Progressive Exercise for Anabolism in Kidney Disease (PEAK): A Randomized, Controlled Trial of Resistance Training during Hemodialysis

Wasting in chronic kidney disease

Wasting/cachexia is prevalent among patients with chronic kidney disease (CKD). It is to be distinguished from malnutrition, which is defined as the consequence of insufficient food intake or an improper diet. Malnutrition is characterized by hunger, which is an adaptive response, whereas anorexia is prevalent in patients with wasting/cachexia. Energy expenditure decreases as a protective mechanism in malnutrition whereas it remains inappropriately high in cachexia/wasting. In malnutrition, fat mass is preferentially lost and lean body mass and muscle mass is preserved. In cachexia/wasting, muscle is wasted and fat is relatively underutilized. Restoring adequate food intake or altering the composition of the diet reverses malnutrition. Nutrition supplementation does not totally reverse cachexia/wasting. The diagnostic criteria of cachexia/protein-energy wasting in CKD are considered. The association of wasting surrogates, such as serum albumin and prealbumin, with mortality is strong making them robust outcome predictors. At the patient level, longevity has consistently been observed in patients with CKD who have more muscle and/or fat, who report better appetite and who eat more. Although inadequate nutritional intake may contribute to wasting or cachexia, recent evidence indicates that other factors, including systemic inflammation, perturbations of appetite-controlling hormones from reduced renal clearance, aberrant neuropeptide signaling, insulin and insulin-like growth factor resistance, and metabolic acidosis, may be important in the pathogenesis of CKD-associated wasting. A number of novel therapeutic approaches, such as ghrelin agonists and melanocortin receptor antagonists are currently at the experimental level and await confirmation by randomized controlled clinical trials in patients with CKD-associated cachexia/wasting syndrome.

Association of self-reported physical activity with laboratory markers of nutrition and inflammation: the Comprehensive Dialysis Study

OBJECTIVE

Patients on dialysis maintain extremely low levels of physical activity. Prior studies have demonstrated a direct correlation between nutrition and physical activity but provide conflicting data on the link between inflammation and physical activity. Using a cohort of patients new to dialysis from the Comprehensive Dialysis Study (CDS), we examined associations of self-reported physical activity with laboratory markers of nutrition and inflammation.

DESIGN, SETTING, AND PATIENTS

Between June 2005 and June 2007, CDS collected data on self-reported physical activity, nutrition, and health-related quality of life from patients starting dialysis in 296 facilities located throughout the United States. Baseline serum samples were collected from participants in a nutrition sub-study of CDS.

MEASURES

Serum albumin and prealbumin were measured as markers of nutrition, and C-reactive protein (CRP) and α-1-acid glycoprotein as markers of inflammation. Self-reported physical activity was characterized by the maximum activity score (MAS) and adjusted activity score (AAS) of the Human Activity Profile.

RESULTS

The mean age of participants in the analytic cohort (n = 201) was 61 years. The MAS and AAS were below the 10th and first percentile, respectively, in comparison with healthy 60 year-old norms. Both activity scores were directly correlated with albumin (r(2) = 0.3, P < .0001) and prealbumin (r(2) = 0.3, P < .0001), and inversely correlated with CRP (AAS: r(2) = -0.2, P = .01; MAS: r(2) = -0.1, P = .08). In multivariate analyses adjusting for age, gender, race/ethnicity, diabetes status, and center, both activity scores were directly correlated with prealbumin and inversely correlated with CRP.

CONCLUSIONS

Patients new to dialysis with laboratory-based evidence of malnutrition and/or inflammation are likely to report lower levels of physical activity.

Changes in quality of life over time--Dutch haemodialysis patients and general population compared

BACKGROUND

Improving the health-related quality of life (HRQOL) for haemodialysis patients is a considerable challenge. The aim of the present study was to compare changes in HRQOL in haemodialysis patients with those observed in the general population over a 10-year period and explore factors that might explain possible differences.

