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Social behavior across animal species ranges from simple pairwise interactions to thousands of individuals coordinating goal-directed movements. Regardless of the scale, these interactions are governed by the interplay between multimodal sensory information and the internal state of each animal. Here, we investigate how animals use multiple sensory modalities to guide social behavior in the highly social zebrafish ( Danio rerio ) and uncover the complex features of pairwise interactions early in development. To identify distinct behaviors and understand how they vary over time, we developed a new hidden Markov model with constrained linear-model emissions to automatically classify states of coordinated interaction, using the movements of one animal to predict those of another. We discovered that social behaviors alternate between two interaction states within a single experimental session, distinguished by unique movements and timescales. Long-range interactions, akin to shoaling, rely on vision, while mechanosensation underlies rapid synchronized movements and parallel swimming, precursors of schooling. Altogether, we observe spontaneous interactions in pairs of fish, develop novel hidden Markov modeling to reveal two fundamental interaction modes, and identify the sensory systems involved in each. Our modeling approach to pairwise social interactions has broad applicability to a wide variety of naturalistic behaviors and species and solves the challenge of detecting transient couplings between quasi-periodic time series.

Social behavior across animal species ranges from simple pairwise interactions to thousands of individuals coordinating goal-directed movements. Regardless of the scale, these interactions are governed by the interplay between multimodal sensory information and the internal state of each animal. Here, we investigate how animals use multiple sensory modalities to guide social behavior in the highly social zebrafish ( Danio rerio ) and uncover the complex features of pairwise interactions early in development. To identify distinct behaviors and understand how they vary over time, we developed a new hidden Markov model with constrained linear-model emissions to automatically classify states of coordinated interaction, using the movements of one animal to predict those of another. We discovered that social behaviors alternate between two interaction states within a single experimental session, distinguished by unique movements and timescales. Long-range interactions, akin to shoaling, rely on vision, while mechanosensation underlies rapid synchronized movements and parallel swimming, precursors of schooling. Altogether, we observe spontaneous interactions in pairs of fish, develop novel hidden Markov modeling to reveal two fundamental interaction modes, and identify the sensory systems involved in each. Our modeling approach to pairwise social interactions has broad applicability to a wide variety of naturalistic behaviors and species and solves the challenge of detecting transient couplings between quasi-periodic time series.

Background: Home health use is rising rapidly in the United States as the population ages, the prevalence of chronic disease increases, and older Americans express their desire to age at home. Enrollment in Medicare Advantage (MA) plans rather than Traditional Medicare (TM) has grown as well, from 13% of total Medicare enrollment in 2004 to 39% in 2020. Despite these shifts, little is known about outcomes and costs following home health in MA as compared with TM., Objective: The objective of this study was to measure the association of MA enrollment with outcomes and costs for patients using home health., Design: This was a retrospective cohort study., Participants: Patients enrolled in plans offered by 1 large, national MA organization and patients enrolled in TM, with at least 1 home health visit between January 1, 2017, and June 30, 2018., Exposure: MA enrollment., Main Measures: We compared the intensity of home health services and types of care delivered. The main outcome measures were hospitalization, the proportion of days in the home, and total allowed costs during the 180-day period following the first qualifying home health visit during the study period., Key Results: Among patients who used home health, our models demonstrated enrollment in MA was associated with 14%, and 6% decreased odds of 60- and 180-day hospitalization, respectively, a 12.8% and 14.7% decrease in medical costs exclusive and inclusive of home health costs, respectively, and a 0.27% increase in the proportion of days at home during the 180-day follow-up, equivalent to an additional half-day at home. There were few differences in home health care delivered for MA and TM [mean number of visits in the first episode of care (17.1 vs. 17.3) and mean visits per week (3.2 vs. 3.3)]. The mean number of visits by visit type and percent of patients with each type was similar between MA and TM as well., Conclusions: Compared with enrollment in TM, enrollment in MA was associated with improved patient-centered outcomes and lower cost and utilization, despite few differences in the way home health was delivered. These findings might be explained by structural components of MA that encourage better care management, but further investigation is needed to clarify the mechanisms by which MA enrollment may lead to higher value home health care., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Objectives: To compare outcomes and costs following skilled nursing facility (SNF) discharge for patients within a Medicare Advantage (MA) organization vs traditional Medicare (TM)., Study Design: Retrospective analysis of adults with a postacute SNF admission identified from MA claims (MA cohort: n = 56,228) and the Medicare 5% Limited Data Sets (TM cohort: n = 67,859)., Methods: Outcomes included hospitalization, proportion of days at home, and total medical costs during the 180 days post SNF discharge, and successful community discharge. Regression models accounted for patient characteristics and health care utilization in the 180 days prior to the proximal hospitalization and characteristics of the proximal hospitalization using backward variable selection and fixed effects for MA enrollment. To control for observable differences between individuals who selected MA vs TM, inverse probability of treatment weighting (IPTW) was conducted., Results: The MA cohort was younger than the TM cohort (median age, 77 vs 81 years), more likely to have qualified for Medicare based on disability (29% vs 20%), and less likely to have dual Medicare/Medicaid eligibility (16% vs 23%). After adjustment, MA was associated with 22% decreased odds of hospitalization during the 180 days post SNF discharge, 19% increased odds of successful community discharge, a 4% increase in the proportion of days at home (equating to 6.7 additional days), and a 24% decrease in medical costs post SNF discharge. Results using IPTW were similar., Conclusions: MA was associated with better outcomes and lower costs post SNF discharge, suggesting efficiencies in care for SNF patients with MA. Further research is needed to evaluate specific MA features that may lead to better value.

