Sarcopenia--a critical perspective

Aging is associated with a progressive decline in skeletal muscle mass and function (sarocopenia). Despite several years of research, controversy exists regarding the manifestations and causes of sarcopenia. In the former respect, whereas a preferential loss of so-called "fast-twitch" muscle fibers occurs in rat models of aging, this appears unlikely in human skeletal muscle. In the latter respect, whereas a decline in physical activity with aging contributes to whole-muscle atrophy, it cannot explain the marked heterogeneity in muscle fiber size seen in aged muscles. Similarly, systemic alterations, such as reduced blood levels of anabolic hormones and nutritional deficits, although involved in modulating the degree of whole-muscle atrophy, cannot explain the observation that only some fibers atrophy and die while most appear unaffected. A further significant question remaining is that if death of some muscle fibers is normal and perhaps advantageous (that is, by removing malfunctioning cells), what is the capacity for muscle fiber regeneration in adult skeletal muscle and can this process be augmented in aging muscles?     

Anaerobic performance in masters athletes

With increasing age, it appears that masters athletes competing in anaerobic events (10–100 s) decline linearly in performance until 70 years of age, after which the rate of decline appears to accelerate. This decline in performance appears strongly related to a decreased anaerobic work capacity, which has been observed in both sedentary and well-trained older individuals. Previously, a number of factors have been suggested to influence anaerobic work capacity including gender, muscle mass, muscle fiber type, muscle fiber size, muscle architecture and strength, substrate availability, efficiency of metabolic pathways, accumulation of reaction products, aerobic energy contribution, heredity, and physical training. The effects of sedentary aging on these factors have been widely discussed within literature. Less data are available on the changes in these factors in masters athletes who have continued to train at high intensities with the aim of participating in competition. The available research has reported that these masters athletes still demonstrate age-related changes in these factors. Specifically, it appears that morphological (decreased muscle mass, type II muscle fiber atrophy), muscle contractile property (decreased rate of force development), and biochemical changes (changes in enzyme activity, decreased lactate production) may explain the decreased anaerobic performance in masters athletes. However, the reduction in anaerobic work capacity and subsequent performance may largely be the result of physiological changes that are an inevitable result of the aging process, although their effects may be minimized by continuing specific high-intensity resistance or sprint training.     

Does the road to muscle rejuvenation go through Notch?

The capacity of skeletal muscles to repair and regenerate declines during aging in humans, and this decline may lead to muscle loss and frailty. Conboy et al. show that injured muscles of aging mice are defective in Notch signaling, because up-regulation of the Notch ligand, Delta-1, is impaired. Delta-1 promotes proliferation of the satellite cells that repair damaged muscles, and Conboy et al. show that experimental activation of Notch signaling is sufficient to reverse the age-related decline in muscle regenerative capacity. Extension of these important findings to humans could lead to the development of new therapeutic approaches to maintain muscle function during aging.     

Optimal health and function among the elderly: lessening severity of ADL disability

Despite mounting evidence implicating sedentary behavior as a significant risk factor among the elderly, there is a limited amount of information on the type and amount of activity needed to promote optimal health and function in older people. Overall muscle strength and mass decline 30–50% between the ages of 30 and 80. The loss of muscle mass accounts for most of the observed loss of strength. The loss of muscle tissue is due to a decrease in the number of muscle fibers and to atrophy of the type II muscle fibers. The declining strength reduces the capacity to carry out basic activities of daily life and puts people at risk for falls and dependence on others. The objective of the present review is to examine the role of exercise training as a primary tool for increasing cardiopulmonary and muscular fitness in order to lessen the severity of disability in activities of daily living and to attain optimal health and functioning among the elderly.     

Dividing to keep muscle together: the role of satellite cells in aging skeletal muscle

The factors responsible for the atrophy of skeletal muscle with aging remain to be elucidated. Recent evidence points toward an important role for a population of cells located on the surface of skeletal muscle fibers, known as satellite cells, in maintaining the integrity of skeletal myocytes throughout the life span. This Perspective examines the role that these cells are thought to play in aging muscle atrophy, and highlights a recent study by Brack and colleagues that attempts to understand the role of satellite cells in maintaining the ratio of myonuclear number to cytoplasmic volume within myocytes as we age.     