METHODS

We compared 126 haemodialysis patients assessed in 1995 in the Netherlands Cooperative Study on the Adequacy of Dialysis-1 (NECOSAD-I) with 515 patients enrolled in 2006 in the ongoing Convective Transport Study (CONTRAST). Changes in HRQOL in these cohorts were compared with two representative samples from the general Dutch population, assessed in 1992 (n = 1,063) and 2001 (n = 10,600). HRQOL was measured with the SF-36 questionnaire. Differences in HRQOL were analysed with ANCOVA to adjust for demographic variables. To assess possible differences, we used multivariable regression analysis.

RESULTS

HRQOL in haemodialysis patients in 2006 [CONTRAST, mean age 63 ± 14 years (SD), 62% male] was significantly better than in 1995 (NECOSAD-I, 59 ± 16 years, 53% male) in four domains of the SF-36: bodily pain (+ 5 points, P = 0.009), vitality (+ 7, P < 0.001), role-emotional (+ 14, P < 0.001) and mental health (+ 8, P < 0.001), after adjusting for demographic variables. This increment could partly be explained by improved haemoglobin and phosphate levels. Compared to the general population, HRQOL improvement was most outspoken in two domains: bodily pain (+ 6, P = 0.01) and role-emotional (+ 8, P = 0.007).

CONCLUSIONS

This study showed an improvement of HRQOL in haemodialysis patients over an 11-year period of time, independent of global changes in the general population.

Investigation of skeletal muscle quantity and quality in end-stage renal disease

AIM

A more precise understanding of the aetiology and sequelae of muscle wasting in end-stage renal disease (ESRD) is required for the development of effective interventions to target this pathology.

METHODS

We investigated 49 patients with ESRD (62.6 +/- 14.2 years, 0.3-16.7 years on haemodialysis). Thigh muscle cross-sectional area (CSA), intramuscular lipid and intermuscular adipose tissue (IMAT) were measured via computed tomography as indices of muscle quantity (i.e. CSA) and quality (i.e. intramuscular lipid and IMAT). Additional health and clinical measures were investigated to determine associations with these variables.

RESULTS

Age, energy intake, disease burden, pro-inflammatory cytokines, nutritional status, strength and functioning were related to muscle quantity and quality. Potential aetiological factors entered into forward stepwise regression models indicated that hypoalbuminaemia and lower body mass index accounted significantly and independently for 32% of the variance in muscle CSA (r = 0.56, P < 0.001), while older age and interleukin-8 accounted for 41% of the variance in intramuscular lipid (r = 0.64, P < 0.001) and body mass index accounted for 45% of the variance in IMAT (r = 0.67, P < 0.001). Stepwise regression models revealed that intramuscular lipid was independently predictive of habitual gait velocity and 6 min walk distance, while CSA was independently predictive of maximal isometric strength (P < 0.05).

CONCLUSION

Ageing, poor nutritional status and elevated interleukin-8 are factors potentially contributing to the loss of muscle quality and quantity in ESRD. These deficits can predict functional impairments, with intramuscular lipid accumulation most closely related to decline of submaximal musculoskeletal performance (walking), and low muscle CSA most closely related to decline of maximal performance (peak isometric strength).

Effects of aerobic exercise and resistance training on lipid profiles and inflammation status in patients on maintenance hemodialysis

Physical function limitation is a common disorder in chronic hemodialysis (HD) patients, relating to increased morbidity and mortality. The aim of this study was to determine the effects of aerobic and resistance trainings on blood lipids and inflammation status in HD patients. Out of 30 volunteer males who had been undergoing conventional maintenance HD within an HD unit in Tehran, 21 subjects were enrolled. They were randomly assigned into aerobic exercise group - resistance training group undergoing an 8-week intradialytic exercise program (three times/week) and control group (n = 7, each). Training program consisted of 10-30 min stationary cycling at an intensity of 12-16 out of 20 at the rate of perceived exertion (RPE) of Borg scale in aerobic group and using ankle weights for knee extension, hip abduction and flexions at an intensity of 15-17 out of 20 at the RPE of Borg scale in resistance group. Fasting blood samples for serum biochemistry were drawn at baseline and 8 weeks. The age, HD duration, and physical activity score were 51.6±18.9yrs; 25.1±13.9 mo, and 19.2±7.6, respectively. Diabetes mellitus (43%), hypertension (28%), and obstructive uropathy (14%) were the most common underlying diseases. Aerobic and resistance exercises were correlated with serum creatinine (P< 0.0001 and P<0.001) and hs-CRP levels (P=0.005 and P=0.036) reduction so that aerobic exercise induced more reduction. These exercises had no influence on weight, Kt/V values, serum urea, albumin, hemoglobin, and lipid levels (P>0.05). Both intradialytic aerobic and resistance exercises showed beneficial effects on inflammation status without any influences on serum lipid levels probably due to short duration of the study which was not accompanied with body weight changes. Solute removal had no change during exercise programs. There is a need for more investigation on the role of exercise in HD patients.

