Skeletal muscle alterations in patients with chronic heart failure

Histological changes in skeletal muscle induced by heart failure in human patients and animal models: A scoping review

OBJECTIVE

This scoping review aimed to characterize the histological changes in skeletal muscle after heart failure (HF) and to identify gaps in knowledge.

METHODS

On April 03, 2024, systematic searches were performed for papers in which histological analyses were conducted on skeletal muscle sampled from patients with HF or animal models of HF. Screening and data extraction were conducted by two independent authors.

RESULTS AND CONCLUSION

A total of 118 papers were selected, including 33 human and 85 animal studies. Despite some disagreements among studies, some trends were observed. These trends included a slow-to-fast transition, a decrease in muscle fiber size, capillary to muscle fiber ratio, and mitochondrial activity and content, and an increase in apoptosis. These changes may contribute to the fatigability and decrease in muscle strength observed after HF. Although there were some disagreements between the results of human and animal studies, the results were generally similar. Animal models of HF will therefore be useful in elucidating the histological changes in skeletal muscle that occur in human patients with HF. Because the muscles subjected to histological analysis were mostly thigh muscles in humans and mostly lower leg muscles in animals, it remains uncertain whether changes similar to those seen in lower limb (hindlimb) muscles after HF also occur in upper limb (forelimb) muscles. The results of this review will consolidate the current knowledge on HF-induced histological changes in skeletal muscle and consequently aid in the rehabilitation of patients with HF and future studies.

Sarcopenia and cardiovascular diseases: A systematic review and meta-analysis

Sarcopenia is an age-related disease and is often accompanied by other diseases. Now, many studies have shown that cardiovascular diseases (CVDs) may raise the incidence rate of sarcopenia. Therefore, the purpose of this study was to conduct a systematic review and meta-analysis to investigate the prevalence of sarcopenia in patients with CVDs compared with the general population, defined as relatively healthy non-hospitalized subjects. The databases of PubMed, Embase, Medline and Web of Science were searched for eligible studies published up to 12 November 2022. Two assessment tools were used to evaluate study quality and the risk of bias. Statistical analysis was conducted using STATA 14.0 and R Version 4.1.2. Thirty-eight out of the 89 629 articles retrieved were included in our review. The prevalence of sarcopenia ranged from 10.1% to 68.9% in patients with CVDs, and the pooled prevalence was 35% (95% confidence interval [95% CI]: 28-42%). The pooled prevalence of sarcopenia was 32% (95% CI: 23-41%) in patients with chronic heart failure (CHF), 61% (95% CI: 49-72%) in patients with acute decompensated heart failure (ADHF), 43% (95% CI: 2-85%) in patients with coronary artery disease, 30% (95% CI: 25-35%) in patients with cardiac arrhythmia (CA), 35% (95% CI: 10-59%) in patients with congenital heart disease and 12% (95% CI: 7-17%) in patients with unclassed CVDs. However, in the general population, the prevalence of sarcopenia varied from 2.9% to 28.6% and the pooled prevalence was 13% (95% CI: 9-17%), suggesting that the prevalence of sarcopenia in patients with CVDs was about twice compared with the general population. The prevalence of sarcopenia was significantly higher only in patients with ADHF, CHF and CA compared with the general population. There is a positive correlation between CVDs and sarcopenia. The prevalence of sarcopenia is higher in patients with CVDs than that in the general population. With global aging, sarcopenia has brought a heavy burden to individuals and society. Therefore, it is important to identify the populations with high-risk or probable sarcopenia in order to do an early intervention, such as exercise, to counteract or slow down the progress of sarcopenia.

The role of the microcirculation and integrative cardiovascular physiology in the pathogenesis of ICU-acquired weakness

Skeletal muscle dysfunction after critical illness, defined as ICU-acquired weakness (ICU-AW), is a complex and multifactorial syndrome that contributes significantly to long-term morbidity and reduced quality of life for ICU survivors and caregivers. Historically, research in this field has focused on pathological changes within the muscle itself, without much consideration for their in vivo physiological environment. Skeletal muscle has the widest range of oxygen metabolism of any organ, and regulation of oxygen supply with tissue demand is a fundamental requirement for locomotion and muscle function. During exercise, this process is exquisitely controlled and coordinated by the cardiovascular, respiratory, and autonomic systems, and also within the skeletal muscle microcirculation and mitochondria as the terminal site of oxygen exchange and utilization. This review highlights the potential contribution of the microcirculation and integrative cardiovascular physiology to the pathogenesis of ICU-AW. An overview of skeletal muscle microvascular structure and function is provided, as well as our understanding of microvascular dysfunction during the acute phase of critical illness; whether microvascular dysfunction persists after ICU discharge is currently not known. Molecular mechanisms that regulate crosstalk between endothelial cells and myocytes are discussed, including the role of the microcirculation in skeletal muscle atrophy, oxidative stress, and satellite cell biology. The concept of integrated control of oxygen delivery and utilization during exercise is introduced, with evidence of physiological dysfunction throughout the oxygen delivery pathway - from mouth to mitochondria - causing reduced exercise capacity in patients with chronic disease (e.g., heart failure, COPD). We suggest that objective and perceived weakness after critical illness represents a physiological failure of oxygen supply-demand matching - both globally throughout the body and locally within skeletal muscle. Lastly, we highlight the value of standardized cardiopulmonary exercise testing protocols for evaluating fitness in ICU survivors, and the application of near-infrared spectroscopy for directly measuring skeletal muscle oxygenation, representing potential advancements in ICU-AW research and rehabilitation.

Exertional dyspnea responses to the Dyspnea Challenge in heart failure: Comparison to chronic obstructive pulmonary disease

BACKGROUND

In heart failure (HF), exertional dyspnea is a common symptom, but validated field-based tests for its measurement are limited. The Dyspnea Challenge is a two-minute uphill treadmill walk designed to measure exertional dyspnea in cardiopulmonary disease.

OBJECTIVES

The purpose of this study was to establish the test-retest reliability of the Dyspnea Challenge in HF and to compare the exercise responses to a group with chronic obstructive pulmonary disease (COPD).

METHODS

The study was an experimental, single-blind, randomized, multi-site project that recruited individuals with HF (New York Heart Association I-III) and COPD (Global Initiative for Chronic Obstructive Lung Disease II-IV). Participants completed two visits. On the first visit, participants performed two six-minute walk tests (6MWT), followed by two to three Dyspnea Challenges to calculate treadmill speed and gradient. At Visit Two, participants performed two separate Dyspnea Challenges, with one including measures of pulmonary gas exchange and central hemodynamics.

RESULTS

Twenty-one individuals with HF (10 female; 66±11years; ejection fraction:45.3 ± 6.1%; six-minute distance(6MWD) 520 ± 97 m), and 25 COPD (11 female; 68 ± 10 yr; forced expiratory volume in 1 s:47.6 ± 11.5%; 6MWD: 430 ± 101 m). Intraclass correlation coefficients demonstrated excellent test-retest reliability for HF (0.94, P<.01) and COPD (0.95, P<.01). While achieving similar end-exercise exertional dyspnea intensities (P=.60), the HF group walked at a higher average speed (4.2 ± 0.8 vs. 3.5 ± 0.8km·h^-1) and gradient (10.3 ± 2.8 vs. 9.6 ± 2.8%) and a greater oxygen uptake (P<.01) and ventilation (P<.01) than those with COPD. While achieving similar cardiac outputs (P=.98), stroke volumes (P=.97), and heart rates (P=.83), those with HF displayed a larger arteriovenous oxygen difference (P<.01), while those with COPD exhibited greater decreases in inspiratory capacity (P=.03), arterial oxygen saturation (P=.02), and breathing reserve (P<.01).

CONCLUSIONS

The Dyspnea Challenge is a reliable test-retest measure of exertional dyspnea in HF. Typical to their pathologies, HF seemed limited by an inadequate modulation of cardiac output, while ventilatory constraints hampered those with COPD.

