Exercise strategies should be designed to increase muscle power

Power training for older adults

Resistance training is widely advocated for older adults to alleviate the muscle and strength loss that occurs with aging. While primary and secondary prevention of disability are often mentioned as benefits of strength training, the evidence for this is limited and inconclusive. Researchers have started to examine another form of resistance training that may prove to be more beneficial than strength training in terms of the reduction of age-related disability. Power training is being investigated because several studies have shown a stronger relationship between power and function than between strength and function. Early studies on power training suggest that neuromuscular power can be increased to a greater extent with high velocity or explosive training than strength training alone. In addition, there may be more positive effects on performance tasks measured in the laboratory, although evidence on disability reduction was very limited. Adverse events were reported in several studies, although the risk for injuries appears to be higher for testing than for training itself. Future well-designed studies on the risks and benefits of power training should provide more evidence on this promising form of resistance training for older adults of varying health and functional status.

Chronic exercise and skeletal muscle power in older men

We sought to determine the effects of age and chronic exercise on muscle power in older males. We examined 32 older males 60-74 years of age and grouped as sedentary (CON, n = 11), chronic endurance trained (ET, n = 10), and chronic endurance trained + resistance training (ET + RT, n = 11). Exercise history was obtained by questionnaire. Absolute strength and power measures were obtained by the one-repetition maximum method. Relative strength and power were determined by dividing the absolute measure by the muscle mass involved in the exercise. Total and regional muscle mass was measured by DXA. Absolute and relative leg power were not significantly different among the 3 groups. In contrast, absolute leg press strength was greater in ET + RT compared with CON, and relative leg press strength was greater in ET and ET + RT compared with CON. Chronic running combined with resistance training may therefore enhance absolute and relative muscle strength in older adults, but does not influence muscle power. Endurance exercise may inhibit the ability of resistance exercise to positively influence skeletal muscle power.Key words: aging, strength, running, resistance training.

Leg Extension Power Asymmetry and Mobility Limitation in Healthy Older Women

OBJECTIVE

To investigate the association of asymmetry in leg extension power (LEP) with walking and standing balance.

DESIGN

Cross-sectional analysis.

SETTING

Research laboratory.

PARTICIPANTS

Healthy female twins (N=419), ages 63 to 75 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The LEP difference between the stronger and the weaker leg, measured with the Nottingham power rig, was calculated. Ten-meter maximal walking velocity was assessed in a laboratory corridor on a wide (170 cm) and narrow (35 cm) track, and the ability to maintain tandem stance for 20 seconds was recorded.

RESULTS

The mean LEP difference +/- standard deviation between the legs was 15%+/-9% (P<.001). Those with large LEP difference had lower walking velocity and poorer standing balance than those with small LEP difference, in particular when the LEP of the stronger leg was below the median.

CONCLUSIONS

Even in healthy older women, substantial LEP asymmetry between the lower limbs was present, encumbering walking and standing balance. Lower-limb muscle power asymmetry warrants further study in order to develop well-targeted strategies for preventing mobility limitation in older people.

Serum Albumin and Muscle Strength: A Longitudinal Study in Older Men and Women

OBJECTIVES

To examine whether low serum albumin is associated with low muscle strength and future decline in muscle strength in community-dwelling older men and women.

DESIGN

Population-based cohort study.

SETTING

The Longitudinal Aging Study Amsterdam.

PARTICIPANTS

Six hundred seventy-six women and 644 men aged 65 to 88.

MEASUREMENTS

Serum albumin was determined at baseline. Muscle strength was assessed using grip strength at baseline, after 3 (n=1,009), and 6 (n=741) years. The outcomes were continuous baseline muscle strength, 3- and 6-year change in muscle strength, and a dichotomous indicator for substantial decline (a decrease if > or =1 standard deviations for women=11 kg, for men=12 kg) in muscle strength.

RESULTS

Mean serum albumin concentration+/-standard deviation was 45.0+/-3.3 g/L for women and 45.2+/-3.2 g/L for men. At baseline, adjusting for age, lifestyle factors, and chronic conditions, lower serum albumin was cross-sectionally associated with weaker muscle strength (P<.001) in women and men. After 3 years of follow-up, mean decline in muscle strength was -5.6+/-10.9 kg in women and -9.6+/-11.9 kg in men. After adjustment for potential confounders, lower serum albumin was associated with muscle strength decline over 3 years (P<.01) in women and men (beta=0.57, standard error (SE)=0.18; beta=0.37, SE=0.16, respectively). Lower serum albumin was also associated with substantial decline in muscle strength in women (per unit albumin (g/L) adjusted odds ratio (OR)=1.14, one-sided 95% confidence limit (CL)=1.07) and men (per unit albumin (g/L) adjusted OR=1.14, 95% CL=1.08). Similar but slightly weaker associations were found between serum albumin and 6-year change in muscle strength (P<.05).