Sustaining a hemodialysis exercise program: a review

This article reviews the literature addressing exercise programs for dialysis patients to identify elements necessary for sustaining exercise programs in this population. Literature searches for publications (January 1980-February 2009) in Medline (OVID), PubMed, CINAHL (EBSCO), EBSCOhost EJS, ProQuest Central, Web of Science, Cochrane Library, Google Scholar, ScienceDirect, SpringerLink (Kluwer), and Wiley Interscience (Blackwell) were performed. Reference lists from relevant articles were hand-searched for further publications. Criteria for inclusion included full-text primary research and review articles focused on exercise for adult hemodialysis patients. One hundred and seventy one publications were found with a primary focus on exercise in hemodialysis. Of these, 28 primary research and 14 review articles addressed one or more aspects of sustainability of hemodialysis exercise programs. Factors contributing to sustainable exercise programs included: dedicated exercise professionals; encouragement to exercise intradialytically; dialysis and medical staff commitment; adequate physical requirements of equipment and space; interesting and stimulating; cost implications need to be addressed; exercise is not for everyone; requires individual prescription; and there is no age barrier to exercise on hemodialysis.

The effect of resistance exercise to augment long-term benefits of intradialytic oral nutritional supplementation in chronic hemodialysis patients

BACKGROUND

Resistance exercise combined with intradialytic oral nutrition (IDON) supplementation improves net protein balance in the acute setting in chronic hemodialysis patients. We hypothesized that combination of long-term resistance exercise and IDON would improve markers of muscle mass and strength further compared with IDON alone.

METHODS

Thirty-two participants (21 male; mean age, 43 ± 13 years) on chronic hemodialysis were randomly assigned to IDON plus resistance exercise (NS + EX), or IDON (NS) alone for 6 months. IDON consisted of a lactose-free formula consisting of protein, carbohydrate, and fat. Three sets of 12 repetitions of leg-press were completed before each dialysis session in the NS + EX arm. Primary outcome measurement was lean body mass. Muscle strength and other nutritional parameters were measured as secondary outcomes.

RESULTS

Of 32 participants, 22 completed the 6-month intervention. There were no statistically significant differences between the study interventions with respect to changes in lean body mass and body weight, when comparing NS + EX to NS. There were also no statistically significant differences in any of the secondary outcomes measured in the study. Body weight (80.3 ± 16.6 kg, 81.1 ± 17.5 kg, and 80.9 ± 18.2 kg at baseline, month 3, and month 6, respectively; P = .02) and 1-repetition maximum (468 ± 148 lb, 535 ± 144 lb, and 552 ± 142 lb, respectively; P = .001) increased statistically significantly during the study for all patients combined.

CONCLUSION

This study did not show further benefits of additional resistance exercise on long-term somatic protein accretion above and beyond nutritional supplementation alone. When both treatments groups were combined, body weight and muscle strength improved during the study.

Effect of intra-dialytic, low-intensity strength training on functional capacity in adult haemodialysis patients: a randomized pilot trial

BACKGROUND

Kidney failure is associated with muscle wasting and physical impairment. Moderate- to high-intensity strength training improves physical performance, nutritional status and quality of life in people with chronic kidney disease and in dialysis patients. However, the effect of low-intensity strength training has not been well documented, thus representing the objective of this pilot study.

