New evidence shows that older adults need more dietary protein than do younger adults to support good health, promote recovery from illness, and maintain functionality. Older people need to make up for age-related changes in protein metabolism, such as high splanchnic extraction and declining anabolic responses to ingested protein. They also need more protein to offset inflammatory and catabolic conditions associated with chronic and acute diseases that occur commonly with aging. With the goal of developing updated, evidence-based recommendations for optimal protein intake by older people, the European Union Geriatric Medicine Society (EUGMS), in cooperation with other scientific organizations, appointed an international study group to review dietary protein needs with aging (PROT-AGE Study Group). To help older people (>65 years) maintain and regain lean body mass and function, the PROT-AGE study group recommends average daily intake at least in the range of 1.0 to 1.2 g protein per kilogram of body weight per day. Both endurance- and resistance-type exercises are recommended at individualized levels that are safe and tolerated, and higher protein intake (ie, ≥ 1.2 g/kg body weight/d) is advised for those who are exercising and otherwise active. Most older adults who have acute or chronic diseases need even more dietary protein (ie, 1.2-1.5 g/kg body weight/d). Older people with severe kidney disease (ie, estimated GFR <30 mL/min/1.73 m(2)), but who are not on dialysis, are an exception to this rule; these individuals may need to limit protein intake. Protein quality, timing of ingestion, and intake of other nutritional supplements may be relevant, but evidence is not yet sufficient to support specific recommendations. Older people are vulnerable to losses in physical function capacity, and such losses predict loss of independence, falls, and even mortality. Thus, future studies aimed at pinpointing optimal protein intake in specific populations of older people need to include measures of physical function.

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The aging process is associated with gradual and progressive loss of muscle mass along with lowered strength and physical endurance. This condition, sarcopenia, has been widely observed with aging in sedentary adults. Regular aerobic and resistance exercise programs have been shown to counteract most aspects of sarcopenia. In addition, good nutrition, especially adequate protein and energy intake, can help limit and treat age-related declines in muscle mass, strength, and functional abilities. Protein nutrition in combination with exercise is considered optimal for maintaining muscle function. With the goal of providing recommendations for health care professionals to help older adults sustain muscle strength and function into older age, the European Society for Clinical Nutrition and Metabolism (ESPEN) hosted a Workshop on Protein Requirements in the Elderly, held in Dubrovnik on November 24 and 25, 2013. Based on the evidence presented and discussed, the following recommendations are made: (1) for healthy older people, the diet should provide at least 1.0 to 1.2 g protein/kg body weight/day (2) for older people who are malnourished or at risk of malnutrition because they have acute or chronic illness, the diet should provide 1.2 to 1.5 g protein/kg body weight/day, with even higher intake for individuals with severe illness or injury, and (3) daily physical activity or exercise (resistance training, aerobic exercise) should be undertaken by all older people, for as long as possible.

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Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.

The rates of protein synthesis and degradation and of amino acid transport were determined in the leg muscle of untrained postabsorptive normal volunteers at rest and approximately 3 h after a resistance exercise routine. The methodology involved use of stable isotopic tracers of amino acids, arteriovenous catheterization of the femoral vessels, and biopsy of the vastus lateralis muscle. During postexercise recovery, the rate of intramuscular phenylalanine utilization for protein synthesis increased above the basal value by 108 +/- 18%, whereas the rate of release from proteolysis increased by 51 +/- 17%. Muscle protein balance improved (P < 0.05) after exercise but did not become positive (from -15 +/- 12 to -6 +/- 3 nmol phenylalanine.min-1.100 ml leg volume-1). After exercise, rates of inward transport of leucine, lysine, and alanine increased (P < 0.05) above the basal state from 132 +/- 16 to 208 +/- 29, from 122 +/- 8 to 260 +/- 8, and from 384 +/- 71 to 602 +/- 89 nmol.min-1.100 ml leg-1, respectively. Transport of phenylalanine did not change significantly. These results indicate that, during recovery after resistance exercise, muscle protein turnover is increased because of an acceleration of synthesis and degradation. A postexercise acceleration of amino acid transport may contribute to the relatively greater stimulation of protein synthesis.

The COVID-19 pandemic is an unprecedented health crisis as entire populations have been asked to self-isolate and live in home-confinement for several weeks to months, which in itself represents a physiological challenge with significant health risks. This paper describes the impact of sedentarism on the human body at the level of the muscular, cardiovascular, metabolic, endocrine and nervous systems and is based on evidence from several models of inactivity, including bed rest, unilateral limb suspension, and step-reduction. Data form these studies show that muscle wasting occurs rapidly, being detectable within two days of inactivity. This loss of muscle mass is associated with fibre denervation, neuromuscular junction damage and upregulation of protein breakdown, but is mostly explained by the suppression of muscle protein synthesis. Inactivity also affects glucose homeostasis as just few days of step reduction or bed rest, reduce insulin sensitivity, principally in muscle. Additionally, aerobic capacity is impaired at all levels of the O 2 cascade, from the cardiovascular system, including peripheral circulation, to skeletal muscle oxidative function. Positive energy balance during physical inactivity is associated with fat deposition, associated with systemic inflammation and activation of antioxidant defences, exacerbating muscle loss. Importantly, these deleterious effects of inactivity can be diminished by routine exercise practice, but the exercise dose-response relationship is currently unknown. Nevertheless, low to mediumintensity high volume resistive exercise, easily implementable in home-settings, will have positive effects, particularly if combined with a 15-25% reduction in daily energy intake. This combined regimen seems ideal for preserving neuromuscular, metabolic and cardiovascular health.. Just few days of sedentary lifestyle are sufficient to induce muscle loss, neuromuscular junction damage and fibre denervation, insulin resistance, decreased aerobic capacity, fat deposition and low-grade systemic inflammation. . Regular low/medium intensity high volume exercise, together with a 15-25% reduction in caloric intake are recommended for preserving neuromuscular, cardiovascular, metabolic and endocrine health.2 M. Narici et al.