Ceasing of muscle function with aging: is it the consequence of intrinsic muscle degeneration or a secondary effect of neuronal impairments?

Aging is associated with a significant decline in neuromuscular function leading to an eventual loss of independence and mobility of senescent people. Age-related sarcopenia, characterised by a reduction in muscle mass and strength, is considered one of the most striking features of aging at the level of the skeletal muscle. Morphological alterations in skeletal muscle can be considered as one of the consequences responsible for muscle weakness in the aged population. Beyond 60 years of age, human muscle undergoes a process of continuous denervation and reinnervation, due to an accelerating loss of motor units. It appears evident that phenotypic alterations in muscle depend on the motor drives provided by the nervous system. Because the peripheral nerves, the neuromuscular junction and motor neurons exhibit degenerative features during advanced age, sarcopenia does not seem to intrinsically develop, but is rather a secondary effect of impaired neuronal function. It is therefore recommended that elderly subjects undergo an exercise program that is aimed towards the improvement of coordinative skills and of muscle strength.     

Muscle weakness in the elderly: role of sarcopenia, dynapenia, and possibilities for rehabilitation

Aging is a multifactorial process leading to changes in skeletal muscle quantity and quality, which cause muscle weakness and disability in the aging population. This paper discusses the reasons for muscle weakness??and its biological and physiological mechanisms??in the elderly and describes the role of sarcopenia and dynapenia, and the possibilities to modify the age-associated decline in muscle function and decelerate the development of muscle weakness and disability. Resistance and endurance training are effective measures of exercise therapy in the elderly, which improve muscle metabolism and thereby muscle function and life quality.     

Alterations in IGF-I affect elderly: role of physical activity

The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. However, it is clear that overexpression of IGF-I in the muscle can protect against age-related sarcopenia. Strength training appears to be the intervention of choice for the prevention and treatment of sarcopenia. IGF-I has been implicated in the loss of the muscle with age, and IGF-I expression levels change as a consequence of strength training in older adults. However, it seems that advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition in women and men. We concluded that resistive exercise is a significant determinant of muscle mass and function. Elevated levels of IGF-I have been found in physically active compared to sedentary individuals. Recent work suggests that IGF-I as a mediator plays an important role in muscle hypertrophy and angiogenesis, both of which characterize the anabolic adaptation of muscles to exercise.     

Anabolic responses to resistance training in older men and women: a brief review

Resistance training has been shown to be the most effective exercise mode to induce anabolic adaptations in older men and women. Advances in imaging techniques and histochemistry have increased the ability to detect such changes, confirming the high level of adaptability that remains in aging skeletal muscle. This brief review presents a summary of the resistance-training studies that directly compare chronic anabolic responses to training in older (>60 years) men and women. Sixteen studies are summarized, most of which indicate similar relative anabolic responses between older men and women after resistance training. Relatively small sample sizes in most of the interventions limited their ability to detect significant sex differences and should be considered when interpreting these studies. Future research should incorporate larger sample sizes with multiple measurement time points for anabolic responses.     

The differences of sarcopenia-related phenotypes: effects of gender and population

Sarcopenia is a serious condition especially in the elderly population mainly characterized by the loss of skeletal muscle mass and strength with aging. Extremity skeletal muscle mass index (EMMI) (sum of skeletal muscle mass in arms and legs/height²) is gaining popularity in sarcopenia definition (less than two standard deviations below the mean of a young adult reference group), but little is known about the gender- and population-specific differences of EMMI. This study aimed at investigating the differences of EMMI, arm muscle mass index (AMMI), and leg muscle mass index (LMMI) between gender groups and populations (Chinese vs. Caucasians). The participants included 1,809 Chinese and 362 Caucasians with normal weight aged from 19 to 45 years old. Extremity muscle mass, arm muscle mass, and leg muscle mass were measured by using dual energy x-ray absorptiometry. Independent sample t tests were used to analyze the differences in muscle mass indexes between the studied groups. All the study parameters including EMMIs, AMMIs, and LMMIs were significantly higher (P ≤ 0.0003) in the Caucasian group than in the Chinese group and also higher in the male group than in the female group, and these significant differences (P ≤ 0.0005) remained after adjusting for age by simple regressions. The detected differences of muscle mass indexes between different gender and ethnic groups may provide important implications in their different risk of future sarcopenia.     

