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To highlight the losses in muscle mass, strength, power and functional capacity incurred in older adults during bed rest-mediated inactivity and to provide practical recommendations for both the prevention and rehabilitation of these losses. In addition to sarcopenic muscle loss, older adults lose lean tissue more rapidly than the young during prolonged periods of physical inactivity.
Amino acid or protein supplementation has the potential to maintain muscle protein synthesis and may reduce inactivity-induced muscle loss, but should ideally be part of an integrated countermeasure regimen consisting of nutrition, exercise and where appropriate, pharmacologic interventions. In accord with recent mechanistic advances we recommend an applied, broad-based 2-phase approach to limit inactivity-mediated losses of muscle mass and function in older adults:. Lifestyle: a consume a moderate amount g of high quality protein with each meal; b incorporate habitual exercise in close temporal proximity to protein-containing meals.
Crises: react aggressively to combat the accelerated loss of muscle mass and function during acute catabolic crises and periods of reduced physical activity. As a base strategy, this should include nutritional support such as targeted protein or amino acid supplementation and integrated physical therapy. Sarcopenia is an age-related, multi-factorial process that is phenotypically characterized by the loss of lean tissue mass.
The onset of sarcopenia is insidious, but its progression may be greatly accelerated by physical inactivity and poor nutrition. The basic descriptors of sarcopenia are well known. Over time, the loss of lean tissue contributes to a decrease in muscle strength and power; important predictors of balance, the occurrence of falls [ 1 ] and mortality [ 2 ]. Bed rest, or acute inactivity associated with hospitalization or disease state, poses a potent threat to muscle tissue and functional capacity. In older adults, physical inactivity during hospitalization is almost an accepted part of the inpatient experience, yet clearly contributes to a host of negative outcomes, including a reduction in the ability to perform activities of daily living, increased incidence of readmission and institutionalization [ 4 ].
While reduced or limited physical inactivity may be indicated in many patient populations, the practice of subjecting patients to continuous bed rest without a clear medical indication is a regrettable default position [ 5 ]. Aging per se also appears to facilitate inactivity-mediated muscle loss see below. Thus, with advancing age, it becomes increasingly likely that even a brief, clinically mandated period of bed rest could initiate a serious decline in Older sexy women Aalane strength and functional capacity, i.
This distinction is highlighted in Figure 1 and as detailed in the following sections, provides a tactical framework for targeted intervention strategies. Proposed model of age-related muscle loss punctuated by episodes of acute illness or injury and characterized by accelerated muscle loss and incomplete recovery. In the absence of a robust countermeasure nutritional, exercise, or pharmacologiclean tissue loss is largely inevitable during prolonged bed rest.
LeBlanc et al. In a similar cohort, Paddon-Jones et al. More recently, Trappe et al. No studies to date have directly compared young and older adults during bed rest. Nevertheless, data from the only study to examine older adults suggests that the loss of lean tissue in healthy older adults during bed rest far exceeds the losses experienced by their younger counterparts. Specifically, Kortebein et al. Notably, muscle loss in all age groups has been observed despite the provision of diets meeting or exceeding the current recommended daily allowance RDA for protein 0.
Muscle loss during bed rest appears to be driven primarily by a reduction in muscle protein synthesis [ 13 - 15 ]. However, while it appears that muscle protein breakdown is largely unaltered by bed rest in young adults [ 915 ], we are lacking corresponding data in older populations. Although not studied during bed rest, Volpi et al. Consistent with the anabolic resistance hypothesis, muscle protein breakdown did not change in either age-group, however, muscle protein synthesis increased only in the young.
Supporting data have also been reported by researchers using a 14 day unilateral knee immobilization protocol [ Older sexy women Aalane ]. The authors conclude that the decrease in post-absorptive muscle protein synthesis coupled with an anabolic resistance to feeding causes much of the muscle loss that occurs during immobilization [ 19 ]. In more clinical contexts, an increased stress response e. For example, recent work has demonstrated that the concomitant effects of pharmacologically induced hypercortisolemia i. The resultant muscle loss, particularly in the ambulatory and postural muscles of the lower extremities, can have devastating consequences on muscle strength and function [ 820 ].
Functional disability due to a loss of muscular strength and power is arguably more important than changes in lean muscle mass alone [ 821 ]. In terms of predicting the likelihood of a poor outcome due to physical inactivity, it appears clear that older adults are at increased risk [ 4723 ]. Not only do they start out with less lean muscle mass and strength than their younger Older sexy women Aalane, but they also experience an accelerated rate of loss once subjected to bed rest. Manini et al. To illustrate the potential of something as simple as bed rest without concomitant pathology to influence mobility, data from Kortebein et al.
Functional capacity, such as the ability to walk at a reasonable speed for a moderate duration, are vital components of independence. Although some performance measures e. A similar pattern has been observed in community-dwelling elders.
Gill et al. They found a relationship between the amount of time spent at home in bed rest and the magnitude of functional decline in instrumental activities of daily living, mobility, physical activity, and social activity. Although not specifically evaluated in older adults during bed rest, there is clear evidence that resistance exercise is an effective means of combating the loss of muscle mass and function in a variety of populations [ 25 - 34 ]. An important caveat, however, is that resistance exercise should be accompanied by an adequate protein- and energy-rich diet to optimize the potential for a synergistic anabolic response.
Exercise in the post-absorptive state increases muscle protein synthesis, but net balance synthesis — breakdown remains negative [ 3536 ]. While challenging to implement in some populations, resistance exercise remains an effective stimuli to combat inactivity-induced losses in muscle mass, strength, and functional capacity. A recent study Older sexy women Aalane the potency of resistance exercise to improve key physiologic outcomes in older, chronically ill individuals. Specifically, in a cohort of chronic heart failure patients, improvements in strength, VO2 peakwork capacity, and economy were identified following a resistance and endurance exercise program [ 25 ].
