Postural change, gait, and physical function in older adults.

In a more clinical setting, abrupt posture change may be used to determine the presence of orthostatic hypotension, a hemodynamic response with relationships to physical function. Certain gait features and physical function performance are also associated with risk of falling in older adults. However, the extent to which posture change is associated with subsequent gait and physical function has received little attention in the literature. This study aims to determine the effects of posture change on spatiotemporal parameters of gait and Timed Up-and-Go (TUG) performance. METHODS: Forty-two volunteers (age 73.21 ± 6.22 years) participated in the study. A custom Tekscan Strideway (Tekscan, Boston, MA.) gait system was used to measure gait velocity (VEL), cadence (CAD), stride length (SL), and percent of time spent in active propulsion (AP). Dependent t-tests were used to compare TUG time, VEL, CAD, SL and AP after at least 10 mins of seated rest and supine rest. RESULTS: Time to complete the TUG was significantly slower after supine rest compared to seated (11.47 ± 0.51 and 10.01 ± 0.33 s, respectively, p<0.001); VEL was significantly slower after supine rest compared to seated (0.888 ± 0.042 and 1.049 ± 0.033 m/s, respectively, p=0.003); CAD was significantly slower after supine rest compared to seated (111.21 ± 2.87 and 120.97 ± 2.56spm, respectively, p=0.001); and AP was significantly lower after supine rest compared to seated (56.87 ± 4.76 and 70.79 ± 4.05 %, respectively, p<0.001). No significant differences were detected in stride length between conditions. CONCLUSIONS: Among this sample of older adults, standing from a supine posture is associated with spatiotemporal gait parameters consistent with a risk for falling and aging. Additionally, TUG performance worsens significantly after supine rest. Future studies could explore the sensitivity and specificity of falls risk screening after supine rest.

Impact of cardiovascular risk factors on the relationships of physical activity with mood and cognitive function in a diverse sample.

Physical activity has well-known benefits for older adults' mood and cognitive functioning; however, it is not clear whether risk factors for cardiovascular disease (CVD) affect the relationships of physical activity with these health outcomes among diverse older adults. This study investigated the impact of CVD risk burden on the relationships among self-reported physical activity, mood, and cognitive functioning in a diverse sample of 62 adults age 45 and older. We found that higher physical activity was associated with better attention and verbal working memory at lower CVD risk, but with worse attention and verbal working memory at higher CVD risk levels. Thus, higher CVD risk might limit the effectiveness of exercise interventions for mood and cognitive functioning. Future studies are needed to further clarify individual differences that impact the relationships among physical activity, CVD risk, and cognitive outcomes.

Communication: Combining non-Boltzmann sampling with free energy perturbation to calculate free energies of hydration of quantum models from a simulation of an approximate model.

This paper proposes combining non-Boltzmann sampling with free energy perturbation to allow calculations of the free energy of hydration of a solute with both solute-water and water-water interactions with the nearest waters calculated by high-level quantum models. The method involves simulation of an approximate model of all interactions and uses both free energy perturbation and non-Boltzmann sampling to calculate the difference in energy between the approximate and quantum models.

Falls risk factors and a compendium of falls risk screening instruments.

CLINICAL PROBLEM: Falls are the leading cause of nonfatal injuries and injurious death among older adults; the aftermath of a fall stresses the health care system and places financial and psychological burdens on the patient and family. Because of this, fall prevention/risk reduction is a primary focus of numerous health care agendas. Over the last 2 decades, clinical research has provided clinicians with a variety of screening tools to quantify risk factors for falls. The majority of these measures focus on single domain intraindividual (eg, balance, strength, vision) or extraindividual (eg, home safety) falls risk factors. Some of these single domain instruments are easily introduced and administered by community lay leaders. When a more comprehensive assessment across multiple domains is required, the assessment cannot easily be administered by community program leaders. A physical therapist must determine which instrument, or combination of instruments, best targets risk of falling for a given older adult. PURPOSE: This integrative review of the literature will provide clinicians and researchers a concise examination of falls risks factors and a compendium of falls risk screening and assessment instruments. METHODS: Searchable databases, such as Medline and CINAHL were used to identify articles about strategies used for fall risk assessment. Information about measurement properties and characteristics were extracted and are presented in table format. CONCLUSION: Comparison of recently developed multidimensional and comprehensive screening algorithms for falls risk identification may aid in lowering the rates of false negatives associated with using very specific instruments that screen or assess in only 1 falls risk factor domain.

Sodium chloride in supercritical water as a function of density: potentials of mean force and an equation for the dissociation constant from 723 to 1073 K and from 0 to 0.9 g/cm(3).