Background: Slow walk (gait) speed predicts functional decline, institutionalization, and mortality risks in the geriatric population. A gait speed evidence base for dialysis patient outcomes is needed., Study Design: Prospective cohort study., Setting & Participants: 752 prevalent hemodialysis (HD) patients aged 20 to 92 years evaluated in 2009 to 2012 in 7 Atlanta and 7 San Francisco clinics in a US Renal Data System special study., Predictor: Usual walk speed in meters per second, categorized as ≥0.6 m/s (baseline n=575), <0.6 m/s (baseline n=94), and unable to perform walk test (baseline n=83)., Outcomes: Survival; hospitalization; activities of daily living (ADL) difficulty; 36-Item Short Form Health Survey (SF-36) Physical Function score., Measurements: Cox proportional hazards models investigated gait speed and mortality over a median follow-up of 703 days. Multivariable logistic or linear regression models estimated associations of baseline gait speed with hospitalization, need for ADL assistance, and SF-36 Physical Function score after 12 months., Results: Participants who walked ≥0.6 m/s had 53 (9%) deaths, those who walked <0.6 m/s had 19 (20%) deaths, and those unable to walk had 37 (44%) deaths. Adjusted mortality hazard ratios were 2.17 (95% CI, 1.19-3.98) for participants who walked <0.6 m/s and 6.93 (95% CI, 4.01-11.96) for those unable to walk, compared with participants walking ≥0.6 m/s. After 12 months, compared with baseline walk speed ≥ 1.0 m/s (n=169 participants), baseline walk speed of 0.6 to <0.8 m/s (n=116) was associated with increased odds of hospitalization (OR, 2.04; 95% CI, 1.19-3.49) and ADL difficulty (OR, 3.88; 95% CI, 1.46-10.33) and a -8.20 (95% CI, -13.57 to -2.82) estimated change in SF-36 Physical Function score., Limitations: Cohort not highly representative of overall US in-center HD population., Conclusions: Because walking challenges the heart, lungs, and circulatory, nervous, and musculoskeletal systems, gait speed provides an informative marker of health status. The association of gait speed with HD patients' risk for functional decline warrants continued study., (Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Objectives: It is unknown whether muscle wasting accounts for impaired physical function in adults on maintenance hemodialysis (MHD)., Design: Observational study., Setting: Outpatient dialysis units and a fall clinic., Subjects: One hundred eight MHD and 122 elderly nonhemodialysis (non-HD) participants., Exposure Variable: Mid-thigh muscle area was measured by magnetic resonance imaging., Main Outcome Measure: Physical function was measured by distance walked in 6 minutes., Results: Compared with non-HD elderly participants, MHD participants were younger (49.2 ± 15.8 vs. 75.3 ± 7.1 years; P < .001) and had higher mid-thigh muscle area (106.2 ± 26.8 vs. 96.1 ± 21.1 cm2; P = .002). However, the distance walked in 6 minutes was lower in MHD participants (322.9 ± 110.4 vs. 409.0 ± 128.3 m; P < .001). In multiple regression analysis adjusted for demographics, comorbid conditions, and mid-thigh muscle area, MHD patients walked significantly less distance (-117 m; 95% confidence interval: -177 to -56 m; P < .001) than the non-HD elderly., Conclusions: Even when compared with elderly non-HD participants, younger MHD participants have poorer physical function that was not explained by muscle mass or comorbid conditions. We speculate that the uremic milieu may impair muscle function independent of muscle mass. The mechanism of impaired muscle function in uremia needs to be established in future studies., (Published by Elsevier Inc.)

Carbohydrates exhibit either van der Waals and ionic interactions or strong hydrogen bonding interactions. The prominence and large number of hydrogen bonds results in major contributions to phase behavior. A thermodynamic framework that accounts for hydrogen bonding interactions is therefore necessary. We have developed an extension of the thermodynamic model based on the Veytsman association theory to predict the contribution of hydrogen bonds to the behavior of glucose-water and dextran-water systems and we have calculated the free energy of mixing and its derivative leading to chemical potential and water activity. We compared our calculations with experimental data of water activity for glucose and dextran and found excellent agreement far superior to the Flory-Huggins theory. The validation of our calculations using experimental data demonstrated the validity of the Veytsman model in properly accounting for the hydrogen bonding interactions and successfully predicting water activity of glucose and dextran. Our calculations of the concentration of hydrogen bonds using the Veytsman model were instrumental in our ability to explain the difference between glucose and dextran and the role that hydrogen bonds play in contributing to these differences. The miscibility predictions showed that the Veytsman model is also able to correctly describe the phase behavior of glucose and dextran., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Chronic kidney disease (CKD) is becoming a serious health problem throughout the world and is one of the most potent known risk factors for cardiovascular disease, which is the leading cause of morbidity and mortality in this patient population. Physical inactivity has emerged as a significant and independent risk factor for accelerated deterioration of kidney function, physical function, cardiovascular function and quality of life in people in all stages of CKD. CKD specific research evidence, combined with the strong evidence on the multiple health benefits of regular and adequate amounts of PA in other cardiometabolic conditions, has resulted in physical inactivity being identified by national and international CKD clinical practice guidelines as one of the multiple risk factors that require simultaneous and early intervention for optimum prevention/management of CKD. Despite this realisation, physical inactivity is not systematically addressed by renal care teams. The purpose of this expert statement is therefore to inform exercise and renal care specialists about the clinical value of exercise therapy in CKD, as well as to provide some practical recommendations on how to more effectively translate the existing evidence into effective clinical practice.

Objectives: Physical activity questionnaires usually focus on moderate to vigorous activities and may not accurately capture physical activity or variation in levels of activity among extremely inactive groups like dialysis patients., Design: Cross-sectional study., Setting: Three dialysis facilities in the San Francisco Bay Area., Subjects: Sixty-eight prevalent hemodialysis patients., Intervention: We administered a new physical activity questionnaire designed to capture activity in the lower end of the range, the Low Physical Activity Questionnaire (LoPAQ)., Main Outcome Measure: Outcome measures were correlation with a validated physical activity questionnaire, the Minnesota Leisure Time Activity (LTA) questionnaire and with self-reported physical function (physical function score of the SF-36) and physical performance (gait speed, chair stand, balance, and short physical performance battery). We also determined whether patients who were frail or reported limitations in activities of daily living were less active on the LoPAQ., Results: Sixty-eight participants (mean age 59 ± 14 years, 59% men) completed the study. Patients were inactive according to the LoPAQ, with a median (interquartile range) of 517 (204-1190) kcal/week of physical activity. Although activity from the LTA was lower than on the LoPAQ (411 [61-902] kcal/week), the difference was not statistically significant (P = .20), and results from the 2 instruments were strongly correlated (rho = 0.62, P < .001). In addition, higher physical activity measured by the LoPAQ was correlated with better self-reported functioning (rho = 0.64, P < .001), better performance on gait speed (rho = 0.32, P = .02), balance (rho = 0.45, P < .001), and chair rising (rho = -0.32, P = .03) tests and with higher short physical performance battery total score (rho = 0.51, P < .001). Frail patients and patients with activities of daily living limitations were less active than those who were not frail or limited., Conclusions: The LoPAQ performed similarly to the Minnesota LTA questionnaire in our cohort despite being shorter and easier to administer., (Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Background: New information from various clinical settings suggests that tight blood pressure control may not reduce mortality and may be associated with more side effects., Methods: We performed cross-sectional multivariable ordered logistic regression to examine the association between predialysis blood pressure and the short physical performance battery (SPPB) in a cohort of 749 prevalent hemodialysis patients in the San Francisco and Atlanta areas recruited from July 2009 to August 2011 to study the relationship between systolic blood pressure and objective measures of physical function. Mean blood pressure for three hemodialysis sessions was analyzed in the following categories: <110 mmHg, 110-129 mmHg (reference), 130-159 mmHg, and ≥160 mmHg. SPPB includes three components: timed repeated chair stands, timed 15-ft walk, and balance tests. SPPB was categorized into ordinal groups (≤6, 7-9, 10-12) based on prior literature., Results: Patients with blood pressure 130-159 mmHg had lower odds (OR 0.57, 95% CI 0.35-0.93) of scoring in a lower SPPB category than those whose blood pressure was between 110 and 129 mmHg, while those with blood pressure≥160 mmHg had 0.56 times odds (95% CI 0.33-0.94) of scoring in a lower category when compared with blood pressure 110-129 mmHg. When individual components were examined, blood pressure was significantly associated with chair stand (130-159 mmHg: OR 0.59, 95% CI 0.38-0.92) and gait speed (≥160 mmHg: OR 0.59, 95% CI 0.35-0.98). Blood pressure≥160 mmHg was not associated with substantially higher SPPB score compared with 130-159 mmHg., Conclusions: Patients with systolic blood pressure at or above 130 mmHg had better physical performance than patients with lower blood pressure in the normotensive range. The risk-benefit tradeoff of aggressive blood pressure control, particularly in low-functioning patients, should be reexamined.

