The goal of this clinical trial is to investigate the effects of protein ingestion post-exercise on bone turnover markers. The main questions it aims to answer is:

Does protein ingestion independently influence the bone metabolic response to exercise in endurance runners?

We will compare dietary protein to a placebo (water) to detect changes in bone turnover markers.

Participants will:

In a within-subject design, participants will perform an exhaustive run and take either protein or placebo immediately post-exercise.

Track physical activity and diet before each arm of the intervention and during the washout period.

Endurance athletes are at increased risk for bone loss and injury due to high-volume training, muscle weakness, and elevated nutritional demand. Dietary practices influence short- and long-term bone health and nutrition supplementation post-exercise may improve the short-term response of bone to exercise and benefit musculoskeletal recovery. However, we have a limited understanding of which dietary practices are most beneficial to optimize bone health in athletic populations. Protein supplementation has long been recommended for muscle adaptation and athletic performance but its potential for bone health has not been thoroughly investigated in endurance athletes. The purpose of this study is to is to investigate the acute independent effects of dietary protein ingestion on bone metabolism in healthy adults aged 18-35 years participating in high-volume endurance running.

Inclusion Criteria:

• 18-35 years of age
• Healthy-range body mass index (BMI) (18.5-24.9 kg/m2)
• Competitive runner for at least one season (minimum 40 km/week for the past 6-months)
• Can read, speak, and understand French and/or English

Exclusion Criteria:

• Disease or medication known to affect bone metabolism
• Disease (e.g., uncontrolled thyroid disease, malabsorptive or inflammatory disorder, metabolic bone disease)
• Medication (e.g., hormonal contraceptives the past 3 months, glucocorticoids, anti-hypertensive drugs, anti-epileptic drugs, osteoporosis therapy)
• Orthopedic or musculoskeletal injury/disease that limits the capacity to exercise
• Current smoker or tobacco user
• Current diagnosis of an eating disorder
• Female participants with self-reported or diagnosed:
• Hypothalamic amenorrhea
• Polycystic ovarian syndrome
• Hyperprolactinemia
• Primary ovarian insufficiency
• Pregnant or breastfeeding
• Donated blood within the past two months