CONCLUSION

These results suggest that low serum albumin, even within the normal range, is independently associated with weaker muscle strength and future decline in muscle strength in older women and men.

Upper and lower limb muscle power relationships in mobility-limited older adults

BACKGROUND

Lower limb muscle power impairments are modifiable factors underlying mobility limitations in older adults. This study examined relationships between upper and lower limb muscle power and their role in predicting mobility performance among community-dwelling older adults.

METHODS

A cross-sectional analysis was conducted. Participants included 37 mobility-limited adults (24 women, 13 men), aged 65 to 93 years. Measures included upper (elbow extension) and lower limb (double leg press) one repetition maximum (1RM), and muscle power at both 40% and 70% one repetition maximum. Physical performance measures included stair climb time, the Short Physical Performance Battery, and 4-meter walk time. Factors commonly mediating the relationship between impairments and physical performance were analyzed as covariates.

RESULTS

Participants had a mean age of 76 years, had five chronic medical conditions, and manifested moderate mobility limitations. Although the associations between the upper and lower limbs were strong (p <.001), the magnitude of association was greater for power (r =.88-.89) as compared to strength (r =.69). Multivariate regression analyses revealed consistently strong relationships between limb muscle power and mobility performance measures. Substituting upper for lower limb power within these models did not materially weaken the relationships.

CONCLUSION

Muscle power appears to be a more generalized attribute between the upper and lower limbs than is muscle strength, suggesting that mechanisms underlying velocity of movement, as opposed to force production, may be important factors underlying muscle power in elderly persons. Additionally, upper limb muscle power measures may serve as a useful surrogate measure of limb power having implications for clinicians and researchers.

Improved physical performance in older adults undertaking a short-term programme of high-velocity resistance training

BACKGROUND

The age-related loss of muscle power in older adults is greater than that of muscle strength and is associated with a decline in physical performance.

OBJECTIVE

To investigate the effects of a short-term high-velocity varied resistance training programme on physical performance in healthy community-dwelling adults aged 60-80 years.

METHODS

Subjects undertook exercise (EX; n=15) or maintained customary activity (controls, CON; n=10) for 8 weeks. The EX group trained 2 days/week using machine weights for three sets of eight repetitions at 35, 55, and 75% of their one-repetition maximum (the maximal weight that an individual can lift once with acceptable form) for seven upper- and lower-body exercises using explosive concentric movements.

RESULTS

Fourteen EX and 10 CON subjects completed the study. Dynamic muscle strength significantly increased (p=0.001) in the EX group for all exercises (from 21.4 +/- 9.6 to 82.0 +/- 59.2%, mean +/- SD) following training, as did knee extension power (p <0.01). Significant improvement occurred for the EX group in the floor rise to standing (10.4 +/- 11.5%, p=0.004), usual 6-metre walk (6.6 +/- 8.2%, p=0.010), repeated chair rise (10.4 +/- 15.6%, p=0.013), and lift and reach (25.6 +/- 12.1%, p=0.002) performance tasks but not in the CON group.

CONCLUSIONS

Progressive resistance training that incorporates rapid rate-of-force development movements may be safely undertaken in healthy older adults and results in significant gains in muscle strength, muscle power, and physical performance. Such improvements could prolong functional independence and improve the quality of life.

Role of Protein and Amino Acids in the Pathophysiology and Treatment of Sarcopenia

Sarcopenia, the loss of skeletal muscle mass and function with aging, is a multifactorial condition that slowly develops over decades and becomes a significant contributor to disability in the older population. Malnutrition and alterations in the muscle anabolic response to nutritional stimuli have been identified as potentially preventable factors that may significantly contribute to sarcopenia. Thus, nutritional interventions may be useful for the prevention and treatment of sarcopenia.

Optimizing functional exercise capacity in the elderly surgical population

PURPOSE OF REVIEW

There are several studies on the effect of exercise post surgery (rehabilitation), but few studies have looked at augmenting functional capacity prior to surgical admission (prehabilitation). A programme of prehabilitation is proposed in order to enhance functional exercise capacity in elderly patients with the intent to minimize the postoperative morbidity and accelerate postsurgical recovery.