Background and Objectives: Physical activity has been associated with better health status in diverse populations, but the association in patients on maintenance hemodialysis is less established. Patient-reported physical activities and associations with mortality, health-related quality of life, and depression symptoms in patients on maintenance hemodialysis in 12 countries were examined., Design, Setting, Participants, & Measurements: In total, 5763 patients enrolled in phase 4 of the Dialysis Outcomes and Practice Patterns Study (2009-2011) were classified into five aerobic physical activity categories (never/rarely active to very active) and by muscle strength/flexibility activity using the Rapid Assessment of Physical Activity questionnaire. The Kidney Disease Quality of Life scale was used for health-related quality of life. The Center for Epidemiologic Studies Depression scale was used for depression symptoms. Linear regression was used for associations of physical activity with health-related quality of life and depression symptoms scores. Cox regression was used for association of physical activity with mortality., Results: The median (interquartile range) of follow-up was 1.6 (0.9-2.5) years; 29% of patients were classified as never/rarely active, 20% of patients were classified as very active, and 20.5% of patients reported strength/flexibility activities. Percentages of very active patients were greater in clinics offering exercise programs. Aerobic activity, but not strength/flexibility activity, was associated positively with health-related quality of life and inversely with depression symptoms and mortality (adjusted hazard ratio of death for very active versus never/rarely active, 0.60; 95% confidence interval, 0.47 to 0.77). Similar associations with aerobic activity were observed in strata of age, sex, time on dialysis, and diabetes status., Conclusions: The findings are consistent with the health benefits of aerobic physical activity for patients on maintenance hemodialysis. Greater physical activity was observed in facilities providing exercise programs, suggesting a possible opportunity for improving patient outcomes., (Copyright © 2014 by the American Society of Nephrology.)

Background: Despite practice guidelines (KDOQI [Kidney Disease Outcomes Quality Initiative]) recommending regular assessment of physical function and encouragement of physical activity, few clinics in the United States objectively assess physical function/physical activity or provide recommendations for physical activity in their patient care., Study Design: Qualitative methods were used to develop an understanding of practice patterns related to physical function assessment and physical activity encouragement by dialysis staff., Setting & Participants: Data were collected in one outpatient university-based hemodialysis clinic. 15 patient care staff were interviewed and 6 patients were observed., Methodology: Semistructured interviews of patient care staff were conducted, along with nonparticipant observations of the clinic environment and operations and review of archival materials., Analytic Approach: Coding of the interviews was descriptive, followed by interpretive coding by the research team. On-site field notes were transcribed for analysis., Results: There was universal unawareness of the KDOQI guideline related to physical function/physical activity; however, all staff thought their patients would benefit from physical activity. There were no objective assessments of physical function and no resources or training to facilitate physical activity encouragement. Staff described deteriorating physical function in their patients, which was frustrating and disappointing. Barriers to physical activity included clinical/disease factors, staff "overaccommodation," and a system of dialysis care that facilitates sedentary behavior and does not require or incentivize clinics to promote physical activity. The patient care technicians were interested and thought that they had time to promote physical activity, but thought that they were unprepared to do so, indicating a need for education and training and a need to develop protocols to address the issue as routine practice., Limitations: This was a single university-based center; however, because hemodialysis procedures are prescribed by Centers for Medicare & Medicaid Services regulations, it is likely that practice in this clinic is representative of nationwide practice., Conclusions: Development of strategies to implement practice change that addresses low physical function and physical activity is warranted., (Copyright © 2014 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Purpose of Review: Despite guidelines supporting the regular assessment of physical functioning and encouragement of physical activity in management of the patient with chronic kidney disease (CKD), implementation has been undermined by a lack of understanding of the evidence for this recommendation. The purpose of this review is to present a summary of emerging data from larger epidemiologic cohorts that report associations between low levels of physical functioning and/or low physical activity and clinical outcomes in patients with CKD., Recent Findings: Low levels of physical activity and poor physical functioning are strongly associated with mortality and poor clinical outcomes in adult patients with CKD, regardless of treatment modality. Low physical performance and activity limitations are more prevalent in patients with CKD, regardless of age, compared to older community-dwelling adults., Summary: The strength of the evidence presented should strongly motivate a focus of treatment on assessing and improving physical activity and physical function as part of routine patient-centered management of persons with CKD. Physical activity interventions are warranted because patients with CKD, regardless of age, have a high prevalence of low physical functioning and frailty that is similar to or higher than the general population of elderly adults; physical activity, physical function, and performance are strongly associated with all-cause mortality; and exercise training and exercise counseling have been shown to improve measures of physical functioning.

Patients with chronic kidney disease (CKD) who are treated with dialysis have impaired physical functioning that is associated with poor outcomes. Gait speed is an important measure of mobility that predicts adverse events and mortality in older people. Gait speed is low in patients with CKD, and those treated with hemodialysis average below cut-points known to indicate increased risk of reduced survival and adverse health events. Measurement of gait speed in patients with CKD may be valuable in identifying those at risk for adverse events, including disability and mortality.

Hospital readmissions in the Medicare population may be related to a number of factors, including reoccurrence of illness, failure to understand or follow physician direction, or lack of follow-up care, among others. These readmissions significantly increase cost and utilization in this population, and are expected to increase with the projected growth in Medicare enrollment. The authors examined whether a postdischarge telephonic intervention for patients reduced 30-day hospital readmissions as compared to a matched control population. Postdischarge telephone calls were placed to patients after discharge from a hospital. Readmissions were monitored through health care claims data analysis. Of 48,538 Medicare members who received the intervention, 4504 (9.3%) were readmitted to the hospital within 30 days, as compared to 5598 controls (11.5%, P<0.0001). A direct correlation was observed between the timing of the intervention and the rate of readmission; the closer the intervention to the date of discharge the greater the reduction in number of readmissions. Furthermore, although emergency room visits were reduced in the intervention group as compared to controls (8.1% vs. 9.4%, P<0.0001), physician office visits increased (76.5% vs. 72.3%, P<0.0001), suggesting the intervention may have encouraged members to seek assistance leading to avoidance of readmission. As a group, overall cost savings were $499,458 for members who received the intervention, with $13,964,773 in savings to the health care plan. Support for patients after hospital discharge clearly affected hospital readmission and associated costs and warrants further development.

Deep eutectic solvents, considered ionic liquid (IL) analogues, show promise for many material science and engineering applications over typical ILs because they are readily available and relatively inexpensive. Atomistic molecular dynamics simulations have been performed over a range of temperatures on one eutectic mixture, 1:2 choline chloride/urea, using different force field modifications. Good agreement was achieved between simulated density, volume expansion coefficient, heat capacity, and diffusion coefficients and experimental values in order to validate the best performing force field. Atom-atom and center-of-mass radial distribution functions are discussed in order to understand the atomistic interactions involved in this eutectic mixture. Experimental infrared (IR) spectra are also reported for choline chloride-urea mixtures, and band assignments are discussed. The distribution of hydrogen-bond interactions from molecular simulations is correlated to curve-resolved bands from the IR spectra. This work suggests that there is a strong interaction between the NH2 of urea and the chlorine anion where the system wants to maximize the number of hydrogen bonds to the anion. Additionally, the disappearance of free carbonyl groups upon increasing concentrations of urea suggests that at low urea concentrations, urea will preferentially interact with the anion through the NH2 groups. As this concentration increases, the complex remains but with additional interactions that remove the free carbonyl band from the spectra. The results from both molecular simulations and experimental IR spectroscopy support the idea that key interactions between the moieties in the eutectic mixture interrupt the main interactions within the parent substances and are responsible for the decrease in freezing point.

