Aging is associated with the loss of lean muscle mass, termed sarcopenia. Food intake and in particular the ingestion of protein or amino acids has been shown to be a powerful stimulus to promote net muscle protein anabolism. However this anabolic response following a meal-like protein bolus seems to be blunted in the elderly as compared to young adults.

The first aim of this proposal is to investigate the post-prandial muscle protein synthesis rates in young and elderly men in response to a meal-like protein bolus after a period of rest or physical activity (study A). The rest trial (REST) will act as a proof-of-principle study to examine the blunted protein synthetic response in the elderly, and as a control trial in comparison with the exercise trial (EXC) to establish the surplus value of physical activity prior to protein intake on muscle protein synthesis.

The second aim of this proposal is to determine the surplus value of an increased quantity of the ingested protein bolus (study B). Large amounts of protein (40 and 60 g) will be compared to a meal-like amount of protein (20 g) as a means to maximize plasma amino acid availability and/or to stimulate muscle protein anabolism.

The third aim of this proposal is to study the differences in quality of the ingested protein bolus (study C). Instead of significantly increasing the quantity of the protein bolus, we will also apply a more practical approach to augment skeletal muscle protein synthesis rates; modifying the digestibility or amino acid composition of a meal-like protein bolus.

Inclusion Criteria:

• In study A, non-obese male subjects (BMI <27) between the age of 18-30 yrs and 70-85 yrs will be selected.
• In studies B and C, non-obese male subjects (BMI <27) between the age of 70-85 yrs will be selected.

Exclusion Criteria:

• Type II diabetes or other known diseases
• Use of medication
• Female
• Other ages or BMI than indicated above
• Participation in any regular exercise program.