METHODS

Fifty participants (mean +/- SD, age 69 +/- 13 years) receiving long-term haemodialysis (3.7 +/- 4.2 years) were randomized to intra-dialytic low-intensity strength training or stretching (attention-control) exercises twice weekly for a total of 48 exercise sessions. The primary study outcome was physical performance assessed by the Short Physical Performance Battery score (SPPB) after 36 sessions, if available, or carried forward from 24 sessions. Secondary outcomes included lower body strength, body composition and quality of life. Measurements were obtained at baseline and at completion of 24 (mid), 36 (post) and 48 (final) exercise sessions.

RESULTS

Baseline median (IQR) SPPB score was 6.0 (5.0), with 57% of the participants having SPPB scores below 7. Exercise adherence was 89 +/- 15%. The primary outcome could be computed in 44 participants. SPPB improved in the strength training group compared to the attention-control group [21.1% (43.1%) vs. 0.2% (38.4%), respectively, P = 0.03]. Similarly, strength training participants exhibited significant improvements from baseline compared to the control group in knee extensor strength, leisure-time physical activity and self-reported physical function and activities of daily living (ADL) disability; all P < 0.02. Adverse events were common but not related to study participation.

CONCLUSIONS

Intra-dialytic, low-intensity progressive strength training was safe and effective among maintenance dialysis patients. Further studies are needed to establish the generalizability of this strength training program in dialysis patients.

New insights into the role of anabolic interventions in dialysis patients with protein energy wasting

PURPOSE OF REVIEW

Patients on maintenance dialysis commonly develop protein-energy wasting (PEW), which is associated with poor survival. There have been several advances in anabolic interventions aimed at improving PEW in these patients in recent years.

RECENT FINDINGS

Oral or parenteral nutritional supplementation, especially if administered during dialysis, improves net protein anabolism in chronic hemodialysis patients. These beneficial effects have been extended to long-term benefits in recent clinical trials. Resistance exercise, alone or combined with intradialytic oral nutrition supplementation, also improves net protein balance in the acute setting although recent studies indicated a limited beneficial effect of long-term exercise alone on muscle protein accretion in chronic hemodialysis patients. Anabolic agents such as growth hormone and androgens have been shown to exert significant benefits on visceral protein stores, muscle mass and strength. Ghrelin, a hormone with combined orexigenic and anti-inflammatory effects, is a potential new nutritional intervention in maintenance dialysis patients.

SUMMARY

Existing anabolic therapeutic strategies have proven to be effective in improving PEW in maintenance dialysis patients. Combined anabolic interventions and several new and established anabolic hormones represent further promising nutritional interventions. Large-scale randomized controlled trials examining the effects of anabolic interventions on mortality and morbidity are still lacking.

The Role of Resistance Training in the Prevention and Treatment of Chronic Disease

Recent research suggests that resistance training (RT) in adults has the potential to prevent, treat, and possibly even reverse the impact of several chronic diseases. A properly designed progressive program can have profound effects on the musculoskeletal system, resulting in enhanced physical and mental health. In this review, the authors summarize recent research detailing the numerous benefits gained from participating in an RT program in those with or at risk for chronic disease. This includes increases in muscle mass and strength; enhanced physical function; reduced risks for osteoporosis and cardiovascular and metabolic diseases; improved management of cancer, neuromuscular disorders, HIV, and chronic obstructive pulmonary disease; and reductions in negative mood states. Given these benefits, numerous national organizations, including the committee commissioned to create the National Physical Activity Guidelines for Americans, have endorsed the participation in RT as a necessary component of maintaining health. Fortunately, the most current estimates show that a growing number of individuals are participating in RT, but these national estimates still fall below the goal of 30% set by Healthy People 2010. Future research will therefore need to focus on increasing the adoption and adherence of RT, as it carries the potential to dramatically affect public health.

Exercise performance by hemodialysis patients: a review of the literature

Hemodialysis (HD) patients exhibit poor functional capacity and reduced quality of life as a result of the complications associated with end-stage renal disease (ESRD). A review of the literature indicates that regular physical activity can reduce the complications associated with ESRD by inducing adaptations in the cardiovascular, nervous, and musculoskeletal systems. In turn, this increases functional capacity and enhances quality of life in patients on HD. Hemodialysis patients can safely participate in a variety of exercise programs with minimal adverse effects. Intradialytic exercise programs that can incorporate aerobic and resistance exercise promote exercise adherence and should be encouraged on dialysis units.