We investigated the impact of continuous-flow left ventricular assist devices (LVAD) on the carotid elastic properties. Carotid artery parameters (diameter distensibility (DD), cross-sectional distensibility (CSD), diameter compliance (DC), cross-sectional compliance (CSC), and incremental elastic modulus (IEM)) were measured in a cross-sectional study using a standard ultrasound with a 10-MHz linear array probe. Measurements (mean ± SEM) were made in separate groups at various clinical time points: prior to LVAD surgery (baseline; 13 male/3 female; age 48 ± 3 years), 1 week following LVAD placement (acute; 12 male/2 female; age 47 ± 3 years), approximately 24 weeks following LVAD surgery (chronic; 13 male/2 female; age 52 ± 3 years), and in a group of healthy subjects (controls; 9 male/1 female; age 51 ± 4 years). Distensibility properties were lower (P < 0.05) in the acute (DD 2.3 % ± 0.4 %; CSD 4.7 % ± 0.8 %) and chronic (DD 2.2 % ± 0.4 %; CSD 4.5 ± 0.9 %) compared with the baseline (DD 5.9 % ± 0.7 %; CSD 12.2 % ± 1.5 %) and control (DD 5.8 % ± 0.6 %; CSD 11.9 % ± 1.3 %) groups. Compliance properties were lower (P < 0.05) in the chronic (DC 4.4 ± 0.7 mm/mmHg × 10(-3); CSC 1.2 ± 0.2 mmHg(-1) × 10(-3)) compared with acute (DC 9.0 ± 1.6 mm/mmHg × 10(-3); CSC 2.6 ± 0.4 mmHg(-1) × 10(-3)) and baseline (DC 11.1 ± 1.1 mm/mmHg × 10(-3); CSC 3.3 ± 0.4 mmHg(-1) × 10(-3)) groups. The compliance properties in the control (DC 8.3 ± 0.8 mm/mmHg × 10(-3); CSC 2.4 ± 0.2 mmHg(-1) × 10(-3)) group were not different from any of the patient groups. The IEM was higher (P < 0.05) in the chronic (6908 ± 1269 mmHg) compared with acute (2739 ± 412 mmHg), baseline (1849 ± 177 mmHg), and control (2349 ± 241 mmHg) groups. Chronic continuous-flow LVAD support is associated with lower carotid artery compliance and distensibility, which may place further strain on the left ventricle.

Patients with CKD are characterized by low levels of physical functioning, which, along with low physical activity, predict poor outcomes in those treated with dialysis. The hallmark of clinical care in geriatric practice and geriatric research is the orientation to and assessment of physical function and functional limitations. Although there is increasing interest in physical function and physical activity in patients with CKD, the nephrology field has not focused on this aspect of care. This paper provides an in-depth review of the measurement of physical function and physical activity. It focuses on physiologic impairments and physical performance limitations (impaired mobility and functional limitations). The review is based on established frameworks of physical impairment and functional limitations that have guided research in physical function in the aging population. Definitions and measures for physiologic impairments, physical performance limitations, self-reported function, and physical activity are presented. On the basis of the information presented, recommendations for incorporating routine assessment of physical function and encouragement for physical activity in clinical care are provided.

Patients treated with dialysis have low levels of physical functioning and activity. Whether this translates into frailty or not may depend on how the frailty phenotype is operationalized. This is a secondary analysis of data from the Renal Exercise Demonstration Project to evaluate two methods of operationalizing the Fried phenotype for frailty: Using measured walking speed and muscle weakness (FRAILmeas) and using substitution of the Physical Function Scale (PF) from the SF-36 questionnaire for walking speed and muscle weakness (FRAILsubst). Complete data for both measures were available for 188 hemodialysis patients. The frailty score (FRAILmeas) was the sum of criteria scores for measured gait speed, chair stand, body mass index, vitality, and physical activity. The frailty score (FRAILsubst) substituted the PF scale score (<75) as a surrogate measure for gait speed and for weakness. The frailty score ranged from 0 to 5. Scores ≥3 were categorized as frail, and <3 as not frail. The substitution of the PF score for walking speed and muscle weakness resulted in 78% of patients being categorized as frail compared to 24% using actual measured walking speed and muscle weakness (P < .001). The component of frailty that had the highest prevalence was low physical activity (average 54% of subjects). Frailty (using the FRAILmeas) was higher in patients with increasing age, female gender, and lower self-reported PF. Frailty is highly prevalent in hemodialysis patients; however, measured constructs of the components of frailty should be used to report the frailty phenotype., (© 2012 The Authors. Hemodialysis International © 2012 International Society for Hemodialysis.)

Patients with end-stage renal disease (ESRD) requiring renal replacement have impaired health-related quality of life (HRQoL), and there is general consensus that HRQoL improves with successful transplant and evidence of improvement with frequent hemodialysis. This study reports changes in HRQoL associated with changes in treatment modality to daily hemodialysis (DHD) and transplant among patients requiring renal replacement. This cohort study had assessments at baseline and 6-month following modality change. Subjects were nondiabetic individuals receiving conventional hemodialysis who (a) remained on conventional hemodialysis (n = 13), (b) changed to daily hemodialysis (DHD) (n = 10), or (c) received a living donor transplant (n = 20). Thirty-four healthy controls were assessed once for comparison. HRQoL was measured using the Kidney Disease Quality of Life Instrument. The Physical Functioning and Physical Composite Scale scores were primary outcomes. Transplantation resulted in significant improvements in six of eight generic scales and the physical composite scale (PCS). Those changing to DHD had significant improvements in Physical Function and PCS scales. Those remaining on dialysis remained lower than controls on all scales except for Vitality; the transplant group remained lower than controls only on the Vitality and General Health scales. Transplant resulted in significant improvements in four of the seven disease-specific scales (symptoms, effects, and burden of kidney disease, work). DHD resulted in improvements in the effects of kidney disease. Modality change to transplant results in significant improvement in HRQoL, achieving levels similar to controls. Change to daily hemodialysis improves only select HRQoL domains and remains low in disease-specific domains., (© 2012 The Authors. Hemodialysis International © 2012 International Society for Hemodialysis.)