RECENT FINDINGS

Few studies have looked at exercise prehabilitation to improve functional capacity prior to surgical admission. Prehabilitation prior to orthopaedic surgery does not seem to improve quality of life or recovery. However, prehabilitation prior to abdominal or cardiac surgery, based on 275 elderly patients, results in fewer postoperative complications, shorter postoperative length of stay, improved quality of life, and reduced declines in functional disability compared to sedentary controls.

SUMMARY

A concentrated 3-month progressive exercise prehabilitation programme consisting of aerobic training at 45-65% of maximal heart rate reserve (%HRR) along with periodic high-intensity interval training ( approximately 90% HRR) four times per week, 30-50 minutes per session, is recommended for improving cardiovascular functioning. A strength training programme of about 10 different exercises focused on large, multi-jointed muscle groups should also be implemented twice per week at a mean training intensity of 80% of one-repetition maximum. Finally, a minimum of 140 g ( approximately 560 kcal) of carbohydrate (CHO) should be taken 3 h before training to increase liver and muscle glycogen stores and a minimum of about 200 kcal of mixed protein-CHO should be ingested within 30 min following training to enhance muscle hypertrophy.

Age-related differences in rapid muscle activation after rate of force development training of the elbow flexors

In young adults, improvements in the rate of force development as a result of resistance training are accompanied by increases in neural drive in the very initial phase of muscle activation. The purpose of this experiment was to determine if older adults also exhibit similar adaptations in response to rate of force development (RFD) training. Eight young (21-35 years) and eight older (60-79 years) adults were assessed during the production of maximum rapid contractions, before and after four weeks of progressive resistance training for the elbow flexors. Young and older adults exhibited significant increases (P<0.01) in peak RFD, of 25.6% and 28.6% respectively. For both groups the increase in RFD was accompanied by an increase in the root mean square (RMS) amplitude and in the rate of rise (RER) in the electromyogram (EMG) throughout the initial 100 ms of activation. For older adults, however, this training response was only apparent in the brachialis and brachioradialis muscles. This response was not observed in surface EMG recorded from the biceps brachii muscle during either RFD testing or throughout training, nor was it observed in the pronator teres muscle. The minimal adaptations observed for older adults in the bifunctional muscles biceps brachii and pronator teres are considered to indicate a compromise of the neural adaptations older adults might experience in response to resistance training.

Benefits of exercise for community-dwelling older adults

This focused review highlights the benefits of exercise and physical activity for community-dwelling older adults. It is part of the study guide on geriatric rehabilitation in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article specifically focuses on the benefits of physical activity and exercise for older adults with regard to morbidity, mortality, and disability. It discusses the appropriate preexercise screening and evaluation procedures for older adults contemplating exercise. Last, it reviews the current literature on the benefits of varying modes of exercise to modify the most prevalent chronic medical conditions of late life, including arthritis, heart disease, diabetes, stroke, pulmonary disease, and osteoporosis.

OVERALL ARTICLE OBJECTIVE

To summarize the current knowledge regarding the therapeutic benefits of exercise for community-dwelling older adults.

Exercise and aging

There is increasing evidence that the black box we have referred to as"biologic aging" is composed of genetic factors and many types of environmental exposures. Some of the most potentially modifiable elements of this syndrome are those attributable to disuse or insufficient exposure to certain kinds or intensities of physical stressors during the course of the life span. Beneficial adaptations to exercise once thought restricted to genetically endowed master athletes now are seen to occur just as predictably in frail elders with chronic disease, opening the door to vastly improved physical function and associated health benefits. Knowledge of the benefits of physical activity, however well substantiated, may be necessary, but it is not sufficient to change either physician-prescribing habits or the likelihood of adoption and long-term adherence to exercise on the part of patients. Ultimately, the penetration of an exercise prescription to optimize aging into the most inactive cohorts in the community,who have the most to gain from increases in levels of physical activity and fitness, will depend on a combination of clear evidence-based guidelines coupled with health professional training and behavioral programs tailored to age-specific barriers and motivational factors.

