.008 < f < 0.08 Hz) coherence of cognitively relevant and sensory brain networks in older adults who participated in a 1-year intervention trial, comparing the effects of aerobic and non-aerobic fitness training on brain function and cognition. Results showed that aerobic training improved the aging brain's resting functional efficiency in higher-level cognitive networks. One year of walking increased functional connectivity between aspects of the frontal, posterior, and temporal cortices within the Default Mode Network and a Frontal Executive Network, two brain networks central to brain dysfunction in aging. Length of training was also an important factor. Effects in favor of the walking group were observed only after 12 months of training, compared to non-significant trends after 6 months. A non-aerobic stretching and toning group also showed increased functional connectivity in the DMN after 6 months and in a Frontal Parietal Network after 12 months, possibly reflecting experience-dependent plasticity. Finally, we found that changes in functional connectivity were behaviorally relevant. Increased functional connectivity was associated with greater improvement in executive function. Therefore the study provides the first evidence for exercise-induced functional plasticity in large-scale brain systems in the aging brain, using functional connectivity techniques, and offers new insight into the role of aerobic fitness in attenuating age-related brain dysfunction.
PMCID: PMC2947936  PMID: 20890449
exercise; aging; functional connectivity; fMRI; default mode network; executive function; aerobic fitness

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