Sarcopenia describes the progressive decline of muscle mass and strength with advancing age and is associated with increased frailty and morbidity, however we do not currently have an effective treatment. Protein feeding and exercise is known to increase muscle mass, but aged muscle shows a lower response to these stimuli leading to muscle loss over time. We do know that ingesting leucine, a building block of protein, can overcome this reduced response to protein feeding and exercise leading to increased muscle mass in older people. However, we do not understand when the optimum time to ingest leucine is to maximise muscle mass after exercise in older people. In this study we will examine the effect of feeding leucine after exercise either with a meal or between meals.

Inclusion Criteria:

• Male, 65-75 years of age
• BMI 18-28 kg/m2
• Non smoker
• Not performing regular resistance type exercise
• Participant is willing and able to give informed consent for participation in the study

Exclusion Criteria:

• A BMI <18 or >28 kg·m-2
• Active cardiovascular disease: uncontrolled hypertension (BP > 160/100), angina, heart failure (class III/IV), arrhythmia, right to left cardiac shunt or recent cardiac event
• Cerebrovascular disease: previous stroke, aneurysm (large vessel or intracranial)
• Respiratory disease including pulmonary hypertension or chronic obstructive pulmonary disease (COPD)
• Metabolic disease: hyper and hypo parathyroidism, untreated hyper and hypothyroidism, Cushing's disease, types 1 or 2 diabetes (treated and untreated), inborn/ congenital errors of metabolism (e.g. phenylketonuria (PKU), galactosaemia)
• Active inflammatory bowel disease
• Acute infection
• Acute or chronic renal disease
• Malignancy (or history of malignancy with 5 y)
• Recent steroid treatment (within 6 mo), or hormone replacement therapy
• Coagulopathy
• Musculoskeletal or neurological disorders
• Known allergies to any of the product ingredients
• Having taken part in a research study in the last 3 months involving invasive procedures or an inconvenience allowance