Assessment and monitoring of physical function for people with CKD

Although low and deteriorating physical function are increasingly recognized as key characteristics of CKD, assessment of physical function does not yet form part of the routine clinical monitoring of this patient group. This is somewhat surprising as measures of physical function, from across the entire functional measurement spectrum, have been shown to be related to clinically important outcomes (morbidity, quality of life and increasingly survival) in patients being treated for CKD. In order to promote a standardized approach to assessment of people with CKD, it is recommended that renal professionals adopt the physical function and measurement classification systems of the International Classification Framework of Functioning, Disability and Health. Selection of physical function assessment "tool(s)" is influenced by the intended goal of the assessment (e.g., clinical assessment, tracking of progress with physical activity, research purposes, diagnostic purposes), the personal characteristics of the patient, and also by the prevailing information quality requirements and potential operational constraints (e.g., measurement burden, patient inclusiveness/sample size, cost). As exercise tolerance, functional capacity, and functional status assessments have been shown to be safe, feasible, and clinically useful, it is recommended that their implementation be incorporated within clinical management protocols for the patient with CKD.

Exercise training and reduction of cardiovascular disease risk factors in patients with chronic kidney disease

Observational studies have reported a significant inverse association between physical function/aerobic capacity and mortality in patients with CKD. Several randomized controlled trials have provided evidence of a cardioprotective effect of exercise training via multiple mechanisms, which may result in a reduction of cardiovascular disease risk factors in patients with CKD. This review focuses on the available evidence for the role of exercise training in the reduction of cardiovascular disease risk factors as classified into antiatherosclerotic, anti-ischemic, antiarrhythmic, and antithrombotic protective effects. Preliminary evidence, primarily from studies in patients requiring hemodialysis, suggests that exercise training improves arterial compliance, cardiac autonomic control, and left ventricular systolic function while decreasing inflammation, oxidative stress, and blood pressure levels. It is concluded that these studies have provided preliminary evidence that exercise training may result in a reduction of cardiovascular disease risk factors. The available evidence supports the use of therapeutic exercise training as an adjunct component of a comprehensive treatment program for patients with CKD. However, it is clear that much additional research is required to confirm the apparent, multiple, cardioprotective effects of exercise training and to identify additional mechanisms, especially in patients with predialysis CKD.

Implementing exercise: what do we know? Where do we go?

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.

Anabolic interventions in ESRD

ESRD produces a chronic catabolic state that results in significant skeletal muscle atrophy, weakness, and physical dysfunction. Any intervention that can ameliorate this process can significantly improve quality of life. Some studies have shown that endurance exercise training, even at low intensities, may exhibit anabolic effects and improved physical function. However, resistance exercise training is of primary interest as an anabolic intervention because it is the mode of exercise that is most efficacious in stimulating anabolic responses, improved muscle performance, and physical function. A relatively small number of controlled trials of resistance training in ESRD patients have failed to show significant changes in LBM, although some studies have shown significant improvements in other markers of anabolism. Increases in muscle strength with resistance training are typical but improved physical function, either by objective measurement or self-report, are equivocal. Study durations, loads used during training, and relatively small sample sizes may in part explain the inability of previous studies to observe more substantial changes in LBM and physical function. Androgens and growth hormone have been shown to significantly improve LBM and strength, although longer-term studies for safety and efficacy are necessary before their general recommendation for patients with ESRD.

Soluble CD14 levels, interleukin 6, and mortality among prevalent hemodialysis patients

BACKGROUND

CD14 is a pattern-recognition receptor that has a central immunomodulatory role in proinflammatory signaling in response to a variety of ligands, including endotoxin. CD14 protein is present in 2 forms: soluble (sCD14) and membrane bound. Here, we studied the implications of increased sCD14 levels in hemodialysis patients. We hypothesized that sCD14 level increase may link to cytokine activation and protein-energy wasting, predisposing to increased mortality risk.

STUDY DESIGN

Prospective observational study of prevalent hemodialysis patients.