Prevalence and Mechanisms of Skeletal Muscle Atrophy in Metabolic Conditions

Skeletal muscle atrophy is prevalent in a myriad of pathological conditions, such as diabetes, denervation, long-term immobility, malnutrition, sarcopenia, obesity, Alzheimer's disease, and cachexia. This is a critically important topic that has significance in the health of the current society, particularly older adults. The most damaging effect of muscle atrophy is the decreased quality of life from functional disability, increased risk of fractures, decreased basal metabolic rate, and reduced bone mineral density. Most skeletal muscle in humans contains slow oxidative, fast oxidative, and fast glycolytic muscle fiber types. Depending on the pathological condition, either oxidative or glycolytic muscle type may be affected to a greater extent. This review article discusses the prevalence of skeletal muscle atrophy and several mechanisms, with an emphasis on high-fat, high-sugar diet patterns, obesity, and diabetes, but including other conditions such as sarcopenia, Alzheimer's disease, cancer cachexia, and heart failure.

Quantifying the relationship and contribution of mitochondrial respiration to systemic exercise limitation in heart failure

AIMS

Heart failure with reduced ejection fraction (HFrEF) induces skeletal muscle mitochondrial abnormalities that contribute to exercise limitation; however, specific mitochondrial therapeutic targets remain poorly established. This study quantified the relationship and contribution of distinct mitochondrial respiratory states to prognostic whole-body measures of exercise limitation in HFrEF.

METHODS AND RESULTS

Male patients with HFrEF (n = 22) were prospectively enrolled and underwent ramp-incremental cycle ergometry cardiopulmonary exercise testing to determine exercise variables including peak pulmonary oxygen uptake (V̇O2peak ), lactate threshold (V̇O2LT ), the ventilatory equivalent for carbon dioxide (V̇E /V̇CO2LT ), peak circulatory power (CircPpeak ), and peak oxygen pulse. Pectoralis major was biopsied for assessment of in situ mitochondrial respiration. All mitochondrial states including complexes I, II, and IV and electron transport system (ETS) capacity correlated with V̇O2peak (r = 0.40-0.64; P < 0.05), V̇O2LT (r = 0.52-0.72; P < 0.05), and CircPpeak (r = 0.42-0.60; P < 0.05). Multiple regression analysis revealed that combining age, haemoglobin, and left ventricular ejection fraction with ETS capacity could explain 52% of the variability in V̇O2peak and 80% of the variability in V̇O2LT , respectively, with ETS capacity (P = 0.04) and complex I (P = 0.01) the only significant contributors in the model.

CONCLUSIONS

Mitochondrial respiratory states from skeletal muscle biopsies of patients with HFrEF were independently correlated to established non-invasive prognostic cycle ergometry cardiopulmonary exercise testing indices including V̇O2peak , V̇O2LT , and CircPpeak . When combined with baseline patient characteristics, over 50% of the variability in V̇O2peak could be explained by the mitochondrial ETS capacity. These data provide optimized mitochondrial targets that may attenuate exercise limitations in HFrEF.

[Functional recovery of the cardio-respiratory patient]

Introduction

Heart failure (HF), chronic obstructive pulmonary disease (COPD), and most chronic diseases are associated with mild to moderate chronic or recurrent inflammation. This inflammation contributes to malnutrition through different mechanisms: anorexia, decreased intake, alteration of metabolism with increased energy expenditure at rest and increased muscle catabolism. The decrease in lean mass has been included as a phenotypic criterion in the recently coined definition of malnutrition. In addition, a greater importance is given to the evaluation of the function, together with that of the morphological parameters. The grip strength, measured with a manual dynamometer and compared to reference populations, is a simple measure of muscle strength and correlates with the strength of the legs. On the other hand, the so-called "paradox of obesity" occurs in both patients with HF and COPD, since overweight and obese patients have lower overall mortality than patients with normal or low body mass index (BMI). The nutritional treatment, with an adequate contribution of macro and micronutrients and a contribution of proteins of fast absorption, with a higher content of leucine or its metabolite β-hydroxy-β-methylbutyrate, seems to offer a benefit in the preservation of muscle mass and its functionality in the patient with cardiorespiratory pathology. Nutritional treatment, associated with a pulmonary or cardiac rehabilitation regimen, is essential to obtain good morphological and functional results.

Skeletal muscle fiber characteristics in patients with chronic heart failure: impact of disease severity and relation with muscle oxygenation during exercise

INTRODUCTION

Skeletal muscle function in patients with heart failure and reduced ejection fraction (HFrEF) greatly determines exercise capacity. However, reports on skeletal muscle fiber dimensions, fiber capillarization, and their physiological importance are inconsistent.

METHODS

Twenty-five moderately-impaired patients with HFrEF and 25 healthy control (HC) subjects underwent muscle biopsy sampling. Type I and type II muscle fiber characteristics were determined by immunohistochemistry. In patients with HFrEF, enzymatic oxidative capacity was assessed, and pulmonary oxygen uptake (VO₂) and skeletal muscle oxygenation during maximal and moderate-intensity exercise were measured using near-infrared spectroscopy.

RESULTS

While muscle fiber cross-sectional area (CSA) was not different between patients with HFrEF and HC, percentage of type I fibers was higher in HC (46±15% versus 37±12%, respectively, P=0.041). Fiber type distribution and CSA were not different between patients in New York Heart Association (NYHA) class II and III. Type I muscle fiber capillarization was higher in HFrEF compared with controls (capillary-to-fiber perimeter exchange (CFPE) index: 5.70±0.92 versus 5.05±0.82, respectively, P=0.027). Patients in NYHA class III had slower VO₂ and muscle deoxygenation kinetics during onset of exercise, and lower muscle oxidative capacity than those in class II (P<0.05). Also, fiber capillarization was lower, but not compared with HC. Higher CFPE index was related to faster deoxygenation (r_spearman=-0.682, P=0.001), however, not to muscle oxidative capacity (r=-0.282, P=0.216).

CONCLUSIONS

Type I muscle fiber capillarization is higher in HFrEF compared with HC, but not in patients with greater exercise impairment. Greater capillarization may positively affect VO₂ kinetics by enhancing muscle oxygen diffusion.

Effects of aging and comorbidities on nutritional status and muscle dysfunction in patients with COPD

Chronic obstructive pulmonary disease (COPD) is a prevalent, complex and debilitating disease which imposes a formidable burden on patients and the healthcare system. The recognition that COPD is a multifaceted disease is not new, and increasing evidence have outlined the importance of its extra-pulmonary manifestations and its relation to other comorbid conditions in the clinical course of the disease and its societal cost. The relationship between aging, COPD and its comorbidities on skeletal muscle function and nutritional status is complex, multidirectional and incompletely understood. Despite this, the current body of knowledge allows the identification of various, seemingly partially independent factors related both to the normal aging process and to the independent deleterious effects of chronic diseases on muscle function and body composition. There is a dire need of studies evaluating the relative contribution of each of these factors, and their potential synergistic effects in patients with COPD and advanced age/comorbid conditions, in order to delineate the best course of therapeutic action in this increasingly prevalent population.

Controlled, cross-sectional, multi-center study of physical capacity and associated factors in women with fibromyalgia

Background

Health and physical capacity are commonly associated with disease, age, and socioeconomic factors. The primary objective of this study was to investigate the degree to which physical capacity, defined as muscle strength and walking ability, is decreased in women with fibromyalgia (FM), as compared to healthy women, who are matched for age and level of education. The secondary aim was to investigate whether muscle strength and walking ability are associated with age, symptom duration, activity limitations and, Body Mass Index (BMI) in women with FM and control subjects.

Methods

This controlled, cross-sectional, multi-center study comprised 118 women with FM and 93 age- and education-level-matched healthy women. The outcome measures were isometric knee-extension force, isometric elbow-flexion force, isometric hand-grip force, and walking ability. Differences between the groups were calculated, and for the women with FM analyses of correlations between the measures of physical capacity and variables were performed.