Background and Objectives: Relatively little is known about the effects of hemodialysis frequency on the disability of patients with ESRD., Design, Setting, Participants, & Measurements: This study examined changes in physical performance and self-reported physical health and functioning among subjects randomized to frequent (six times per week) compared with conventional (three times per week) hemodialysis in both the Frequent Hemodialysis Network daily (n=245) and nocturnal (n=87) trials. The main outcome measures were adjusted change in scores over 12 months on the short physical performance battery (SPPB), RAND 36-item health survey physical health composite (PHC), and physical functioning subscale (PF) based on the intention to treat principle., Results: Overall scores for SPPB, PHC, and PF were poor relative to population norms and in line with other studies in ESRD. In the Daily Trial, subjects randomized to frequent compared with conventional in-center hemodialysis experienced no significant change in SPPB (adjusted mean change of -0.20±0.19 versus -0.41±0.21, P=0.45) but experienced significant improvement in PHC (3.4±0.8 versus 0.4±0.8, P=0.009) and a relatively large change in PF that did not reach statistical significance. In the Nocturnal Trial, there were no significant differences among subjects randomized to frequent compared with conventional hemodialysis in SPPB (adjusted mean change of -0.92±0.44 versus -0.41±0.43, P=0.41), PHC (2.7±1.4 versus 2.1±1.5, P=0.75), or PF (-3.1±3.5 versus 1.1±3.6, P=0.40)., Conclusions: Frequent in-center hemodialysis compared with conventional in-center hemodialysis improved self-reported physical health and functioning but had no significant effect on objective physical performance. There were no significant effects of frequent nocturnal hemodialysis on the same physical metrics.

There are few studies evaluating exercise in the nondialysis chronic kidney disease (CKD) population. This review covers the rationale for exercise in patients with CKD not requiring dialysis and the effects of exercise training on physical functioning, progression of kidney disease, and cardiovascular risk factors. In addition, we address the issue of the risk of exercise and make recommendations for implementation of exercise in this population. Evidence from uncontrolled studies and small randomized controlled trials shows that exercise training results in improved physical performance and functioning in patients with CKD. In addition, although there are no studies examining cardiovascular outcomes, several studies suggest that cardiovascular risk factors such as hypertension, inflammation, and oxidative stress may be improved with exercise training in this population. Although the current literature does not allow for definitive conclusions about whether exercise training slows the progression of kidney disease, no study has reported worsening of kidney function as a result of exercise training. In the absence of guidelines specific to the CKD population, recent guidelines developed for older individuals and patients with chronic disease should be applied to the CKD population. In sum, exercise appears to be safe in this patient population if begun at moderate intensity and increased gradually. The evidence suggests that the risk of remaining inactive is higher. Patients should be advised to increase their physical activity when possible and be referred to physical therapy or cardiac rehabilitation programs when appropriate., (Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Patients served by ESRD Network 11 were surveyed on participation in regular physical activity (physical activity). National recommendations (3 days/week, 30 minutes/session, and intensity of "moderate level") were used to categorize respondents into three physical activity categories: no physical activity, some physical activity, and recommended levels of physical activity. Analysis of 1323 returned questionnaires indicated that 57% of respondents reported participation in regular physical activity; however, only 13.2% achieved recommended levels based on frequency, duration, and intensity. The primary reasons for no physical activity were '"too tired" and "not motivated." The most frequently cited benefits in those who reported regular physical activity were "increased energy," "increased muscle strength," and "enhanced ability to do things needed in life." Fifty-seven percent reported they had "been talked to about exercise;" only 34% received any written information on initiating physical activity. Greater effort to incorporate education and motivation into the routine care is warranted to increase physical activity to levels that may result in health benefits.

Background: Exercise capacity as measured by peak oxygen uptake (Vo₂(peak)) is low in hemodialysis patients. The present study assesses determinants of VO₂(peak) in patients with chronic kidney failure who either changed kidney replacement modality to frequent hemodialysis therapy or received a kidney transplant., Study Design: Cohort study with assessment at baseline and 6 months after modality change., Setting & Participants: Participants included nondiabetic individuals receiving conventional hemodialysis who: (1) remained on conventional hemodialysis therapy (n = 13), (2) changed to short daily hemodialysis therapy (n = 10), or (3) received a transplant (n = 5) and (4) individuals who underwent a pre-emptive transplant (n = 15). Additionally, 34 healthy controls were assessed at baseline only., Predictor: Modality change., Measurement & Outcomes: Exercise capacity, assessed using the physiologic components of the Fick equation (Vo₂ = cardiac output × a-vo₂(dif), where a-vo₂(dif) is arterial to venous oxygen difference) was determined using measurement of Vo₂(peak) and cardiac output during symptom-limited exercise testing. Analysis of covariance was used to compare differences in changes in Vo₂(peak), cardiac output, heart rate, stroke volume, and a-vo₂(dif) at peak exercise between participants who remained on hemodialysis therapy and those who underwent transplant., Results: Transplant was the only modality change associated with a significant change in Vo₂(peak), occurring as a result of increased peak cardiac output and reflecting increased heart rate without a change in peak a-vo₂(dif) despite increased hemoglobin levels. There were no differences in participants who changed to daily hemodialysis therapy compared with those who remained on conventional hemodialysis therapy., Limitations: Small nonrandomized study., Conclusions: Vo₂(peak) increases significantly after kidney transplant, but not with daily hemodialysis; this improvement reflects increased peak cardiac output through increased peak heart rate. Despite statistical significance, the increase in Vo₂(peak) was not clinically significant, suggesting the need for interventions such as exercise training to increase Vo₂(peak) in all patients regardless of treatment modality., (Copyright © 2010 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Background: Self-reported physical health and functioning and direct measures of physical performance are decreased in hemodialysis patients and are associated with mortality and hospitalization., Study Design: We determined baseline cross-sectional associations of physical performance, health, and functioning with demographics, clinical characteristics, nutritional indexes, laboratory benchmarks, and measures of body composition in participants in the Frequent Hemodialysis Network (FHN) trial., Setting & Participants: 375 persons enrolled in the FHN with data for physical performance, health, and functioning., Predictors: Explanatory variables were categorized into fixed factors of age, race, comorbid conditions (diabetes mellitus, heart failure, and peripheral arterial disease) and potentially modifiable factors of dialysis dose, phosphorus level, hemoglobin level, equilibrated normalized protein catabolic rate (enPCR), body composition, body mass index, phase angle, and ratio of intracellular water volume to body weight (calculated from bioelectrical impedance)., Outcomes: Scores on tests of physical performance, health, and functioning., Measurements: Physical performance measured using the Short Physical Performance Battery, self-reported physical health and functioning using the 36-Item Short Form Health Survey (SF-36). Body composition (body mass index and bioimpedance analysis) and laboratory data were obtained from affiliated dialysis providers., Results: Relative to population norms, scores for all 3 physicality metrics were low. Poorer scores on all 3 metrics were associated with diabetes mellitus and peripheral arterial disease. Poorer scores on the SF-36 Physical Functioning subscale and Short Physical Performance Battery also were associated with age, lower ratio of intracellular water volume to body weight, and lower enPCR. Black race was associated with poorer scores on the Short Physical Performance Battery., Limitations: This was a cross-sectional study of individuals agreeing to participate in the FHN study and may not be generalizable to the general dialysis population., Conclusions: Hemodialysis patients show markedly impaired physical performance, health, and functioning relative to population norms. Although some factors associated with these impairments are not modifiable, others may change with improvement in nutritional status or body composition., (Published by Elsevier Inc.)