The potential of mean force (PMF) of sodium chloride in water has been calculated by using the ab initio classical free-energy perturbation method at five state points: at 973 K with densities of 0.2796, 0.0935, and 0.0101 g/cm (3) and at 723 K with densities of 0.0897 and 0.0098 g/cm (3). The method is based on a QM-MM model in which Na-H 2O, Cl-H 2O, and Na-Cl interactions are calculated by ab initio methods. The water-water interactions are from the polarizable TIP4P-FQ model. The logarithm of the dissociation constant (log K c) has been calculated from the PMF. These predictions, together with experimental measurements, were used to derive an equation for log K c at densities from 0 to 0.9 g/cm (3) and temperatures from 723 to 1073 K, as well as from 600 to 1073 K for densities from 0.29 g/cm (3) to 0.9 g/cm (3). Extrapolation of the present equation below 723 K for densities less than 0.29 g/cm (3) does not fit the experimental results. This is attributed to long-range changes in the local dielectric constant due to the high compressibility. Comparisons with previous predictions and simulations are presented.

Structure of an accurate ab initio model of the aqueous Na+ ion at high temperatures.

The structure of an accurate ab initio model of aqueous sodium ion was calculated at two high temperature state points (573 K, 0.72 g/cm(3) and 723 K, 0.0098 g/cm(3)) by a two-step procedure. First, the structure of an approximate model (the TIP4-FQ model for water and Na-H2O interactions from Liu et al.) was calculated from a molecular dynamics simulation of the model. Then the difference between the structure of the ab initio model and the approximate model was calculated by non-Boltzmann weighting of a sample of 500 configurations taken from the approximate model simulation. Radial distribution functions, average coordination numbers, the distribution of coordination numbers, and an analysis of orientations of water in the first coordination shell are reported for both state points. The average oxygen coordination number (calculated up to the inflection point in the running coordination number) was 4.71 at 573 K and 3.48 at 723 K. Most configurations have four or five coordinated waters at 573 K and three or four at 723 K. At 723 K, waters with their dipole moments pointed at the sodium ion were most common. A wider variety of orientations was found at 573 K and higher density. The difference in structure between the approximate and quantum models was small but significant.

The association between flow-mediated dilation and physical function in older men.

UNLABELLED: The probability that an individual is able to live independently decreases sharply below the threshold score of 57 units on the physical functional performance (PFP-10) test. PURPOSE: To examine the relation between brachial artery flow-mediated dilation (BAFMD) on individual and total scores on the PFP-10. We hypothesized that lower scores on the PFP-10 test would be associated with lower BAFMD. METHODS: Sixty-four men (age, 84 +/- 11 yr) from the Louisiana Healthy Aging Study were studied. Participants were classified by their performance on the PFP-10 test (Class I, score <26; Class II, score between 26 and 57; and Class III, score > 57). BAFMD was assessed after 5 min of forearm occlusion, using high-resolution ultrasonography. RESULTS: The average total score on the PFP-10 test and BAFMD were 42.9 +/- 22 U and 2.76 +/- 2.13%, respectively. The BAFMD was associated with total PFP-10 score (r = 0.45, P = 0.0001) and age (r = -0.36, P = 0.003). BAFMD was significantly different (P = 0.001) between the PFP-10 classes (Class I, 1.44% [95% CI, 0.49-2.39]; Class II, 2.67% [95% CI, 1.95-3.38]; and Class III, 4.01% [95% CI, 3.16-4.85]). CONCLUSIONS: This study reports significant relationships between BAFMD and individual and combined measures of physical function in elderly men. More specifically, when individuals were categorized based on their PFP-10 total score, those in the highest functional class, exhibited the highest BAFMD, compared to those in the middle class, who had greater vasoreactivity than those in the lowest functional class.

Physical activity level and physical functionality in nonagenarians compared to individuals aged 60-74 years.