Results

The women with FM showed 20% (p < 0.001) lower isometric knee-extension force, 36% (p < 0.001) lower isometric elbow-flexion force, 34% (p < 0.001) lower isometric hand-grip force, and 16% lower walking ability (p < 0.001), as compared to the healthy controls. All measures of muscle strength in women with FM showed significant weak to moderate relationship to symptom duration (r_s = − 0.23–0.32) and walking ability (r_s = 0.25–0.36). Isometric knee-extension force correlated with activity limitations, as measured using the SF-36 Physical function subscale (r_s=0.23, p = 0.011).

Conclusions

Physical capacity was considerably decreased in the women with FM, as compared to the age- and education-level-matched control group. All measures of physical capacity showed a significant association with symptom duration. Knee-extension force and walking ability were significantly associated with activity limitations, age, and BMI. It seems important to address this problem and to target interventions to prevent decline in muscle strength. Assessments of muscle strength and walking ability are easy to administer and should be routinely carried out in the clinical setting for women with FM.

Trial registration

ClinicalTrials.gov identification number: NCT01226784, Oct 21, 2010.

Benefits of resistance exercise in lean women with fibromyalgia: involvement of IGF-1 and leptin

Background

Chronic pain and fatigue improves by exercise in fibromyalgia (FM) but underlying mechanisms are not known. Obesity is increased among FM patients and associates with higher levels of pain. Symptom improvement after aerobic exercise is affected by body mass index (BMI) in FM. Metabolic factors such as insulin-like growth factor 1 (IGF-1) and leptin may be involved. In this study, the aim was to evaluate the role of metabolic factors in lean, overweight and obese women during resistance exercise, in relation to symptom severity and muscle strength in women with FM.

Methods

Forty-three women participated in supervised progressive resistance exercise, twice weekly for 15-weeks. Serum free and total IGF-1, IGF-binding protein 3 (IGFBP3), adiponectin, leptin and resistin were determined at baseline and after 15-weeks. Level of current pain was rated on a visual analogue scale (0–100 mm). Level of fatigue was rated by multidimensional fatigue inventory (MFI-20) subscale general fatigue (MFIGF). Knee extension force, elbow flexion force and handgrip force were assessed by dynamometers.

Results

Free IGF-1 (p = 0.047), IGFBP3 (p = 0.025) and leptin (p = 0.008) were significantly decreased in lean women (n = 18), but not in the overweight (n = 17) and the obese (n = 8). Lean women with FM benefited from resistance exercise with improvements in current pain (p= 0.039, n = 18), general fatigue (MFIGF, p = 0.022, n = 18) and improved elbow-flexion force (p = 0.017, n = 18). In overweight and obese women with FM there was no significant improvement in pain or fatigue but an improvement in elbow flexion (p = 0.049; p = 0.012) after 15 weeks of resistance exercise.

Conclusion

The clearest clinical response to resistance exercise was found in lean patients with FM. In these individuals, individualized resistance exercise was followed by changes in IGF-1 and leptin, reduced pain, fatigue and improved muscular strength. In overweight and obese women FM markers of metabolic signaling and clinical symptoms were unchanged, but strength was improved in the upper limb. Resistance exercise combined with dietary interventions might benefit patients with FM and overweight.

Trial registration

The trial was registered 21 of October 2010 with ClinicalTrials.gov identification number: NCT01226784.

Skeletal muscle inflammation and atrophy in heart failure

Heart failure represents a systemic disease with profound effects on multiple peripheral tissues including skeletal muscle. Within the context of heart failure, perturbations in skeletal muscle physiology, structure, and function strongly contribute to exercise intolerance and the morbidity of this devastating disease. There is growing evidence that chronic heart failure imparts specific pathological changes within skeletal muscle beds resulting in muscle dysfunction and tissue atrophy. Mechanistically, systemic and local inflammatory responses drive critical aspects of this pathology. In this review, we will discuss pathological mechanisms that drive skeletal muscle inflammation and highlight emerging roles for distinct innate immune subsets that reside within damage muscle tissue focusing on the recently described embryonic and monocyte-derived macrophage lineages. Within this context, we will discuss how immune mechanisms can be differentially targeted to stimulate skeletal muscle inflammation, catabolism, fiber atrophy, and regeneration.

Increased Interstitial Concentrations of Glutamate and Pyruvate in Vastus Lateralis of Women with Fibromyalgia Syndrome Are Normalized after an Exercise Intervention - A Case-Control Study

BACKGROUND

Fibromyalgia syndrome (FMS) is associated with central alterations, but controversies exist regarding the presence and role of peripheral factors. Microdialysis (MD) can be used in vivo to study muscle alterations in FMS. Furthermore for chronic pain conditions such as FMS, the mechanisms for the positive effects of exercise are unclear. This study investigates the interstitial concentrations of algesics and metabolites in the vastus lateralis muscle of 29 women with FMS and 28 healthy women before and after an exercise intervention.

METHODS

All the participants went through a clinical examination and completed a questionnaire. In addition, their pressure pain thresholds (PPTs) in their upper and lower extremities were determined. For both groups, MD was conducted in the vastus lateralis muscle before and after a 15-week exercise intervention of mainly resistance training of the lower limbs. Muscle blood flow and interstitial muscle concentrations of lactate, pyruvate, glutamate, glucose, and glycerol were determined.

RESULTS

FMS was associated with significantly increased interstitial concentrations of glutamate, pyruvate, and lactate. After the exercise intervention, the FMS group exhibited significant decreases in pain intensity and in mean interstitial concentrations of glutamate, pyruvate, and glucose. The decrease in pain intensity in FMS correlated significantly with the decreases in pyruvate and glucose. In addition, the FMS group increased their strength and endurance.

CONCLUSION

This study supports the suggestion that peripheral metabolic and algesic muscle alterations are present in FMS patients and that these alterations contribute to pain. After an exercise intervention, alterations normalized, pain intensity decreased (but not abolished), and strength and endurance improved, all findings that suggest the effects of exercise are partially peripheral.

Exertional dyspnoea in chronic heart failure: the role of the lung and respiratory mechanical factors

Exertional dyspnoea is among the dominant symptoms in patients with chronic heart failure and progresses relentlessly as the disease advances, leading to reduced ability to function and engage in activities of daily living. Effective management of this disabling symptom awaits a better understanding of its underlying physiology.

Cardiovascular factors are believed to play a major role in dyspnoea in heart failure patients. However, despite pharmacological interventions, such as vasodilators or inotropes that improve central haemodynamics, patients with heart failure still complain of exertional dyspnoea. Clearly, dyspnoea is not determined by cardiac factors alone, but likely depends on complex, integrated cardio-pulmonary interactions.

A growing body of evidence suggests that excessively increased ventilatory demand and abnormal “restrictive” constraints on tidal volume expansion with development of critical mechanical limitation of ventilation, contribute to exertional dyspnoea in heart failure. This article will offer new insights into the pathophysiological mechanisms of exertional dyspnoea in patients with chronic heart failure by exploring the potential role of the various constituents of the physiological response to exercise and particularly the role of abnormal ventilatory and respiratory mechanics responses to exercise in the perception of dyspnoea in patients with heart failure.

Effect of exercise training on respiratory muscle oxygenation in children with congenital heart disease

BACKGROUND

Diminished aerobic capacity and weakness of both respiratory and peripheral muscles have been observed in cardiac patients and may contribute to exercise limitation. The aim of this study was to evaluate the effects of a home-based training programme on aerobic fitness and oxygenation of the respiratory muscles in children with congenital heart disease (CHD).