Endurance performance in masters athletes

Masters athletes are typically older than 35 years of age and systematically train for, and compete in, organized forms of sport specifically designed for older adults. They are motivated to participate in masters sport for a wide variety of reasons. Age-related declines in endurance performance are observed across the endurance sports of running, orienteering, rowing, and swimming. These declines are curvilinear from age 35 years until approximately age 60–70 years and exponential thereafter. The decline in endurance performance appears primarily due to an age-related decrease in VO_2max secondary to an age-related decrease in HR_max and possible age-related declines in stroke volume and arteriovenous oxygen difference. While performance velocity at lactate threshold decreases with age in masters endurance athletes, it appears to increase relative to VO_2max while exercise economy is maintained. There also appears an age-related decrease in active muscle mass, type II muscle fiber size, and blood volume that contribute to decreased endurance performance. However, research suggests that maintenance of training intensity and volume into older age may mediate the rate of age-related decline in VO_2max, stroke volume, arteriovenous oxygen difference, blood volume, and muscle mass in masters endurance athletes.     

To be or not to be: Control and balancing of type I and type II errors

The various costs of Type I and Type II errors of inference from data are discussed. Unfortunately, other things equal, Types I and II errors are inversely related. Six methods of minimizing Type I error in studies are presented, each of which may be employed even after data are collected. Type II errors may also be minimized by a combination of study design and analytic means. Although some of these techniques must be built into the study others can be undertaken when beginning work on a data set. Only one of these techniques will increase Type I error, and those involving data reduction may decrease both types of error.     

The effect of aging on skeletal-muscle recovery from exercise: possible implications for aging athletes

Recovery from exercise is integral to the physical training process. There is a perception among older athletes that aging negatively affects the recovery process. Plausible arguments for an impaired recovery with aging are a greater susceptibility of older muscle to exercise-induced skeletal-muscle damage and a slower repair and adaptation response. Differences in the physical activity level of the research participants are rarely considered, however. This makes it difficult to differentiate the respective roles of declining physical activity and aging on the recovery process. Furthermore, the type of exercise used to induce damage and monitor recovery is often not indicative of a normal training stimulus for athletes. This review discusses the effects of aging on skeletal-muscle damage and recovery processes and highlights the limitations of many of these studies with respect to older athletes. Future research should use an exercise intervention representative of a normal training stimulus and take the physical activity level of the participants into account.     

Aging and sexual health: getting to the problem

Erectile dysfunction (ED) is one of the most common disorders in male and is often associated with other age-related comorbidities. The aging process affects the structural organization and function of penile erectile components such as smooth muscle cell and vascular architecture. These modifications affect penile hemodynamics by impairing cavernosal smooth muscle cell relaxation, reducing penile elasticity, compliance and promoting fibrosis. This review aims to identify the mechanisms of ED in the penile aging process in experimental and clinical data. It also highlights areas that are in need of more research. The search strategies yielded total records screened from PubMed. Clarification of the molecular mechanisms that accompanies corpus cavernosum aging and aging-associated ED will aid new perspectives in the development of novel mechanism-based therapeutic approaches. Age is not a limiting factor for ED medical management, and it is never too late to treat. Hypogonadism should be managed regardless of age, and synergistic effects have been found during testosterone (T) replacement therapy when used along with oral phosphodiesterase-5 (PDE-5) inhibitors. Therefore, the clinical management of ED related to aging can be done by therapeutic interventions that include PDE-5 inhibitors, and other pharmacological treatments.     

Relation between hand grip strength,respiratory muscle strength and spirometric measures in male nursing home residents

Abstract

Adverse-outcomes related to sarcopenia are mostly mentioned as physical disability. As the other skeletal muscles, respiratory muscles may also be affected by sarcopenia. Respiratory muscle strength is known to affect pulmonary functions. Therefore, we aimed to investigate the relations between extremity muscle strength, respiratory muscle strengths and spirometric measures in a group of male nursing home residents. Among a total of 104 male residents, residents with obstructive measures were excluded and final study population was composed of 62 residents. Mean age was 70.5?±?6.7 years, body mass index: 27.7?±?5.3?kg/m² and dominant hand grip strength: 29.7?±?6.5?kg. Hand grip strength was positively correlated with maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) (r?=?0.35, p?<?0.01 and r?=?0.26, p?<?0.05, respectively). In regression analysis, the only factor related to MIP was hand grip strength; among spirometric measures only parameter significantly related to grip strength was peak cough flow (PCF). The association of PCF with grip strength disappeared when MIP alone or “MIP and MEP” were included in the regression analysis. In the latter case, PCF was significantly associated only with MIP. We found peripheric muscle strength be associated with MIP and PCF but not with MEP or any other spirometric parameters. The relation between peripheral muscle strength and PCF was mediated by MIP. Our findings suggest that sarcopenia may affect inspiratory muscle strength earlier or more than the expiratory muscle strength. Sarcopenia may cause decrease in PCF in the elderly, which may stand for some common adverse respiratory complications.     