SETTING & PARTICIPANTS

211 prevalent hemodialysis patients, median age of 65 years, with 29 months of vintage dialysis time followed up for mortality for a median of 31 months.

PREDICTORS

Tertiles of baseline circulating sCD14 levels corresponding to less than 2.84, 2.85 to 3.62, and greater than 3.63 microg/mL.

OUTCOME

The major outcome of interest was all-cause mortality.

MEASUREMENTS

sCD14 and endotoxin, together with other markers of inflammation and protein-energy wasting.

RESULTS

Median sCD14 level was 3.2 microg/mL (25th to 75th percentile, 2.7 to 3.9). sCD14 level correlated positively with C-reactive protein, interleukin 6, endotoxin, and pentraxin 3 levels and negatively with serum albumin level, muscle mass, and handgrip strength. Patients with increased sCD14 levels had lower body mass index and increased prevalence of muscle atrophy. Patients within the highest sCD14 tertile had a crude morality hazard ratio of 1.94 (95% confidence interval, 1.13 to 3.32) that persisted after adjustment for multiple confounders (hazard ratio, 3.11; 95% confidence interval, 1.49 to 6.46). In patients with persistent inflammation, the presence of a concurrent sCD14 level increase gradually increased mortality risk, but this effect was less than multiplicative and failed to show a statistical interaction.

LIMITATIONS

Those inherent to an observational study.

CONCLUSIONS

sCD14 level is associated with inflammation and protein-energy wasting in hemodialysis patients. It is a strong and independent predictor of mortality that warrants further assessment in the clinical setting regarding its usefulness as a complementary prognosticator to other general inflammatory markers.

Progressive resistance strength training for improving physical function in older adults

BACKGROUND

Muscle weakness in old age is associated with physical function decline. Progressive resistance strength training (PRT) exercises are designed to increase strength.

OBJECTIVES

To assess the effects of PRT on older people and identify adverse events.

SEARCH STRATEGY

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialized Register (to March 2007), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to May 01, 2008), EMBASE (1980 to February 06 2007), CINAHL (1982 to July 01 2007) and two other electronic databases. We also searched reference lists of articles, reviewed conference abstracts and contacted authors.

SELECTION CRITERIA

Randomised controlled trials reporting physical outcomes of PRT for older people were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted data. Data were pooled where appropriate.

MAIN RESULTS

One hundred and twenty one trials with 6700 participants were included. In most trials, PRT was performed two to three times per week and at a high intensity. PRT resulted in a small but significant improvement in physical ability (33 trials, 2172 participants; SMD 0.14, 95% CI 0.05 to 0.22). Functional limitation measures also showed improvements: e.g. there was a modest improvement in gait speed (24 trials, 1179 participants, MD 0.08 m/s, 95% CI 0.04 to 0.12); and a moderate to large effect for getting out of a chair (11 trials, 384 participants, SMD -0.94, 95% CI -1.49 to -0.38). PRT had a large positive effect on muscle strength (73 trials, 3059 participants, SMD 0.84, 95% CI 0.67 to 1.00). Participants with osteoarthritis reported a reduction in pain following PRT(6 trials, 503 participants, SMD -0.30, 95% CI -0.48 to -0.13). There was no evidence from 10 other trials (587 participants) that PRT had an effect on bodily pain. Adverse events were poorly recorded but adverse events related to musculoskeletal complaints, such as joint pain and muscle soreness, were reported in many of the studies that prospectively defined and monitored these events. Serious adverse events were rare, and no serious events were reported to be directly related to the exercise programme.

AUTHORS' CONCLUSIONS

This review provides evidence that PRT is an effective intervention for improving physical functioning in older people, including improving strength and the performance of some simple and complex activities. However, some caution is needed with transferring these exercises for use with clinical populations because adverse events are not adequately reported.