METHODS AND RESULTS

Eighteen patients with CHD aged 12-15 years participated in this study. Ten patients (training group, TG) underwent a training programme for 12 weeks and eight patients served as a non-training control group (CG). All subjects performed a cardiopulmonary exercise test before and after the study period. Oxygenation of the respiratory muscles was assessed using near-infrared spectroscopy. No significant differences were observed, at baseline and after the completion of the study, between the CG and TG in peak exercise workload, oxygen uptake (VO2), carbon dioxide output (VCO2), pulmonary ventilation (VE), and heart rate (HR). However, a significant improvement in exercise performance was found in the TG versus the CG when results were compared at the ventilatory threshold (Vth): workload (45.2+/-8.0 versus 58.5+/-7.4%; P<0.05), VO2 (62.3+/-7.5 versus 69.8+/-5.1%; P<0.05), VCO2 (49.8+/-5.7 versus 60.0+/-5.8%; P<0.05), VE (42.8+/-9.9 versus 50.1+/-9.5%; P<0.05), and HR (69.5+/-6.1 versus 76.0+/-3.5%; P<0.05). After training, an improvement in oxygenation of the respiratory muscles was found in the TG from 60% of VO2max until the end of exercise. At the Vth, the TG showed greater oxygenation after training (55.1+/-6.6 versus 43.0+/-6.9%, P<0.01, respectively). Furthermore, we showed a significant correlation of the change in respiratory muscle oxygenation and VO2 in the TG (r=0.90, P<0.01).

CONCLUSION

It is concluded that general physical training at submaximal intensity induces better aerobic fitness and improves respiratory muscle oxygenation in children with CHD.

Determinants of maximal exercise performance in chronic heart failure

BACKGROUND

Chronic heart failure (CHF) is characterized by symptoms like fatigue, dyspnoea and limited exercise performance. It has been postulated that maximal exercise performance (Wmax) is predominantly limited by skeletal muscle function and less by heart function.

AIM

To study the interrelation between most relevant muscle and anthropometrical variables and Wmax in CHF patients in order to develop a model that describes the impact of these variables for maximal exercise performance.

DESIGN

In 77 patients with CHF Wmax was assessed by incremental cycle ergometry until exhaustion (20 Watt/3 min). Peak torque (strength) and total work (endurance) for the quadriceps and hamstrings were assessed by isokinetic dynamometry. Isometric strength was measured by hand dynamometry. Relevant muscle areas were calculated by computerized tomography scan.

RESULTS

Significant correlations between Wmax and isokinetic muscle parameters (peak torque and total work) ranged from 0.41-0.65 (P<0.01). Other significant relationships (P<0.01) with Wmax were obtained for age (r=-0.22), gender (r=0.45), fat free mass (FFM) (r=0.51), quadriceps muscle area (r=0.73), hamstrings muscle area (r=0.50), upper leg muscle function (i.e., a combination of muscle strength and muscle endurance) (r=0.71) and isometric strength (r=0.63). Multiple regression analysis showed that upper leg muscle function and quadriceps muscle area could predict 57% of the variance in Wmax.

CONCLUSION

Muscle strength and muscle endurance, combined with quadriceps muscle area are the main predictors of maximal exercise performance in patients with CHF.

Effects of 15 weeks of resistance exercise on pro-inflammatory cytokine levels in the vastus lateralis muscle of patients with fibromyalgia

Background

This study aimed at investigating the effect of a resistance exercise intervention on the interstitial muscle levels of pro-inflammatory cytokines in fibromyalgia (FMS) and healthy controls (CON).

Methods

Twenty-four female patients with FMS (54 ± 8 years) and 27 female CON (54 ± 9 years) were subjected to intramuscular microdialysis of the most painful vastus lateralis muscle before and after 15 weeks of progressive resistance exercise twice per week. Baseline dialysates were sampled in the resting muscle 140 min after insertion of the microdialysis catheter. The participants then performed repetitive dynamic contractions (knee extension) for 20 min, followed by 60 min rest. Pain intensity was assessed with a 0–100 mm visual analogue scale (VAS), and fatigue was assessed with Borg’s RPE throughout microdialysis. Dialysates were sampled every 20 min and analyzed with Luminex for interleukin (IL)-1β, tumor necrosis factor (TNF) alpha, IL-6, and IL-8.

Results

At both sessions and for both groups the dynamic contractions increased pain (P < 0.012) and fatigue (P < 0.001). The levels of TNF were lower in the FMS group than the CON group at both sessions (P < 0.05), but none of the other cytokines differed between the groups. IL-6 and IL-8 increased after the dynamic contractions in both groups (P < 0.010), while TNF increased only in CON (P < 0.05) and IL-1β did not change. Overall pain intensity was reduced after the 15 weeks of resistance exercise in FMS (P < 0.05), but there was no changes in fatigue or cytokine levels.

Conclusion

Progressive resistance exercise for 15 weeks did not affect the interstitial levels of IL-1β, TNF, IL-6, and IL-8 in the vastus lateralis muscle of FMS patients or CON.

Trial registration

Clinicaltrials.gov NCT01226784, registered 21 October 2010.

Slow recovery of the impaired fatigue resistance in postunloading mouse soleus muscle corresponding to decreased mitochondrial function and a compensatory increase in type I slow fibers

Unloading or disuse rapidly results in skeletal muscle atrophy, switching to fast-type fibers, and decreased resistance to fatigue. The recovery process is of major importance in rehabilitation for various clinical conditions. Here we studied mouse soleus muscle during 60 days of reloading after 4 wk of hindlimb suspension. Unloading produced significant atrophy of soleus muscle with decreased contractile force and fatigue resistance, accompanied by switches of myosin isoforms from IIa to IIx and IIb and fast troponin T to more low-molecular-weight splice forms. The total mass, fiber size, and contractile force of soleus muscle recovered to control levels after 15 days of reloading. However, the fatigue resistance showed a trend of worsening during this period with significant infiltration of inflammatory cells at days 3 and 7, indicating reloading injuries that were accompanied by active regeneration with upregulations of filamin-C, αB-crystallin, and desmin. The fatigue resistance partially recovered after 30-60 days of reloading. The expression of peroxisome proliferator-activated receptor γ coactivator 1α and mitofusin-2 showed changes parallel to that of fatigue resistance after unloading and during reloading, suggesting a causal role of decreased mitochondrial function. Slow fiber contents in the soleus muscle were increased after 30-60 days of reloading to become significantly higher than the normal level, indicating a secondary adaption to compensate for the slow recovery of fatigue resistance.

Exercise training in chronic heart failure: improving skeletal muscle O2 transport and utilization

Chronic heart failure (CHF) impairs critical structural and functional components of the O2 transport pathway resulting in exercise intolerance and, consequently, reduced quality of life. In contrast, exercise training is capable of combating many of the CHF-induced impairments and enhancing the matching between skeletal muscle O2 delivery and utilization (Q̇mO2 and V̇mO2 , respectively). The Q̇mO2 /V̇mO2 ratio determines the microvascular O2 partial pressure (PmvO2 ), which represents the ultimate force driving blood-myocyte O2 flux (see Fig. 1). Improvements in perfusive and diffusive O2 conductances are essential to support faster rates of oxidative phosphorylation (reflected as faster V̇mO2 kinetics during transitions in metabolic demand) and reduce the reliance on anaerobic glycolysis and utilization of finite energy sources (thus lowering the magnitude of the O2 deficit) in trained CHF muscle. These adaptations contribute to attenuated muscle metabolic perturbations (e.g., changes in [PCr], [Cr], [ADP], and pH) and improved physical capacity (i.e., elevated critical power and maximal V̇mO2 ). Preservation of such plasticity in response to exercise training is crucial considering the dominant role of skeletal muscle dysfunction in the pathophysiology and increased morbidity/mortality of the CHF patient. This brief review focuses on the mechanistic bases for improved Q̇mO2 /V̇mO2 matching (and enhanced PmvO2 ) with exercise training in CHF with both preserved and reduced ejection fraction (HFpEF and HFrEF, respectively). Specifically, O2 convection within the skeletal muscle microcirculation, O2 diffusion from the red blood cell to the mitochondria, and muscle metabolic control are particularly susceptive to exercise training adaptations in CHF. Alternatives to traditional whole body endurance exercise training programs such as small muscle mass and inspiratory muscle training, pharmacological treatment (e.g., sildenafil and pentoxifylline), and dietary nitrate supplementation are also presented in light of their therapeutic potential. Adaptations within the skeletal muscle O2 transport and utilization system underlie improvements in physical capacity and quality of life in CHF and thus take center stage in the therapeutic management of these patients.