Effects of testosterone supplementation on prevention of age-related penile remodeling

Abstract

Erectile dysfunction develops among 46.2% of men between 40 and 70 years. Studies demonstrated substitution on detrusor muscle by collagen due testosterone deprivation. It is clear the correlation among aging and oxidative stress, accelerating apoptosis process in many tissues. This study aims to demonstrate the collagen substitution over the muscle fibers on muscle structure of rat’s penis and the effects of testosterone supplementation. Sixteen senescent Wistar rats were divided into two groups: treatment (receiving standard supplementation testosterone dose) and control (receiving equivalent saline solution). Testosterone was dosed on D0 and D56 of study. All penises were prepared with picrosirius colored histology; stereology was applied to determine the volumetric density of collagen fibers (Vv). Analysis of variance demonstrated testosterone group’s replacement therapy to be effective, while the androgenic decline continued by the time of experiment in control group (p?<?0.05). Testosterone group had Vv of 20.6%, lower than control group (47.8%); t-test (p?<?0.001). Pearson’s correlation demonstrated an inverse correlation between the Vv and testosterone’s levels (p?<?0.001). This is a pioneer study on demonstration of structural alterations over the cavernous corpora muscle caused by deprivation of testosterone on elderly rat. These finding implicate that the testosterone levels can influence, not only the libido, but also the erectile function.     

Testosterone supplementation's effects on age-related bladder remodeling – experimental study in rats

Abstract

Objective: This study was designed to evaluate the effect of testosterone replacement on the fibrotic process of the detrusor bladder muscle during the normal aging process.

Methods: 15 Wistar senile rats, aged between 18 and 20 months were divided into two groups: testosterone group – 11 animals submitted to the administration of testosterone undecanoate (50?mg/kg intramuscular), once per month; and, Control group – four animals underwent a sham procedure. At the end of eight weeks, animals from both groups were sacrificed; bladders were removed and subsequently stereologically evaluated to determine the volumetric density of collagen fibers. The success of testosterone administration was confirmed by the measurement of serum testosterone at the beginning and end of the experiment.

Results: In the replacement group, testosterone average was 3.2?ng/ml, whereas in the control group, the mean testosterone at the end of the experiment was 0.64?ng/ml (p?<?0.05). Analysis of stereological collagenous fiber showed higher density in the control group compared to the testosterone group I (56% versus 37.02%, respectively). The difference of volume concentration of collagen between both groups was statistically significant (p?<?0.000).

Conclusion: Bladder wall fibrosis was reduced in senile rats subjected to testosterone replacement.     

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.     

Process of precocious functional aging in workers of laundries

The World Health Organization (WHO), as well as researchers of the whole world, it has been demonstrating concern with the subject of the aging related to the work and it recognizes that modifications in the several systems of the human body take to the gradual decrease in the effectiveness of each one of them, because the aging caused by the work advances apprenticeships of the cycle of the man's life, not respecting the natural state of that process. In this sense, it was aimed at with this research to investigate the relative aspects to the capacity for the work and to the workers' with responsibility to realize the work in the laundries service, verifying if they present signs of precocious functional aging.     

Aging in Which Place? Connecting Aging in Place with Individual Responsibility,Housing Markets,and the Welfare State

This article proposes an analytical framework for the understanding of aging in place, and asks: Which housing alternatives are compatible with aging in place? Who are responsible for providing housing in old age? A literature review demonstrates that there is no agreement on the “place” in aging in place, but that aging in place policies entail joint individual and public responsibility for housing. An empirical example demonstrates different policy expressions of aging in place at national and local government levels in Norway. The article questions whether a need to move to receive care is compatible with aging in place.