Resistance Training Limits Age-Related Muscle & Strength Loss

Can J Appl Physiol. 2001 Feb;26(1):123-41.
The effects of strength training on sarcopenia.
[Article in English, French]
Porter MM.
In the past decade strength training has been investigated extensively as a means of reversing the muscle mass loss that occurs with aging (sarcopenia). High intensity resistance training (HIRT) has led to increased protein synthesis, along with muscle hypertrophy measured at the whole body, whole muscle, and muscle fibre levels, in older adults. Typically, the strength increments associated with HIRT have been much larger than the hypertrophic response. However, most HIRT periods have been quite short. Less is known about the long-term hypertrophic response to HIRT in older adults. In order to lessen the effects of sarcopenia, HIRT should continue over the long term in older adults, to improve functional performance and health.

Sports Med. 2004;34(5):329-48.
Effects of resistance training on older adults.
Hunter GR, McCarthy JP, Bamman MM.
Using an integrative approach, this review highlights the benefits of resistance training toward improvements in functional status, health and quality of life among older adults. Sarcopenia (i.e. muscle atrophy) and loss of strength are known to occur with age. While its aetiology is poorly understood, the multifactorial sequelae of sarcopenia are well documented and present a major public health concern to our aging population, as both the quality of life and the likelihood of age-associated declines in health status are influenced. These age-related declines in health include decreased energy expenditure at rest and during exercise, and increased body fat and its accompanying increased dyslipidaemia and reduced insulin sensitivity. Quality of life is affected by reduced strength and endurance and increased difficulty in being physically active. Strength and muscle mass are increased following resistance training in older adults through a poorly understood series of events that appears to involve the recruitment of satellite cells to support hypertrophy of mature myofibres. Muscle quality (strength relative to muscle mass) also increases with resistance training in older adults possibly for a number of reasons, including increased ability to neurally activate motor units and increased high-energy phosphate availability. Resistance training in older adults also increases power, reduces the difficulty of performing daily tasks, enhances energy expenditure and body composition, and promotes participation in spontaneous physical activity. Impairment in strength development may result when aerobic training is added to resistance training but can be avoided with training limited to 3 days/week.

Can J Appl Physiol. 2001 Feb;26(1):90-101.
Functional and metabolic consequences of sarcopenia.
[Article in English, French]
Vandervoot AA, Symons TB.
Sarcopenia associated with the normal aging process is often combined with the detrimental effects of a sedentary lifestyle in older adults, leading to a significant reduction in reserve capacity of the neuromuscular system. A clear example of the aging effect is the pattern of reduction in muscle strength after the sixth decade for both isometric and concentric contractions. However, older adults are relatively stronger for movements in which muscles lengthen, due to the inherent advantage of eccentric contractions, plus their stiffer muscle structures and prolonged myosin cross-bridge cycles. Also, the capacity for physiological adaptations in the motor pathways remains into very old age when an appropriate exercise stimulus is given, and older adults can obtain adaptations in both enhanced neural control of motor units and increased protein synthesis leading to moderate muscle hypertrophy. Since periods of sedentary lifestyle or bed rest due to illness can have severe detraining consequences on the neuromuscular function of an older person, long-term prevention strategies are advocated to avoid excessive physical impairments and activity restrictions in this age group.

J Am Coll Nutr. 2004 Dec;23(6 Suppl):601S-609S.
Protein nutrition, exercise and aging.
Evans WJ.
Aging is associated with remarkable changes in body composition. Loss of skeletal muscle, a process called sarcopenia, is a prominent feature of these changes. In addition, gains in total body fat and visceral fat content continue into late life. The cause of sarcopenia is likely a result of a number of changes that also occur with aging. These include reduced levels of physical activity, changing endocrine function (reduced testosterone, growth hormone, and estrogen levels), insulin resistance, and increased dietary protein needs. Healthy free-living elderly men and women have been shown to accommodate to the Recommended Dietary Allowance (RDA) for protein of 0.8 g . kg(-1) . d(-1) with a continued decrease in urinary nitrogen excretion and reduced muscle mass. While many elderly people consume adequate amounts of protein, many older people have a reduced appetite and consume less than the protein RDA, likely resulting in an accelerated rate of sarcopenia. One important strategy that counters sarcopenia is strength conditioning. Strength conditioning will result in an increase in muscle size and this increase in size is largely the result of increased contractile proteins. The mechanisms by which the mechanical events stimulate an increase in RNA synthesis and subsequent protein synthesis are not well understood. Lifting weight requires that a muscle shorten as it produces force (concentric contraction). Lowering the weight, on the other hand, forces the muscle to lengthen as it produces force (eccentric contraction). These lengthening muscle contractions have been shown to produce ultrastructural damage (microscopic tears in contractile proteins muscle cells) that may stimulate increased muscle protein turnover. This muscle damage produces a cascade of metabolic events which is similar to an acute phase response and includes complement activation, mobilization of neutrophils, increased circulating an skeletal muscle interleukin-1, macrophage accumulation in muscle, and an increase in muscle protein synthesis and degradation. While endurance exercise increases the oxidation of essential amino acids and increases the requirement for dietary protein, resistance exercise results in a decrease in nitrogen excretion, lowering dietary protein needs. This increased efficiency of protein use may be important for wasting diseases such as HIV infection and cancer and particularly in elderly people suffering from sarcopenia. Research has indicated that increased dietary protein intake (up to 1.6 g protein . kg(-1) . d(-1)) may enhance the hypertrophic response to resistance exercise. It has also been demonstrated that in very old men and women the use of a protein-calorie supplement was associated with greater strength and muscle mass gains than did the use of placebo.