Resistance exercise improves muscle strength, health status and pain intensity in fibromyalgia--a randomized controlled trial

Introduction

Fibromyalgia (FM) is characterized by persistent widespread pain, increased pain sensitivity and tenderness. Muscle strength in women with FM is reduced compared to healthy women. The aim of this study was to examine the effects of a progressive resistance exercise program on muscle strength, health status, and current pain intensity in women with FM.

Methods

A total of 130 women with FM (age 22–64 years, symptom duration 0–35 years) were included in this assessor-blinded randomized controlled multi-center trial examining the effects of progressive resistance group exercise compared with an active control group. A person-centred model of exercise was used to support the participants’ self-confidence for management of exercise because of known risks of activity-induced pain in FM. The intervention was performed twice a week for 15 weeks and was supervised by experienced physiotherapists. Primary outcome measure was isometric knee-extension force (Steve Strong®), secondary outcome measures were health status (FIQ total score), current pain intensity (VAS), 6MWT, isometric elbow-flexion force, hand-grip force, health related quality of life, pain disability, pain acceptance, fear avoidance beliefs, and patient global impression of change (PGIC). Outcomes were assessed at baseline and immediately after the intervention. Long-term follow up comprised the self-reported questionnaires only and was conducted after 13–18 months. Between-group and within-group differences were calculated using non-parametric statistics.

Results

Significant improvements were found for isometric knee-extension force (p = 0.010), health status (p = 0.038), current pain intensity (p = 0.033), 6MWT (p = 0.003), isometric elbow flexion force (p = 0.02), pain disability (p = 0.005), and pain acceptance (p = 0.043) in the resistance exercise group (n = 56) when compared to the control group (n = 49). PGIC differed significantly (p = 0.001) in favor of the resistance exercise group at post-treatment examinations. No significant differences between the resistance exercise group and the active control group were found regarding change in self-reported questionnaires from baseline to 13–18 months.

Conclusions

Person-centered progressive resistance exercise was found to be a feasible mode of exercise for women with FM, improving muscle strength, health status, and current pain intensity when assessed immediately after the intervention.

Trial registration

ClinicalTrials.gov identification number: NCT01226784, Oct 21, 2010.

Reduced skeletal muscle oxidative capacity and impaired training adaptations in heart failure

Systolic heart failure (HF) is associated with exercise intolerance that has been attributed, in part, to skeletal muscle dysfunction. The purpose of this study was to compare skeletal muscle oxidative capacity and training-induced changes in oxidative capacity in participants with and without HF. Participants with HF (n = 16, 65 ± 6.6 years) were compared with control participants without HF (n = 23, 61 ± 5.0 years). A subset of participants (HF: n = 7, controls: n = 5) performed 4 weeks of wrist-flexor exercise training. Skeletal muscle oxidative capacity was determined from the recovery kinetics of muscle oxygen consumption measured by near-infrared spectroscopy (NIRS) following a brief bout of wrist-flexor exercise. Oxidative capacity, prior to exercise training, was significantly lower in the HF participants in both the dominant (1.31 ± 0.30 min⁻¹ vs. 1.59 ± 0.25 min⁻¹, P = 0.002; HF and control groups, respectively) and nondominant arms (1.29 ± 0.24 min⁻¹ vs. 1.46 ± 0.23 min⁻¹, P = 0.04; HF and control groups, respectively). Following 4 weeks of endurance training, there was a significant difference in the training response between HF and controls, as the difference in oxidative training adaptations was 0.69 ± 0.12 min⁻¹ (P < 0.001, 95% CI 0.43, 0.96). The wrist-flexor training induced a ∼50% improvement in oxidative capacity in participants without HF (mean difference from baseline = 0.66 ± 0.09 min⁻¹, P < 0.001, 95% CI 0.33, 0.98), whereas participants with HF showed no improvement in oxidative capacity (mean difference from baseline = −0.04 ± 0.08 min⁻¹, P = 0.66, 95% CI −0.24, 0.31), suggesting impairments in mitochondrial biogenesis. In conclusion, participants with HF had reduced oxidative capacity and impaired oxidative adaptations to endurance exercise compared to controls.

Action potential-evoked calcium release is impaired in single skeletal muscle fibers from heart failure patients

BACKGROUND

Exercise intolerance in chronic heart failure (HF) has been attributed to abnormalities of the skeletal muscles. Muscle function depends on intact excitation-contraction coupling (ECC), but ECC studies in HF models have been inconclusive, due to deficiencies in the animal models and tools used to measure calcium (Ca2+) release, mandating investigations in skeletal muscle from HF patients. The purpose of this study was to test the hypothesis that Ca2+ release is significantly impaired in the skeletal muscle of HF patients in whom exercise capacity is severely diminished compared to age-matched healthy volunteers.

METHODS AND FINDINGS

Using state-of-the-art electrophysiological and optical techniques in single muscle fibers from biopsies of the locomotive vastus lateralis muscle, we measured the action potential (AP)-evoked Ca2+ release in 4 HF patients and 4 age-matched healthy controls. The mean peak Ca2+ release flux in fibers obtained from HF patients (10±1.2 µM/ms) was markedly (2.6-fold) and significantly (p<0.05) smaller than in fibers from healthy volunteers (28±3.3 µM/ms). This impairment in AP-evoked Ca2+ release was ubiquitous and was not explained by differences in the excitability mechanisms since single APs were indistinguishable between HF patients and healthy volunteers.

CONCLUSIONS

These findings prove the feasibility of performing electrophysiological experiments in single fibers from human skeletal muscle, and offer a new approach for investigations of myopathies due to HF and other diseases. Importantly, we have demonstrated that one step in the ECC process, AP-evoked Ca2+ release, is impaired in single muscle fibers in HF patients.

Skeletal muscle myofilament adaptations to aging, disease, and disuse and their effects on whole muscle performance in older adult humans

Skeletal muscle contractile function declines with aging, disease, and disuse. In vivo muscle contractile function depends on a variety of factors, but force, contractile velocity and power generating capacity ultimately derive from the summed contribution of single muscle fibers. The contractile performance of these fibers are, in turn, dependent upon the isoform and function of myofilament proteins they express, with myosin protein expression and its mechanical and kinetic characteristics playing a predominant role. Alterations in myofilament protein biology, therefore, may contribute to the development of functional limitations and disability in these conditions. Recent studies suggest that these conditions are associated with altered single fiber performance due to decreased expression of myofilament proteins and/or changes in myosin-actin cross-bridge interactions. Furthermore, cellular and myofilament-level adaptations are related to diminished whole muscle and whole body performance. Notably, the effect of these various conditions on myofilament and single fiber function tends to be larger in older women compared to older men, which may partially contribute to their higher rates of disability. To maintain functionality and provide the most appropriate and effective countermeasures to aging, disease, and disuse in both sexes, a more thorough understanding is needed of the contribution of myofilament adaptations to functional disability in older men and women and their contribution to tissue level function and mobility impairment.

Exercise physiology in heart failure and preserved ejection fraction

Recent advances in the pathophysiology of exercise intolerance in patients with heart failure with preserved ejection fraction (HFPEF) suggest that noncardiac peripheral factors contribute to the reduced peak V(o2) (peak exercise oxygen uptake) and to its improvement after endurance exercise training. A greater understanding of the peripheral skeletal muscle vascular adaptations that occur with physical conditioning may allow for tailored exercise rehabilitation programs. The identification of specific mechanisms that improve whole body and peripheral skeletal muscle oxygen uptake could establish potential therapeutic targets for medical therapies and a means to follow therapeutic response.