Review article: Tackling the survival issue in end-stage renal disease: time to get physical on haemodialysis

Life expectancy in haemodialysis patients is reduced fourfold on average versus healthy age-matched individuals. The purpose of this review is to present empirical evidence that intradialytic exercise can mitigate primary independent risk factors for early mortality in end-stage renal disease. These risk factors include measures of skeletal muscle wasting, systemic inflammation, cardiovascular functioning and dialysis adequacy. Overall, the available literature provides support for the integration of exercise within the conventional outpatient haemodialysis unit. The amelioration of various physiological risk factors through an appropriate exercise prescription may enhance survival in this vulnerable cohort. Investigations are required to determine the effects of various doses of intradialytic exercise on a broad range of clinical outcomes, and more thoroughly elucidate the relationship between exercise-induced adaptations and survival advantage in end-stage renal disease.

Alterations in muscle attenuation following detraining and retraining in resistance-trained older adults

BACKGROUND

Aging skeletal muscle is characterized not only by a reduction in size (sarcopenia) and strength but also by an increase in fatty infiltration (myosteatosis). An effective countermeasure to sarcopenia is resistance exercise; however, its effect on fatty infiltration is less clear.

OBJECTIVE

To examine in resistance-trained older persons whether muscle attenuation, a noninvasive measure of muscle density reflecting intramuscular lipid content, is altered with training status.

METHODS

Thirteen healthy community-dwelling men and women aged 65-83 years (body mass index 27.0+/-1.2, mean+/-SE) had computed-tomography scans of the mid-thigh performed following 24 weeks of training, 24 weeks of detraining, and 12 weeks of retraining. Training and retraining were undertaken twice weekly for several upper- and lower-body muscle groups. Skeletal muscle attenuation in Hounsfield units (HU) as well as mid-thigh muscle volume was obtained for the quadriceps and hamstrings. Muscle strength was assessed by 1-repetition maximum and physical function by a battery of tests.

RESULTS

The average change in muscle strength following training, detraining and retraining was 48.8+/-2.9%, -17.6+/-1.3%, and 19.8+/-2.0%, respectively. Strength changes were accompanied by significant alterations in muscle density (p<0.001), with the quadriceps HU decreasing by 7.7+/-1.0% following detraining and increasing by 5.4+/-0.5% with retraining. For the hamstrings HU measure, detraining and retraining resulted in an 11.9+/-1.4% loss and a 5.5+/-1.8% gain, respectively. There was no significant change in muscle volume.

CONCLUSION

Cessation of resistance exercise in trained older persons increases the fatty infiltration of muscle, while resumption of exercise decreases it. Monitoring changes in both muscle size and fat infiltration may enable a more comprehensive assessment of exercise in combating age-related muscular changes.

Physical function, muscle strength and muscle mass in children on peritoneal dialysis

The aim of this study was to examine the physical function and muscle strength of children on peritoneal dialysis (PD) and to assess whether the muscle structure alterations influence physical function and muscle strength in these children. Twenty-two children on PD and 16 healthy children were enrolled into the study. A 6-min walk distance and gait speed tests were used to evaluate physical performance. Quadriceps muscle strength (QMS) was measured with a hand-held dynamometer. Magnetic resonance imaging was used to determine the cross-sectional area (CSA) and T2 signal intensity of the quadriceps muscle. Significant differences in the performance of these functional tests were found between PD patients and controls. Quadriceps muscle strength was significantly lower in PD patients than in controls. The CSA corrected for the body mass index (CSA/BMI) was not different between groups, whereas T2 signal intensity was significantly higher in PD patients than in the controls. Physical functioning tests and QMS had a close relationship with muscle CSA/BMI and with T2 signal intensity. In conclusion, along with the other previously documented mechanisms, increased fat in muscles may contribute to the decreased physical functioning and muscle strength in PD patients.

Therapeutic strategy for cachexia in chronic kidney disease

PURPOSE OF REVIEW

This review will provide an update on advances in the understanding of the pathophysiology and novel therapeutic approach to cachexia in chronic kidney disease.

RECENT FINDINGS

Recent studies examine the metabolic effects of nutritional supplementation and show short-term salutary effects. Studies on peripheral hormones involved in energy homeostasis and their hypothalamic signaling in the pathophysiology of uremic cachexia have led to potential novel therapeutic strategies.