Reference isolates of Mycobacterium neoaurum, Mycobacterium aurum, and the nonvalidated species "Mycobacterium lacticola" were the focus of two recent molecular taxonomic studies. On the basis of this grouping, we identified 46 clinical pigmented, rapidly growing mycobacterial isolates. By 16S rRNA gene sequencing, only two major taxa were identified: M. neoaurum and a previously uncharacterized "M. neoaurum-like" group. The M. neoaurum-like group exhibited only 99.7% identity to M. neoaurum by 16S rRNA gene sequencing and 96.5% identity to M. neoaurum by rpoB sequencing and was named M. bacteremicum. No clinical isolates of M. aurum or M. lacticola were identified. Of isolates with known sources, 4/8 (50%) of M. bacteremicum isolates and 22/34 (65%) of M. neoaurum isolates were recovered from blood, and 35% of these were known to be from patients with catheter-related sepsis. MIC and clinical data on these 46 isolates of M. neoaurum and M. bacteremicum along with a review of 16 previously reported cases of infection with the M. neoaurum-M. lacticola group demonstrated that the isolates were highly susceptible to all drugs tested except clarithromycin, and most clinical cases were successfully treated. The clarithromycin resistance suggested the presence of an inducible erm gene reported in other species of rapidly growing mycobacteria. Sequencing studies are currently required to identify these two species. Strain ATCC 25791 (originally submitted as an example of Mycobacterium aurum) is proposed to be the type strain of M. bacteremicum.

There are many ways to measure physical functioning. Oxygen uptake at peak exercise is considered to be the most objective or 'gold-standard' measure and is determined by the integrated functioning of multiple physiological systems. Renal failure can affect the functioning of several of these systems which results in low levels of peak oxygen uptake. This review examines the determinants of oxygen uptake as defined by the Fick Equation, and presents data from studies that have reported these physiological measures. It becomes clear that there are many factors that may limit peak oxygen uptake in these patients and any one mechanism may be difficult to identify.

Exercise capacity, physical functioning, and physical activity are all low in patients with CKD treated with dialysis. Although there is robust evidence that these patients benefit from regular exercise training and/or increasing physical activity, the nephrology community has not adopted recommendations and encouragement for physical activity as a part of the routine care plan. This article reviews what is known regarding the implementation of exercise and provides suggestions as to how exercise counseling might become a routine part of the care of patients with CKD.

We compared motor unit synchronization and firing rate variability within and across synergistic hand muscles during a pinching task following short-term light-load training to improve force steadiness in older adults. A total of 183 motor unit pairs before training and 158 motor unit pairs after training were recorded with intramuscular fine-wire electrodes within and across the first dorsal interosseous (FDI) and adductor pollicis (AdP) muscles during a pinch task performed by ten older adults before and after a 4-week short-term light-load training program. Nine younger adults performed the same experimental sessions 4 weeks apart with no training intervention. Two-minute sustained contractions of 2, 4, 8, and 12% maximal voluntary contraction (MVC) were performed with the non-dominant hand. The coefficient of variation (CV) of force was greater in older than in younger adults and was lower at the 2 and 4% MVC levels in both the finger (0.12 +/- 0.01 vs. 0.08 +/- 0.01, and 0.08 +/- 0.01 vs. 0.05 +/- 0.01, respectively) and thumb (0.11 +/- 0.01 vs. 0.08 +/- 0.01, and 0.09 +/- 0.01 vs. 0.05 +/- 0.01, respectively) compared to higher force levels following training in the older adults. There were no changes in CIS or k'-1 values following training. Motor unit firing rate variability significantly decreased at low force levels in the FDI muscle and also tended to decrease with training in the AdP muscle (p = 0.06). No changes occurred in the younger control group. These findings are the first to show that motor unit synchronization does not change during light-load training. Thus, it is likely that force steadiness in older adults improves by reducing motor unit firing variability rather than by changing motor unit synchronization.

Background: Patients with chronic kidney disease (CKD) treated with dialysis have reduced levels of physical functioning. Little is known of the physical functioning in patients prior to initiation of renal replacement therapy (RRT). The purpose of the study was 2-fold: (i) to document physical functioning of patients with CKD not requiring RRT, using objective laboratory tests, physical performance measures and self-reported functioning; and (ii) to determine the correlations between these measures of physical functioning and renal function., Methods: Thirty-two patients with CKD (mean estimated glomerular filtration rate [eGFR] 29.9 +/- 17.0) were recruited for the study. Subjects completed symptom-limited treadmill test (peak oxygen uptake [VO2peak]), physical performance measures (gait speed, sit-to-stand and 6-minute walk) and the SF-36 Health Status Questionnaire (physical functioning scale [PF] and physical composite scale [PCS]). Descriptive and correlational analyses were performed on the data., Results: VO2peak (O2 17.8 +/- 6.7 ml/kg body weight per minute), physical performance measures and self-reported functioning were reduced compared with sedentary age-predicted norms. Significant correlations were found between VO2peak and all other physical functioning measures; however, only maximal gait speed and PCS correlated significantly with eGFR., Conclusions: Patients with CKD have reduced physical functioning as measured using objective laboratory tests (VO2peak), physical performance measures and self-reported functioning. Given that low physical functioning predicts outcomes in dialysis patients, interventions to maintain or improve physical functioning are warranted prior to initiation of dialysis.

Regular exercise training may be important for many patients with chronic disease, but research is needed to justify incorporation of exercise into their routine care. Education of health care providers on the importance of exercise is also needed to effectively pursue research and for exercise to be incorporated as a part of the health care plan.

Studies of exercise capacity in children with chronic kidney disease (CKD) are limited. We tested 25 pediatric kidney transplant (TX) recipients and 15 pediatric dialysis (DX) patients. Nine children in the DX group received kidney transplants and were retested 3 months following surgery (pre/post). Testing involved treadmill testing with measurement of peak oxygen uptake (VO(2peak)), muscle strength, body composition (percent fat), and "field" tests of physical fitness using the FITNESSGRAM, which included the PACER test. Values obtained were compared with gender- and age-based criterion-referenced standards [healthy fitness zone (HFZ)]. The previous day physical activity recall (PDPAR) was used to assess physical activity participation. There were no differences between TX and DX subjects for VO(2peak) and muscle strength measurements, and all values were below the normative values. The TX group achieved significantly higher PACER scores, but only one TX and no DX subjects achieved the HFZ for the PACER test. No improvement in any measures were observed from pre- to post-TX in the nine subjects tested, except for a significant increase in percent fat, which negatively affected the change in muscle strength and VO(2peak). All subjects were physically inactive, with less than 10% of nonschool time being physical activity participation. Pediatric patients with CKD had low exercise capacity, were physically inactive, and gained significant fat weight following TX. Counseling and encouragement for more physical activity is warranted as a part of routine medical care in these children.

We report results of a randomized clinical trial of a combined intervention of exercise and dietary counseling (ExD) after orthotopic liver transplantation (OLT). Of the 151 patients randomized into ExD or usual care (UC), 119 completed testing 2, 6 and 12 months post-OLT. Testing included assessment of exercise capacity (VO(2peak)), quadricep muscle strength, body composition (DXA), nutritional intake (Block 95) and health-related quality of life (SF-36). The intervention consisted of individualized counseling and follow-up to home-based exercise and dietary modification. Repeated measure ANOVA was performed to determine differences over time between ExD and UC with a secondary analysis to determine differences over time between adherers (Adh), nonadherers (Nadh) to the intervention and UC. The ExD group showed greater increases in VO(2peak) (p = 0.036), and self-reported general health (p = 0.038) compared to UC. Both groups demonstrated increases in muscle strength, body weight, body fat and other SF-36 scale scores. Adherence to the intervention was 37% with positive trends in VO(2peak) and body composition observed in Adh compared to Nadh and UC. These data suggest improvements in exercise capacity and body composition are achieved with nutrition and exercise behavior modifications initiated early after OLT and with regular follow-up.