BACKGROUND: Functional dependence and the risks of disability increase with age. The loss of independence is thought to be partially due to a decrease in physical activity. However, in populations, accurate measurement of physical activity is challenging and may not provide information on functional impairment. METHODS: This study therefore assessed physical functionality and physical activity level in a group of nonagenarians (11 men/11 women; 93+/-1 years, 66.6+/-2.4 kg, body mass index [BMI]=24+/-1 kg/m2) and a group of participants aged 60-74 years (17 men/15 women; 70+/-1 years, 83.3+/-3.0 kg, BMI=29+/-1 kg/m2) from the Louisiana Healthy Aging Study. Physical activity level was calculated from total energy expenditure (TEE) and resting metabolic rate (RMR). Physical functionality was assessed using the Reduced Continuous Scale Physical Functional Performance Test (CS-PFP10). RESULTS: Nonagenarians had lower absolute (p<.001) and adjusted (p<.007) TEE compared to participants aged 60-74 years which was attributed to a reduction in both RMR and physical activity level. Nonagenarians also had reduced functional performance (p<.001) which was correlated with activity level (r=0.68, p<.001). CONCLUSIONS: When compared to individuals aged 60-74 years, 73% of the reduction in TEE in nonagenarians can be attributed to a reduction in physical activity level, the remaining being accounted for by a reduction in RMR. The reduced physical activity in nonagenarians is associated with less physical functionality. This study provides the first objective comparison of physical functionality and actual levels of physical activity in older individuals.

Age-related deterioration in flexibility is associated with health-related quality of life in nonagenarians.

BACKGROUND AND PURPOSE: Studies indicate that age is associated with deterioration in physical function and a concomitant decrease in health-related quality of life (HRQL). The contribution of physical function to HRQL in nonagenarians (ages 90-99) is unknown. The purposes of this study were to examine age-related changes in physical function and HRQL among community-dwelling nonagenarians and to determine the relationship between their physical function and HRQL. METHODS: Seventy-four community-dwelling nonagenarians participated. The Continuous Scale Physical Function Performance Test-10 (CS-PFP10) was used to measure their physical function and the Short Form (SF)-36 was used to measure their HRQL. Pearson correlations were used to assess associations among age, physical function, and HRQL scores. RESULTS: Age was inversely associated with the upper body flexibility (r = -.365, p = .001) subscale of the CS-PFP10, but not significantly associated with any other physical function or HRQL score. Significant associations between physical function and HRQL were limited to those between upper body flexibility and the physical function subscale (r = .424, p < .001) and physical function component summary score (r = .376, p = .001) of the SF-36. CONCLUSION: These data suggest that upper body flexibility continues to decline during the 10th decade of life and has implications for influence on aspects of HRQL in this segment of the population.

Biphasic responses of the brachial artery diameter following forearm occlusion: a blunted response in the elderly.

BACKGROUND: The purpose was to examine the temporal response of the brachial artery diameter following 5 minutes of forearm occlusion in young men. A secondary objective was to compare the main features of the temporal pattern between young and old. METHODS: Sixteen young (28 +/- 8 yrs) and fifteen older (85 +/- 8 yrs) men underwent high-resolution ultrasonography of the brachial artery before and after five minutes of forearm occlusion. RESULTS: Following release of the pressure cuff the brachial artery diameter exhibits a temporal biphasic response. Initially, there is a significant reduction in brachial diameter (NIL) compared to baseline (BASE), followed by a rapid increase to a PEAK at 41 sec post release. When comparing the magnitude of the decrease in diameter and the Brachial Artery Flow Mediated Dilation (BAFMD) between Young and Old, older subjects demonstrated a blunted response (Magnitude of Decrease: Young: 2.0%; Old: 0.4%, p = 0.015, and BAFMD: Young: 7.7%; Old: 2.3%, p = 0.001). Finally, a significant relationship was noted between the magnitude of decrease and BAFMD (r = -0.44, p = 0.04). CONCLUSION: Examination of the temporal response of the brachial artery diameter following 5 minutes of forearm occlusion reveals a biphasic pattern in all participants. Specific features of this pattern are blunted in older adults compared with younger subjects. Finally, the magnitude of the drop in diameter following forearm occlusion correlates with the magnitude of the BAFMD.

Electrical conductances of aqueous Na2SO4, H2SO4, and their mixtures: limiting equivalent ion conductances, dissociation constants, and speciation to 673 K and 28 MPa.

The electrical conductivities of aqueous solutions of Na(2)SO(4), H(2)SO(4), and their mixtures have been measured at 373-673 K at 12-28 MPa in dilute solutions for molalities up to 10(-2) mol kg(-1). These conductivities have been fit to the conductance equation of Turq et al.(1) with a consensus mixing rule and mean spherical approximation activity coefficients. Provided the concentration is not too high, all of the data can be fitted by a solution model that includes ion association to form NaSO(4)(-), Na(2)SO(4)(0), HSO(4)(-), H(2)SO(4)(0), and NaHSO(4)(0). The adjustable parameters of this model are the dissociation constants of the SO(4)(-) species and the H(+), SO(4)(-2), and HSO(4)(-) conductances (ion mobilities) at infinite dilution. For the 673 K and 230 kg m(-3) state point with the lowest dielectric constant, epsilon = 3.5, where the Coulomb interactions are the strongest, this model does not fit the experimental data above a solution molality of 0.016. Including the species H(9)(SO(4))(5)(-) gave satisfactory fits to the conductance data at the higher concentrations.