SUMMARY

Most of the information on therapeutic strategy for cachexia of chronic kidney disease is currently at the experimental level and awaits confirmation by clinical trials. The few available clinical studies are preliminary and have the limitation of not having a randomized placebo-controlled group. Further long-term well designed studies to assess the clinical applicability as well as side-effects are needed before these therapeutic strategies can be recommended for treatment of cachexia in chronic kidney disease.

Randomized Controlled Trial of Intradialytic Resistance Training to Target Muscle Wasting in ESRD: The Progressive Exercise for Anabolism in Kidney Disease (PEAK) Study

BACKGROUND

To determine whether prolonged (24 weeks) intradialytic progressive resistance training (PRT) could counteract muscle wasting more effectively than short-duration training (12 weeks) in patients with end-stage renal disease.

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

49 patients (age, 62.6 +/- 14.2 years; 0.3 to 16.7 years on hemodialysis therapy) were randomly assigned to PRT plus usual care for 24 weeks (24WK group) or a crossover control group that received usual care for the first 12 weeks, then PRT plus usual care for the latter 12 weeks (12WK group).

INTERVENTION

Two sets of 10 free-weight PRT exercises were performed at a high intensity during routine thrice-weekly hemodialysis treatment under direct supervision.

OUTCOMES & MEASUREMENTS

Primary outcomes include thigh muscle cross-sectional area by means of computed tomography and intramuscular lipid content estimated through attenuation. Secondary outcomes include muscular strength, exercise capacity, and C-reactive protein level.

RESULTS

The 24WK group increased muscle cross-sectional area (+1.82 +/- 3.25 cm(2)) compared with losses in the 12WK group (-1.37 +/- 6.87 cm(2); relative effect size, 0.59; 95% confidence interval [CI], -0.27 to 6.65; P = 0.04). However, this outcome did not achieve the level of statistical significance required (P = 0.025) after Bonferroni correction for multiple primary outcomes. There was no significant change in intramuscular lipid content between groups (+0.19 +/- 1.32 versus +0.16 +/- 1.69 Hounsfield units in the 24WK and 12WK groups, respectively; P = 0.31). Log C-reactive protein level tended to decrease in the 24WK group compared with the 12WK group (relative effect size, -0.63; 95% CI, -0.27 [-0.54 to 0.00]; P = 0.05). The 24WK group improved muscular strength measures and exercise capacity throughout the trial.

LIMITATIONS

Single geographic site used; no control group without exercise exposure; unblinded assessment of some secondary outcome measures.

CONCLUSIONS

Prolonged intradialytic PRT did not significantly improve muscle cross-sectional area or intramuscular lipid content compared with a shorter duration of exercise. Future trials are required to more thoroughly investigate the clinical importance and magnitude of myogenic adaptations to PRT in this cohort.

Progressive resistance training in breast cancer: a systematic review of clinical trials

BACKGROUND

Progressive resistance training (PRT) may be effective for targeting the sequelae of breast cancer and its treatment given the unique anabolic nature of this exercise modality. Therefore, our objectives were: (1) to systematically review studies that have prescribed PRT after breast cancer surgery, (2) to summarize the efficacy of PRT in this cohort, and (3) to delineate areas for future investigations.

METHOD

A systematic review using computerized databases was performed.

RESULTS

The systematic review located 10 trials: Four uncontrolled trials, one controlled trial and five randomized controlled trials (RCTs). PRT was prescribed with aerobic training in 8/10 trials reviewed, and in isolation in 2/10 trials reviewed. Upper body PRT was prescribed in 7/10 trials, including 4/5 RCTs. No exacerbation of objectively measured or subjectively reported lymphedema symptoms was reported in any of these trials. Adverse events were rare, generally musculoskeletal in nature, and were managed effectively by conservative means. Overall, the studies we reviewed suggest that women surgically treated for breast cancer can derive health-related and clinical benefits by performing PRT after breast cancer surgery. Further research may be required to stimulate greater advocacy for PRT among oncologists, and in community care settings.

CONCLUSIONS

Robustly designed RCTs prescribing targeted PRT regimens throughout various phases of breast cancer treatment are warranted. RCTs with thorough, standardized reporting of interventions and adverse events are required to establish the efficacy of this intervention for the post-treatment management of breast cancer patients and survivors as a means to improve health status and quality of life.