Exercise intolerance in chronic heart failure: the role of cortisol and the catabolic state

Chronic heart failure (CHF) is a complex clinical syndrome leading to exercise intolerance due to muscular fatigue and dyspnea. Hemodynamics fail to explain the reduced exercise capacity, while a significant skeletal muscular pathology seems to constitute the main underlying mechanism for exercise intolerance in CHF patients. There have been proposed several metabolic, neurohormonal and immune system abnormalities leading to an anabolic/catabolic imbalance that plays a central role in the pathogenesis of the wasting process of skeletal muscle myopathy. The impairment of the anabolic axes is associated with the severity of symptoms and the poor outcome in CHF, whereas increased cortisol levels are predictive of exercise intolerance, ventilatory inefficiency and chronotropic incompetence, suggesting a significant contributing mechanism to the limited functional status. Exercise training and device therapy could have beneficial effects in preventing and treating muscle wasting in CHF. However, specific anabolic treatment needs more investigation to prove possible beneficial effects.

Intrinsic skeletal muscle alterations in chronic heart failure patients: a disease-specific myopathy or a result of deconditioning?

Chronic heart failure (CHF) patients frequently experience impaired exercise tolerance due to skeletal muscle fatigue. Studies suggest that this in part is due to intrinsic alterations in skeletal muscle of CHF patients, often interpreted as a disease-specific myopathy. Knowledge about the mechanisms underlying these skeletal muscle alterations is of importance for the pathophysiological understanding of CHF, therapeutic approach and rehabilitation strategies. We here critically review the evidence for skeletal muscle alterations in CHF, the underlying mechanisms of such alterations and how skeletal muscle responds to training in this patient group. Skeletal muscle characteristics in CHF patients are very similar to what is reported in response to chronic obstructive pulmonary disease (COPD), detraining and deconditioning. Furthermore, skeletal muscle alterations observed in CHF patients are reversible by training, and skeletal muscle of CHF patients seems to be at least as trainable as that of matched controls. We argue that deconditioning is a major contributor to the skeletal muscle dysfunction in CHF patients and that further research is needed to determine whether, and to what extent, the intrinsic skeletal muscle alterations in CHF represent an integral part of the pathophysiology in this disease.

Skeletal muscle molecular alterations precede whole-muscle dysfunction in NYHA Class II heart failure patients

Background

Heart failure (HF), a debilitating disease in a growing number of adults, exerts structural and neurohormonal changes in both cardiac and skeletal muscles. However, these alterations and their affected molecular pathways remain uncharacterized. Disease progression is known to transform skeletal muscle fiber composition by unknown mechanisms. In addition, perturbation of specific hormonal pathways, including those involving skeletal muscle insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein-5 (IGFB-5) appears to occur, likely affecting muscle metabolism and regeneration. We hypothesized that changes in IGF-1 and IGFB-5 mRNA levels correlate with the transformation of single–skeletal muscle fiber myosin heavy chain isoforms early in disease progression, making these molecules valuable markers of skeletal muscle changes in heart failure.

Materials and methods

To investigate these molecules during “early” events in HF patients, we obtained skeletal muscle biopsies from New York Heart Association (NYHA) Class II HF patients and controls for molecular analyses of single fibers, and we also quantified isometric strength and muscle size.

Results

There were more (P < 0.05) single muscle fibers coexpressing two or more myosin heavy chains in the HF patients (30% ± 7%) compared to the control subjects (13% ± 2%). IGF-1 and IGFBP-5 expression was fivefold and 15-fold lower in patients with in HF compared to control subjects (P < 0.05), respectively. Strikingly, there was a correlation in IGF-1 expression and muscle cross-sectional area (P < 0.05) resulting in a decrease in whole-muscle quality (P < 0.05) in the HF patients, despite no significant decrease in isometric strength or whole-muscle size.

Conclusion

These data indicate that molecular alterations in myosin heavy chain isoforms, IGF-1, and IGFB-5 levels precede the gross morphological and functional deficits that have previously been associated with HF, and may be used as a predictor of functional outcome in patients.

Cardiac resynchronization therapy reduces metaboreflex contribution to the ventilatory response in heart failure population

Background. Metaboreflex overactivation has been proprosed to explain exaggerated hyperventilation in heart failure population. We investigated the metaboreflex activation after cardiac resynchronization therapy (CRT). Methods. 10 heart failure patients (mean left ventricular ejection fraction (LVEF) 27 ± 4%) schedulded for CRT implantation were prospectively studied. At baseline and after 6 month follow up two maximal cardiopulmonary exercise tests with and without regional circulatory occlusion (RCO) during recovery were performed. RCO was achieved by inflation of bilateral upper thigh tourniquets 30 mmHg above peak systolic blood pressure during 3 minutes after peak exercise. Metaboreflex contribution to the ventilatory response was assessed as the difference in ventilatory data at the third minute during recovery between the two tests (Δ). Results. Patients had enhanced VE/VCO(2) slope (40 ± 9) and an evident metaboreflex contribution to the high ventilatory response (ΔVE: 3 ± 4 L/min; P = 0.05, ΔRR: 4.5 ± 4/min; P = 0.003 and ΔVE/VCO(2): 5.5 ± 4; P = 0.007). 6 months after CRT implantation, NYHA class, LVEF, peak VO(2) and VE/VCO(2) were significantly improved (1.4 ± 0.5; P < 0.001, 42 ± 7%; P < 0.001, 16.5 ± 3 mL/kg/min; P = 0.003; 33 ± 10; P = 0.01). Metaboreflex contribution to VE, RR, and VE/VCO(2) was reduced compared with baseline (P = 0.08, P = 0.01 and P = 0.4 resp.). Conclusion. 6 months after CRT metaboreflex contribution to the ventilatory response is reduced.

Effects of eccentric and concentric training on capillarization and myosin heavy chain contents in rat skeletal muscles after hindlimb suspension

We studied the effects of different protocols of post-disuse rehabilitation on angiogenesis and myosin heavy chain (MHC) content in rat hindlimb muscles after caudal suspension. Thirty female Wistar rats were divided into five groups: (1) Control I, (2) Control II, (3) Suspended, (4) Suspended trained on declined treadmill, and (5) Suspended trained on flat treadmill. Fragments of the soleus and tibialis anterior (TA) muscles were frozen and processed by electrophoresis and immunohistochemistry (CD31 antibody). Hindlimb suspension caused reduction of capillary/fiber (C/F) ratios and contents of MHC type I (MHCI) in the soleus in parallel to increased capillary density. Flat treadmill protocols increased the content of the MHCI isoform. The C/F ratio was increased by concentric training after hypokinesis, but was not modified by eccentric training, which caused a greater reduction of capillary density compared to the other protocols. In the TA muscle, hindlimb suspension caused a non-significant increase in capillary density and C/F ratio with limited changes in MHC. The present data demonstrate that the different training protocols adopted and the functional performance of the muscles analyzed caused specific changes in capillarization and in the content of the various MHC types.

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.