Cycling as a novel approach to resistance training increases muscle strength, power, and selected functional abilities in healthy older women

Cycling on a mechanically braked cycle ergometer was used as a novel approach to compare the effects of three different 16-wk resistance-training programs on isometric force, power output, and selected functional abilities in 31 healthy 65- to 74-yr-old women. Training was conducted three times per week. During each session, individuals of the speed group performed 8 sets of 16 pedal revolutions at 40% of the maximal resistance to complete two revolutions (2 RM); strength group performed 8 sets of 8 revolutions at 80% of 2 RM; and combination group performed 4 sets of 16 revolutions at 40% and 4 sets of 8 revolutions at 80% of 2 RM. During each set, all participants were required to pedal as fast as possible with a 2-min interval between sets. All training groups significantly increased force, power, and functional abilities (maximal treadmill walking speed, vertical jumping, and box stepping) at week 8 (in the range from 6.5 to 20.8%) with no further improvement at week 16 (except maximal treadmill walking speed), but no significant differences were observed between the three groups. The novel approach to performing both low- and high-resistance training, based on the use of a cycle ergometer, has been shown to be effective in improving strength, power, and functional abilities in a group of healthy women. Even fit older women can still improve in functional abilities. Interestingly, the "high-speed" and "low-speed" programs induced an increase in both power and strength of similar magnitude.

Muscle strength, power and adaptations to resistance training in older people

Muscle strength and, to a greater extent, power inexorably decline with ageing. Quantitative loss of muscle mass, referred to as "sarcopenia", is the most important factor underlying this phenomenon. However, qualitative changes of muscle fibres and tendons, such as selective atrophy of fast-twitch fibres and reduced tendon stiffness, and neural changes, such as lower activation of the agonist muscles and higher coactivation of the antagonist muscles, also account for the age-related decline in muscle function. The selective atrophy of fast-twitch fibres has been ascribed to the progressive loss of motoneurons in the spinal cord with initial denervation of fast-twitch fibres, which is often accompanied by reinnervation of these fibres by axonal sprouting from adjacent slow-twitch motor units (MUs). In addition, single fibres of older muscles containing myosin heavy chains of both type I and II show lower tension and shortening velocity with respect to the fibres of young muscles. Changes in central activation capacity are still controversial. At the peripheral level, the rate of decline in parameters of the surface-electromyogram power spectrum and in the action-potential conduction velocity has been shown to be lower in older muscle. Therefore, the older muscle seems to be more resistant to isometric fatigue (fatigue-paradox), which can be ascribed to the selective atrophy of fast-twitch fibres, slowing in the contractile properties and lower MU firing rates. Finally, specific training programmes can dramatically improve the muscle strength, power and functional abilities of older individuals, which will be examined in the second part of this review.

Measuring power during the sit-to-stand transfer

Power has been demonstrated to be an early and potent marker of frailty. The measurements currently available are tied to locality. Usually, measurements include single joint movements or movements of only the legs and the resistance is not adjusted for body weight. In this study, a portable method to measure power in the sit-to-stand transfer was developed and tested. Mean power was calculated from the vertical ground reaction force of body weight, the difference between height in a sitting and in an upright position and the time taken to stand up. The results of this power measurement were compared with an isokinetic force measurement, the "Nottingham power rig", and measurement of physical performance in a five-repetition chair rise (five-chair rise). A convenience sample of 33 healthy elderly subjects [mean (SD) age: 67.8 (6.7) years; 17 men, 16 women] was included. Measurement of power during the sit-to-stand transfer showed good correlation to isokinetic force measurement (r=0.68) and to the "Nottingham power rig" (r=0.6). Correlation to five-chair rise was poor (r=-0.08). In conclusion, the study shows that the method presented is able to measure power during performance of a daily task. The poor correlation between the introduced measurement and the five-chair rise suggests that it might be able to detect decline in muscle function earlier by the introduced measurement than by measurement of the functional status. As it is inexpensive and portable, its use in clinical practice and research contexts, including home-bound individuals, is feasible.

Mixed-methods resistance training increases power and strength of young and older men

PURPOSE

This study examined the effects of mixed-methods resistance training on young and older men to determine whether similar increases in muscle power were elicited.

METHODS

Effects of 10 wk of a periodized resistance-training program designed to increase muscle size, strength, and maximal power on isometric squat strength, time course of force development, muscle fiber characteristics, and muscle activation (iEMG), as well as force and power output during squat jumps, were compared in young (YM, 30 +/- 5 yr, N = 8) and older men (OM, 61 +/- 4 yr, N = 10).