Patient physical functioning level is an indicator of medical fitness that may predict outcomes after kidney transplantation. A small study of patients at a single center found a correlation between patient-rated physical functioning pretransplantation and the number of emergency hospital visits posttransplantation. In a national multicenter cohort, the association of incident dialysis patients' physical functioning scores with their risk for posttransplantation all-cause hospitalization/death was investigated using Cox proportional hazards analysis. The study cohort included patients who participated in the Dialysis Morbidity and Mortality Study (DMMS) Wave 2 and received a first transplant no more than 24 mo after treatment start. Updated patient information was available in the 2004 United States Renal Data System Standard Analysis Files. Higher pretransplantation physical functioning score was found to be a significant predictor of transplant recipients' reduced risk for hospitalization/death. Patients in the Cox model who were aged 55+ had increased risk for hospitalization/death. Gender, race, diabetic ESRD, and cardiovascular comorbidity were NS predictors. A potential explanation for the ability of the Medical Outcomes Study Short-Form 36 physical functioning measure to predict risk for posttransplantation morbidity/mortality is that physical activity/exercise behavior is likely to be closely associated with an individual's physical functioning level, and pretransplantation activity levels may be indicative of lifestyle habits that continue to influence patient behavior posttransplantation. More research investigating patients' pre- and posttransplantation physical functioning levels in relation to transplant outcomes would be valuable.

Physical functioning in patients with end-stage renal disease treated with dialysis is low, whether measured using objective laboratory measures, physical performance testing, or self-reported measures. Peak oxygen uptake (VO2peak), self-reported functioning measures, and physical activity levels are independent predictors of mortality in these patients. Cardiovascular exercise training studies result in improvements in VO2peak, physical performance tests, and self-reported functioning. Resistance exercise training improves muscle strength. Exercise training may have positive benefits on other factors that are important clinical issues in dialysis patients, including cardiovascular risk profile, oxidative stress, and inflammation. Endothelial function, a surrogate marker of atherosclerosis, has been shown to improve with exercise training in dialysis patients. Although there have been numerous recent studies on benefits of exercise, few dialysis clinics or nephrologists provide encouragement or programs as a part of their routine care of their patients. There are many national guidelines that include exercise or increasing physical activity as a part of the treatment of many conditions that are relevant in dialysis patients, including hypertension, hyperlipidemia, and high cardiovascular disease risk. The nephrology community continues to state concern for outcomes; however, a simple, low-tech intervention that has many benefits to their patients (i.e., encouragement, recommendations, and opportunity for increasing physical activity) has not been adopted as part of the standard care. Adoption of routine counseling and encouragement for physical activity has the potential to improve outcomes, improve physical functioning, and optimize quality of life and overall health of dialysis patients.

There are many reasons for recommendation of regular physical activity for organ transplant recipients, including 1) Restoration of physical functioning following deconditioning experienced prior to transplant; 2) Most patients are physically inactivity, 3) The high prevalence of cardiovascular risk factors that may be modified by regular physical activity; 4) Physical activity will optimize physical functioning following transplant; and 5) p; hysical activity may reduce or attenuate side effects of immunosuppression. There are many recommendations for regular physical activity as an integral part of treatment of conditions that are common to transplant recipients, including: hypertension management; hyperlipidemia; Diabetes; and elevated cardiovascular disease risk. Transplant recipients tolerate progressive exercise training well and can achieve levels of functioning similar or higher than normal individuals. In order to optimize functioning and overall health in organ transplant recipients, regular physical activity should be prescribed and encouraged as a part of the routine post transplant care.

The objective of this study was to survey patient care staff to (a) determine their perceived skills for and attitudes toward assessing physical functioning and encouraging exercise, (b) assess practice related to assessment of physical functioning and exercise encouragement, and (c) identify factors that predict encouragement of exercise in patient care staff. This was a cross-sectional, descriptive study in which questionnaires were completed by 100 patient care staff (RN, LVN, RD, SW, and patient care technicians) in five freestanding hemodialysis clinics. Frequency responses were calculated for the items of interest, and multiple regression analysis was performed to identify predictor variables of exercise encouragement practice (i.e., frequency of encouragement of exercise to patients). Four variables significantly predicted exercise encouragement activity: job position requiring professional training, the perception that patients lacked motivation to exercise, the perception that the staff member did not have skills to motivate patients to exercise, and the perception that it was not a part of the job responsibility.

Background: Limitations in exercise capacity in kidney transplant recipients are thought to result in part from changes in muscle structure and function associated with immunosuppression therapy., Methods: We compared the percent distribution of skeletal muscle fiber types, cross-sectional areas, and ultrastructural morphologies in kidney transplant recipients treated with standard prednisone maintenance therapy (n=21) to those undergoing rapid withdrawal of prednisone using Simulect (interleukin 2 receptor inhibitor) (n=13). Skeletal muscle biopsy specimens from the vastus lateralis were analyzed at 3 and 12 months after transplantation and compared with sedentary controls (n=15)., Results: Compared with the control group, the group receiving prednisone maintenance therapy had a significantly lower percentage of type I fibers and a higher percentage of type IIB/x fibers, evident at 3 and 12 months. Fiber type distribution in patients withdrawn from prednisone did not differ from controls. In patients withdrawn from prednisone, the cross-sectional areas of type I and IIA fibers were lower and the area of type IIB/x fibers was higher compared with controls. Likewise, ultrastructural studies revealed reduced volume densities of myofibrils and higher densities of interfibrillar and subsarcolemmal mitochondria. At 12 months there were no ultrastructural differences between the patients withdrawn from prednisone and controls., Conclusions: We conclude that prednisone maintenance therapy contributes to the lower exercise capacity by altering the ratio of type I to type IIB/x fibers and by reducing myofilament density. The increase in mitochondria in patients receiving prednisone may reflect a switch from carbohydrate to lipid metabolism resulting from the glucocorticoid therapy.

Exercise capacity and muscle function are known to be abnormal in patients with renal disease. We present a case study in which we studied a kidney transplant recipient who received a kidney from his identical twin. Testing included maximal exercise testing with measurement of oxygen uptake (VO2max), isokinetic muscle function testing, body composition analysis using dual energy X-ray absorptiometry (DEXA) imaging and quality of life using The Medical Outcomes Short Form (SF-36) questionnaire. Muscle biopsies were also analysed for fibre composition and size and ultrastructure. We found that the twin recipient had lower values for VO2max, muscle strength, muscle mass and quality of life scales (physical domains) compared with the twin donor. Muscle fibre composition was identical in the twins, however, muscle fibres size was reduced in the twin donor in Type I, and Type IIA fibre types. The twin recipient also showed lower fibre density (volume percentage) and greater intrafibrillar space than the donor. The twins were both sedentary, thus we conclude that the low exercise capacity and abnormalities observed in the recipient are characteristics of renal failure, and not the result of physical deconditioning, nor was it related to prednisone therapy, which may negatively affect muscle function.