J Nutr Health Aging. 2007 Mar-Apr;11(2):185-8.
Effect of creatine supplementation during resistance training on muscle accretion in the elderly.
Candow DG, Chilibeck PD.
Sarcopenia, defined as the age-related loss of muscle mass, is a serious health concern. Contributing factors to sarcopenia include physical inactivity and undernutrition. Resistance training has a positive effect on muscle mass in the elderly. However, muscle loss is still observed in older adults who perform weight bearing exercise; suggesting that nutrition is important. Creatine supplementation has the potential to increase muscle accretion during resistance training, although the mechanism for its ergogenic effect is unclear. Creatine has the potential to increase cellular hydration and myogenic transcription factors and facilitate the up-regulation of muscle specific-genes such as myosin heavy chain possibly leading to muscle hypertrophy.

J Nutr Health Aging. 2000;4(3):143-55.
Strength training for the prevention and treatment of sarcopenia.
Roth SM, Ferrell RF, Hurley BF.
There is a progressive loss of muscle strength, muscle mass and muscle quality with advanced age, which results in a condition known as sarcopenia. In this review, the authors outline the magnitude of these losses, their functional consequences, and the efficacy of strength training (ST) as an intervention strategy for delaying, preventing or reversing the effects of sarcopenia. The question of whether sex differences and genetics influence the effects of sarcopenia and responses to ST are also discussed. Although many potential mechanisms for sarcopenia exist, their specific contributions are still unknown. Nevertheless, proposed mechanisms of sarcopenia are outlined and, where information is available, we examine the effects of ST on these potential mechanisms, which include neurogenic factors, anabolic hormones, protein synthesis, gene expression, muscle morphology, and muscle regeneration. Finally, the potential impact of genetics in the muscle response to both sarcopenia and ST is discussed. The evidence presented suggests that ST is an effective intervention for improving strength, muscle mass and muscle quality and delaying the onset of physical disability in the elderly. However, sex differences and genetic factors may play an important role in determining the muscular response to aging and ST.

Ital J Anat Embryol. 2008 Oct-Dec;113(4):217-25.
Role of adapted physical activity to prevent the adverse effects of the sarcopenia. A pilot study.
Marini M, Sarchielli E, Brogi L, Lazzeri R, Salerno R, Sgambati E, Monaci M.
Sarcopenia is the physiological age related decline in muscle mass and strength. It is a main cause of muscle weakness and reduced locomotory ability and its adverse effects contributes to a reduction in physical function and performance with decreased independence and quality of life. In fact, sarcopenia has been associated with disability and morbidity in the elderly population. Therefore, prevention and treatment of sarcopenia are areas of intense interest. The studies suggest that the pathogenesis of sarcopenia is multifactorial, but the decreased physical activity with aging appears to be a key factor involved in producing this pathology. We investigated the role of adapted physical activity on the adverse effects of the sarcopenia: we examined the effect of a specific resistance training program in twenty sedentary older men, 60-80 years old, with sarcopenia. The program was performed three days a week for 18 total weeks with isotonic machines; in particular the exercises effected with leg press, chest press and vertical row were monitored using a Globus-Tesys dynamometer with Real Power. The maximum repetition test (1RM) was used to calculate the percentage of work and formulate the methodology. Our results demonstrated that the proposed training can improve the dynamic characteristics of muscle strength. In particular, we showed that a medium-low intensity training, structured in series and repetitions with gradual increased workload, produced a time-dependent improvement of strength. Our training increased the muscle strength mainly in the lower limbs reducing the risk of falls which frequently occurs in the elderly. Therefore, a planned resistance training could be an effective countermeasure to prevent or reduce the adverse effects of the sarcopenia improving the quality of life. The physical activity should be personalized and adapted to subject’s age and/or disability.