RESULTS

Isometric squat strength was higher in the YM compared with OM at all testing occasions and increased over the training period by 23 +/- 15% and 40 +/- 42% for the YM and OM, respectively. The early phase of the force-time curve was shifted upward in both groups over the course of the training. During the squat jumps, the YM produced higher force and power at all test occasions and at all loads tested compared with the OM. The YM increased power output by 15 +/- 14%, 33 +/- 16%, and 26 +/- 12%, and the OM by 7 +/- 5%, 36 +/- 23%, and 25 +/- 16% for the 17 kg, and 30% and 60% 1RM loads, respectively.

CONCLUSION

Although the results of this study confirm age-related reductions in muscle strength and power, the older men did demonstrate similar capacity to young men for increases in these variables via an appropriate periodized resistance-training program that includes rapid, high-power exercises.

A conceptual framework of frailty: a review

This article presents an overview of the increasingly common condition of frailty, which by and large lacks clarity of definition. A variety of sources provide this statement regarding definition, incidence, causation, rate, and time of appearance. Utilizing the newly elaborated process of symmorphosis, which explains the coadaptation of structure and function secondary to altered energy loads, I propose that frailty is a body-wide set of linked deteriorations including, but not confined to, musculoskeletal, cardiovascular, metabolic, and immunologic systems. The common final pathway that leads to this constellation of findings is usually keyed to a decline in physical activity either as a result of habit or disease inputs. As such, the state of frailty is largely separable from the process of aging and should thereby be susceptible to active intervention and reversal.

Weighted stair climbing in mobility-limited older people: a pilot study

OBJECTIVES

To evaluate weighted stair climbing exercise (SCE) as a means of increasing lower extremity muscle power in mobility-limited older people.

DESIGN

Single-blinded, randomized controlled pilot study.

SETTING

Human physiology laboratory of a metropolitan university.

PARTICIPANTS

Forty-five community-dwelling people aged 65 and older who had baseline mobility limitations manifested by scores of 11 or lower on the Short Physical Performance Battery (SPPB).

INTERVENTIONS

Subjects were randomized into one of two 12-week exercise programs. The intervention group (SCE) (n = 23) ascended and descended stairs, at a set pace, while wearing a weighted vest. The control group (WALK) (n = 22) participated in a standardized walking program.

MEASUREMENTS

Primary and secondary outcomes included measures of muscle power and strength, submaximal aerobic capacity, and physical performance.

RESULTS

SCE produced 17% improvement in double leg press peak power in comparison with WALK (P =.013) and significant improvement in stair climbing power from baseline (12%). Improvement in submaximal aerobic performance was equivalent for both groups. Although not statistically significant, effect size estimates suggest that SCE can potentially influence knee extension power and strength. Stair climb time was improved in both groups, whereas SCE produced significant improvements from baseline SPPB score in a subcohort of participants.

CONCLUSIONS

These findings suggest that SCE maybe a useful component of a home exercise program designed to enhance lower extremity muscle power, aerobic capacity, and functional performance. Further investigation is needed involving larger sample sizes and direct comparisons with other forms of resistance training.

The relationship between leg power and physical performance in mobility-limited older people

OBJECTIVES

The purpose of this study was to assess the influence of leg power and leg strength on the physical performance of community-dwelling mobility-limited older people.

DESIGN

Cross-sectional analysis of baseline data from a 12-week randomized controlled exercise-intervention study.

SETTING

Exercise laboratory within the Department of Health Science of an urban university.

PARTICIPANTS

Forty-five community-dwelling mobility-limited people (34 women, 11 men), aged 65 to 83.

MEASUREMENTS

Health status, depression, cognition, physical activity, and falls efficacy; physiological measures of lower extremity strength and power; and measures of physical performance.

RESULTS

Through bivariate analyses, leg power was significantly associated with physical performance as measured by stair-climb time, chair-stand time, tandem gait, habitual gait, maximal gait, and the short physical performance battery describing between 12% and 45% of the variance (R2). Although leg power and leg strength were greatly correlated (r = .89) in a comparison of bivariate analyses of strength or power with physical performance, leg power modeled up to 8% more of the variance for five of six physical performance measures. Despite limitations in sample size, it appeared that, through quadratic modeling,the influence of leg power on physical performance was curvilinear. Using separate multivariate analyses, partial R2 values for leg power and leg strength were compared, demonstrating that leg power accounted for 2% to 8% more of the variance with all measures of physical performance.

CONCLUSION

Leg power is an important factor influencing the physical performance of mobility-limited older people. Although related to strength, it is a separate attribute that may exert a greater influence on physical performance. These findings have important implications for clinicians practicing geriatric rehabilitation.

Velocity training induces power-specific adaptations in highly functioning older adults

OBJECTIVE

To test the efficacy of high-velocity training in healthy older persons.