Conductance study of association in aqueous CaCl2, Ca(CH3COO)2, and Ca(CH3COO)2.nCH3COOH from 348 to 523 K at 10 MPa.

The conductances of aqueous CaCl2, Ca(CH3COO)2, and Ca(CH3COO)2.nCH3COOH were measured from 348 to 523 K at pressures near 10 MPa using a flow conductometric technique. The first association constant for calcium chloride and the first and second association constants for calcium acetate in water, were derived from a least-squares fit of the measurements to a conductance model in which activity coefficients were calculated using the mean spherical approximation (MSA) and the conductance was modeled by the Turq, Blum, Bernard, and Kunz (TBBK) equation, plus a mixture model.

Heart rate variability and the exercise pressor reflex during dynamic handgrip exercise and postexercise arterial occlusion.

BACKGROUND: The exercise pressor reflex is thought to be an important cardiovascular control mechanism that may be compromised in disease states such as congestive heart failure and other metabolic syndromes. The purpose was to describe the exercise pressor reflex by observing heart rate variability and blood pressure responses to handgrip-exercise and postexercise arterial occlusion. METHODS: Continuous electrocardiography, arterial blood pressure, and pneumotachogram data were collected on 38 participants (age, 20 +/- 1 year) during spontaneous breathing, venous-occluded exercise (60% maximal voluntary contraction, 0.5 Hz) and immediate postexercise arterial occlusion. Data were analyzed for mean R-R interval, standard deviation of R-R intervals (SDNN), normalized low (0-0.15 Hz) frequency power (LFnu), mean arterial pressure (MAP), and respiratory rate. RESULTS: During exercise, increases in respiratory rate (+4.55 +/- 6.48 breaths/min), LFnu (+9.39 +/- 16.83%), and MAP (+25.40 +/- 17.55 mm Hg) were observed. Mean R-R interval (-230.73 +/- 125.79 msec) and SDNN (-38.54 +/- 36.02 msec) decreased (P < 0.05). Respiratory rate (+0.12 +/- 4.61 breaths/min), SDNN (-17.89 +/- 64.41 msec), and LFnu (9.89 +/- 21.01%) recovered during forearm arterial occlusion (P < 0.05). However, Mean R-R interval and MAP remained elevated above spontaneous breathing (P < 0.05). CONCLUSIONS: The sustained elevation in MAP during postexercise arterial occlusion suggests metaboreceptor-mediated heightened sympathetic activity. The increase in LFnu during exercise and its subsequent recovery during postexercise occlusion is consistent with dynamic exercise-induced parasympathetic withdrawal but a strong vagal activation upon cessation of dynamic activity despite persistent sympathetic activity originating from afferent input from the occluded forearm.

Classification of older adults with/without a fall history using machine learning methods.

Falling is a serious problem in an aged society such that assessment of the risk of falls for individuals is imperative for the research and practice of falls prevention. This paper introduces an application of several machine learning methods for training a classifier which is capable of classifying individual older adults into a high risk group and a low risk group (distinguished by whether or not the members of the group have a recent history of falls). Using a 3D motion capture system, significant gait features related to falls risk are extracted. By training these features, classification hypotheses are obtained based on machine learning techniques (K Nearest-neighbour, Naive Bayes, Logistic Regression, Neural Network, and Support Vector Machine). Training and test accuracies with sensitivity and specificity of each of these techniques are assessed. The feature adjustment and tuning of the machine learning algorithms are discussed. The outcome of the study will benefit the prediction and prevention of falls.

Influence of short-term endurance exercise training on heart rate variability.

PURPOSE: To examine the influence of 2 wk (eight sessions) of endurance training on cardiac autonomic modulation, as measured by heart rate variability (HRV). METHODS: Twenty-four males (mean age: 23.1 yr) were randomized to an exercise (EX; N = 12) or control group (CT; N = 12). EX trained for eight sessions (4x wk-1, 40 min, 80-85% HRreserve) on a cycle ergometer. ECG tracings were collected during 5 min of paced breathing (12 breaths x min-1 (PB)), 5 min of spontaneous breathing (SB1), 5 min of 70 degrees head-up tilt (TILT), and a second 5-min period of spontaneous breathing (SB2). Data were collected before (test 1), during (tests 2-4), and 48 h after (test 5) the 2-wk period. HRV was reported as the standard deviation of RR intervals, and as natural logarithm of the normalized units (NU) of high- and low-frequency power (lnHF and lnLF). RESULTS: EX exhibited a significant increase in peak oxygen consumption (8%). During PB and TILT conditions, ANOVA revealed a group x time interaction such that EX exhibited lower lnLFNU and lnLF/lnHF during test 5 compared with test 1. CONCLUSION: These data suggest that eight endurance exercise-training sessions performed over 2 wk enhance the relative vagal modulation of the heart during PB and TILT, but not during SB.