J Nutr Health Aging. 2000;4(3):140-2.
Sarcopenia: a major modifiable cause of frailty in the elderly.
Roubenoff R.
Sarcopenia is the loss of muscle mass and strength that occurs with aging. It is a consequence of normal aging, and does not require a disease to occur, although muscle loss can be accelerated by chronic illness. Sarcopenia is a major cause of disability and frailty in the elderly. There are many candidate mechanisms leading to sarcopenia, including age-related declines in alpha-motor neurons, growth hormone production, sex steroid levels, and physical activity. In addition, fat gain, increased production of catabolic cytokines, and inadequate intake of dietary energy and protein are also potentially important causes of sarcopenia. The relative contribution of each of these factors is not yet clear. Sarcopenia can be reversed with high-intensity progressive resistance exercise, which can probably also slow its development. A major challenge in preventing an epidemic of sarcopenia-induced frailty in the future is developing public health interventions that deliver an anabolic stimulus to the muscle of elderly adults on a mass scale.

Ugeskr Laeger. 2003 Aug 25;165(35):3307-11.
[Sarcopenia and strength training. Age-related changes: effect of strength training].
[Article in Danish]
Jespersen J, Pedersen TG, Beyer N.
Sarcopenia signifies the age-related loss of muscle mass and consequently muscle strength. Sarcopenia appears to be caused by both muscular and neural factors. Concurrently with the muscle atrophy, a non-linear loss of muscle strength is observed. The decline accelerates after the age of 60. The ability to produce muscular power is reduced even more than the muscle strength. Strength training increases muscle strength and muscular power in the elderly thus counteracting part of the age-related reduction. Improvements, however, depend on the initial strength in the elderly person. The benefit of strength training is greatest in frail elderly and the oldest old, although elderly in general could benefit from strength training. Considering the growing section of elderly in the population, the focus on sarcopenia and measures to counteract this seems more relevant than ever.

J Gerontol A Biol Sci Med Sci. 2003 Oct;58(10):M911-6.
Sarcopenia: causes, consequences, and preventions.
Marcell TJ.
With the onset of advancing age, muscle tissue is gradually lost, resulting in diminished mass and strength, a condition referred to as sarcopenia. The sequela of sarcopenia often contributes to frailty, decreased independence, and subsequently increased health care costs. The following was adapted from an introduction to the conference “Sarcopenia, Age-Related Muscle Loss-Causes, Consequences, and Prevention,” sponsored by the Kronos Longevity Research Institute in June 2002. This brief review will introduce potential mechanisms that may contribute to sarcopenia, although no one mechanism has yet, and may not completely, define this process. The only agreed-upon intervention from these proceedings was regular physical exercise, stressing weight-training for elderly men and women. However, even those individuals who maintain their fitness through exercise do not appear to be immune to sarcopenia.

J Nutr. 1997 May;127(5 Suppl):998S-1003S.
Functional and metabolic consequences of sarcopenia.
Evans W.
The capacity of older men and women to adapt to regularly performed exercise has been demonstrated by many laboratories. Aerobic exercise results in improvements in functional capacity and reduced risk of developing type II diabetes in the elderly. High intensity resistance training (above 60% of the 1 repetition maximum) causes large increases in strength in the elderly, and resistance training significant increases muscle size. Resistance training also significantly increases energy requirements and insulin action of the elderly. We recently demonstrated that resistance training has a positive effect on multiple risk factors for osteoporotic fractures in previously sedentary post-menopausal women. Because the sedentary lifestyle of individuals in a long-term care facility may exacerbate losses of muscle function, we applied this same training program to frail, institutionalized elderly men and women. In a population of 100 nursing home residents, a randomly assigned high intensity strength training program resulted in significant gains in strength and functional status. In addition, spontaneous activity, measured by activity monitors, increased significantly in those participating in the exercise program; there was no change in the sedentary control group. Before the strength training intervention, the relationship of whole-body potassium and leg strength was relatively weak (r2 = 0.29, P < 0.001), indicating that in very old persons muscle mass is an important but not the only determiner of functional status. Thus exercise may minimize or reverse the syndrome of physical frailty prevalent among very old individuals. Because of their low functional status and high incidence of chronic disease, there is no segment of the population that can benefit more from exercise training than the elderly.

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