Myoglobin concentration in skeletal muscle fibers of chronic heart failure patients

The purpose of this study was to determine the myoglobin concentration in skeletal muscle fibers of chronic heart failure (CHF) patients and to calculate the effect of myoglobin on oxygen buffering and facilitated diffusion. Myoglobin concentration, succinate dehydrogenase (SDH) activity, and cross-sectional area of individual muscle fibers from the vastus lateralis of five control and nine CHF patients were determined using calibrated histochemistry. CHF patients compared with control subjects were similar with respect to myoglobin concentration: type I fibers 0.69 +/- 0.11 mM (mean +/- SD), type II fibers 0.52 +/- 0.07 mM in CHF vs. type I fibers 0.70 +/- 0.09 mM, type II fibers 0.49 +/- 0.07 mM in control, whereas SDH activity was significantly lower in CHF in both fiber types (P < 0.01). The myoglobin concentration in type I fibers was higher than in type II fibers (P < 0.01). Consequently, the oxygen buffering capacity, calculated from myoglobin concentration/SDH activity was increased in CHF: type I fibers 11.4 +/- 2.1 s, type II fibers 13.6 +/- 3.9 s in CHF vs. type I fibers 7.8 +/- 0.9 s, type II fibers 7.5 +/- 1.0 s in control, all P < 0.01). The calculated extracellular oxygen tension required to prevent core anoxia (Po2(crit)) in muscle fibers was similar when controls were compared with patients in type I fibers 10.3 +/- 0.9 Torr in CHF and 11.5 +/- 3.3 Torr in control, but was lower in type II fibers of patients 6.1 +/- 2.8 Torr in CHF and 14.7 +/- 6.2 Torr in control, P < 0.01. The lower Po2(crit) of type II fibers may facilitate oxygen extraction from capillaries. Reduced exercise tolerance in CHF is not due to myoglobin deficiency.

Muscle wastage in heart failure: orphan of the heart failure

The patients with heart failure (HF) often exhibit some degree of muscle wasting restricted to the lower limbs. This loss of tissue may become more extensive in some patients, usually when their HF is more advanced, and may affect all body compartments. The underlying metabolic causes are very complex and differ from patient to patient. Three essential contributors are dietary deficiency and loss of nutrients through the digestive tract and metabolic dysfunction. The development of cachexia is an ominous sign and new drugs will be added into our therapeutic armamentarium to fight against cardiac cachexia in the near-future.

Anaerobic and aerobic relative contribution to total energy release during supramaximal effort in patients with left ventricular dysfunction

Energetic metabolism during effort is impaired in patients with left ventricular dysfunction (Dysf), but data have been lacking up to now on the relative anaerobic vs. aerobic contribution to total energy release during supramaximal effort. Recently, the maximal accumulated oxygen deficit (MAOD) has been shown to be measurable in Dysf patients, making it possible to evaluate the anaerobic/aerobic interaction under conditions of maximal stress of both anaerobic and aerobic metabolic pathways in this population. Nineteen Dysf patients and 17 normal patients (N) underwent one ramp cardiopulmonary, three moderate-intensity constant-power, and three supramaximal constant-power (1- to 2-min, 2- to 3-min, and 3- to 4-min duration) exercise tests. MAOD was the difference between accumulated O2demand (accO2dem; estimated from the moderate-intensity O2uptake/watt relationship) and uptake during supramaximal tests. Percent anaerobic (%Anaer) and aerobic (%Aer) energetic release were [(MAOD/accO2dem)·100] and 100 − %Anaer, respectively. MAOD did not vary between 1–2, 2–3, and 3–4 min supramaximal tests, whereas accO2dem increased significantly with and was linearly related to test duration in both Dysf and N. Consequently, %Anaer and %Aer decreased and increased, respectively, with increasing test duration but did not differ between Dysf and N in 1–2 min, 2–3 min, and 3–4 min tests. Our study demonstrates a similar relative anaerobic vs. aerobic contribution to total energy release during supramaximal effort in Dysf and N. This finding indicates that energetic metabolism during supramaximal exercise is exercise tolerance independent and that relative anaerobic vs. aerobic contribution in this effort domain remains the same within the physiology- or pathology-induced limits to individual peak exercise performance.

Why does chronic heart failure cause breathlessness and fatigue?

Traditional explanations for the symptoms of fatigue and breathlessness experienced by patients with chronic heart failure (CHF) focus on how reduced cardiac output on exercise leads to impaired skeletal muscle blood supply, thus causing fatigue, and on how the requirement for a raised left ventricular filling pressure to maintain cardiac output results in reduced pulmonary diffusion owing to interstitial edema, thus causing breathlessness. However, indices of left ventricular function relate poorly to exercise capacity and symptoms, suggesting that the origin of symptoms may lie elsewhere. There is a specific heart failure myopathy that is present early in the condition which may contribute largely to the sensation of fatigue. Receptors present in skeletal muscle sensitive to work (ergoreceptors) are overactive in patients with CHF, presumably as a consequence of the myopathy, and their activity is related both to the ventilatory response to exercise and breathlessness, and to the sympathetic overactivity of CHF. In the present paper, we review the systemic consequences of left ventricular dysfunction to understand how they relate to the symptoms of heart failure.

Physiological Basis of Fatigue

This work summarizes our knowledge of the physiological basis of fatigue and the effects of exercise and pharmacological interventions on fatigue. Fatigue may be defined as physical and/or mental weariness resulting from exertion, that is, an inability to continue exercise at the same intensity with a resultant deterioration in performance. The concept of deconditioning in patients is discussed as well as the implications for their rehabilitation and exercise. Because fatigue may result from a number of causes, including loss of muscle mass, deconditioning, nutritional deficiencies, oxygen delivery, and anemia, it should be treated comprehensively. Antifatigue therapy should be the standard of care for most chronic conditions associated with fatigue.

Effect of heart transplantation on skeletal muscle metabolic enzyme reserve and fiber type in end-stage heart failure patients

BACKGROUND

Skeletal muscle myopathy is a hallmark of chronic heart failure (HF). Phenotypic changes involve shift in myosin heavy chain (MHC) fiber type from oxidative, MHC type I, towards more glycolytic MHC IIx fibers, reductions in oxidative enzyme activity, and increase in glycolytic enzyme activity. However, it is unknown if muscle myopathy is reversed following heart transplantation. The purpose of this study was to determine the effect of heart transplantation on skeletal muscle metabolic enzyme reserve and MHC fiber type in end-stage HF patients.

METHODS

Thirteen HF subjects were prospectively studied before and two months after heart transplantation and a subgroup (n = 6) at eight months after transplantation. Skeletal muscle biopsy of the vastus lateralis was performed and relative MHC composition was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Lactate dehydrogenase (LDH), citrate synthase (CS), and 3-hydroxyacyl-CoA-dehydrogenase (HACoA) enzyme activity assays were performed to assess glycolytic, oxidative, and beta-oxidative metabolic enzyme reserves, respectively.

RESULTS

Lactate dehydrogenase activity (130.5 +/- 13.3 vs. 106.1 +/- 13.2 micromol/g wet wt/min, p < 0.05), CS activity (14.0 +/- 1.2 vs. 9 +/- 0.9 micromol/g wet wt/min, p < 0.05), and HACoA activity (4.5 +/- 0.48 vs. 3.6 +/- 0.3 micromol/g wet wt/min, p < 0.05) decreased two months after heart transplantation. At eight months, LDH activity was restored (139.0 +/- 11 micromol/g wet wt/min), but not CS or HACoA activity compared with before transplantation. There was no significant change in muscle %MHC type I (28.7 +/- 3.5% vs. 25.3 +/- 3.0%, p = NS), %MHC type IIa (33.2 +/- 2.0% vs. 34.6 +/- 1.9%, p = NS), or %MHC type IIx (38.1 +/- 2.8% vs. 40.1 +/- 3.7%, p = NS) fiber type two months after heart transplantation. However, %MHC type I (19.3 +/- 6.6%) was decreased and %MHC type IIx (51.0 +/- 6.5%) was increased at eight months after (p < 0.05) compared with before transplantation.

CONCLUSIONS

Skeletal muscle glycolytic, oxidative, and beta-oxidative enzymatic reserves are diminished early after heart transplantation, with reduced oxidative capacity persisting late in the first year. The myopathic MHC phenotype present in end-stage HF persists early in the post-operative state and declines further by eight months.