DESIGN

A 12-week randomized trial, with subjects blocked for gender and residence, comparing high-velocity resistance training with a self-paced walking program.

SETTING

Retirement community.

PARTICIPANTS

Forty-three volunteers over the age of 70 years.

INTERVENTION

Power group: high-velocity leg exercises 3 times weekly with weekly increases in resistance combined with 45 minutes of moderate, nonresistance exercise weekly. Walking group: moderate intensity exercise 30 minutes daily, 6 days weekly.

MAIN OUTCOME MEASURES

Variables measured included leg press peak power and leg extensor strength. Functional performance outcomes included: 6-minute walk distance, Short Physical Performance Battery, Physical Performance Test, and Medical Outcomes Study Short-Form Health Survey.

RESULTS

Peak power improved 22% (p =.004) in the power group (3.7 +/- 1.0 W/kg to 4.5 +/- 1.4 W/kg) but did not change in the walking group (3.99 +/-.76 W/kg to 3.65 +/-.94 W/kg). Leg extensor power at resistance of 50%, 60%, and 70% of body weight increased 50%, 77%, and 141%, respectively, in the power group (p <.0001, repeated-measures analysis of variance). Strength improved 22% in the power-trained individuals and 12% in the walkers (p <.0001). Training did not improve functional task performance in either group. One subject developed a radiculopathy during training.

CONCLUSIONS

Resistance training focusing on speed of movement improved leg power and maximal strength substantially, but did not improve functional performance in healthy high-functioning older volunteers.

Sarcopenia

Sarcopenia is a term utilized to define the loss of muscle mass and strength that occurs with aging. Sarcopenia is believed to play a major role in the pathogenesis of frailty and functional impairment that occurs with old age. Progressive muscle wasting occurs with aging. The prevalence of clinically significant sarcopenia is estimated to range from 8.8% in young old women to 17.5% in old old men. Persons who are obese and sarcopenic (the "fat frail") have worse outcomes than those who are sarcopenic and non-obese. There is a disproportionate atrophy of type IIa muscle fibers with aging. There is also evidence of an age-related decrease in the synthesis rate of myosin heavy chain proteins, the major anabolic protein. Motor units innervating muscle decline with aging, and there is increased irregularity of muscle unit firing. There are indications that cytokines-especially interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6-play a role in the pathogenesis of sarcopenia. Similarly, the decline in anabolic hormones-namely, testosterone, dehydroepiandrosterone growth hormone, and insulin-like growth factor-I-is also implicated in the sarcopenic process. The role of the physiologic anorexia of aging remains to be determined. Decreased physical activity with aging appears to be the key factor involved in producing sarcopenia. An increased research emphasis on the factors involved in the pathogenesis of sarcopenia is needed.

Anorexia, body composition, and ageing

Over the lifespan there is a decline in food intake. This has been termed the physiological anorexia of aging. It has many causes, including alterations in the gastrointestinal satiating system, the effect of elevated leptin levels, especially in men, and a variety of changes in central nervous system neurotransmitters. Beyond the age of 70 years body mass declines. This includes both loss of adipose tissue and muscle mass. The loss of muscle mass in older individuals is termed sarcopenia. There is increasing evidence that this is caused, in men, partly by the decline in testosterone. Illness results in an increase of cytokines that produce both anorexia and cause protein wasting. Many of the causes of cachexia in older individuals are treatable. Depression is the most common cause of weight loss in older individuals. Dieting in older individuals is associated with a loss of skeletal tissue as well as fat mass. This can place older individuals at risk of becoming the 'fat frail'.

The utility of resistance exercise training and amino acid supplementation for reversing age-associated decrements in muscle protein mass and function

Advancing age is associated with reduced skeletal muscle protein synthesis, altered expression of and chemical modifications to muscle proteins, reduced muscle strength, muscle strength per unit muscle mass and muscle power (sarcopenia). These age-associated impairments in the quantity and quality of contractile protein contribute to physical disability and frailty, a loss of independent function, the risk of falling and fractures, and escalating health-care costs. Progressive resistance exercise training is a potent, non-pharmacologic, efficacious therapy for the impairment in muscle quantity and quality in middle age and physically frail adults. Evidence is accumulating that dietary amino acid supplementation may also improve muscle protein balance in the elderly. Several potential cellular mechanisms for the loss of muscle protein and resistance exercise-induced improvements in muscle quantity and quality in elderly adults are reviewed.