Masters level cyclists are a population above the age of 35 years who frequently participate in prolonged as well as heavy-volume training. Like most endurance-trained athletes, a greater recommended dietary allowance (RDA) for protein of 1.2-1.4 g/kg/bw is suggested.

Dietary protein intake is vital for maximizing the benefits of training and ensuring optimal recovery. Dietary recommendations traditionally have been determined through nitrogen balance techniques, however, recent research indicates how this method is potentially underestimating protein requirements. Therefore, there is a need to reassess current dietary recommendations in order to meet the demands of physical activity for highly active populations.

Recent efforts to understand protein requirements during rest and following exercise have been completed using the indicator amino acid technique (IAAO). This non-invasive method is reported to provide a robust measure of protein requirements. However, there is limited work in older (≥60 years) active populations.

The purpose of this study is to measure the protein requirements in master cyclists, following an endurance training session, using the non-invasive IAAO technique.

Inclusion Criteria:

• 18.5< BMI <35 kg/m^2
• Overtly healthy masters level cyclists ≥65 years
• Masters level cyclist training (>4 days per week; ~100 km per week)
• Body mass stable over previous 6-months
• Availability for multiple metabolic trials (~7 trials)
• Ability to travel to and from laboratory facility

Exclusion Criteria:

• Recent history of weight loss or weight gain (>5% body weight)
• Uncontrolled hypertension
• ≥2 chronic diseases (e.g. diabetes, osteoporosis, dyslipidemia)
• Acute illness that could affect protein metabolism (HIV, renal dysfunction, influenza)
• Currently using anti-inflammatory medications
• Inability to adhere to study protocol (i.e., alcohol, caffeine, dietary restrictions)
• Regular tobacco user
• Illicit drug use
• Habitually ingesting ≥3 g/kg/bw