Despite general acceptance of its efficacy, the volume or intensity threshold of resistance training needed to protect skeletal muscle mass and function during bed rest is still unclear. Many studies have successfully employed relatively high intensity resistance training programs [ 3238 ]. However, in acutely ill patient populations, high intensity exercise interventions may be medically contraindicated or simply not feasible. While limited in direct applicability, there are recent data suggesting that even relatively low intensity, short duration bouts of physical activity such as weight bearing or walking many confer some benefit.
In situations where resistance training or ambulation is impossible either due to illness severity or injury, neuromuscular electrical stimulation NMES may represent a viable alternative. Gibson et al.
Similar data in a variety of patient groups have been presented, and efforts to refine the technique and reduce skin discomfort continue. Unfortunately, there is a lack of implementation of these standards [ 42 - 44 ]. The adequacy of the recommended dietary allowance RDA for protein 0. We recently recommended an approach based more specifically on the quality and quantity of protein consumed with each meal [ 49 ]. In broad terms, we propose that individuals should consume a moderate amount of high quality protein with each meal.
This recommendation was based on a series of recent studies [ 50 - 53 ] and focuses on the potential longer-term benefits of increased muscle protein synthesis at each meal period. For a reference 75 kg individual, an intake of g of protein for each of three daily meals represents a daily protein consumption of 1. Essential amino acid EAA supplementation represents another nutritional option for some older adults - one that avoids some, but not all of the pitfalls associated with traditional protein-energy supplementation [ 29 ].
EAA also protected functional abilities such as floor transfer time and exhibited a trend for the protection of stair ascent power and standing plantar flexion [ 54 ]. While these data are encouraging, the successful translation or application to a less controlled, real-world population is uncertain and should be treated with a measure of skepticism.
Ideally, protein or amino acid supplementation should be implemented in concert with resistance exercise as together they are more effective at attenuating the loss of muscle mass and strength than supplementation alone [ 55 ]. When exercise during chronic unloading is performed without adequate nutritional Older sexy women Aalane i.
In older adults, bed rest facilitates a reduction in protein synthesis and an accelerated loss of muscle mass, strength, power, and functional capacity. The negative metabolic and morphologic consequences of bed rest are compounded by pre-existing sarcopenia. We recommend a broad-based approach to limit losses of muscle mass and function in older adults: a consume a moderate amount g of high quality protein with each meal; b incorporate habitual exercise in close temporal proximity to protein-containing meals; c react aggressively to combat the accelerated loss of muscle mass and function during acute catabolic crises and periods of impaired physical activity.
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National Center for Biotechnology InformationU. Author manuscript; available in PMC Feb 9. Kirk L. English and Douglas Paddon-Jones. Author information Copyright and information Disclaimer. The University of Texas Medical Branch. Galveston, TX Galveston, TX Phone: Fax: ude. Copyright notice.
See other articles in PMC that cite the published article. Abstract Purpose of review To highlight the losses in muscle mass, strength, power and functional capacity incurred in older adults during bed rest-mediated inactivity and to provide practical recommendations for both the prevention and rehabilitation of these losses. Recent findings In addition to sarcopenic muscle loss, older adults lose lean tissue more rapidly than the young during prolonged periods of physical inactivity.
Summary In accord with recent mechanistic advances we recommend an applied, broad-based 2-phase approach to limit inactivity-mediated losses of muscle mass and function in older adults: 1. Keywords: sarcopenia, aging, inactivity, muscle protein synthesis, nutrition. Introduction Sarcopenia is an age-related, multi-factorial process that is phenotypically characterized by the loss of lean tissue mass.
Models of muscle loss: sarcopenia and catabolic crises Bed rest, or acute inactivity associated with hospitalization or disease state, poses a potent threat to muscle tissue and functional capacity. Open in a separate window.
Figure 1. Muscle loss is accelerated in older adults during bed rest In the absence of a robust countermeasure nutritional, exercise, or pharmacologiclean tissue loss is largely inevitable during prolonged bed rest. Muscle strength, power, and functional capacity following bed rest Functional disability due to a loss of muscular strength and power is arguably more important than changes in lean muscle mass alone [ 821 ]. Exercise countermeasures Although not specifically evaluated in older adults during bed rest, there is clear evidence that Older sexy women Aalane exercise is an effective means of combating the loss of muscle mass and function in a variety of populations [ 25 - 34 ].
Conclusion In older adults, bed rest facilitates a reduction in protein synthesis and an accelerated loss of muscle mass, strength, power, and functional capacity. Acknowledgements Supported by U. Footnotes Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. References 1. Strength is a major factor in balance, gait, and the occurrence of falls. Spec No. Knee extension strength cutpoints for maintaining mobility. J Am Geriatr Soc. Epidemiology of sarcopenia among the elderly in New Mexico.
Am J Epidemiol. Loss of independence in activities of daily living in older adults hospitalized with medical illnesses: increased vulnerability with age. Prevalence and outcomes of low mobility in hospitalized older patients. Janssen I. Influence of sarcopenia on the development of physical disability: the Cardiovascular Health Study. The natural history of functional morbidity in hospitalized older patients. Change in muscle mass and muscle strength after a hip fracture: relationship to mobility Older sexy women Aalane. Prolonged bed rest decreases skeletal muscle and whole body protein synthesis.Older sexy women Aalane
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Protecting muscle mass and function in older adults during bed rest