Patients with chronic disease typically become severely deconditioned, which often leads to physical disability. Every effort should be made to recommend and encourage patients to adopt and maintain a program of physical activity. Although there are no specific exercise guidelines for many chronic conditions, patients should be instructed to start a routine of physical activity that is gradual for most (if not all) days of the week, working up to 30 minutes per session at an exertion level that is easily tolerated. It is critical that assessment of physical functioning and recommendations for physical activity be included as a part of routine medical care. In doing so, we change the expectations of patients and family members, and work toward optimizing physical functioning and quality of life.

End-stage liver disease (ESLD) affects thousands of people in the United States annually. Improvements in survival after liver transplantation have broadened the indications for its use as a proven therapy for ESLD, rapidly increasing the number of transplant candidates. However, the number of patients awaiting transplantation far surpasses the donor supply, resulting in lengthy waiting times. During this wait, these patients experience progressive disease-related decompensation that is often accompanied by malnutrition and reduced physical activity. This chronic disease triad can have profound effects on musculoskeletal complications, such as cachexia and osteoporosis. In the absence of proper interventional strategies before transplantation, these complications can intensify after the transplantation, as a result of continued poor nutrition intake, bed rest, and pharmacotherapies. This article discusses levels of physical functioning and nutrition status in both the pre-and post-transplant populations, the risks associated with current levels, and the roles that diet and activity therapies can have to improve outcomes.

The limitation to exercise capacity in hemodialysis patients has been attributed to anemia. We report the effects of normalization of hematocrit levels by using r-hu-recombinant erythropoietin and exercise training on exercise capacity and self-reported physical functioning in hemodialysis patients. Sixty-five patients were randomized into 1 of 4 groups: usual hematocrit (30%-33%) with no exercise training (UH); usual hematocrit (30%-33%) plus exercise training (UHX); normalized hematocrit (40%-42%) with no exercise training (NH); and normalized hematocrit (40%-42%) plus exercise training (NHX). Treadmill exercise testing was conducted at baseline and at 5 months after the initiation of the interventions. Analysis was performed on the data collapsed for 48 patients who met the criteria for hematocrit and exercise adherence and completed both baseline and post intervention (5.6 +/- 1.6 months) testing. Significant effects of exercise were found in peak oxygen uptake measurements (P = 0.03) and in self-reported physical functioning as measured by the Short Form-36 questionnaire (P = 0.01). There was a significant effect of hematocrit on the General Health scale on the SF-36 (P = 0.03). The changes in peak oxygen uptake with exercise training were small and levels remained lower than age-predicted values at the end of the study. These results indicate that there are other physiologic limitations to exercise capacity that are not overcome by exercise training or normalization of hematocrit. The effects of exercise training on self-reported physical functioning may be of clinical importance because these scores have been shown to be highly predictive of outcomes such as hospitalizations and mortality in hemodialysis patients., (Copyright 2002 by the National Kidney Foundation, Inc.)

Background: Physical performance measures, particularly gait speed, have been useful as predictors of loss of independence, institutionalization, and mortality in older nonuremic individuals. Gait speed has not been evaluated as a predictor of these important outcomes in patients on hemodialysis, nor have the determinants of gait speed in the dialysis population been studied., Methods: We performed a cross-sectional analysis to determine whether demographic, clinical, or nutritional status variables were related to physical performance in a group of 46 hemodialysis patients treated at three University of California San Francisco-affiliated dialysis units. Three physical performance measures were examined, including gait speed, time to climb stairs, and time to rise from a chair five times in succession. Forward stepwise linear-regression analysis was performed with each physical performance measure as the dependent variable and the following candidate predictor variables: age, gender, body mass index, dialysis vintage, Kt/V, albumin, blood urea nitrogen, creatinine, hematocrit, lean body mass, phase angle, ferritin, and the following comorbidities: hypertension, diabetes mellitus, coronary artery disease, peripheral vascular disease, and cerebrovascular disease., Results: Subjects included 31 men and 15 women aged 22 to 87 years (mean +/- SD, 52 +/- 17). The mean gait speed for the group was 113.1 +/- 34.5 cm/s (low compared with norms established for persons of similar age). Results of multivariable regression showed that age, albumin, and Kt/V were important determinants of gait speed in this population. Overall, the model explained 52% of the variability in gait speed (r = 0.72, P < 0.0001). Qualitatively similar results were obtained using stair-climbing time or chair-rising time as the dependent variables, except that comorbidity was more important than age for stair climbing. The addition of physical activity level to the models did not eliminate the associations of albumin or Kt/V with physical performance., Conclusions: Physical performance is significantly impaired in ambulatory hemodialysis patients and is related to age, serum albumin, and dialysis dose. Prospective studies are needed to determine whether modification of dialysis dose or nutritional interventions can improve physical performance in patients on hemodialysis.

The US Surgeon General's Report on Physical Activity and Health recommends that people of all ages engage in regular physical activity, and that significant health benefits can be obtained through a moderate amount of physical activity. Physical activity appears to improve health-related quality of life (HRQOL) by enhancing physical functioning in persons compromised by poor health. The Medical Outcomes Study Short Form-36 (SF-36) Health Status Questionnaire was sent to all patients who were 5 years or more post-liver transplantation at the University of California at San Francisco. Additional questions related to coexisting medical conditions and participation in regular physical activity were included. SF-36 scale scores were compared between active and inactive patients. Regression analysis was also performed to determine the contributions of coexisting medical conditions and physical activity to the physical scales of the SF-36 questionnaire. Patients who participated in regular physical activity had significantly higher scores on all physical scales and the physical component scale (PCS). The regression model, which included age, sex, time posttransplantation, retransplantation, recurrence of hepatitis C, number of comorbid conditions, and physical activity participation showed that both the number of comorbid conditions and participation in physical activity were significant independent contributors to the physical functioning scale and PCS. This study indicates that physical activity is related to HRQOL after liver transplantation independent of other coexisting medical conditions.

Background: Patients on dialysis are less physically active than sedentary persons with normal kidney function. To assess the consequences of inactivity and the results of efforts to increase activity in the end-stage renal disease (ESRD) population, valid instruments to measure physical activity and physical functioning in this group are needed., Methods: We performed a cross-sectional study to establish the validity in ESRD of several questionnaires designed to measure physical activity or physical functioning in the general population. Questionnaires studied included the Stanford 7-day Physical Activity Recall questionnaire (PAR), the Physical Activity Scale for the Elderly (PASE), the Human Activity Profile (HAP), and the Medical Outcomes Study Short Form 36-item questionnaire (SF-36). Physical activity was measured using three-dimensional activity monitors (accelerometers) over a seven-day period (the "gold standard"). Patients also underwent physical performance tests, including measurement of gait speed, stair climbing time, and chair rising time. Study questionnaires were administered, and questionnaire results were compared with each other and with activity monitor and physical performance test results., Results: Thirty-nine maintenance hemodialysis patients participated in the study. Dialysis patients scored worse than previously published healthy norms on all tests. All questionnaires correlated with seven-day accelerometry and with at least one measure of physical performance. The HAP correlated best with accelerometry (r = 0.78, P < 0.0001). Seventy-five percent of the variability in physical activity measured by accelerometry could be explained by a model that combined information from the HAP and the PASE. The HAP and the physical functioning scale of the SF-36 were about equally well correlated with physical performance measures., Conclusions: These questionnaires are valid in patients on hemodialysis and should be used to study the physical activity and rehabilitation efforts in this population further.