Micronutrients and their supplementation in chronic cardiac failure. An update beyond theoretical perspectives

Physicians' use of micronutrients to improve symptoms or outcomes in chronic illness has until recently been guided by limited data on the actions of individual agents in vitro or in animal studies. However several recently published clinical trials have provided information about which groups of patients are likely to benefit from which combination of micronutrients. Patients with chronic cardiac failure (CCF), particularly elderly individuals, have several reasons to be deficient in micronutrients including reduced intake, impaired gastrointestinal absorption and increased losses on the background of increased utilisation due for example to increased oxidative stress. Studies of nutritional supplementation in CCF patients have usually concentrated on specific agents. However given that many micronutrients have synergistic influences upon metabolic processes this strategy might merely lead to a shifting of a limiting step. Rather, a strategy of increasing the availability of multiple agents at once might be more logical. The aim of this article is to briefly review the experimental rationale for each of the micronutrients of potential benefit in chronic heart failure and examine the current clinical trial evidence supporting their use.

Heart failure: a model of cardiac and skeletal muscle energetic failure

Chronic heart failure (CHF), the new epidemic in cardiology, is characterized by energetic failure of both cardiac and skeletal muscles. The failing heart wastes energy due to anatomical changes that include cavity enlargement, altered geometry, tachycardia, mitral insufficiency and abnormal loading, while skeletal muscle undergoes atrophy. Cardiac and skeletal muscles also have altered high-energy phosphate production and handling in CHF. Nevertheless, there are differences in the phenotype of myocardial and skeletal muscle myopathy in CHF: cardiomyocytes have a lower mitochondrial oxidative capacity, abnormal substrate utilisation and intracellular signalling but a maintained oxidative profile; in skeletal muscle, by contrast, mitochondrial failure is less clear, and there is altered microvascular reactivity, fibre type shifts and abnormalities in the enzymatic systems involved in energy distribution. Underlying these phenotypic abnormalities are changes in gene regulation in both cardiac and skeletal muscle cells. Here, we review the latest advances in cardiac and skeletal muscle energetic research and argue that energetic failure could be taken as a unifying mechanism leading to contractile failure, ultimately resulting in skeletal muscle energetic failure, exertional fatigue and death.

Maximum oxygen uptake corrected for skeletal muscle mass accurately predicts functional improvements following exercise training in chronic heart failure

BACKGROUND

Skeletal muscle mass and peak oxygen uptake are important predictors of functional status and outcome in patients with stable chronic heart failure.

AIMS

To assess changes in skeletal muscle mass and peak oxygen uptake following an exercise training program.

METHODS

Thirty-six patients with moderate stable chronic heart failure were randomly allocated to either a bicycle ergometer (bike) or functional electrical muscle stimulators (FES) applied to quadriceps and gastrocnemius muscles to be used daily for six weeks. Dual-energy X-ray absorptionometry (DEXA) scanning was performed before and after training along with symptom limited cardiopulmonary exercise test, quadriceps strength and fatigue resistance, and 6-min walk test.

RESULTS

Both exercise modalities resulted in improvements in treadmill exercise time, leg strength, 6-min walk test and peak oxygen uptake per kilogram of skeletal muscle. Despite significant improvements in functional capacity, there were no significant changes in body composition for total skeletal muscle mass, leg muscle mass or total body fat content. Skeletal muscle mass was strongly predictive of maximum oxygen uptake at baseline (r=0.61, p<0.001) and after exercise training (r=0.68, p<0.001).

CONCLUSIONS

In moderate stable chronic heart failure, exercise training using bicycle ergometer or FES results in favourable qualitative rather than quantitative changes in skeletal muscle. Correction of maximum oxygen uptake for skeletal muscle mass rather than total body mass is a more sensitive measure of changes associated with exercise training.

Reliability of clinical muscular endurance tests in patients with chronic heart failure

BACKGROUND

In clinical praxis it is important to be able to assess the effect of rehabilitation in patients with chronic heart failure (CHF). There is therefore a need for simple clinical tests that are objective, reliable and valid measures.

AIM

The aim of this study was to examine the reliability of three muscle endurance tests for patients with CHF and to compare the results to a healthy control group.

METHOD

The study included 20 patients (7 women) with CHF and 20 healthy persons. Dynamic endurance of the shoulder and calf muscle was measured as well as static shoulder endurance. All three tests were performed twice, within 5-10 days.

RESULTS

The reliability (rs) of the tests for the patients with CHF was between 0.90-0.99 and for the healthy persons between 0.79-0.98. There was also a significant difference in dynamic endurance in shoulder flexion and in heel-rise left leg test between patients with CHF and healthy persons.

CONCLUSION

Tests of dynamic and static endurance of the shoulder muscle and dynamic calf muscle endurance are reliable assessment tools for use in clinical practice. Patients with CHF have reduced isotonic muscular endurance compared with healthy persons.

Effect of resistance exercise on skeletal muscle myopathy in heart transplant recipients

The purpose of this study was to determine the efficacy of resistance exercise in reversing skeletal muscle myopathy in heart transplant recipients. Myopathy, engendered by both heart failure and immunosuppression with glucocorticoids, is a post-transplant complication. The sequelae of myopathic disease includes fiber-type shifts and deficits in aerobic metabolic capability. We randomly assigned patients to either 6 months of resistance exercise (training group; n = 8) or a control (control group; n = 7) group. Exercise was initiated at 2 months after transplant. Biopsy of the right vastus lateralis was performed before and after the 6-month intervention. Myosin heavy chain (MHC) composition was assessed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Biochemical assays were performed to determine citrate synthase, 3-hydroxyacyl-CoA-dehydrogenase, and lactate dehydrogenase activity. There were no group differences (p >or=0.05) in MHC composition and enzymatic reserve at baseline. Improvements in the training group for citrate cynthase (+40%), 3-hydroxyacyl-CoA-dehydrogenase (+10%), and lactate dehydrogenase activity (+48%) were significantly greater (p <or=0.05) than in the control group (+10%, -15%, and +20%, respectively). Oxidative type 1 MHC isoform concentration increased significantly in the training group (+73%, p <or=0.05) but decreased in the control group (-28%; p <or=0.05). Glycolytic type 2x MHC isoform increased significantly (17%; p <or=0.05) in the control group but decreased (-33%; p <or=0.05) in the training group. This is the first study to demonstrate that resistance training elicits myofibrillar shifts from less oxidative type II fibers to more oxidative fatigue-resistant type I fibers in heart transplant recipients. Resistance exercise initiated early in the post-transplant period is efficacious in changing skeletal muscle phenotype through increases in enzymatic reserve and shifts in fiber morphology.

Chronic Obstructive Pulmonary Disease and Chronic Heart Failure

Chronic obstructive pulmonary disease and congestive heart failure are two increasingly prevalent chronic diseases. Although care for these patients often is provided by different clinical teams, both disease conditions have much in common. In recent decades, more knowledge about the systemic impact of both diseases has become available, highlighting remarkable similarities in terms of prognostic factors and disease management. Rehabilitation programs deal with the systemic consequences of both diseases. Although clinical research also is conducted by various researchers investigating chronic obstructive pulmonary disease and chronic heart failure, it is worthwhile to compare the progress in relation to these two diseases over recent decades. Such comparison, the purpose of the current review, may help clinicians and scientists to learn about progress made in different, yet related, fields. The current review focuses on the similarities observed in the clinical impact of muscle weakness, the mechanisms of muscle dysfunction, the strategies to improve muscle function, and the effects of exercise training on chronic obstructive pulmonary disease and chronic heart failure.

Cancer-related fatigue: can exercise physiology assist oncologists?

Most patients with cancer experience fatigue, a severe activity-limiting symptom with a multifactorial origin. To avoid cancer-related fatigue, patients are frequently advised to seek periods of rest and to reduce their amount of physical activity. This advice is reminiscent of that formerly given to patients with heart disease. However, such recommendations can paradoxically compound symptoms of fatigue, since sedentary habits induce muscle catabolism and thus cause a further decrease in functional capacity. By contrast, there is scientific evidence that an exercise programme of low to moderate intensity can substantially reduce cancer-related fatigue and improve the quality of life of these patients. Current knowledge, combined with findings soon to be published, could launch new opportunities for patients with cancer. In this new century, exercise physiology could soon prove to be very useful for oncologists.