Social engagement and health in younger, older, and oldest-old adults in the Louisiana Healthy Aging Study.

Social support has been shown to influence health outcomes in later life. In this study, we focus on social engagement as an umbrella construct that covers select social behaviors in a life span sample that included oldest-old adults, a segment of the adult population for whom very little data currently exist. We examined relationships among social engagement, positive health behaviors, and physical health to provide new evidence that addresses gaps in the extant literature concerning social engagement and healthy aging in very old adults. Participants were younger (21-59 years), older (60-89 years), and oldest-old (90-97 years) adults (N = 364) in the Louisiana Healthy Aging Study (LHAS). Linear regression analyses indicated that age, gender, and hours spent outside of the house were significantly associated with self-reported health. The number of clubs and hours outside of home were more important factors in the analyses of objective health status than positive health behaviors, after considering age group and education level. These data strongly suggest that social engagement remains an important determinant of physical health into very late adulthood. The discussion focuses on practical applications of these results including social support interventions to maintain or improve late-life health.

Comparison of the validity of four fall-related psychological measures in a community-based falls risk screening.

We examined the measurement properties offall-related psychological instruments with a sample of 133 older adults (M age = 74.4 years, SD = 9.4). Measures included the Comprehensive Falls Risk Screening Instrument, Falls-efficacy Scale-International (FES-I), Activities-specific Balance Confidence (ABC), modified Survey ofActivities and Fear ofFalling in the Elderly (mSAFFE), Consequences of Falling (CoF), Physical Activity Scale for the Elderly (PASE), and 36-Item Short-Form Health Survey (SF-36). The FES-I, ABC, mSAFFE, and CoF were significantly correlated with each othe, with SF-36, and with mobility. The ABC and mSAFFE were significantly correlated with PASE. The ABC differentiated between fallers and nonfallers and predicted total falls risk. Findings can assist with the selection of psychological instruments in a falls risk screening context.

Problems with Some Current Water Models for Close Pair Interactions That Are Not Near the Minimum Energy.

The ability of an empirical, polarizable model of water to predict a thermal ensemble of molecular configurations at ambient conditions was examined using first-principle quantum mechanics. The empirical model of water selected for this evaluation was the TTM2-F model. The quantum mechanical methodology selected was the second-order Møller-Plesset model (MP2). Only pairwise interaction energies were considered. Significant deviations from the empirical model were found. Similar results were found for ad-hoc comparisons with several other common water models including the TIP3P, TIP4P, TIP4P-FQ, TIP5P, TTM2.1-F, TTM2.2-F, TTM3-F, and POL5/QZ potential models. Our results show that spatially close dimer configurations with interaction energies notably above the potential well minimum (but are still thermally accessible at ambient conditions) are the source of the largest deviations. To assist others in future water model parametrizations we report the MP2 near complete basis set limit energies for 840 water dimer configurations sampled from an approximate thermal ensemble at ambient conditions.

Predictors of ADL Disability in Culturally Diverse Older Adults.

The purpose of this study was to utilize the disablement pathway model to examine the contribution of physical function, dyspnea, and pain to disability in activities-of-daily-living (ADL) in culturally diverse older adults. Participants were 51 older adults (age = 69.0 years ± 9.7; 76.5% African-American, 51.0% < high school education, 52.9% < $20,000 annual income) from an urban community center and an independent living housing facility for seniors. Participants completed the Functional Status Index (FSI), which provides ratings of need for assistance (FSIA) and pain (FSIP) with ADL, the Continuous Scale Physical Functional Performance 10-item Test (CS-PFP10), and an analog dyspnea scale. Hierarchical multiple regression analyses revealed that facility, physical function, pain, and dyspnea accounted for 50.5% of the variance in disability and that pain (ß = .43, p < .01) and physical function (ß = -.39, p < .01) were the only significant predictors. In the second model, facility, dyspnea, and pain explained 27.6% of the variance in physical function, and facility (ß = .39, p < .01) and dyspnea (ß = -.26, p = .05) were the only significant predictors. Based on the disablement pathway model, physical functional improvement and pain prevention and management should be targeted when designing culturally appropriate strategies for delaying disability and maintaining independent life.